NL1039833C2 - Polymer, process for producing such polymer and composition comprising such polymer. - Google Patents
Polymer, process for producing such polymer and composition comprising such polymer. Download PDFInfo
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- NL1039833C2 NL1039833C2 NL1039833A NL1039833A NL1039833C2 NL 1039833 C2 NL1039833 C2 NL 1039833C2 NL 1039833 A NL1039833 A NL 1039833A NL 1039833 A NL1039833 A NL 1039833A NL 1039833 C2 NL1039833 C2 NL 1039833C2
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
- C08G63/66—Polyesters containing oxygen in the form of ether groups
- C08G63/668—Polyesters containing oxygen in the form of ether groups derived from polycarboxylic acids and polyhydroxy compounds
- C08G63/672—Dicarboxylic acids and dihydroxy compounds
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
- C08G63/78—Preparation processes
- C08G63/80—Solid-state polycondensation
Abstract
The invention relates to a polymer comprising one or more residues derived from a diol, defining a diol component of the polymer; and one or more residues derived from an acid selected from the group of a dicarboxylic acid and carbonic acid, defining an acid component of the polymer; wherein the diol component of the polymer comprises one or more residues derived from a diol selected from the group of dimethylene isosorbide, dimethylene isomannide and dimethylene isoidide.
Description
Polymer, process for producing such polymer and composition comprising such polymer
The invention relates to a polymer, to a method for preparing the 5 polymer and to a composition comprising the polymer.
Now that raw materials of fossil origin become increasingly scarce and expensive, there is a strong desire for a structural transition from fossil-based feedstocks to sustainable, bio-based raw materials. An example is the use of bio-based monomers in engineering plastics such as polyesters and 10 polycarbonates. Diols that are conventionally used in these plastics are usually derived from fossil feedstocks, for example glycols such as ethylene glycol. Many efforts have been made to substitute such conventional diols with bio-based diols in the production of polyesters and polycarbonates, with the aim to obtain materials having properties that are similar or improved 15 compared to those of the materials of fossil origin.
Whereas flexible biobased glycols are already being produced by hydrogenolysis of sugars, and commercially applied in polyesters for packaging (e.g. Coca Cola's "Plant Bottle") there is an increasing need for # more rigid biobased diols, which would enable the development of biobased 20 engineering type materials.
It has for example been tried to use 1,4:3,6-dianhydrohexitols as rigid bio-based diols in the preparation of polyesters and polycarbonates. The aim is to substitute part or all of the flexible glycol in e.g. polyethylene terephthalate) and hence provide potential for polyesters and polycarbonates 25 with attractive structural properties.
However, a disadvantage of isohexides is that, when compared to e.g. ethylene glycol, isohexides are relatively unreactive and require severe polymerization conditions and long polymerization times in order to achieve the desired levels of incorporation into the polymer. This in turn often leads to 30 dark colours and unsatisfactory molar masses (see e.g. “Incorporation of
Isosorbide into Poly(butylenes terephthalate) via Solid-State Polymerization”, Rafael Sablong etal., Biomacromolecules, 2008, 9(11), 3090-3097; and “Co-and Terpolyesters Based on Isosorbide and Succinic Acid for Coating 1 0 3 & 8 3 3 2
Applications: Synthesis and Characterization”, Bart A.J. Noordover et al. Biomacromolecules 2006, 7, 3406-3416).
It is therefore an object of the present invention to provide a bio-based polyester and/or polycarbonate having improved material 5 properties. It is in particular an object to provide a bio-based polyester and/or polycarbonate that has no or a low colour, and/or that has a high glass transition temperature Tg and/or a high thermal stability.
It is also an object of the present invention to provide a process for preparing a bio-based polyester and/or polycarbonate that is faster, less 10 complicated and/or more energy-efficient than processes for bio-based polyesters and/or polycarbonates known in the art.
Therefore, the invention relates to a polymer comprising - one or more residues derived from a diol, defining a diol component of the polymer; and 15 - one or more residues derived from an acid selected from the group of a dicarboxylic acid and carbonic acid, defining an acid component of the polymer; wherein the diol component of the polymer comprises one or more residues derived from a diol selected from the group of dimethylene isosorbide, 20 dimethylene isomannide and dimethylene isoidide.
As stated in claim 1, the one or more residues derived from a diol define a diol component of the polymer. This means that the diol component consists of all residues present in the polymer that are derived from a diol.
Analogously, claim 1 states that the one or more residues derived 25 from an acid selected from the group of a dicarboxylic acid and carbonic acid define an acid component of the polymer. This means that the acid component consists of all residues present in the polymer that are derived from dicarboxylic acid and carbonic acid.
As specified in claim 1, the diols from which the one or more residues 30 in the diol component are derived, are selected from the group of dimethylene isosorbide, dimethylene isomannide and dimethylene isoidide. These diols are isohexides of which each of the two hydroxyl groups are extended from the bicyclic structure by a methylene unit. Figure 1 shows the structures of these extended diols.
3
For the purpose of the invention, these three diols are indicated with the generic term “extended diols”.
The dicarboxylic acid from which one or more residues in the acid component may be derived may in principle be any dicarboxylic acid. With a 5 dicarboxylic acid is usually meant an organic compound of the general formula HOOC-R-COOH, where R may be a group selected from the group of alkyl groups, alkenyl groups, alkynyl groups, aryl groups, and groups that are a combination thereof.
The dicarboxylic acid is usually an aliphatic dicarboxylic acid or an 10 aromatic dicarboxylic acid.
An aliphatic dicarboxylic acid may be cyclic (/.e. alicyclic) or acyclic. The aliphatic dicarboxylic acid is usually a saturated dicarboxylic acid, but may also be an unsaturated dicarboxylic acid. The carbon chain of the aliphatic dicarboxylic acid may be an unbranched carbon chain or a branched 15 carbon chain. In case of an unbranched chain, each of the two carboxy groups is usually at one end of the unbranched chain (constituting an alpha, omega aliphatic linear dicarboxylic acid). In case of a branched carbon chain, the two carboxy groups are usually connected to a primary carbon atom of the chain. A branch of a branched carbon chain may be an alkyl or an 20 alkylene group. Itaconic acid is an example of a branched aliphatic dicarboxylic acid having a methylene group linked to the carbon chain that connects the two carboxy groups.
The carboxylic acid may also be an alicyclic dicarboxylic acid. Such acid may be selected from the group of cyclopropane-1,2-dicarboxylic acid, 25 cyclobutane-1,2- dicarboxylic acid, cyclobutane-1,3- dicarboxylic acid, cyclopentane-1,2- dicarboxylic acid, cyclopentane-1,3- dicarboxylic acid, cyclohexane-1,2-dicarboxylic acid, cyclohexane-1,3-dicarboxylic acid, cyclohexane-1,4-dicarboxylic acid, cyclohexene-4,5-dicarboxylic acid, cyclohexene-3,6-dicarboxylic acid and 3,6-dimethylcyclohexene-4,5-30 dicarboxylic acid.
Usually, the number of carbon atoms in a saturated dicarboxylic acid is in the range of 2-20, in the range of 2-16 or in the range of 2-12. In particular a saturated dicarboxylic acid is selected from the group of oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, 4 suberic acid, azelaic acid, sebacic acid, undecanedioic acid dodecanedioic acid and brassylic acid.
A saturated dicarboxylic acid may also be a sugar dicarboxylic acid.
A sugar dicarboxylic acid is a dicarboxylic acid of the general formula HOOC-5 (CHOH)n-COOH. The subscript n may be in the range of 1-10, in particular in the range of 1-4. A sugar dicarboxylic acid may for example be selected from the group of tartronic acid (n=1), tartaric acid (n=2) and the stereoisomers thereof (/.e. (S,S)-tartaric acid, (/?,/?)-tartaric acid, (RS)-tartaric acid), mucic acid (n=3) and the stereoisomers thereof, and saccharic acid (n=4) and the 10 stereoisomers thereof.
A carboxylic acid may also be an unsaturated dicarboxylic acid. Such acid may be selected from the group of maleic acid, fumaric acid, glutaconic acid, traumatic acid, muconic acid and itaconic acid.
Further, an aliphatic dicarboxylic acid may be selected from the 15 group of isosorbide dicarboxylic acid, isomannide dicarboxylic acid and isoidide dicarboxylic acid.
The dicarboxylic acid from which one or more residues in the acid component may be derived may also be an aromatic dicarboxylic acid. An aromatic dicarboxylic acid usually comprises a five- membered aromatic ring 20 and/or a six-membered aromatic ring. This also includes a structure of fused rings. Fused rings may for example be a fusion of a plurality of six-membered rings or a fusion of a five-membered ring and a six-membered ring. For the purpose of the invention, two rings are considered as fused when they share two or more ring members.
25 A ring or structure of fused rings in an aromatic dicarboxylic acid is in particular composed of only carbon atoms, i.e. every aromatic ring that is present is a homocyclic aromatic ring. Examples of such rings or fused rings are benzene, naphthalene or anthracene.
A ring or structure of fused rings in an aromatic dicarboxylic acid may 30 however also contain heteroatoms, i.e. at least one of the one or more aromatic rings that are present is a heterocyclic aromatic ring. Such a ring or structure of fused rings may be selected from the group of furan, benzofuran, isobenzofuran, pyrrole, indole, isoindole, thiophene, benzothiophene, benzo[c]thiophene, imidazole, benzimidazole, purine, pyrazole, indazole, 5 oxazole, benzoxazole, isoxazole, benzisoxazole, thiazole, benzothiazole, pyridine, quinolone, isoquinoline, pyrazine, quinoxaline, acridine, pyrimidine, quinazoline, pyridazine, cinnoline and phthalazine.
An aromatic dicarboxylic acid is in particular selected from the group 5 of dibenzoic acids, benzenedicarboxylic acids, naphthalenedicarboxylic acids, furandicarboxylic acids, pyrroledicarboxylic acids, pyridinedicarboxylic acids and thiophenedicarboxylic acids. More in particular, an aromatic dicarboxylic acid is selected from the group of phthalic acid, isophthalic acid, terephthalic acid, 1,8-naphthalic acid, 2,6-naphthalic acid and other positional isomers of 10 naphthalic acid (i.e. isomers differing in the positions of the two carboxy groups), 2,5-furandicarboxylic acid, 2,4-furandicarboxylic acid and 3,4-furandicarboxylic acid.
As specified in claim 1, one or more residues in the diol component are derived from a diol selected from the group of dimethylene isosorbide, 15 dimethylene isomannide and dimethylene isoidide. However, the diol component of a polymer of the invention may comprise one or more further residues. Such further residues may be derived from a diol selected from the group of aliphatic diols and aromatic diols. In particular, the number of carbon atoms in such an aliphatic diol or aromatic diol is from 2-30, 2-18 or 2-12.
20 In case the eventual further residues are derived from an acyclic aliphatic diol, the aliphatic diol is in particular selected from the group of ethyleneglycol, 1,2-propandiol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 1,5-pentanediol, 1,4-pentanediol, 2,4-pentanediol 1,6-hexanediol, 1,5-hexanediol, 1,4-hexanediol, 2,5-25 hexanediol and 3,4-hexanediol. It may also be selected from higher aliphatic diols such as decanediols, dodecanediols, hexadecane diols, octadecanediols, and positional isomers thereof (i.e. isomers differing in the positions of the two hydroxy groups).
In case the eventual further residues are derived from an alicyclic 30 diol, the alicyclic diol is in particular selected from the group of cyclobutane- 1,2-dimethanol, cyclobutane-1,3-dimethanol, cyclopentane-1,2-dimethanol, cyclopentane-1,3-dimethanol, cyclohexane-1,2-dimethanol, cyclohexane-1,3-dimethanol, cyclohexane-1,4-dimethanol. It may also be selected from the group of isosorbide, isomannide and isoidide. More in particular it is selected 6 from the group of bis(hydroxycyclohexyl)alkanes, e.g.
2,2-bis(4-hydroxycyclohexyl)propane (also known as “hydrogenated Bisphenol A”).
In case the eventual further residues are derived from an aromatic 5 diol, the aromatic diol is in particular selected from the group of catechol, resorcinol, hydroquinone, 1,2-benzenedimethanol, 1,3- benzenedimethanol and 1,4 benzenedimethanol. More in particular it is selected from the group of bis(hydroxyphenyl)alkanes, e.g. 2,2-bis(4-hydroxyphenyl)propane (also known as “Bisphenol A”).
10 A polymer of the invention may further comprise one or more residues that are derived from other species than a diol, a dicarboxylic acid and carbonic acid. Such one or more residues are in particular derived from the group of polyfunctional alcohol having three or more hydroxy groups, polyfunctional carboxylic acid having three or more carboxy groups, 15 monocarboxylic acid, monoalcohol and hydroxyacid. A polyfunctional alcohol having three or more hydroxy groups may be a triol like glycerol. A polyfunctional carboxylic acid having three or more carboxy groups may be a tricarboxylic acid like cyclohexane-1,3,5-tricarboxylic acid, tricarballylic acid or citric acid. A hydroxyacid is a compound having an hydroxy and a carboxy 20 functionality, e.g. lactic acid. An example wherein the hydroxy and carboxy group form an internal ester is caprolactone.
The function of the above polyfunctional alcohols and/or polyfunctional carboxylic acids is in particular to obtain a polymer network. Monocarboxylic acids and/or monoalcohols can be used to decrease the 25 (number average) molar mass of the polymer, and provide chains that do not have a terminal carboxy and/or hydroxyl group, respectively. If present, a residue derived from a monocarboxylic acid is preferably present in an amount of up to 1 mol% of the total amount of acid-derived residues present in the acid component. Herein, it is understood that a residue derived from a 30 monocarboxylic acid does not form part of the acid component in any case, which is in accordance with the definition given hereinabove for the term acid component. If present, a residue derived from a monoalcohol is preferably present in an amount of up to 1 mol% of the total amount of diol-derived residues present in the diol component. Herein, it is understood that a residue 7 derived from a monoalcohol does not form part of the diol component in any case, which is in accordance with the definition given hereinabove for the term diol component.
It has been found that the extended diols are more reactive in 5 polymerization than the corresponding parent (/.e. non-extended) isohexides. This results in higher molar masses of polymers of the invention.
Also, the extended diols of the invention have a higher thermal stability. This results in less degradation during the polymerization, providing the corresponding polymers with low colour and more reactive end-groups, 10 which in turn leads to higher molar masses of polymers of the invention.
Further, the extended diol monomers are incorporated into the polymer to an unexpectedly high extent. The best results are obtained with dimethylene isoidide, which is capable of 100% incorporation into the polymer.
15 Further, it is highly surprising that polymers of the invention have a high degree of crystallinity. Known polymers prepared from isohexides (i.e. from the non-extended diols) have almost no crystallinity, especially not when the isohexides constitute 40% or more of the diol monomers in the polymer. Polymers of the invention have a high degree of crystallinity, especially when 20 the isohexides constitute up to 100% or more of the diol monomers in the polymer.
The high degree of crystallinity has the great advantage that it allows a solid state post condensation (SSPC) after a pre-polymerisation. The application of SSPC allows milder reaction conditions whilst achieving an 25 increased number average molar mass (Mn), a higher glass temperature (Tg) and lower colour than when - instead of applying SSPC - the melt-polymerization is continued. The highest Tg’s are found for polymers wherein the diol component contains the highest amounts of residues derived from an extended isohexide. This concerns amounts of or near 100 mol%, so 30 that the diol component essentially consists of residues derived from an extended isohexide. Particularly high Tg’s are found for polymers wherein the diol component contains 100 mol% of the residue derived from isoidide.
A high Tg, however, may result in a lower processability of the polymer. Also, a high degree of crystallinity in the polymer may conflict with 8 applications that require transparency. It is an advantage of polymers of the invention that the Tg, the processability and/or the degree of crystallinity can be tuned by including in the diol component and/or in the acid component other residues derived from a diol and/or an acid, respectively. Such an 5 additional residue is usually included in the respective diol or acid component in an amount of 0.01-10 mol%, preferably in an amount of 0.1-5 mol%.
For example, a non-cyclic aliphatic diol can be included in the diol component. The non-cyclic aliphatic diol may be selected from the group of ethylene glycol, propane diols, butane diols and pentane diols.
10 Alternatively or additionally, a residue derived from an aliphatic dicarboxylic acid can be included in the acid component, preferably when the other residue or residues in the acid component are also derived from an aliphatic dicarboxylic acid (e.g. inclusion of a residue derived from adipic acid in the case of poly(1,4-butylene succinate)). The aliphatic dicarboxylic acid 15 from which the included residue is derived may be selected from the group of oxalic acid, malonic acid, succinic acid, glutaric acid and adipic acid.
Also, alternatively or additionally, a residue derived from an aromatic dicarboxylic acid can be included in the acid component, preferably when the other residue or residues in the acid component are also derived from an 20 aromatic dicarboxylic acid (e.g. inclusion of a residue derived from isophthalic acid in the case of polyethylene terephthalate)).
The effect of the presence of another residue in the diol or acid component as described hereinabove is usually that the Tg and the degree of crystallinity are lower than without the other residue in the diol and/or acid 25 component.
Generally, a residue derived from an extended diol constitutes at least 50 mol%, at least 75 mol%, at least 85 mol%, at least 90 mol%, at least 95 mol% or at least 98 mol% of the diol component.
Generally, the acid component contains at least 50 mol%, at least 75 30 mol%, at least 85 mol%, at least 90 mol%, at least 95 mol% or at least 98 mol% of a residue derived from a dicarboxylic acid selected from the group of isophthalic acid, terephthalic acid and 2,5-furandicarboxylic acid.
A particular polymer of the invention is a polymer wherein 9 - the acid component of the polymer comprises a first residue derived from terephthalic acid and a second residue derived from 2,5-furandicarboxylic acid or isophthalic acid; and wherein - the diol component of the polymer comprises a first residue derived from 5 dimethylene isoidide and a second residue derived from a diol selected from the group of ethyleneglycol, 1,3-propanediol and 1,4-butanediol.
The molar ratio of first residue : second residue in the acid component of this polymer is usually at least 90 : 10 or at least 95 : 5. The molar ratio of first residue : second residue in the diol component of this 10 polymer is usually at least 90 :10 or at least 95: 5.
Another particular polymer of the invention is a polymer wherein - the acid component of the polymer comprises a residue derived from succinic acid or adipic acid; and wherein - the diol component of the polymer comprises a first residue derived from 15 dimethylene isoidide and a second residue derived from a diol selected from the group of ethyleneglycol, 1,3-propanediol and 1,4-butanediol.
The molar ratio of first residue : second residue in the diol component of this polymer is usually at least 90 :10 or at least 95: 5.
A polymer of the invention may also be polycarbonate. It may for 20 example be a polymer wherein - the acid component of the polymer comprises a residue derived from carbonic acid; and wherein - the diol component of the polymer comprises a first residue derived from dimethylene isoidide and a second residue derived from a diol selected 25 from the group of ethyleneglycol, 1,3-propanediol, 1,4-butanediol, isohexides, bisphenol A, bisphenol F, bisphenol S and hydrogenated bisphenol A.
The molar ratio of first residue : second residue in the diol component of this polymer is usually at least 90 :10 or at least 95: 5.
30 A polymer of the invention may also be polymer comprising polycarbonate moieties as well as polyester moieties. It may for example be a polymer wherein 10 - the acid component of the polymer comprises a first residue derived from terephthalic acid and a second residue derived from carbonic acid; and wherein - the diol component of the polymer comprises a first residue derived from 5 dimethylene isoidide and a second residue derived from a diol selected from the group of ethyleneglycol, 1,3-propanediol, 1,4-butanediol, isohexides, bisphenol A, bisphenol F, bisphenol S and hydrogenated bisphenol A.
In principle, every molar ratio of first residue : second residue in the 10 acid component of this polymer is possible. It may for example be at least 90 : 10 or at least 95 : 5. The molar ratio of first residue : second residue in the diol component of this polymer is usually at least 90 :10 or at least 95: 5.
The invention further relates to a process for preparing a polymer of the invention, comprising forming a mixture of at least the following three 15 components - one or more monomers selected from the group of dimethylene isosorbide, dimethylene isomannide, dimethylene isoidide and ester-forming derivatives thereof; and - one or more monomers selected from the group of a dicarboxylic acid, an 20 ester-forming derivative of a dicarboxylic acid, carbonic acid, and a carbonate ester-forming derivative of carbonic acid; and - a catalyst, followed by performing a melt polymerization by exposing the mixture to a temperature of at least 100 °C, yielding a semi-crystalline pre-polymer.
25 Usually, the semi-crystalline pre-polymer is subjected to solid state post condensation, yielding a polymer with a higher Mn than that of the prepolymer. A solid state post condensation of a pre-polymer is usually carried out at a temperature between the Tg and the Tm of the pre-polymer.
Preferably, the temperature is between 20-30 °C below the Tm of the pre-30 polymer.
With an ester-forming derivative of a diol, a carboxylic acid or a carbonic acid is meant a derivative that is capable of being transformed into an ester. This is also meant to include a monomeric ester from which a 11 polyester is formed. In the latter case, a transesterification reaction takes place.
An ester-forming derivative of a diol may be an ester, for example an acetate ester. An ester-forming derivative of a carboxylic acid may be its 5 diacid chloride or its diester such as a dimethyl ester or a diethyl ester. An ester-forming derivative of a carbonic acid may be selected from the group of phosgene, diphosgene, triphosgene, diaryl carbonate, dialkyl carbonate, alkylaryl carbonate, disalicyl carbonate, urea and dialkylurea.
The invention further relates to a polymer obtainable by the process 10 of the invention.
12
EXAMPLES
1. Materials and methods ((3S,6S)-Hexahydrofuro[3,2-b]furan-3,6-diyl)dimethanol (dimethylene 5 isoidide or IIDML) was synthesized according to the literature procedure (Wu, J.; Eduard, P.; Thiyagarajan, S.; Van Haveren, J.; Van Es, D. S.; Koning, C. E.; Lutz, M.; Fonseca Guerra, C. ChemSusChem 2011, 4, (5), 599-603; and Wu, J.; Van Haveren, J.; Van Es, D. WO 2011144353 A1 2011) with purity >99.5% (GLC). 2,5-Furandicarboxylic acid (FDCA) was kindly supplied by Avantium.
10 Hydrochloric acid (HCI, 37 wt %), anhydrous magnesium sulphate (MgS04), methanolic solutions of potassium hydroxide (KOH, 0.5 N), dimethyl terephthalate (DMT, >99%), dimethyl isophthalate (99%,) titanium(IV) isopropoxide (97%), dibutyltin(IV) oxide (98%), chloroform-D (99.8 atom % D) were purchased from Sigma-Aldrich. Trifluoroacetic acid-d (99.5 atom %D) was 15 purchased from Cambridge Isotope Laboratories, Inc.. 1,1,1,3,3,3-Hexafluoro-2-propanol (HFIP), methanol and chloroform were purchased from Biosolve.
Nuclear magnetic resonance (NMR) spectra were recorded on a Bruker Avance III spectrometer operating at 400.17 MHz (1H) and 100.62 MHz (13C) at room temperature. Fourier transform infrared (FT-IR) spectra were obtained on 20 a Varian Scimitar 1000 FT-IR spectrometer equipped with a Pike MIRacle ATR Diamond/ZnSe single reflection plate and a DTGS-detector. The measurement resolution was set at 4 cm'1, and the spectra were collected in the range 4000-650 cm'1 with 32 co-added scans. Size exclusion chromatography (SEC) in hexafluoroisopropanol (HFIP) was performed on a system equipped with a 25 Waters 1515 Isocratic HPLC pump, a Waters 2414 refractive index detector (35 °C), a Waters 2707 auto sampler, a PSS PFG guard column followed by 2 PFG-linear-XL (7 pm, 8 χ 300 mm) columns in series at 40 °C. HFIP with potassium trifluoroacetate (3 g/L) was used as eluent at a flow rate of 0.8 mL/min. The molecular weights were calculated against polymethyl 30 methacrylate standards (Polymer Laboratories, Mp = 580 Da up to Mp = 7.1 χ 106 Da). The thermal stability of the polymers was determined by thermogravimetric analysis (TGA) with a TGA Q500 apparatus from TA Instruments. The samples were heated from 30 to 600 °C at a heating rate of 13 10°C /min under a nitrogen flow of 60 mL/min. Glass transition temperatures (7g) and melting temperatures (Tm) were measured by differential scanning calorimetry (DSC) using a DSC Q100 from TA Instruments. The measurements were carried out at a heating and cooling rate of 10°C /min from -50 °C to 5 320 °C.
Analysis of the crystalline structure of the materials was performed using wide-angle X-ray scattering measurements by means of computer controlled goniometer coupled to a sealed-tube source of CuKa radiation (Philips), operating at 50 kV and 30 mA. The CuKa line was filtered using 10 electronic filtering and the usual thin Ni filter. The data were collected at room temperature. The 1D profiles were subsequently background-corrected and normalized.
The degree of crystallinity was calculated on the basis of diffractograms. Since reflections from the crystalline phase and the amorphous 15 halo frequently overlap each other, it was necessary to separate them. Analysis of diffraction profiles of the examined samples and separation of peaks was performed using WAXSFit software designed by M. Rabiej of the University of Bielsko-Biata (AHT) (Rabiej, M. Polimery (Polish) 2003,48, 288). The software allows to approximate the shape of the peaks with a linear combination of 20 Gauss and Lorentz or Gauss and Cauchy functions and adjusts their settings and magnitudes to the experimental curve with a “genetic” minimizing algorithm. Siich calculated surfaces of peaks, corresponding to given crystallographic planes, and amorphous halo allowed to determine the degree of crystallinity of the sample.
25
Synthesis of ((3S, 6S)-hexahydrofuro[3,2-b]furan-3,6-diyl)dimethanol (IIDML): IIDML was synthesized and purified according to the procedure described in Chapter 2.15,16 The purities and stereo chemistry of the monomers 30 were analysed by GC, GC-MS, FT-IR, 1H, 13C and 2D-COSY NMR.
Synthesis of dimethyl-2,5-furandicarboxylate (DM-FDCA): 2,5-Furandicarboxylic acid (10 g, 0.064 mol) was reacted with methanol (118.7 g, 3.4 mol) in the presence of hydrochloric acid (1 mL) as a catalyst. This reaction was allowed to continue for 18 h and subsequently the catalyst was 14 deactivated by adding 30 mL of 0.5 N methanolic KOH solution. The solvent was evaporated and the obtained white solid product was dissolved in CHCI3. The solution was filtered and washed with brine (1 x 200 mL) and demi-water (2 x 200 mL). Subsequently, this solution was dried over MgSCV Then the solution 5 was filtered and the solvent evaporated using a rotary evaporator. The obtained solids were recrystallized from CHCI3, affording white crystals. Yield: 80 %. Purity: >99.5%.
1H NMR (CDCI3, δ, ppm): 3.94 (s, 6H), 7.23 (d, 2H). 13C NMR (CDCI3, δ, ppm): 52.36 (OCH3), 118.44 (furan ring C3 and C4), 146.67 (furan ring C2 10 and C5), 158.29 (C=0). FT-IR (cm'1); 3118 (=CH); 2964 (C-H); 1719 (C=0); 1583, 1515 (C=C); 1264 (C-O); 987, 834, 765 (=CH).
Melt Polymerization, procedure A: This example is representative for poly(isoididedimethylene terephthalate) and poly(isoididedimethylene furan-2,5-15 dicarboxylate) (PleT and PleF-a, Table 1): IIDML (0.26 g, 1.5 mmol) and dimethyl 2,5-furandicarboxylate (0.18 g, 1.0 mmol) were charged into a 10 mL round bottom flask located inside a Kugelrohr oven. The apparatus was flushed with nitrogen several times at room temperature to remove oxygen, and then internally heated to 150 °C and rotated at a speed of 20 rpm. The reactants 20 gradually turned into a clear homogenous melt in about 5-10 min. Next, 0.01 mmol of dibutyltin(IV) oxide was added into the flask and the pre-polymerization was continued at a rotating speed of 20 rpm under N2 atmosphere. The polymerization temperature was increased from 150 °C to 180 °C step-wise. After about 1 h, the formed polyester started to crystallize into a white solid.
25 After cooling down to room temperature, the resulting polymer was dissolved in TFA/CHCI3 (VA/ = 1:4) and precipitated into methanol. The precipitate was collected by filtration and further dried in vacuo. The product was grounded to a powder and subsequently subjected to solid-state post-condensation to further increase the molecular weight.
30 Melt Polymerization, procedure B: The synthesis of PleF-b (Table 1): IIDML (0.26 g, 1.5 mmol) and dimethyl 2,5-furandicarboxylate (0.18 g, 1.0 mmol) were charged into a 10 mL round bottom flask located inside a Kugelrohr oven. The apparatus was flushed with nitrogen several times at room temperature to remove oxygen, and then internally heated to 150 °C and 15 rotated at a speed of 20 rpm. The reactants gradually turned into a clear homogenous melt in about 5-10 min. Next, 0.01 mmol of dibutyltin(IV) oxide was added into the flask and the pre-polymerization was continued at a rotating speed of 20 rpm under N2 atmosphere. The polymerization temperature was 5 increased from 150 °C to 180 °C step-wise. After about 1 h, the formed polyester started to crystallize into a white solid. Then the polymerization temperature was elevated to about 260 °C. The prepolymer gradually melted and the reaction mixture was kept at this temperature for 2h at a rotating speed of 20 rpm. During the course of the reaction, discoloration of the reaction 10 mixture into a brownish melt was observed. After cooling down to room temperature, the resulting polymer was dissolved in TFA/CHCI3 (V/V = 1:4) and precipitated into methanol. The precipitate was collected by filtration and further dried in vacuo.
Melt Polymerization, procedure C: The preparation of 15 poly(isoididedimethlyene isophthalate) (PlelP, Table 1) follows a conventional two-stage melt polymerization: IIDML (0.260 g, 1.5 mmol) and dimethyl isophthalate (0.194 g, 1.0 mmol) were charged into a 10 mL round bottom flask located inside a Kugelrohr oven. The apparatus was flushed with nitrogen several times at room temperature to remove oxygen. Then the Kugelrohr oven 20 was internally heated to 140 °C at a rotating speed of 20 rpm. After 5-10 min, the reactants turned into a clear homogenous mixture. Next, 0.01 mmol dibutyltin oxide (DBTO) was added into the flask. The pre-polymerization temperature was further increased to 180 °C and maintained at this temperature for 3 h. Subsequently, the reaction temperature was increased to 230 °C and 25 vacuum (0.01-0.05 mbar) was applied step-wise and maintained for 3 h. The resulting polymer was cooled down, dissolved in chloroform and precipitated into methanol. The product was collected by filtration and further dried in vacuo to afford PlelP as a white solid.
30 Solid-state Post-condensation (SSPC): In order to increase the molecular weight of the polyester prepolymers (PleT and PleF-a, Table 1), solid state post-condensation (SSPC) was applied. SSPC of the prepolymers was carried out in a glass tube reactor (2.5 cm diameter) equipped with a sintered glass plate at the bottom on which the polyester powder was deposited. Below 16 this glass plate the SSPC reactor was fitted with an inert gas inlet through which preheated N2 gas was introduced. The SSPC reactor was immersed into a salt bath preheated to the desired temperature. The reactor was heated using a salt mixture of KN03 (53 wt%), NaN02 (40 wt %), NaN03 (7 wt%). SSPC was 5 carried out in N2 atmosphere at a gas flow rate of 2.5 L/min.
poly(isoidide2,5-dimethylene terephthalate) (PleT) 1H NMR (CDCI3, δ, ppm]: 8.10(s, 4H), 4.92(s, 2H), 4.86-4.84(end-group), 4.45(m, 4H), 4.42 (end-group), 4.31 (m, 2H), 4.26 (end-group) 4.04 (m, 2H), 3.96 (end-group). 13C NMR (CDCI3, δ, ppm): 167.34, 133.25, 129.91, 10 85.55, 85.35, 85.10, 69.96, 69.67, 65.96, 64.37, 45.49, 45.13; FT-IR (cm1): 2943, 2877, 1711(C=0), 1454, 1406, 1270, 1123, 1094, 1050, 1016, 975, 889, 727 poly(isoidide 2,5-dimethylene isophthalate) (PlelP) 1H NMR (CDCI3) δ, ppm]: 8.65(s, 1H), 8.20(d, 2H), 7.52(t, 1H), 4.60(s, 15 2H), 4.34(m, 4H), 4.09(m, 2H), 3.76(m, 2H), 2.78(m, 2H). 13C NMR (CDCI3, δ, ppm): 165.31, 133.87, 130.28, 128.71, 85.30, 69.87, 64.13, 46.23.; FT-IR (cm* 1): 2950, 2878, 1720 (C=0), 1301, 1231, 1138, 1074, 1052, 971, 726 poly(isoididedimethylene furan-2,5-dicarboxylate) (PleF) 1H NMR (CDCI3, δ, ppm]: 4.91 (s, 2H), 4.35(m, 4H), 4.10(m, 2H), 20 4.02(m, 2H), 3.15(m, 2H).13C NMR (CDCI3, δ, ppm): 170.99 (C=0), 85.80, 69,91,62.56, 51.41.; FT-IR (cm'1): 3454(OH-end groups), 3116, 2949, 2875, 1726(C=0), 1575, 1509, 1465, 1394, 1274, 1226, 1145, 1055, 989, 893, 766.
Table 1. Temperatures and reaction times of the prepolymerization and polymerization or solid-state postcondensation.
symbol prepolymerization polymerization SSPC
__TTO t(h) T(eC) _t(h) T(°C) t(h|
PleT 180 1 24Ö 4
PlelP 180 3 220-240 3
PleF-a 180 1 230 4
PleF-b 180 1 230-260 2 25 17 2. Results and Discussion
Synthesis and Molecular Characterization: Due to the relatively low reactivity of the secondary hydroxyl groups of the parent isohexides, the 5 reported high molecular isohexides-based semi-aromatic polyesters are almost exclusively prepared from isohexides in combination with the activated comonomers, e.g. diacid chlorides.
These methods are either too expensive or not suitable to be used in an industrial setting. It appeared that the primary hydroxyl groups of IIDML are 10 more reactive than the secondary ones of the parent isohexides.
Table 2. Molecular weights and polydispersityes of the synthesized IIDML-based polyesters3
before SSP after SSP
| symbol Mn (g/mol) Λ4 (g/mol) PDI Mn (g/mol) Λ4 (g/mol) PDI
Tiëï 2j3ÖÖ 3£ÖÖ 17 7JÖÖ 17,710 Z3
PlelP 9,800 67,620 6.9 -
PleF-a 6,900 15,200 2.2 30 300 60,600 2.0
PleF-b 13,400 38,700_2.9 _-_- aMn\ number-average molecular weight, Λ4: weight-average molecular weight, PDI: polydispersity index. Molecular weights determined by HFIP-SEC.
15 Poly(isoidide-2,5-bismethylene terephthalate) (PleT) and poly(isoidide-2,5-bismethylene furan-2,5-dicarboxylate) (PleF) were synthesized by melt polymerization followed by SSPC. During the synthesis, both polyesters start to crystalize rapidly from the melt after polymerization at 180 °C for about 1 h. The crystallized PleT and PleF are white solids having 20 relatively low molecular weights (Mn = 2,300 g/mol and 6,900 g/mol, respectively, Table 2) and rather high melting points (around 250 °C and 290 °C, respectively). Further increasing the polymerization temperature causes discoloration and thermal degradation of the two prepolymers. For PleF, although a higher molecular weight product (M„ = 13,400 g/mol, PleF-b, 25 Table 2) can be obtained by continuing melt polymerization at 260 °C, the thermal degradation was observed to be significant, as evidenced by the 18 brownish color of the final product and a considerably high PDI value of 2.9.
The prepolymer of PleT displays an even higher melting point of approximately 290 °C. Continuing melt polymerization is detrimental to this low molecular weight prepolymer. Therefore, to obtain the desired PleT and 5 PleF with low degrees of discoloration, high molecular weights and satisfactory PDI values, SSPC was applied to the prepolymers to further enhance the molecular weight. SSPC is a common and energy-efficient industrial method to enhance molecular weight so as to improve the quality of commercial products, such as PET and nylons.
10 Since poly(isoidide 2,5-bismethylene isophthalate) (PlelP) is an amorphous material, the molecular weight is impossible to be enhanced through SSPC. A conventional two-stage polycondensation procedure was used: pre-polymerization at 180 °C under N2 atmosphere in combination with a polymerization at 230 °C under reduced pressure (0.01-0.05 mbar). After 15 precipitation from methanol, the final product of PlelP was obtained as a white material with Mn = 9,800 g/mol.
The molecular structures of the synthesized semi-aromatic polyesters were analyzed by nuclear magnetic resonance (NMR) spectroscopy. The bridge protons a of the three polyesters appear as singlets located at 4.6-4.9 ppm 20 region, which are indicative of the exo-exo configurations of IIDML units.
During the melt polymerizations, 0.5 molar equivalent excess of diols (with respect to the respective dimethyl carboxylate) were used to compensate the weight loss caused by evaporation.
The obtained semi-aromatic polyesters were further characterized by 25 infrared spectroscopy. The absorptions of the major valence vibrations are collected in Table 3. The formation of ester bonds was confirmed by the very characteristic C=0 stretching signals appearing at 1710-1720 cm'1 as well as the multiple ester C-O-C stretching vibration absorptions in the region of 1200-1300 cm'1. The C-H asymmetric and symmetric stretching vibrations of 30 methylene skeleton appear as two major bands at 2950 cm'1 and 2880 cm'1, respectively; the C-H stretching signals of the furan ring appear at 3154 cm'1 and 3118 cm'1, while the C=C absorptions of the furan or phenyl rings located at around 1580-1600 cm'1.
19
Table 3. FT-IR absorptions of the synthesized polyesters recorded at room temperature.
_frequency (cm·1)__ j assignment PleT PlelP PleF ; =C-H (Fu) - - 3154,3118 ”.....
C-H (CH2) 2947,2878 2949,2878 2950,2877 C=0 (ester) 1710 1719 1722 C=C (Fu/Ph) 1581 1609 1577 C-O-C (ester) 1261 1231 1273
Disubstituted Fu/Ph 937,825,726 970,827,726 988,829,764
Wide Angle X-Ray Diffraction (WAXD) Study: Wide-angle X-ray 5 diffractograms of the derived aliphatic-aromatic polyesters are represented in Figure 2. The degrees of crystallinity were estimated according to the ratio between the surfaces of peaks corresponding to crystalline and amorphous components, respectively. Due to the overlapping of diffraction signals, peak separation (deconvolution) is necessary to distinguish the signals arising from 10 the crystalline and amorphous regions. The deconvolution results of the diffractogram of poly(isoidide-2,5-bismethylene terephthalate) (PleT) is representatively shown in Figure 3. As shown in Figure 2, PleT and PleFare semicrystalline materials, as evidenced by the sharp diffraction signals. The estimated degrees of crystallinity of PleT and PleF are 66.0% and 42.2%, 15 respectively. In contrast, the polyisophthalate PlelP is an amorphous material. According to the DSC analysis as mentioned earlier, a weak melting endotherm was present for PlelP during the first DSC heating run. However, the recorded melting enthalpy is very low of only 6.5 J/g, indicating the amount of the crystals in the analyzed sample is rather small. These crystals may be 20 strongly defected making them “invisible” by WAXD technique.
The degree of crystallinity of the obtained polyesters is also dependent on the synthetic method. The diffractograms of a few PleF samples are presented in Figure 4. These samples are different in the synthetic method as well as the molecular weights. Since all the diffraction profiles are comparable, 25 the crystal packing patterns of these samples are not substantially affected. In other words, they have identical crystal unit cells. The two polyfurandicarboxylate samples obtained from melt polymerization, i.e. PleF-a 20 prepolymer and PleF-b, have similar degrees of crystallinity amounting to 16.0 % and 19.9 % respectively. SSPC apparently increases the degree of crystallinity significantly. Starting from the same prepolymer PleF-a (M„ = 6,900 g/mol), SSPC at 200°C for 23 h yields a polyester with a much 5 enhanced degree of crystallinity of 33.8% (Mn = 27,700 g/mol); while SSPC at 230°C for only 4 h results in a polyester with an even higher degree of crystallinity of 42.2% (Mn = 30,300 g/mol). The observed difference in the degree of crystallinity is mainly induced by SSPC conditions, in particular the reaction temperature. As mentioned earlier in the synthesis section, sufficient 10 high SSPC temperature increases the mobility of the polymer chain.
Therefore, they have the opportunity to adjust their position for a more ordered chain alignment patterns, which, as a result, enhances the degree of crystalinity of the polymer sample.
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