WO2014083035A1

WO2014083035A1 - Method for determining information about molecular weight of polymers

Info

Publication number: WO2014083035A1
Application number: PCT/EP2013/074818
Authority: WO
Inventors: Olivier Lavastre; Kevin FOUYER
Original assignee: Total Research & Technology Feluy; Centre National De La Recherche Scientifique (Cnrs)
Priority date: 2012-11-27
Filing date: 2013-11-27
Publication date: 2014-06-05
Also published as: EP2788750A1

Abstract

The present invention relates to a method for determining information about the molecular weight of at least one polymer comprised in a polymer composition using planar chromatography, said method comprising the steps of: a') eluting at least one polymer composition in at least one elution trail along at least one elution axis of a planar chromatography plate; said polymer composition comprising at least two polymers; a) exposing said planar chromatography plate or part thereof having said at least one elution trail along said at least one elution axis of said planar chromatography plate to an incident radiation; b) recording the emission response of said planar chromatography plate or part thereof in response to said incident radiation; c) converting said emission response into image data which comprise a plurality of pixels and intensity data associated with each of the pixels; d) selecting from said image data at least one elution trail along said at least one elution axis of said planar chromatography plate; e) segmenting each of said at least one elution trail into at least two segments positioned next to each other along the elution axis of the elution trail to create segmented data sets; f) calculating the mean intensity value of each segment from the segmented data sets; g) reporting the mean intensity value of each segment as a function of the position of each segment along the elution axis of the elution trail; h) comparing the results of step (g) with a reference; and j) determining information about the molecular weight of said at least one polymer.

Description

METHOD FOR DETERMINING INFORMATION ABOUT MOLECULAR WEIGHT OF

POLYMERS

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a method for determining information about the molecular weight of at least one polymer mixture.

BACKGROUND OF THE INVENTION

One distinguishing feature of most synthetic polymers is that they are polydisperse. The entire polymer sample is made up of individual polymer molecules that have a distribution of degrees of polymerization determined by the particular synthesis method. Hence, in many instances, average molecular weight and molecular weight dispersities are insufficient to describe the properties of a polymer, and more complete information on the molecular weight distribution is required. This is particularly important for polymers that have molecular weight distributions which are broad, non-uniform, e.g. having low or high molecular weight shoulder, and/or multimodal. However, even for polymers with relatively simple molecular weight distributions, it is advantageous to know the complete molecular weight distribution, because any molecular weight average such as number average molecular weight or weight average molecular weight can be calculated from the molecular weight distribution curve.

During the first few decades of polymer science, there were no techniques available for determining directly complete molecular weight distributions of polymers. Hence, it was necessary to fractionate the polymer into a number of fractions each of which has a narrow distribution of molecular weight. The molecular weight of each polymer fraction could then be determined for instance by membrane osmometry, thereby enabling the molecular weight distribution to be constructed. Nowadays, such procedures are rarely used because much more rapid and powerful methods are available for determining molecular weight distributions of polymers, the most important of which is gel permeation chromatography (GPC).

In GPC, a dilute polymer solution is injected into a solvent stream, which then flows through a column packed with beads of a porous gel. The porosity of the gel is of critical importance. The small solvent molecules pass both through and around the beads, carrying the polymer molecules with them where possible. The smallest polymer molecules are able to pass through most of the pores in the beads and so have a relatively long flow-path through the column. However, the largest polymer molecules are excluded from all but the largest of the pores because of their greater molecule size and consequently have a much shorter flow-path. The concentration of polymer in the eluate is monitored continuously and the chromatogram obtained is a plot of concentration against elution volume, which could provide a qualitative indication of the molecular weight distribution.

However, such method tends to be time-consuming and do not readily lend themselves to the fast screening of numerous samples. In addition, filtrations must be performed before using the instrument to prevent dust and other particulates from ruining the columns and interfering with the detectors. Such pre-filtration step requires additional handling of the polymer, which is costly and time-consuming and not amenable to high throughput screening.

In view of the above, there remains a need in the art for providing further and/or improved methods for determining molecular weight information of polymers.

SUMMARY OF THE INVENTION

The present inventors have now found a method for determining information about the molecular weight of at least one polymer overcoming one or more of the above-mentioned problems of the prior art. The present invention thus provides a method for determining information about the molecular weight, such as the molecular weight and/or the molecular weight distribution, of at least one polymer comprised in a polymer composition using planar chromatography, said method comprises the steps of:

a') eluting at least one polymer composition in at least one elution trail along at least one elution axis of a planar chromatography plate; said polymer composition comprising at least two polymers;

a) exposing said planar chromatography plate or part thereof having said at least one elution trail along said at least one elution axis of said planar chromatography plate to an incident radiation;

b) recording the emission response of said planar chromatography plate or part thereof in response to said incident radiation;

c) converting said emission response into image data which comprise a plurality of pixels and intensity data associated with each of the pixels;

d) selecting from said image data at least one elution trail along said at least one elution axis of said planar chromatography plate; e) segmenting each of said at least one elution trail into at least two segments positioned next to each other along the elution axis of the elution trail to create segmented data sets;

f) calculating the mean intensity value of each segment from the segmented data sets; g) reporting mean intensity value of each segment as a function of the position of each segment along the elution axis of the elution trail;

h) comparing the results of step (g) with a reference; and

j) determining information about the molecular weight of said at least one polymer.

The inventors have found that the method of the present invention advantageously allows determining the molecular weight and/or the molecular weight distribution of a polymer with a straightforward and economical technique. The present invention is particularly suited for determining the molecular weight and/or the molecular weight distribution of all the polymers which are comprised in a polymer mixture. Indeed, the method of the present invention advantageously allows to determine the molecular weight and/or the molecular weight distribution of one or more polymer samples such as for instance of up to 40 polymer samples in the same assay. In addition, the method of the present invention allows to use the same polymer sample for determining the molecular weight and/or the molecular weight distribution as for obtaining information about the chemical structure of the polymer for instance by Raman spectroscopy.

The independent and dependent claims set out particular and preferred features of the invention. Features from the dependent claims may be combined with features of the independent or other dependent claims as appropriate.

In the following passages, different aspects of the invention are defined in more detail. Each aspect so defined may be combined with any other aspect or aspects unless clearly indicated to the contrary. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature or features indicated as being preferred or advantageous.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1 represents a photography of an TLC plate on which four polystyrene mixtures have been eluted.

Figure 2 represents a photography of an TLC plate with one elution trail, said elution trail was divided into 30 segments (zones) (schematically shown on the picture). FIG. 3, 4, 5, and 6, each represents a graph plotting the intensity of each segment of the elution trail of mixture A, B, C and D respectively..

Figure 7 represents a photography of an TLC plate on which seven polystyrene mixtures have been eluted.

Figure 8 represents a photography of an TLC plate on which seven polystyrene mixtures have been eluted.

Figure 9 represents a graph plotting the absorbance versus Rf for seven polymers.

Figure 10 represents a graph plotting Mp as a function of the Rf.

DETAILED DESCRIPTION OF THE INVENTION

Before the present process of the invention are described, it is to be understood that this invention is not limited to particular methods, components, products or combinations described, as such methods, components, products and combinations may, of course, vary. It is also to be understood that the terminology used herein is not intended to be limiting, since the scope of the present invention will be limited only by the appended claims.

As used herein, the singular forms "a", "an", and "the" include both singular and plural referents unless the context clearly dictates otherwise.

The terms "comprising", "comprises" and "comprised of" as used herein are synonymous with "including", "includes" or "containing", "contains", and are inclusive or open-ended and do not exclude additional, non-recited members, elements or method steps. It will be appreciated that the terms "comprising", "comprises" and "comprised of" as used herein comprise the terms "consisting of, "consists" and "consists of".

The recitation of numerical ranges by endpoints includes all numbers and fractions subsumed within the respective ranges, as well as the recited endpoints.

All documents cited in the present specification are hereby incorporated by reference in their entirety.

The present invention thus provides a method for determining information about the molecular weight, such as the molecular weight and/or the molecular weight distribution, of at least one polymer, preferably comprised in a polymer composition comprising at least two polymers, using planar chromatography, said method comprises the steps of: a) exposing a planar chromatography plate or part thereof having at least one elution trail along at least one elution axis of said planar chromatography plate to an incident radiation;

d) selecting from said image data at least one elution trail along said at least one elution axis of said planar chromatography plate;

e) segmenting each of said at least one elution trail into at least two segments positioned next to each other along the elution axis of the elution trail to create segmented data sets;

h) comparing the results of step (g) with a reference; and

j) determining information about the molecular weight of said at least one polymer, preferably said at least one polymer mixture.

The present invention provides a method for determining one or both of the molecular weight and the molecular weight distribution of at least one polymer using planar chromatography. Preferably the at least one polymer is comprised in a composition comprising at least two polymers. Preferably, said method comprises determining one or both of the molecular weight and the molecular weight distribution of at least two polymers using planar chromatography, wherein said two polymers are comprised in a polymer composition. Preferably, the method comprises:

a') eluting at least one polymer composition in at least one elution trail along at least one elution axis of a planar chromatography plate; preferably wherein said polymer composition comprises at least two polymers, preferably having different weight average molecular weights;

a")exposing said planar chromatography plate or part thereof to an incident radiation; b) recording the emission response of said planar chromatography plate or part thereof in response to said incident radiation;

h) comparing the results of step (g) with a reference; and

j) determining one or both of the molecular weight and the molecular weight distribution of said at least one polymer.

The term "chromatography" refers to a physical method of separation in which the components to be separated are distributed between two phases, one of which is stationary (stationary phase) while the other (the mobile phase) moves in a definite direction.

The term "planar chromatography" refers to a separation technique in which the stationary phase is present as or on a plane (planar stationary phase). The plane can be a paper, used as such or impregnated by a substrate as the stationary bed (paper chromatography, PC) or a layer of solid particles spread on a support e.g. a glass or metal plate.

The term "support" or "plate" or "support plate" refers to the plate that supports the stationary phase, such as the thin layer in thin-layer chromatography.

In accordance with an embodiment of the invention, a planar chromatography plate is any medium on which a planar chromatographic separation can be carried out. In general, a plate consists of a support, for example in the form of a glass plate, metal plate or foil or a plastic film which is covered or coated with the stationary phase. The terms "chromatography step", "chromatography run", "elution step" or "separation step" are used interchangeably and refer to a step wherein the sample to be analyzed, separated and/or characterized is deposited on a stationary phase and wherein the said sample is put in conditions to migrate along at least one axis of the chromatography plate, according to at least one physical or chemical property of the said sample, such as molecular mass, electric charge, acid/basic properties, etc.

The terms "stationary phase" or "stationary bed" or "sorbent bed" or "absorbent" are used interchangeably and refer to an immobile phase or non-fluid phase employed in the chromatography method. The expression chromatographic bed or sorbent bed may be used as a general term to denote any of the different forms in which the stationary phase is used. The stationary phases used are typically the base sorbents known for chromatographic purposes. These are, for example, silica gel, aluminum oxide, cellulose, kieselguhr or other organic or inorganic polymers or organic/inorganic hybrid polymers. The base sorbents may furthermore be derivatized with functional groups which modify their separation properties. Examples thereof are RP phases, in which, for example, silica gel has been derivatized with ligands which have C8 or C18 chains (reversed phase material). Other examples are CN or diol-modified phases. Suitable common sorbent phases for planar chromatography are described in Klaus K. Unger, Packings and Stationary Phases in Chromatographic Techniques, M. Decker, New York 1990.

The term "mobile phase" refers to a fluid which migrates through or along the stationary bed, in a definite direction. It may be a liquid or a supercritical fluid. The term "eluent" is also used for the mobile phase.

The term "thin-layer chromatography" or TLC refers to a chromatography carried out in a thin layer of adsorbent spread on a support e.g. a glass or metal plate.

The term "spot" as used herein, refers generally to a localized deposit of polymer, and is not limited to a round or substantially round region.

The term "retardation factor, R_F" in planar chromatography refers to the ratio of the distance travelled by the centre of the spot (b) to the distance simultaneously travelled by the mobile phase (a): R ^F = ⁽^ⁱ . By definition the R_F values are always less than unity. The present invention provides a method for determining one or both of the molecular weight and the molecular weight distribution of at least one polymer, preferably of at least two polymers comprised in a polymer composition, preferably wherein said polymers have different weight average molecular weights.

The term "polymer" generally refers to a substance composed of molecules which have repeating sequences of one or more monomers linked to each other by covalent bonds. A polymer is generally made up of individual monomer molecules.

The terms "molecular weight" or "molecular mass" can be used interchangeably herein. The molecular weight of a polymer generally refers to the mass of one molecule of that polymer.

The terms "molecular weight distribution", "polydispersity" or "Mw/Mn" can be used interchangeably herein. The molecular mass distribution of a polymer generally refers to the relationship between the number of moles of each molecule of the polymer and the molecular weight of that molecule, and is equal to Mw/Mn wherein Mw is the weight average molecular weight, and Mn is the number average molecular weight,

The at least one polymer of which the molecular weight and/or the molecular weight distribution can be determined with the method of the present invention can be a thermoplastic polymer. Preferably, said at least one polymer is comprised in a polymer composition comprising at least two polymers,

One embodiment of the present invention relates to a method for determining one or both of the molecular weight and the molecular weight distribution of at least one polymer, preferably at least two polymers, using planar chromatography, wherein said polymer is selected from polyolefins, polyamides, poly(hydroxy carboxylic acid), polystyrenes, polyesters, polycarbonates, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polymethylmethacrylate (PMMA), poly(methyl acrylate) (PMA), vinyl polymers, or blends thereof.

One embodiment of the present invention relates to a method for determining one or both of the molecular weight and the molecular weight distribution of at least two polymers, preferably having different weight average molecular weights, using planar chromatography, wherein said at least two polymers are comprised in a composition, and said at least two polymers are selected from polyolefins, polyamides, poly(hydroxy carboxylic acid), polystyrenes, polyesters, polycarbonates, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polymethylmethacrylate (PMMA), poly(methyl acrylate) (PMA), vinyl polymers, or blends thereof. One embodiment of the present invention relates to a method for determining one or both of the molecular weight and the molecular weight distribution of at least two polymers, preferably having different weight average molecular weights, using planar chromatography, wherein said at least two polymers are comprised in a composition, and said at least two polymers are selected from at least two polyolefins, at least two polyamides, at least two poly(hydroxy carboxylic acid), at least two polystyrenes, at least two polyesters, at least two polycarbonates, at least two polyethylene terephthalate (PET), at least two polybutylene terephthalate (PBT), at least two polymethylmethacrylate (PMMA), at least two poly(methyl acrylate) (PMA), at least two vinyl polymers, or blends thereof.

One embodiment of the present invention relates to a method for determining one or both of the molecular weight and the molecular weight distribution of at least two polystyrene polymers, preferably having different weight average molecular weights, using planar chromatography, wherein said at least two polystyrene polymers are comprised in a composition.

One embodiment of the present invention relates to a method for determining one or both of the molecular weight and the molecular weight distribution of at least two polyolefin polymers, preferably having different weight average molecular weights, using planar chromatography, wherein said at least two polyolefin polymers are comprised in a composition.

The polymers are preferably present in a sample before being applied to the thin layer chromatography. The sample can be of natural or synthetic origin. It can be provided as a liquid sample, where the analytes are typically present in an organic solvent or water or mixtures of organic solvents or mixtures of organic solvents and water. The sample can comprise any desired further solid, emulsified or dissolved constituents, which, however, should interfere neither with the planar separation nor with the later optional staining of the analytes for visualization purposes.

Solid samples are generally firstly taken up in one of the below-mentioned solvents in order that they can be applied to the chromatography plate. In the case of concentrated samples, it may be necessary firstly to dilute them. It is known to the person skilled in the art in the area of planar chromatography how large the amount of sample and sample concentration may or must be, depending on the type of plate employed and the particular separation problem, in order to obtain bands which can be evaluated as ideally as possible. The polymers to be determined and/or characterized in the present invention can be produced by any method known in the art. Their production therefore is well known to the person skilled in the art and need not be described further. Preferably, the polymers are selected from the group comprising polyolefins, polyamides, poly(hydroxy carboxylic acid), polystyrenes, polyesters, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polymethylmethacrylate (PMMA), poly(methyl acrylate) (PMA), vinyl polymers, or blends thereof.

In a preferred embodiment, the method is particularly useful for the characterization of polyolefins. The polyolefins may be any olefin homopolymer or any copolymer of an olefin and one or more comonomers. The polyolefins may be atactic, syndiotactic or isotactic. The olefin can for example be ethylene, propylene, 1 -butene, 1 -pentene, 1 -hexene, 4- methyl-1 -pentene or 1 -octene, but also cycloolefins such as for example cyclopentene, cyclohexene, cyclooctene or norbornene. The comonomer may be different from the olefin and chosen such that it is suited for copolymerization with the olefin. The comonomer may be an olefin as defined above. Further examples of suitable comonomers are vinyl acetate (H₃C-C(=0)0-CH=CH₂) or vinyl alcohol ("HOCH=CH₂"), acrylate, methacrylate or styrene. Examples of olefin copolymers that can be analyzed in the present invention are random copolymers of propylene and ethylene, random copolymers of propylene and 1 -butene, heterophasic copolymers of propylene and ethylene, ethylene-butene copolymers, ethylene-hexene copolymers, ethylene-octene copolymers, copolymers of ethylene and vinyl acetate (EVA), copolymers of ethylene and vinyl alcohol (EVOH).

Most preferred polyolefins to be analyzed in the present invention are olefin homopolymers and copolymers of an olefin and optionally one or more comonomers, wherein said olefin and said one or more comonomers are different. Preferably, said olefin is ethylene or propylene. The term "olefin comonomer" refers to olefin comonomers which are suitable for being polymerized with olefin monomers, preferably ethylene or propylene monomers. Comonomers may comprise but are not limited to aliphatic C₂-C₂o alpha- olefins. Examples of suitable aliphatic C₂-C₂₀ alpha-olefins include ethylene, propylene, 1 - butene, 4-methyl-1 -pentene, 1 -hexene, 1 -octene, 1 -decene, 1 -dodecene, 1 -tetradecene, 1 -hexadecene, 1 -octadecene and 1 -eicosene. Preferred polyolefins for use in the present invention are propylene and ethylene polymers. As used herein, the terms "propylene polymer" and "polypropylene" as well as the terms "ethylene polymer" and "polyethylene" are used interchangeably. Preferably, the polyolefin is selected from polyethylene and polypropylene homo- and copolymers. In some embodiments, the method is particularly useful for the characterization of polyamides. Polyamides are characterized in that the polymer chain comprises amide groups (-NHC(=0)-). Polyamides to be analyzed in the present invention have preferably one of the following chemical structures: [-NH-(CH₂)_n-C(=0)-]_x, or

[-NH-(CH2)_m-NH-C(=0)-(CH₂)_n-C(=0)-]_x wherein m and n may be independently chosen from one another and be an integer from 1 to 20. Specific examples of suitable polyamides are polyamides 4, 6, 7, 8, 9, 10, 1 1 , 12, 46, 66, 610, 612, and 613.

The polystyrenes to be characterized in the present invention may be any styrene homopolymer or copolymer. They may be atactic, syndiotactic or isotactic. Styrene copolymers comprise one or more suitable comonomers, i.e. polymerizable compounds different from styrene. Examples of suitable comonomers are butadiene, acrylonitrile, acrylic acid or methacrylic acid and corresponding esters. Examples of styrene copolymers that may be analyzed, separated, or characterized in the present invention are butadiene-styrene copolymers, which are also referred to as high-impact polystyrene (HI PS), acrylonitrile-butadiene-styrene copolymers (ABS) or styrene-acrylonitrile copolymers (SAN).

Polyesters that may be analyzed, or characterized in the present invention can have the following chemical structure: [-C(=0)-C₆H₄-C(=0)0-(CH2-CH2)_n-0-]_x wherein n is an integer from 1 to 10, with preferred values being 1 or 2. Specific examples of suitable polyesters are polyethylene terephthalate (PET) and polybutylene terephthalate (PBT). Furthermore, preferred polyesters can be poly(hydroxy carboxylic acid)s as described below. The poly(hydroxy carboxylic acid)s can be any polymer wherein the monomers comprise at least one hydroxyl group and at least carboxyl group. The hydroxy carboxylic acid monomer is preferably obtained from renewable resources such as corn and rice or other sugar- or starch-producing plants. The term "poly(hydroxy carboxylic acid)" includes homo- and co-polymers herein. The poly(hydroxy carboxylic acid) can be represented as in Formula I II :

Formula II I wherein R" is hydrogen or a branched or linear alkyl comprising from 1 to 12 carbon atoms; R¹ is optional and can be a branched, cyclic or linear alkylene chains comprising from 1 to 12 carbon atoms; and "r" represents the number of repeating units of R and is any integer from 30 to 15000. The monomeric repeating unit is not particularly limited, as long as it is aliphatic and has a hydroxyl residue and a carboxyl residue. Examples of possible monomers include lactic acid, glycolic acid, 3-hydroxybutyric acid, 4- hydroxybutyric acid, 4-hydroxyvaleric acid, 5-hydroxyvaleric acid, 6-hydroxycaproic acid and the like. The monomeric repeating unit may also be derived from a cyclic monomer or cyclic dimer of the respective aliphatic hydroxycarboxylic acid. Examples of these include lactide, glycolide, β-propiolactone, β-butyrolactone, γ-butyrolactone, γ-valerolactone, δ- valerolactone, ε-caprolactone and the like. In the case of asymmetric carbon atoms within the hydroxy carboxylic acid unit, each of the D-form and the L-form as well as mixtures of both may be present. Racemic mixtures can also be present. The term "poly(hydroxy carboxylic acid)" also includes blends of more than one poly(hydroxy carboxylic acid). The poly(hydroxy carboxylic acid) may optionally comprise one or more comonomers. The comonomer can be a second different hydroxycarboxylic acid as defined above in Formula III. The weight percentage of each hydroxycarboxylic acid is not particularly limited. The comonomer can also comprise dibasic carboxylic acids and dihydric alcohols. These react together to form aliphatic esters, oligoesters or polyesters having a free hydroxyl end group and a free carboxylic acid end group, capable of reacting with hydroxy carboxylic acids, such as lactic acid and polymers thereof. The poly(hydroxy carboxylic acid) can be preferably a polylactic acid (PLA). Preferably the polylactic acid is a homopolymer obtained either directly from lactic acid or from lactide, preferably from lactide.

In a preferred embodiment, the at least one polymer can also be selected from polyethylene (PE), polypropylene (PP), polystyrene (PS), polymethylpentene (PMP), polybutene-1 (PB-1 ), polylactic acid (PLA), polybutadiene, polycarbonate, polymethylmethacrylate (PMMA), poly(methyl acrylate) (PMA), or blends thereof.

The present invention provides a method for determining one or both of the molecular weight and the molecular weight distribution of at least one polymer, preferably of at least two polymers, using planar chromatography.

The planar chromatography can be performed on a plate (inert support) coated with a layer of stationary phase, usually bound to the plate. The stationary phase can be selected from a finely divided polar substance such as for example silica gel or aluminium oxide or cellulose.

Typically a solution of the sample to be characterized is deposited on the stationary phase as a small, tight spot and is then allowed to dry. The plate can then be inserted into a tank, a reactor or an overpressurized layer chromatography device. The chromatography (also referred herein as elution or migration) is carried out by capillary action generally in an ascending mode, or by forced flow through the stationary phase.

In one embodiment of the present invention, the planar chromatography is selected from a Thin-layer chromatography (TLC), High Performance Thin-Layer Chromatography (HPTLC), and Overpressurized Layer Chromatography (OPLC).

In one embodiment of the present invention, the chromatography can be performed under external pressure by applying either i) a neutral gas under pressure applied to a membrane on the planar stationary phase; ii) a pneumatic pillow or metallic membrane on the planar stationary phase; or iii) a pneumatic press on the planar stationary phase.

In one embodiment of the present invention, the planar stationary phase is selected from the group comprising silica based normal and reverse-phase thin layer chromatography resin optionally derivatized with alkyl groups or aromatic groups.

In one embodiment, the sorbent bed or plate is pre-treated by wetting with a composition followed by drying. It creates a film on the surface of the support and it is selected in order to control and/or modify the separation conditions and revelation of the polymers under study. The composition can be a solvent alone or a combination of solvent and additives, it can be selected for example from toluene, xylene, tetrahydrofuran, C₄-C₂o branched or non-branched alkane such as heptane, hexane, or isobutane, supercritical carbon dioxide, trichlorobenzene, halogenated solvent, ethyl acetate, dimethylsulfoxide, dimethylformamide, inorganic salts, organic molecules, and mixtures thereof. It is selected in function of the polymer under study.

The solvent used to dissolve the polymer samples is selected in order to completely dissolve said polymer. If necessary, the solution is heated to achieve complete dissolution of the polymer. Complete dissolution of the polymers allows its homogeneous deposition on the sorbent bed. Typical concentrations range between 0.2 and 50 mg/mL, preferably from 1 to 20 mg/mL, more preferably from 1 to 10 mg/mL, more preferably from 1 to 5 mg/mL. A higher concentration results in a better visualization of the migrated sample, but saturation must be avoided. It is adapted to the nature of the polymer and to the nature of the stationary phase.

Small amounts of each polymer solution are then deposited on the starting line of the sorbent bed, at position R_F = 0. The amount of solution deposited can range between 0.1 and 10 μΙ_. Multiple depositions are also possible with drying between each deposition. It is allowed to dry before being submitted to elution.

In some embodiments, the polymers are studied by TLC or HPTLC. The sorbent bed is placed vertically in a tank containing a few millimeters of eluent and separation spontaneously occurs through ascending capillarity.

In another preferred embodiment according to the present invention, OPLC is used to characterize the polymers.

In an embodiment, the planar chromatography performed under pressure as described above, is performed using Overpressure Liquid Chromatography (OPLC). OPLC is based on the same principle as TLC, except that the ascending capillarity is assisted by applying pressure to the system. The commercially available OPLC system comprises a metal cassette supporting the sorbent bed. It is covered with sheet such as a Teflon sheet pierced with 2 parallel slits, one to let the mobile phase in and the other to let the mobile phase out. The system also comprises a seal around its entire perimeter. A pressure of is applied to the system in order to seal it. The mobile phase can then be introduced through the in-slit of the Teflon plate under a pressure, it flows through the system and is recovered at the out-slit of the Teflon plate.

In one embodiment of the present invention, when using OPLC, the mobile phase is injected at a pressure of 2 to 100 bar, preferably at a pressure of 5 to 80 bar, more preferably at a pressure of 2 to 10 bar.

In one embodiment of the present invention, the flow rate of the mobile phase is of 0.1 to 5 mL / min. The mobile phase is preferably pumped through the stationary phase at a flow rate of 0.1 to 5 mL / min, preferably at a flow rate of 0.2 to 3 mL / min.

In one embodiment of the present invention, the planar stationary phase is subjected to a positive external pressure differential of 2-3 bar relative to the injection pressure on the mobile phase, with a maximum pressure of 150 bar.

OPLC allows the study of polymers having molecular weights ranging from dimers up to 1 ,500,000 Da. In some embodiments, the stationary phase, loaded with polymer solutions is covered with a Teflon sheet and sealed by applying an external pressure corresponding to 4 to 103 bar, preferably of 5 to 80 bar, more preferably of 5 to 50 bar, more preferably of 5 to 30 bar, more preferably of 5 to 10 bar. The eluent can then be injected through the in-slit of the Teflon sheet at an inferior pressure of 2 to 3 bars relative to the pressure applied to the planar stationary phase, producing an eluent flow ranging between 0.1 and 5 ml/min, preferably between 2 and 3 ml/min.

The sorbent bed can have usually a size of from 10 to 20 cm and allows the simultaneous study of at least one polymer sample, preferably at least two polymer samples, for example from 5 to 40 polymer samples, for example, in a period of time ranging between 2 and 30 minutes, preferably 2 to 5 minutes, more preferably about 3 minutes. It is therefore very advantageous as compared to GPC that requires a period of time of at least 15 minutes per sample. Preferably, a first migration is interrupted when the fastest sample has reached the end of the sorbent bed, at position R_F= .

The choice of the eluent is determined by the nature of the polymer to be studied or by its expected molecular weight. It is possible to vary the eluent during the process in order to favor the migration of certain molecular weight ranges. For example, a first eluent can be selected to dissolve only the low molecular weight fraction in a polymer and thus migrate it. The eluent can then be modified to dissolve the next molecular weight fraction, and so on, until complete characterization of the polymer is obtained. Alternatively, a mixture of eluents with variable ratio of components can be used.

In one embodiment of the present invention, the mobile phase is selected from the non- limiting group comprising toluene, xylene, tetrahydrofuran, C4-C20 branched or non- branched alkane such as heptane, hexane, or isobutane, supercritical carbon dioxide, trichlorobenzene, ethyl acetate, dimethylsulfoxide, dimethylformamide, an ionic liquid, or mixtures thereof.

The present method comprises step (a) exposing a planar chromatography plate or part thereof having at least one elution trail along at least one elution axis of said planar chromatography plate to an incident radiation.

In an embodiment, the present method comprises prior to step (a), the step of (a') performing a planar chromatography comprising the steps of:

providing a planar chromatography plate,

applying said at least one polymer composition on said planar chromatography plate, eluting said at least one polymer composition in at least one elution trial along at least one elution axis of said planar chromatography plate into one or more spots, and optionally drying said eluted planar chromatography plate.

The start position where the polymer composition is spotted can be referred to as position 0. The position of the mobile phase after elution can be referred to as position 1.

The elution of a polymer composition on a planar chromatography plate can be performed along one or more elution axes such as for example along two elution axes to provide a two-dimensional thin layer chromatography.

As mentioned above, the present method comprises step (a) exposing a planar chromatography plate or part thereof having at least one elution trail along at least one elution axis of said planar chromatography plate to an incident radiation.

The terms "exposing" or "illuminating" may be used interchangeably herein. The recitation "exposing a planar chromatography plate or part thereof to an incident radiation", as used herein, refers to subjecting said planar chromatography plate or part thereof to said incident radiation. The step of exposing the planar chromatography plate or part hereof may comprise the step of exposing the planar chromatography plate or part thereof to at least one pulse of electromagnetic radiation or continuously exposing the planar chromatography plate or part thereof with electromagnetic radiation.

The term "radiation" generally refers to energy transmitted through space. The term "incident radiation" generally refers to radiation hitting a specific surface. The incident radiation can be one or more of visible light, ultraviolet (UV) or infrared (IR).

The source of electromagnetic radiation can be for instance a lamp or a laser.

The visualization of the results can be carried out either directly if the polymers are colored, or with UV, IR light or with a scanner, or with prior chemical and/or physical treatment of the plate. Preferably, for polyolefins such as polyethylene or polypropylene a chemical and/or physical treatment of the planar chromatography is performed.

Hence, in an embodiment, step (a) of the present method can be performed after chemical or physical treatment of the eluted planar chromatography plate after elution. The chemical treatment can be without limitation one or more of oxidation, revealing agent.

The physical treatment can be without limitation one or more of heat treatment, or light exposition. In an embodiment, the method of the invention comprises step (a) exposing a planar chromatography plate or part thereof having at least one elution trail along at least one elution axis of said planar chromatography plate to an incident UV radiation.

In an embodiment, the method of the invention comprises step (a) exposing a planar chromatography plate or part thereof having at least one elution trail along at least one elution axis of said planar chromatography plate to an incident UV radiation after heat treatment of said planar chromatography plate or part thereof. Said heat treatment can be performed at a temperature ranging from about 50°C to about 250°C, for example, said heat treatment can be performed at a temperature ranging from about 180°C to about 220°C, for example, said heat treatment can be performed at a temperature ranging from about 200°C to about 240°C.

Said heat treatment can be performed during at least 1 minute, for example during at least 2 minutes, at least 3 minutes, at least 4 minutes, at least 5 minutes, for example for at least 10 minutes, for example for at least 15 minutes, for example for at least 20 minutes. For example, said heat treatment can be performed for at least 10 minute, at a temperature of at least 180°C.

The present method further comprises the step of (b) recording the emission response of said planar chromatography plate or part thereof in response to said incident radiation. The step of recording the emission response can be effected by means of an ordinary camera, a digital camera, a scanner, a spectrometer or like device which may record or capture an image of the planar chromatography plate or part thereof over a wide range of wavelengths including visible light radiation, infrared radiation or ultraviolet radiation. The digital camera may for instance be an image intensifying camera.

In an embodiment, the present method comprises the steps of:

a) exposing a planar chromatography plate or part thereof having at least one elution trail along at least one elution axis of said planar chromatography plate to an incident radiation; and

b) recording the emission response of said planar chromatography plate or part thereof in response to said incident radiation.

In an embodiment, the present method comprises during steps (a) and (b), the step of determining the chemical structure of said at least one polymer, preferably of at least two polymers comprised in a polymer composition. The chemical structure may be determined by any technique for determining the chemical structure or composition which can be applied to a planar chromatography plate for instance but without limitation spectroscopy such as ultraviolet and visible light absorption spectroscopy, infrared spectroscopy or Raman spectroscopy.

In a further embodiment, the present method comprises prior to exposing said planar chromatography plate or part thereof to an incident radiation, the step of determining the chemical structure of said at least one polymer, preferably of at least two polymers comprised in a polymer composition. Such methods applying the principles of the present invention advantageously allow to determine the molecular weight, the molecular weight distribution and chemical structure of a polymer with one polymer sample and in one assay without the need to isolate the polymer from the planar chromatography plate.

In a further embodiment, the step of determining the chemical structure of said at least one polymer is performed before chemical or physical treatment of the planar chromatography plate.

The present method further comprises the step of (c) converting said emission response into image data which comprise a plurality of pixels and intensity data associated with each of the pixels.

The emission response can be converted into image data by a software program present on a computer or present in said digital camera, scanner, spectrometer, or like device. The image data can be a digital photo (image) or digital video obtained by a digital camera, scanner, spectrometer, or like device.

The emission response can be converted into image data by digitization and Fast Fourier Transform (FFT) or using image analysis software.

The intensity data associated with each pixel can be expressed within a range between a minimum and a maximum including said minimum and said maximum. Preferably, intensity data comprise at least 4 bits per pixel, preferably at least 8 bits per pixel, at least 16 bits per pixel, at least 32 bits per pixel or at least 64 bits per pixel. In an embodiment of the present method, the intensity data comprise at least 8 bits per pixel. As an example and without limitation, intensity data comprising 8 bits per pixel allow 2⁸ = 256 different intensities associated with each of the pixels. As a further example and without limitation, intensity data comprising 16 bits per pixel allow 2¹⁶ = 65536 different intensities associated with each of the pixels.

The intensity data can be grayscale data. In computing, grayscale data associated with each of the pixels can be represented in an abstract way as a range from 0 to 1 , with any fractional values in between. Generally, 0 is black and the maximum value, such as 255 at 8 bits per pixel or 65535 at 16 bits per pixel, is 1 .

The present method further comprises step (d) selecting from said image data at least one elution trail along said at least one elution axis of said planar chromatography plate.

The term "elution trail", as used herein, refers to the path the polymer or polymer sample has followed on the planar chromatography plate during its elution along one of its elution axes.

The at least one elution trail selected during step (d) of the present method can be one elution trail or can be more than one elution trail such as for instance all the elution trails present on a planar chromatography plate, for instance but without limitation, up to 24 elution trails.

The present method further comprises step (e) segmenting each of said at least one elution trail into at least two segments positioned next to each other along the elution axis of the elution trail to create segmented data sets, each comprising a plurality of pixels and intensity data associated with each of the pixels.

The term "segmenting each of said at least one elution trail", as used herein, refers to delimiting said image data in each of said at least one elution trail to segmented data sets each comprising a plurality of pixels and intensity data associated with each of the pixels. The at least two segments are selected along the elution axis of the elution trail.

In an embodiment, said at least two segments are identical. The recitation "at least two segments being identical", as used herein, means that the at least two segments have the same number of pixels or the same size.

In a further embodiment, said at least two segments are different. The recitation "said at least two segments being different", as used herein, means that the at least two segments have different numbers of pixels or different size.

Segmenting each of said at least one elution trail into different segments advantageously allows to select larger segments along the elution trail where there are no spots present and smaller segments along the elution trail in the regions of interest, i.e. where one or more spots are present. Hence, such segmenting will advantageously improve the accuracy of the molecular weight distribution of the polymer, while not unnecessarily increasing the number of segments. In an embodiment, the number of segments is at most 1000. The number of segments can be ranging from 2 to 1000, for example, the number of segments can be ranging from 5 to 500, for example from 10 to 500, for example, from 20 to 250, for example, from 10 to 100. Preferably, the number of segments is ranging from 5 to 15, or from 10 to 50.

In an embodiment, each segment comprises at least 10x10 pixels. This advantageously allows to improve the accuracy of the calculation of the mean intensity value of each segment from the segmented data sets in step (f).

In an embodiment, each of the elution trails is segmented in step (e) and for each of the elution trails, steps (f), (g), (h) and (j) can be performed.

Accordingly, the method of the present invention advantageously allows determining one or both of the molecular weight and the molecular weight distribution of one or more polymers such as for instance of up to 40 polymers in the same assay.

The present method also comprises the step of (f) calculating the mean intensity value of each segment from the segmented data sets. The segmented data sets each comprise a plurality of pixels and intensity data associated with each of the pixels. The mean intensity value may be calculated by summing the intensity data associated with each of the pixels of the segmented data set and dividing by the number of pixels of the segmented data set.

The mean intensity value can be a mean grayscale value, wherein said grayscale value can be represented in an abstract way as a range from 0 to 1 , with any fractional values in between.

A mean intensity value for background may be calculated. In an embodiment, the method further comprises the step of calculating a mean intensity value for background and subtracting said mean intensity value for background from the mean intensity value of each segment calculated from the segmented data sets in step (f).

The present method further comprises step (g) reporting mean intensity value of each segment as a function of the position of each segment along the elution axis of the elution trail.

Step (g) of the method of the present invention may result in a graph representing the mean intensity value of each segment as a function of the position of each segment along the elution axis of the elution trail. The graph resulting from step (g) in the present method may be a line graph or a histogram. Preferably, the graph resulting from step (g) in the present method is a histogram. The term "histogram" generally refers to a graphical representation showing a visual impression of the distribution of data.

The present method comprises the step of (h) comparing the results of step (g) with a reference. The reference may be one or more polymers of known molecular weight. The reference can be obtained using calibration standards. In an embodiment, the present method comprises performing steps (a) to (g) first with polymer standards of known molecular weight in order to establish a calibration standard (or reference). Comparing the results of step (g) in the present method with a reference allows to determine the molecular weight and/or the molecular weight distribution of a polymer.

The present method further comprises the step of (j) of determining one or both of the molecular weight and the molecular weight distribution of said at least one polymer, preferably of at least two polymers comprised in a polymer composition.

In an embodiment, the present method comprises the step of determining the molecular weight of said at least one polymer, preferably of at least two polymers comprised in a polymer composition, preferably said at least two polymers having different weight average molecular weights. In a further embodiment, the present method comprises the step of determining the molecular weight distribution of said at least one polymer, preferably of at least two polymers comprised in a polymer composition, preferably said at least two polymers having different weight average molecular weights. In yet a further embodiment, the present method comprises the step of determining the molecular weight and the molecular weight distribution of said at least one polymer, preferably of at least two polymers comprised in a polymer composition, preferably said at least two polymers having different weight average molecular weights.

The method has an accuracy similar to that of gel permeation chromatography (GPC), of the order of 10 to 15%.

In one embodiment, the methods of the present invention may be applied in a high- throughput screening mode.

The present invention can be further illustrated by the following examples, although it will be understood that these examples are included merely for purposes of illustration and are not intended to limit the scope of the invention unless otherwise specifically indicated. EXAMPLES

Experimental Part:

TLC and HPTLC plates

The TLC (Thin Layer Chromatography) plates used in the present examples were neutral aluminum sheets of silica gel or aluminum oxide from Merck containing a fluorescence indicator at 254 nm (F2₅4). The pore diameter was 60 A and the mean particle size was 7- 13 m.

The HPTLC (High Performance Thin Layer Chromatography) plates used in the present examples were silica gel glass plates or reversed phase modified silica gel (RP-18) from Merck, optionally containing a fluorescence indicator at 254 nm (F2₅4). The pore diameter was 60 A and the mean particle size was 4-8 μηη.

Polymer dissolution

For polystyrene, a stock solution of 500 mg in 10 ml of dichloromethane was made at room temperature, and then diluted solutions were prepared, having a concentration ranging from 0.2 to 50 mg/ml.

Sample application

a. Manual application (OPLC)

For the OPLC elution tests, 0.5 μΙ of polymer solutions were applied with a micropipette. b. Automated application (HPTLC)

1 ml of the polymer solutions was poured in 2 ml vials from CAMAG. The vials were placed in the automatic TLC sampler (ATS4) controlled by the WinCats software. 10cmx20cm. HPTLC silica gel glass plates from Merck were purified by complete methanol elution. 10cmx20cm silica gel or alumina oxide sheets were placed directly on the ATS4 without purification. The application volume was 2 μΙ. For PS, the default parameters for average viscosity solvents were used (methanol parameters). Samples were sprayed by the ATS4 on the plate at a height of 8 mm making 6 mm large bands. Distance between the centers of each band was 15 mm. Between each sample, the syringe was automatically rinsed with the same solvent as the sample.

HPTLC offers certain advantages in that it allows automation of deposits and development, which results in improved accuracy, it provides excellent reproducibility, and the plates used allow a better separation. HPTLC plates are usually made of a silica gel of uniform and finer particles (typically 4-8 μηη compared to 1 1 -13 μηη in OPLC), grafted onto a glass plate, resulting in a certain rigidity of the plate. The rigidity of the plate makes handling easier and reduces edge effects caused by the curvature of some aluminum plates. The automatic sampler ATS4 is capable of providing reproducible deposits in the form of very thin horizontal strips of adjustable width. The amount of material is less important on the vertical axis, the axis of migration, and it is, therefore, easier to separate the products after migration. In addition, a device like the AMD2 of CAMAG can use more different eluents (it produces mixtures from 5 bottles) and allows a greater number of steps (up to 25) to provide a more efficient elution gradient. The analysis of deposits can then be performed by a powerful able to locate deposits several at multiple wavelengths and quantify the absorbance of the latter.

Elution (chromatography step)

a. Manual elution

TLC: the eluent was poured in a 50 ml glass container, then the TLC plate was placed inside and the container closed. Once the eluent had reached about 90% of the plate height, the TLC was removed and dried at room temperature.

HPTLC: 10 ml of eluent was poured in a twin through developing chamber of CAMAG for 20cmx20cm plates so that 5 ml of eluent was present at either side of the chamber. The chamber was closed during 2 minutes before the plate was placed inside. The height of the plate immerged was 4 mm and the eluent front was 7 cm. After development, the plate was removed and dried at room temperature. The eluent was removed as well, the chamber was cleaned and dried at ambient temperature. For gradient elution, the same operation was repeated for each eluent. Mixture of solvents were prepared in a 50ml beaker, manually stirred for homogeneity and poured in the chamber. For classical gradient elution, the first eluent was used up to the height of 2.04 cm (eluent front 2.04 cm). The next height step was increased by 1 .24 cm and so on for the other steps until the final height step was increased by 1 .74 cm for a total eluent front of 7.5 cm (eluent front 7.5 cm).

b. Automated elution

The Automated Multiple Development device from CAMAG (AMD2) controlled by winCats software was used. Migration distances and eluents mentioned in the examples were selected and the development was performed automatically. Dry time between steps was 2 min. Detection

a. Camera pictures

In a Vilber-Lourmet CN-3000 black-box (dark room) coupled with an VF Evolution camera (a CCD black&white camera) from Media Cybernetics placed on the top of the box, the chromatographic plate was horizontally laid on the middle height position layer of the black-box and centered inside the camera. Lights (UV and white light) were switched on. The diaphragm of the camera was settled at 2.8 and zoom at 25. The camera had a resolution of 300 PPI (Pixel Per Inches) and a sensitivity of 12 bits. Photos were taken at an exposure time of 80 ms. All operations were controlled with the ImageProPlus software from Media Cybernetics, which processes the pictures and detects the spots by densitometry. Photos of polymer separations were analyzed using the ImageProPlus software with grey level measurements of fractionated parts of the plates.

b. Scanner analysis

The TLC scanner 3 from CAMAG (managed by a winCATS workstation) detected the products along the plates at 254 nm in absorbance mode and gave the integrated surface of the chromatograms peaks. It has three lamps: tungsten halogen, deuterium and mercury for analyzing a spectral range of from 190 to 800 nm. The combination of a grid (1200 lines / mm), mirrors and a filter selects lines with an accuracy of up to 1 nm. The signal emitted by the chromatographic plate was measured by absorbance or transmission using two photomultipliers and a 16 bit A D converter. The scanner could scan the plate at an adjustable speed of from 1 to 100 mm / s with an incident beam with an adjustable width of from 1 to 8 mm. The width scanned area was equal to the band spotted, i.e. 6 mm.

Polystyrene

7 commercial polystyrenes (PS) from Polymer Laboratories were used. They were selected so as to scan a wide range of average molecular weights and because they have very low polydispersities (<1 .1 ). This allowed to establish a correlation between the mass of a polymer molecule and its migration distance (or Rf retention factor). Their average molecular weights (Mw (Weight Average Molecular Weight) and Mn (Number Average Molecular Weight)), their molecular weight maximum intensity (Mp: Peak molecular weight) and polydispersity (PDi) are shown in Table 1.

Table 1 PS Mp (g/mol) Mw (g/mol) Mn (g/mol) PDi

PS1 2610 2600 2480 1 .05

PS2 6690 6610 6340 1 .04

PS3 10900 10800 10500 1 .03

PS4 17600 17200 16700 1 .03

PS5 43000 42000 41000 1 .03

PS6 1 17000 1 14000 1 1 1000 1 .03

PS7 184000 178000 173000 1 .03

Example 1 : Polystyrenes PS1 -PS4 (OPLC)

A TLC sheet carrying the sorbent bed was wetted with a mixture of heptane and ethylacetate (AcOEt) at a rate of 100 μΙ_Ληίη and then dried.

Several mixtures (MA, MB, MC and MD) of PS1 , PS2, PS3 and PS4 were prepared by dissolving the polymer in dichloromethane at different concentrations. For example, for the mixture A: PS1 had a concentration of 10 mg/ml, PS2 has a concentration of 50 mg/ml, PS3 had a concentration of 50 mg/ml, and PS4 had a concentration of 10 mg/ml, for a total concentration of 120 mg/ml. This particular combination is noted as follows: MA = 10- 50-5010 mg/ml. The various polymer solutions were deposited on the sorbent bed and allowed to dry. A Teflon sheet comprising two slits was placed on top of the sorbent bed and the system was sealed by applying a pressure of 50 bar. The eluent was injected through the in-slit of the Teflon sheet under a pressure of 2 bar, providing an eluent flow of 25 μΙ_/η"ΐίη. Polystyrenes 1 to 4 were eluted with a 80/20 mixture of heptane/AcOEt.

Subsequently, a picture of the plate was taken under a lamp at 254 nm with the Evolution VF black& white camera from Media Cybernetics as described above (see FIG. 1 for the photograph).

Using the ImageProPlus software, the gray levels of the image were measured along the migration distance for each elution trail. Each elution trail was divided into 30 segments (zones) in each of which the average of the gray levels of the pixels was determined (FIG. 2). For each segment, a mean intensity value of gray level was obtained. The results for mixture A (MA= 10-50-50-10 g/ml) are given in Table 2. The peaks of absorbance are shown in bold.

Table 2

As expected the darkest areas result in a higher intensity. FIG. 3 represents the intensity of each segment of the mixture A (MA= 10-50-50-10 g/ml). The four types of PS constituting mixture A are clearly visible. FIGs 4, 5 and 6 represent the intensity of each segment of mixture B (MB = 8-40-40-8 g/ml), mixture C (MC = 6-30-30-6 g/ml) and mixture D respectively (MD = 4-20-20-4 mg/ml).

Example 2: Polystyrenes PS1 -PS7 (HPTLC)

We refer back to the series of polymers PS1 -PS7 described above. CAMAG deposit devices and automated development HPTLC were used.

In the case of HPTLC, the development of the plate by an eluent gradient is different from OPLC. In OPLC, the eluent mixture is injected under pressure and varies in composition without stopping its flow, and therefore without stopping its migration. The first eluent mixture is pushed by the second. In HPTLC, on the other hand, between each eluent mixture, the plate is removed from the liquid phase during the time wherein the device removes the former eluent and fills the tank with the new eluent. Just as in OPLC, this method allows to separate different Rf products that are not separable with a single eluent. In addition, this method allows to concentrate the amount of material corresponding to the Rf for each passage of the following eluents. This reduces the phenomenon of product trails and significantly increases the resolution.

The heptane/AcOEt eluent was kept the same for PS1 to PS7 as described above. Firstly, to evaluate the ability of eluent mixtures to migrate PS on a HPTLC plate, the mixtures were used successively from the weaker to the stronger eluting power. Four different mixtures were used, and for each mixture elution was repeated at three levels of increasing strength. If at the end of the third level there was no improvement in the separation, the following mixture was taken. Each PS was separately dissolved in dichloromethane at 10 mg/ml and deposited (2 μΙ) on a HPTLC plate through an automatic sampler. Between each level the plate was dried by the unit for two minutes (shown in Table 3, H is the level height). A photograph of the migration is shown in FIG. 7.

Table 3

Level Heptane (%) AcOEt (%) H (mm)

1 70 30 12

2 70 30 20

3 70 30 30 Level Heptane (%) AcOEt (%) H (mm)

4 60 40 40

5 60 40 45

6 60 40 50

7 55 45 60

8 55 45 65

9 55 45 70

10 50 50 80

1 1 50 50 85

12 50 50 90

The last three eluent mixtures for PS5-PS7 were kept with their unique levels (60/40, 55/45, 50/50) and then the lowest eluent (70/30) was used to separate the four first PS1 - PS4 (see Table 4 and FIG. 8).

Table 4

The polymers all migrated at different Rf with the same elution gradient. The method of HPTLC migration works for the seven PS, without having to separate them into two groups of different ranges. The concentration of 10 mg/ml did not pose any problem of migration for the highest masses in this range. The HPTLC method is thus very efficient. Once the migration method was defined, the programmable scanner of CAMAG could be used to detect the polymer deposits by absorbance. The chromatograms of absorbance versus Rf for each polymer are given in FIG. 9.

The polymers were properly detected by the scanner and for each a profile of its migration based on Rf was obtained. Integrals under the curves were calculated by the software and it is possible to split the curves into fragments of equivalent widths associated with a particular area and a particular Rf.

The Rf corresponding to the Mp is the Rf of the fragment having the highest absorbance. Knowing each Mp of each PS, it is possible to plot the curve of Mp as a function of Rf (Table 5 and FIG. 10). From FIG. 10, a relationship between Rf and Mp can be obtained through fitting a calibration curve.

Table 5

As discussed above the polymers were separated on HPTLC and a calibration curve was plotted, providing a link between the Rf and the molar mass. The scanner allows measuring of the absorbance of the polymer as a function of Rf. By splitting the area under the absorbance curve, it is possible to associate a fragment area to a particular Rf, and thus to a particular molar mass. Since the measured absorbance is proportional to the quantity of matter, it is then possible to calculate the potential molecular weight distribution of the polymer.

Since the absorbance depends on the mass of polymer deposited and not on the number of molecules, the weight average molecular weight (Mw), can be calculated by equation 1 :

Mw =

^~ (1 ) wherein wi is the mass represented by the chains of molar mass Mi. Since the absorbance is proportional to the mass, in Equation 1 wi can be replaced by the area of the fragment Ai, which is linked to a particular Rf and to a particular molar mass Mi. This results in equation 2:

M_w = ΣΑ-Λί,-

(2)

Mw was first calculated on PS5 that migrated on the plate under the terms of Table 4 (four levels). Table 6 below shows the areas Ai corresponding to the Rf associated with a molar mass Mi according to the calibration curve shown in FIG. 10.

Table 6

Fragment Rf Ai Mi

1 0,22 286 60124

2 0,23 2146 54143

3 0,24 3543 48596

4 0,26 2894 38747

5 0,27 1968 34412

6 0,28 1 192 30450

7 0,3 707 23576

8 0,31 438 20634

9 0,33 143 15660 It was found that the maximum area corresponds to the largest value of Mi, which is close to the value of Mp given by the manufacturer of the PS (PS5: Mw = 43000 g/mol). Applying Equation 2 to Table 8 results in Mw = 38,815 g/mol. The percentage of error with respect to the value of Mw given by the manufacturer (obtained by GPC) is 7.6%. It is furthermore possible to calculate the number average molecular weight Mn from the weight average molecular weight Mw. The number average molecular weight is usually defined by Equation 3:

wherein ni is the number of chains of molar mass Mi, related to the mass wi and the molar mass Mi by Equation 4.

(4)

If Equation 4 is substituted into Equation 3, this results in Equation 5, which provides Mn in function of the mass wi and the molar mass Mi. Finally, since the absorbance is proportional to the mass, in Equation 5 wi can be replaced by the area Ai of the fragment, resulting in Equation 6.

M_n =

(5)

In Table 7, Mw and Mn were calculated for PS2 to PS7 (ranging from a Mp of 6690 g/mol to 184000 g/mol). Comparison with the values given by the supplier was made, and an error percentage was calculated.

Table 7

PS Mp Mp calc. (%error) Mw Mw calc. (%error) Mn Mn calc. (%error)

PS2 6690 5559 (17) 6610 5546 (16) 6340 5452 (14)

PS3 10900 1 1792 (8) 10800 1 1374 (5) 10500 10794 (3)

PS4 17600 18001 (2) 17200 17383 (1 ) 16700 17023 (2) PS5 43000 48596 (13) 42000 41274 (2) 41000 38193 (7)

PS6 1 17000 1 15526 (1 ) 1 14000 98212 (14) 1 1 1000 91807 (17)

PS7 184000 184748 (0) 178000 149043 (16) 173000 138865 (23)

The calculated Mw is close to the values given by the manufacturer, particularly for PS3, PS4 and PS5. It is important to note that the values provided by the manufacturer were obtained by GPC, a completely different technology. In GPC, the passage in the pores of a permeation gel separates the masses according to size, whereas in TLC the phenomenon is based on adsorption/precipitation in the stationary phase. Analysis of the fractions is also quite different, which may explain the few differences

In the above examples, a profile of the weight distribution of a PS or a blend of PS was determined.

With the method of the invention, the weight distribution in a mixture could be determined- by OPLC or HPTLC.

In HPTLC, it was possible to simultaneously migrate PS at different Rf for molar masses between 2600 and 185 000 g / mol using the same elution protocol. Quantitative measurements of the absorbance of the mass of polymer present on the HPTLC plate were used to calculate average molecular weights. The values obtained were close to those provided by the manufacturer for the PS with a Mp ranging of from 10000 to 44000 g/mol.

Claims

1 . A method for determining information about the molecular weight of at least one polymer, preferably at least two polymers, comprised in a polymer composition using planar chromatography, wherein said method comprises the steps of:

f) calculating the mean intensity value of each segment from the segmented data sets;

g) reporting the mean intensity value of each segment as a function of the position of each segment along the elution axis of the elution trail;

h) comparing the results of step (g) with a reference; and

2. The method according to claim 1 , wherein the exposition to an incident radiation is performed after chemical and/or physical treatment of the planar chromatography plate.

3. The method according to claim 1 or 2, wherein said at least one polymer, preferably at least two polymers, is selected from polyolefins, polyamides, poly(hydroxy carboxylic acid), polystyrenes, polyesters, polycarbonate, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polymethylmethacrylate (PMMA), poly(methyl acrylate) (PMA), vinyl polymers; or blends thereof.

4. The method according to any one of claims 1 to 3, wherein said at least one polymer, preferably at least two polymers, is selected from polyethylene (PE), polypropylene (PP), polystyrene (PS), polymethylpentene (PMP), polybutene-1 (PB-1 ), polylactic acid

(PLA), polybutadiene, polycarbonate, polymethylmethacrylate (PMMA), poly(methyl acrylate) (PMA), or blends thereof.

5. The method according to any one of claims 1 to 4, wherein said at least two segments are identical.

6. The method according to any one of claims 1 to 5, wherein the number of segments is at most 1000.

7. The method according to any one of claims 1 to 6, wherein said incident radiation is one or more of visible light, ultraviolet (UV) or infrared (IR).

8. The method according to any one of claims 1 to 7, wherein said intensity data comprise at least 8 bits per pixel.

9. The method according to any one of claims 1 to 8, wherein each segment comprises at least 10x10 pixels.

10. The method according to any one of claims 1 to 9, wherein said planar chromatography is selected from a Thin-Layer Chromatography (TLC), High Performance Thin-Layer Chromatography (HPTLC), and Overpressurized Layer

Chromatography (OPLC).

1 1 . The method according to any one of claims 1 to 10, wherein information about the molecular weight of at least one polymer, preferably at least two polymers, comprised in a polymer composition is the molecular weight and/or the molecular weight distribution of said at least one polymer.

12. The method according to anyone of claims 1 to 1 1 wherein the polymer composition comprises at least two polymers having different weight average molecular weights.

13. The method according anyone of claims 1 to 12 wherein the method is for determining one or both of the molecular weight and the molecular weight distribution of at least two polymers, wherein said at least two polymers are comprised in a composition, and said at least two polymers are selected from at least two polyolefins, at least two polyamides, at least two poly(hydroxy carboxylic acid), at least two polystyrenes, at least two polyesters, at least two polycarbonates, at least two polyethylene terephthalate (PET), at least two polybutylene terephthalate (PBT), at least two polymethylmethacrylate (PMMA), at least two poly(methyl acrylate) (PMA), at least two vinyl polymers, or blends thereof.

14. The method according anyone of claims 1 to 13 wherein the method is for determining one or both of the molecular weight and the molecular weight distribution of at least two polystyrene polymers, wherein said at least two polystyrene polymers are comprised in a composition.

15. The method according anyone of claims 1 to 13 wherein the method is for determining one or both of the molecular weight and the molecular weight distribution of at least two polyolefin polymers, wherein said at least two polyolefin polymers are comprised in a composition