AU663071B2 - polymerisation regulation - Google Patents

Description

a OPI DATE 07/09/99 AnJP DATE 15/10/92 INTERNA (51) International Patent Classification 5 C08F 002/38, C07C 327/26 APPLN. TD 12032 92 PCT MULMBER PCT/AU92/0002q TREATY (PCT) (11) International Publication Number: A (43) International Publication Date: WO 92/13903 20 August 1992 (20.08.92) (21) International Application Number: (22) International Filing Date: 3 Priority data: PK 4465 6 Februar PCT/AU92/00029 1 January 1992 (31.01.92) ry 1991 (06.02.91) AU (71) Applicant (for all designated States except US): COMMON- WEALTH SCIENTIFIC AND INDUSTRIAL RE- SEARCH ORGANISATION [AU/AU]; Limestone Avenue, Campbell, ACT 2601 (AU).

(72) Inventors; and Inventors/Applicants (for US only) MEIJS, Gordon, Francis [AU/AU]; 3 Henty Street, Murrumbeena, VIC 3163 RIZZARDO, Ezio [AU/AU]; 26 Alex Avenue, Wheelers Hill, VIC 3150 (AU).

(74) Agents: CORBETT, Terence, Guy et al.; Davies Collison Cave, 1 Little Collins Street, Melbourne, VIC 3000

(AU).

(81) Designated States: AT (European patent), AU, BE (European patent), CA, CH (European patent), DE (European patent), DK (European patent), ES (European patent), FR (European patent), GB (European patent), GR (European patent), IT (European patent), JP, LU (European patent), MC (European patent), NL (European patent), SE (European patent), US.

Published W7th international search report.

663071 (54) Title: POLYMERISATION REGULATION

R

1

-II

R

1 C Z R 2 (57) Abstract

I

A process for the production of low molecular weight polymers by free radical polymerisation of one or more monomers in the presence of a chain transfer agent, characterized in that the chain transfer agent comprises one or more compounds of general formula wherein RI is a hydrogen atom, an alkyl group, or a group capable of activating the vinylic carbon towards free radical addition; R 2 represents an optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, or optionally substituted satured, unsatured or aromatic carbocyclic or heterocyclic ring; and Z represents an oxygen, sulphur, phosphorus, or nitrogen atom bound to another atom or group of atoms in order to satisfy its valency.

r mn WO 92/13903 PCT/AU92/00029 -1- POLYMERISATION REGULATION The invention relates to processes for radical-iaitiated polymerisation of unsaturated species and for the regulation of molecular weight and end-group functionality of the polymeric products produced from such processes. Polymers of limited molecular weights, or oligomers, are useful as precursors in the manufacture of other polymeric materials and as additives or components of formulations for plastics, elastomerics, and surface coating compositions, as well as being useful in their own right in many applications. For example, low molecular weight polymers are often required for ease of processing. End-functional polymers are important as building-blocks for advanced copolymers. If of sufficiently low molecular weight, end functional polymers often display useful surface active or compatibilising properties.

In conventional polymerisation practice, the manufacture of low molecular weight polymers requires the use of an initiator and a chain transfer agent. The initiator acts as a free radical source, whereas the chain transfer agent or regulator controls the molecular weight of the polyme' molecule by reacting with the propagating polymer radical to terminate its growth. The chain transfer agent then causes the initiation of a new polymer chain thus transferring the growth process from one discrete polymer molecule to another discrete polymer molecule. At least a part of the chain transfer agent is incorporated into the polymer molecule and is thereby consumed in the process.

The chain transfer agents most commonly used are alkanethiols which possess an objectionable odour, lead to a wide distribution of molecular weights in batch polymerisations with certain monomers, do not allow the production of di-end P functional polymers and have limitations as to the types of functional groups that can be installed at the end of the polymer chain. There is also little scope with thiols for the chain transfer constant to be optimised for a particular polymerisation. In many polymerisations with thiols, the chain transfer constant, a measure of the effectiveness of the polymerisation regulator, departs significantly IUBSTTTUTE SHEET -2from the ideal of 1.0 that is the optimunr for batch polymerisations at moderate to high conversions. The desirability of chain transfer constants close to 1.0 is reviewed by an article by T. Corner in Advances in Polymer Science, volume 62, p.

(1985). International Patent Application PCT/AU87/00412 and Australian Provisional Patent Application PJ7146/89 disclose novel polymerisation processes employing regulators that help overcome many of the disadvantages of thiols, particularly in relation to chain transfer constant and, in part, provide polymerisation processes that give alternative end groups. They also allow incorporation of a wider variety of useful functional groups at the ends of polymer chains.

The present invention seeks to overcome the disadvantages of polymerisations regulated with thiols by using alternative polymerisation regulators. These regulators have good stability and shelf life while maintaining many of the advantages over thiols. In the majority of cases, the materials that are part of the present process present a different range of chain transfer activities, allowing more opportunity for an optimal process to be selected for a given polymerisation system of monomers and polymerisation conditions. The chain transfer constant that a given regulator possesses is an important consideration in selecting the optimum process for producing low molecular weight polymers.

The present invention provides a process for the production of low molecular weight polymers by free radical polymerisation, which process is characterised by the addition to the polymerisation system of a compound of the general formula I

R

1 C R2 (I) o 30 wherein SR' is a hydrogen atom, an alkyl group, or preferably, a group capable of activating the carbon-sulphur double bond towards free radical addition; and

R

2 represents an optionally substituted alkyl, optionally substituted alkenyl, N 4% i s'.

-3optionally substituted alkynyl, or optionally substituted saturated, unsaturated or aromatic carbocyclic or heterocyclic ring.

Suitable groups for R 1 are optionally substituted phenyl or other optionally substituted aromatic groups, alkoxycarbonyl or aryloxycarbonyl (-COOR), carboxy (-COOH), acyloxy (-O 2 CR), carbamoyl (-CONR 2 and cyano where R is an alkyl or aryl group.

Optional substituents for R' and/or R 2 in formula I may comprise either reactive or non-reactive groups. "Reactive substituent groups" are groups which do not take part in the actual lowering of the molecular weight but are installed at the ends of the polymer chains and may be capable of subsequent chemical reaction.

The low molecular weight polymer containing such a reactive group or groups is thereby able to undergo further chemical transformation, such as being joined with another polymer chain. Suitable reactive substituents include hydroxy amino (-NH 2 halogen, allyl, cyano, epoxy, and carboxylic acid and its derivatives, such as ester groups (-COOAlkyl). "Non-reactive substituent groups" may be any groups which are not deleterious to the polymerisation reaction or product, for example, alkoxy (-OAlkyl) or alkyl groups, and which are not capable of subsequent chemical reaction..

Substituted rings may have their reactive substituent groups directly attached to the ring or indirectly attached by means of a methylene group or other side chain.

In this specification, the term "alkyl", used either alone or in compound words such as "optionally substituted alkyl" or "optionally substituted cycloalkyl", denotes straight chain, branched or cyclic alkyl containing from 1 to 32 carbon atoms.

Similarly, the terms "alkenyl" and "alkynyl" denote straight chain, branched or cyclic groups containing from 2 to 32 carbon atoms.

Saturated, unsaturated, or aromatic carbocyclic or heterocyclic rings may contain from 3 to 14 atoms. The terms "aromatic" or "aryl", used either alone or in .I9 T- I i -4compound words such as "optionally substituted aryl", "optionally substituted aryloxy" or "optionally substituted heteroaromatic", denote single, polynuclear, conjugated and fused residues of aromatic hydrocarbons or aromatic heterocyclic ring systems.

The term "heterocyclic", used either alone or in compound words such as "optionally substituted saturated or unsaturated heterocyclic", denotes monocyclic or polycyclic heterocyclyl groups containing at least one heteroatom atom selected from nitrogen, sulphur and oxygen.

In this specification "optionally substituted" means that a group may or may not be further substituted with one or more groups selected from alkyl, alkenyl, alkynyl, aryl, halo, haloalkyl, haloalkenyl, haloalkynyl, haloaryl, hydroxy, alkoxy, alkenyloxy, aryloxy, carboxy, benzyloxy haloalkoxy, haloalkenyloxy, haloaryloxy, nitro, nitroalkyl, nitroalkenyl, nitroalkynyl, nitroaryl, nitroheterocyclyl, azido, amino, alkylamino, alkenylamino, alkynylamino, arylamino, benzylamino, acylamino, acyl, alkenylacyl, alkynylacyl, arylacyl, acylamino, acyloxy, aldehydo, alkylsulphonyl, arylsulphonyl, alkylsulphonylamino, arylsulphonylamino, alkylsulphonyloxy, arylsulphonyloxy, heterocyclyl, heterocycloxy, heterocyclylamino, haloheterocyclyl, alkylsulphenyl, arylsulphenyl, carboalkoxy, carboaryloxy, mercapto, alkylthio, arylthio and acylthio.

I I The process of this invention may be adopted by the users of conventional processes using thiols with little change to reaction conditions other than the substitution of the appropriate quantity of a compound of general formula I for the thiol. The proportion of the compound of general formula I used may be in the range of 0.01 to 30 mole percent based on total monomer, with a preferred range 0.1 to 5 mole percent. The process may be operated at any of the reaction conditions appropriate to free radical polymerisation, i.e. temperatures from 100 *C to 400 °C and pressures from below atmospheric to 3000 atmospheres.

Bulk, solution, emulsion, suspension or other conventional polymerisation modes may be used. Any unsaturated monomers susceptible to free radical OIL. MM NMMW -d polymerisation may be used although it should be noted that the chain transfer constant will vary with the monomer used. Suitable unsaturated monomers include acrylic esters, methacrylic esters, acrylonitrile, vinyl halides, vinyl esters, vinyl aromatics, unsaturated or poly unsaturated hydrocarbons, or mixtures of these. For example, the process is applicable to the manufacture of synthetic rubbers, and other polymer formulations where reduced molecular weight aids processing and improves properties. The process can also be used to produce low molecular weight polymers and oligomers for a variety of applications such as high-solids surface coatings, paints, and adhesives.

Compounds of general formula I are readily prepared and, unlike the lower molecular weight thiols, they do not possess an objectionable odour. The compounds used in the process of this invention display an unexpected high activity in controlling molecular weight in polymerisation reactions and have chain transfer constants that may be superior to those of thiols, particularly with styrene and acrylates. Their activity is such that their chain transfer constants can approach the optimum of 1.0 for batch polymerisations and this activity is not as ,highly dependent as that of thiols on the structure of the propagating radical.

A feature of the process of this invention is that, unlike processes described in many of the examples of International Patent Application PCT/AU87/00412, it produces polymer chains that do not contain terminal unsaturation. In addition, those chain transfer agents described in International Patent Application PCT/AU87/00412 that specifically do not introduce terminal unsaturation (for example, a-benzyloxystyrene and derivatives) have less satisfactory chain transfer constants and lower shelf life than the compounds of formula I.

An additional, unique feature of the process is that the resulting polymers can be hydrolysed to give a terminal thiol group. Such hydrolysis cleaves off the residue of the chain transfer agent containing R 1 and therefore there is no need for R 1 to contain a functional substituent for the production of thiol terminated polymers.

If R 2 however, contains a functional substituent, a di-end functional polymer will

V

-6be the product of the process (after the hydrolysis step) and one of the end groups will be a thiol group. Thiol terminated polymers have application as odour-free polymeric chain transfer agents and as building blocks for the preparation of block and graft copolymers.

S

The end functional polymers produced by any of the aspects of the process described above can be converted into polymers with different end functionality by chemical reaction as is well known in the art. For example, hydroxy terminated polymers can be converted into macromonomers by reaction with methacryloyl chloride. These macromonomers are useful materials for the preparation of graft copolymers by free radical copolymerisation.

The materials of formula I that are employed in the process of this invention may be prepared by reaction of the corresponding O-ester with Lawesson's reagent or by treatment of alcohols or alkoxides with thiobenzoyl chloride or the sodium salt of (thiobenzylthio)acetic acid. The reaction of iminoesters with hydrogen sulphide has also been reported to give thionoesters.

sS

ACH

3 S1S S Lawesson's Reagent *,fe I 11 o* WO 92/13903 PCT/AU92/00029 -6- The following illustrates some of the methods used to prepare examples of the compounds used in the process.

Benzyl thionobenzoate: By method A [Lawesson's reagent]. Benzyl benzoate (2.1 g) was heated at 140 C for 24 h with Lawesson's Reagent (4.9 g) in anhydrous xylene (10 ml). After removal of the solvent and subjection of the mixture to chromatography on silica gel and recrystallization from pentane at low temperature, benzyl thionobenzoate was obtained in 67% yield. 'H NMR (CDCI 3 6 5.64 2H), 7.3-8.2 By method B [Thionobenzoyi chloride route]. Thiony! chloride (71 g) was added dropwise to a solution of dithiobenzoic acid (47 g) in anhydrous ether (44 ml).

After 7 h of stirring at ambient temperature, the ether and excess thionyl chloride were removed under reduced pressure. The residue was then distilled twice to afford the thioacid chloride b.p. 54-64 0 C [0.01 mmHg]. Triethylamine (2.03 g) was added in one portion to a solution of the thioacid chloride (3.13 g) and benzyl alcohol (2.16 g) in dry acetone (40 ml) under nitrogen with vigorous stirring. The stirring was continued for 15 h at ambient temperature. The mixture was then poured into water and extracted with ether. The extracts were washed and dried (MgSO4) and the residue was subjected to chromatography on silica gel (eluent: hexane) to give a viscous yellow oil (3.0 g) which was crystallised from pentane to afford benzyl thionobenzoate (2.4 g, m.p. 39-40 *C.

By method C [(Thiobenzylthio)acetic acid route]. Phenylmagnesium bromide was prepared by adding bromobenzene (20 g) in ether (100 'ml) dropwise under nitrogen and reflux to a stirred mixture of magnesium turnings (3.2 g) in anhydrous ether (50 ml). After 30 minutes boiling under reflux, the mixture was cooled in ice and carbon disulfide (12 ml) was added dropwise. The mixture was allowed to warm gradually to 20 "C and stirred for a further 15 h. After this period, ice (130 g) was cautiously added, and the organic layer was separated.

The sodium salt of chloroacetic acid (12 g) was added to the aqueous phase and the mixture was allowed to stand for 24 h. After this period, it was brought to pH UTE

SHEET

SUBSTITUTE

SHEET

WO 92/13903 PCT/AU92/00029 -9- 1 with hydrochloric acid and extracted with ei.er. The ether extracts were washed with water (x dried (CaC1 2 and the solvent was removed to afford a residue that was recrystallised from benzene to give the acid derivative (7.9 m.p. 125- 126 A portion (1.06 g) was dissolved in dry tetrahydrofuran (125 ml) and sodium hydride (0.48 g) was then added. After the effervescence had ceased, imidazole (0.68 g) was added and the mixture was refluxed for 5 minutes. Benzyl alcohol was then added and the mixture was refluxed for a further 5 min. It was then cooled, poured into water, and extracted with ether. The extracts were washed three times with water, dried and the solvent was removed to give benzyl thionobenzoate (0.72 which was further purified by flash chromatography on silica gel (eluent: b.p. 40-60 °C petroleum spirit) and recrystallization from pentane. Yield: 4 g. m.p. 38-39 "C.

(4-Methoxycarbonyibenzyl) thionobenzoate: Method C was used to prepare this compound in low yield (ca. 5% overall) from bromobenzene and methyl (4hydroxymethyi)benzoate. The thionoester was recrystallised from dichloromethane/hexane: m.p. 90-91 'H NMR (CDC1 3 8 3.92 3H), 5.74 2H), 7.2-7.7 SH), 7.9-8.3 4H). MS (CH4): m/z 287 25%),149 Benzy 4-methoxythionobenzoate: This compound was prepared from 4bromoanisole and benzyl alcohol in 5% overall yield by Method C. It was recrystallised from dichloromethane/hexane: m.p. 68-69 'H NMR (CDC13): 6 3.67 3H), 5.60 2H), 6.73 J 9 Hz, 2H), 7.1-7.6 5H), 8.13 J 9 Hz, 2H). MS (CH 4 m/z 259 10%),135 107 91 (4-Methoxycarbonyibenzyi) 4-metharythionobenzoate: Method C was used to prepare this compound in 11% overall yield from 4-bromoanisole and methyl (4hydroxymethyl)benzoate. The crude product was subjected to flash chromatography (eluent: dichloromethane) and recrystallised from dichloromethane/hexane: m.p. 83-85 'H NMR (CDC1 3 6 3.83 3H), 3.93 3H), 5.75 2H), 6.83 J 7.5 Hz, 2H), 7.50 J 7.5 Hz, 2H), 7.9-8.3 SSUBSTITUTE SHEET WO 92/13903 1%,15 PCT/AU92/00029 (in, 4H). IMS (CH 4 m/z 317 Accurate mass ml/z 317.0836. C1 7

H

17 0 4 S requires m/z 317.0847.

(4-Ethoxcarbonibenzyi) 4-methoxythionobenzoate: This compoun~d was prepared from 4-bromoanisole and ethyl (4-hydroxymethyl)benzo ate by Method C. Te overall yield was 18% and recrystallization from dichioromethane/hexane was used for purification. m.p. 75-77 C. 'H NMR (CDC1 3 a 1.40 J 7 Hz, 3H), 3.83 3H), 4.37 J 7 Hz, 2H), 5.73 2H), 6.80 J 7.5 Hz, 2H), 7.50 (di, J 7.5 Hz, 2H), 8.0-8.4 (mn, 4H). MS (CH 4 m/z 331 40%),163 (40%),135 (100%).

4-(Hyryethylfbenzyl thionobenzoate: This compound was prepared using Method B in 26% yield from thiobenzoyl chloride and 1,4-benzenedimethanol.

After recrysta23ization from hexane, yellow needles of the thionoester were obtained. m.p. 80-80.5 'H NMR (CDC 3 85 1.67 1H), 4.68 2H), 5.68 2H), 7.40 (in, 7H), 8.17 J 6 Hz, 2H). MS m/z 257 12%), 241 121 Accurate mass m/z 258.0732. CISH, 4 0,S requires in/z 258.0714.

The following non-limiting examples illustrate the invention.

EXAMPLE 1 Preparation of Low Molecular Weight Polystyrene with Benzd Thionobenzoaze Azobisisobutyronitrile (35 mg) was dissolved in freshly distilled styrene (25 ml).

Aliquots (5.0 ml) were removed and added to ampoules containing the amount of benzyl thionobenzoate shown below in Table 1. The mixtures were polymerised at *C for 1 h in the absence of oxygen. The contents of the ampoule were then poured into methanol and the precipitated polymer was collected and dried in vacuo overnight. A small portion was examined by gel permeation chromatography (GPC) using a Waters Instrument connected to six p-Styragel columns (11 0t 3 500, and 100 A pore size). Tetrahydrofuran was used SUBSTuITUTE SHEET WO 92/13903 P(3r/AU92/000)29 as eluent at a flow rate of 1 ml/min and the system was calibrated using narrow distribution polystyrene standards (Waters). The results appear in Table 1.

Table 1 Amount of benzyl Conversion M thionobenzoate added 81 mg 2.7 11400 41 mg 2.9 20800 21 mg 3.0 37600 0 mg 3.2 124000 The chain transfer constant (Cj, calculated from these data, was 1.0 which compares favourably with that from n-butanethiol 21-25), These results show that the compound is an efficient chain transfer agent and that the process produces polymers of low molecular weight in a controlled manner.

EXAMPLE 2 Preparation of Low Molecular Weight Poly(methy acrylate) with Benzyl Thionobenzoate Azobisisobutyronitrile (9 mg) was dissolved in freshly distilled methyl acrylate ml). Aliquots (2.0 ml) were removed and added to ampoules containing thiophenfree benzene (8 ml) and the amount of benzyl thionobenzoate shown below in Table 2. The mixtures we e polymerised at 60 *C for 1 h in the absence of oxygen. The volatiles were then removed and the polymers were dried in vacuo to constant weight and then examined as before. The results appear in Table 2.

SUBSTITrUTE SHEET i WO 92/13903 PCT/AU92/00029 Table 2 Amount of benzyl Conversion M thionobenzoate added mg 3.8 9020 26 mg 6.0 17700 12 mg 9.2 35600 0 mg 16 473000 Polystyrene-equivalent number average molecular weight, obtained by GPC.

The chain transfer constant (Cj, calculated from these data, was 1.2, which compares favourably with that from n-butanethiol 1.7).

EXAMPLE 3 Preparation of Low Molecular Weight Poly(vinyl acetate) with Benzyl Thionobenzoate Azobisisobutyronitrile (16 mg) was dissolved in freshly distilled vinyl acetate (100 ml). Aliquots (10.0 ml) were removed and added to ampoules containing the amount of benzyl thionobenzoate shown below in Table 3. The mixtures were polymerised at 60 C for 1 h in the absence of oxygen. The volatiles were then removed and the polymers were dried in vacuo to constant weight and then examined as before. The results appear in Table 3.

SUBSTITUTE SHEET

WIIISPY-

WO 92/13903 PCT/AU92/00029 (2. -H- Table 3 Amount of benzyl Mn thionobenzoate added 2.2 mg 1900 0 253000 Polystyrene-equivalent number average molecular weight, obtained by GPC.

The chain transfer constant (Cj, calculated from these data, was 20. These results show that the compound acts as a very active regulator in polymerisation of vinyl acetate.

EXAMPLE 4 Preparation of Low Molecular Weight Polystyrene with (4-Methaxycarbonyibenzyl) Thionobenzoate Samples of polystyrene were prepared on the same scale and in the manner of example 1. The amount of (4-methoxycarbonylbenzyl) thionobenzoate added and the results of the polymerisation are shown in Table 4.

SUBSTITUTE SHEET t r' L;Li~. I ~d li- WO 92/13903 PCr/AU92/00029 13 Table 4 Amount of (4-methoxycarbonylbenzyl) thionobenzoate added mg mg mg 0 mg 23000 41900 66300 142000 The chain transfer constant (Cj, calculated from these data, was 0.59. A sample of low molecular weight polystyrene (M 4570) prepared with (4-methoxycarbonylbenzyl) thionobenzoate was examined by 'H NMR spectroscopy and showed signals at 6 3.83 indicative of the presence of methyl ester groups. Integration of the spectrum and comparison with the integral of the aromatic styrene signal showed there to be an end group functionality of 0.9-1.0.

This experiment shows that the process can be used to prepare end functional polymers.

EXAMPLE Preparation of Low Molecular Weight Poly(methyi acrylate) with (4-Methoycarbonyibenzyi) Thionobenzoate Samples of poly(methyl acrylate) were prepared according to the directions given in Example 2, except that (4-methoxycarbonylbenzyl) thionobenzoate was used rather than benzyl thionobenzoate. The amount of (4-methoxycarbonylbenzyl) thionobenzoate added and the results of the polymerisation are shown in Table SUBSTITUTE SHEET WO 92/13903 PCI'/AU92/ ,0029 t4- Table Amount of (4-methoxycarbonylbenzyl) thionotlenzoate added

M.

mg 26 mg 12 mg 0 mg 7700 14300 28300 772000 Polystyrene-equivalent number average molecular weight, obtained by GPC The chain transfer constant calculated from these data, was 1.4, which compares favourably with that from n-butanethiol 1.7).

EXAMPLE 6 Preparation of Low Molecular We~ft Po4~qv'ene with Benzyi 4-Methaxyfthionobenzoate) Samples of polystyrene were prepared on the same scale and in the manner of example 1. The amount of benzyl 4-methoxy(thionobenzoate) added and the results of the polymerisation are shown in Table 6.

SUBSTITUTE SHEET

I<

-7 WO 92/13903 PCr/AU92/00029 -4- Table 6 Amount of benzyl 4-methoxy(thionobenzoate) added mg mg mg 0 mg 65100 93500 113000 145000 The chain transfer constant calculated from these data, was 0.12.

EXAMPLE 7 Preparation of Low Mblecilar Wei&gh Poay(methy4 aciylate) with Benzyi 4-Methwxy(thionobenzoate) Samples of poly(methyl. acrylate) were prepared according to the directions given in Example 2, except that benzyl 4-methoxy(thionobenzoate) was used rather than benzyl thionobenzoate. The amount of benzyl 4-methoxy(thionobenzoate) added and the results of the polymerisation are shown in Table 7.

Table 7 Amount of benzyl 4-methoxy(thionobenzoate) added k. mg 26 mg 13 mg 0 mg 10700 18600 42600 394000 *Polystyrene-equivalent number average molecular weight, obtained by GPC SUBSTITUTE

SHEET

WO 9213903PCr/AU92/00029 The chain transfer constant calculated from these datz, was 1.1, which compares favourably with that from n-butanethiol (C 1.7).

EXAMPLE 8 Preparation of Low Molecular We~gfit Polystyrene with 4-(Methorycabon4)ben2zyi 4- Methaxy(thionobenzoate) Samples of polystyrene were prepared on the same scale and in the manner of example 1. The amount of 4-(methoxycarbonyl)benzyl 4-methoxy(thionobenzoate) added and the results of the polymerisation are shown in Table 8.

Table 8 Amount of 4-(methoxycarbonyl)benzyl 4-methoxy,,thionobenzoate) added 81 mg 48400 mg 86000 mg 105300 0 mg 150000 The chain transfer constant calculated from these data, was 0.25. The total average functionality (methoxy and methoxycarbonyl groups) calculated by 1

H

NMR on a sample of polystyrene of Mn 13300 (prepared with 4-(methoxycarbonyl)benzyl 4-metho..ty(thionobenzoate) was 2.1, which shows that 4-(methoxycarbonyl)benzyl 4methoxy(thionobenzoate) is efficient in introeucing functional groups at the termini of polymer chains and that this type of chain transfer agent can be used to prepare end-functional polymers.

EXAMPLE 9 Preparation of Low Molecular Weight Poly(methyi acr~ate) with 4-(Mehorycarbonyi)ben2)4 4-Methaxy(thionobenzoate) r R SUBSTITUTE SHEET WO 92/13903 PTA9/02 PC]r/AU92/00029 '7 -46- Samples of poly(methyl acrylate) were prepared according to the directions given in Example 2, except that 4-(methoxycarbonyl)benzyl 4-methoxy(thionobenzoate) was used rather than benzyl thionobenzoate. The amount of 4-(methoxycarbonyl)berizyl 4-methoxy(thionobenzo ate) added and the results of the polymerisation are shown in Table 9.

Table 9 Amount of 4-(methoxycarbonyl)benzyl 4-methoxy(thionobenzoate) added k. mg 26 mg 13 mg 0 mg 10700 18600 42600 394000 Polystyrene-equivalent number average molecular weight, obtained by GPC The chain transfer constant calculated from these data, was 1.1, which compares favourably with that from n-butanethiol 1.7).

EXAMPLE Preparation of Low Molecular WeOUh Polysryrene with 4-(Ehoxyaroni)ben2r4 4- Methaty(thiorzabenzoate) Samples of polystyrene were prepared on the same scale and in the manner of Example 1. The amount of 4-(ethoxycarbonyl)benzyl 4-methoxy(thionobenzoate) added and the results of the polymerisation are shown in Table SUBSTMJTE SHEET WO 92/13903 WO 9213903PCT/AU92/00029 Table Amount of 4-(ethoxycarbonyl)benzyl l 4-methoxv(thionobenzoate) added 616 mg 13500 0 mg 150000 The presence of ethoxycarbonyl. and methoxy end groups in the lower molecular weight sample of polystyrene was shown by signals in the 'H NMR spectrum at 8 4.28 and 3.83, respectively.

EXAMPLE 11 Preparation of Low Moleclar Weight Polystyene with 4-(hyroxmethyf)benzyi thionobenzoate Samples of polystyrene were prepared on the same scale and in the man-Ter of example 1. The amount of 4-(hydroxymnethyl)benzyl thionobenzo ate added and the results of the polymerisation are shown in Table 11.

Table 11 Amount of 4(hydroxymethyl)benzyl thionobenzo ate added ft Nt 81 mg 40 mg mg 0 mg 25600 43900 59500 113000 The chain transfer constant was 0.43. The presence of the end group shown below in a polymer of Mn 6810, prepared with 4-(hydroxymethyl)benzyl SUBSTITUTE SHEET PCI'/AU92/00029 WO 92/1390l3 -4 thionobenzoate, was confirmed by a broad signal in the 'H NMR spectrum at a= 4.4-4.7 (due to the benzyl methylene hydrogens) and an infrared absorption at 3415 cm".

-CH

2 OH1 End group of polymer prepared with 4-(hydroxy'medryl)benzyl thionobenzoate After treatment with t-butyldiniethylsilyl chloride and imidazole, this polymer showed signals at 8 0.08 in the 'H NMR spectrum due to the methyls of a t'butyldimethylsilyl ether group. The formation of this silyl ether further confirms the presence of a hydroxyl end group.

SUBSTITUTE SHEET

Claims (7)

1. A process for the production of low molecular weight polymers by free radical polymerisation of one or more monomers in the presence of a chain transfer agent, characterised in that the chain transfer agent comprises one or more compounds of the general formula I s II R 1 -C R 2 (I) wherein R is a hydrogen atom, an alkyl group, or a group capable of activating the carbon-sulphur double bond towards free radical addition; and R 2 represents an optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, or optionally substituted saturated, unsaturated or aromatic carbocyclic or heterocyclic ring (wherein the term "optionally substituted" has the meaning hereinbefore defined). S 2. A process as claimed in Claim 1, characterised in that R 1 is a substituted phenyl or other optionally substituted (as hereinbefore defined) aromatic group, or an alkoxycarbonyl or aryloxycarbonyl, carboxy, acyloxy, carbamoyl, or cyano group. i

3. A process as claimed in Claim 1 or Claim 2, wherein R 1 and/or R 2 in formula I have one or more substituent groups which do not take part in the actual lowering of the molecular weight but are installed at the ends of the polymer chains. 30 4. A process as claimed in Claim 3, wherein the substituent group(s) on R 1 and/or R 2 are reactive groups and may be capable of subsequent chemical reaction, whereby the low molecular weight polymer product containing the reactive group or groups is thereby able to undergo further chemical transformation. 21 A process as claimed in Claim 3, wherein the substituent group(s) on R 1 and/or R 2 are non-reactive groups which are not deleterious to the polymerization reaction or product and which are not capable of subsequent chemical reaction.

6. A process as claimed in Claim 4, characterised in that the reactive substituent group is an hydroxy, amino, halogen, allyl, cyano, epoxy, or carboxylic acid group or a derivative of a carboxylic acid group.

7. A process as claimed in any one of the preceding Claims, characterised in that the compound of general formula I is added to present in an amount of from 0.01 to 30 mole percent based on total monomer.

8. A process as claimed in any one of the preceding Claims, characterised in that the monomer is selected from the groups consisting of acrylic esters, methacrylic esters, vinyl esters, vinyl aromatics, unsaturated or poly unsaturated hydrocarbons, or mixtures of any two or more of such monomers.

9. A process as claimed in any one of the preceding Claims, characterised in that the resulting polymer is hydrolysed to give a terminal thiol group. A process for the production of low molecular weight polymers by free radical polymerisation, substantially as hereinbefore described with reference to the Examples. 30 June 1995 Commonwealth Scientific and Industrial Research Organisation By its Patent Attorneys DAVIES COLLISON CAVE All /T y\ I 22 ABSTRACT A process for the production of low molecular weight polymers by free radical polymerisation of one or more monomers in the presence of a chain transfer agent, characterised in that the chain transfer agent comprises one or more compounds of the general formula I S II R 1 C R 2 (I) wherein R 1 is a hydrogen atom, an alkyl group, or a group capable of activating the carbon-sulphur double bond towards free radical addition; and R 2 represents an optionally substituted alkyl, optionally substituted alkenyl, optionally substituted alkynyl, or optionally substituted saturated, unsaturated or aromatic carbocyclic or heterocyclic I:ag. II p *I Intern nal Application No. PCT/AU 92/00029 INTERNATIONAL SEARCH REPORT I. CLASSIFICATION OF SUBJECT MATTER if several classification symbol@ apply, indicate all)e According to International Patent classification (IPC) or to both National Classification and IPC Int. CI." C08F 002/38, C07C 327/26 II. FIELDS SEARCHED Minimum Documentation Searched 7 Classification System Classification Symbols IPC C08F 002/38, C08F 001/80 Documenrtation Searched other than Minimum Documen'ation, to the Extent that such Documents are ncluded in theie ds earched AU: IPC as above; Australian Classification 09.4-33, 09.4-35 III. DOCUMENTS CONSIDERED TO BE RELEVANT Category' Citation of Document, 11 with indication, where appropriate of the relevant passages 12 Relevant to Claim No Is X EP,A, 407059 (JAPAN SYNTHETIC RUBBER CO LTD) 9 January 1991 1, 3, 5-7 (09.01.91). Refer to page 3, page 6 lines 1-19, page 13 lines

45-55, page 19 table 1 and claim 1 X WO,A, 89/10371 (NORSOLOR) 2 November 1989 (02.11.89). Refer to 1,3,5-7 the abstract X US,A, 4054731 (MARUBASHI et al) 18 October 1977 (18.10.77). 1, 3, 5-7 Refer to column 2 lines 9-48, column 3 line 44-column 4 line 16, column 5 line 43-column 6 line 11, example 1 and claim 1 X US,A, 3838140 (MAYER-MADER, BOLDT) 24 September 1974 1,3,5-7 (24.09.74). Refer to column 1 and column 2, example II and claim 1 Special categories of cited documents 10 Later document published after the international filing date or priority date and not in conflict Document defining the general state of the art which is with the application but cited to urnderstand the not considered to be of particular relevance principle or theory underlying the invention earlier document but published on or after the document of particular relevance; the alaimed international filing date invention cannot be considered novel or cannot be document which may throw doubts on priority claim(s) considered to involve an inventive step or which is cited to establish the publication date of document of particular relevance; the claimed another citation or other special reason (as specified) invention cannot be considered to involve an document referring to an oral disclosure, use, inventive step when the document is combined exhibition or other means with one or more other such documents, such document published prior t the international filing dalt; combination being obvious to a person skilled in but later than the priority date claimed the art document member of the same patent family IV. CERTIFICATION Date of the Actual Completion of the International Search Date of Mailing of this International Search Report 1 May 1992 (01.05.92) 13 May 1992 (13.05.92) International Searching Authority Signature of Auth i O AUSTRALIAN PATENT OFFICE M BREMERS Fofm PCTIPS/2101 Weoid hi.t) Iwamy 1956) -I I- Intern nal Application No. PCT/AU 92100029 FURTHER INFORMATION CONTINUED FROM THE SECOND SHEET V. OBSERVATIONS WHERE CERTAIN CLAIMS WERE FOUND UNSEARCHABLE This international search report has not been established in respect of certain claims under Article 17(2)(a) for the following reasons: 1. 1 Claim numbers because they relate to subject matter not required to be searched by this Authority, namely: 2. Claim numbers because they relate to parts of the international application that do not comply with the prescribed requirements to suc an extent that no meaningful international search can be carned out, specifically: 3. Claim numbr case they are dependent claims and are not drafted in accordance with the second .nd third sentences o PiTRule .4a VI. OBSERVATIONS WHERE UNITY OF INVENTION IS LACKIG 2 This International Searching Authority found multiple inventions in this international application as follows: 1. As all required additional search fees were timely paid by the applicant, this international search report covers a searchale claims of the international application. 2. As only some of the raquirod additional search fees were timely paid by the applicant, thjs internptional search report covers only those claims o the international application for which fees were paid, specifically claims: 3. l No reauired additional search fees were timely paid.by the applicant Consequently, this international search report is restncted to the invention first mentioned in the claims; it is covered by claim numbers: 4. As all sparchable claims could be searched without effort justifying an additional fee, the International Searching Authority did not invite payment of any additional fee. Remark on Protest The additional search fees were accompanied by applicant's protest. O No protest accompanied the payment of additional search fees. Form PCT/IPS/210/ supplmenul sheet Uramry 19851