WO2000052061A1

WO2000052061A1 - Use of an initiator for controlled polymerisation reactions

Info

Publication number: WO2000052061A1
Application number: PCT/GB2000/000695
Authority: WO
Inventors: Jean De La Croi Habimana; Pierre Chevalier; Tristan Tapper
Original assignee: Dow Corning Corporation
Priority date: 1999-03-05
Filing date: 2000-02-28
Publication date: 2000-09-08
Also published as: CA2363962A1; TW499441B; JP2002538236A; KR20010102496A; AU2815600A; EP1165628A1

Abstract

An initiator is used for initiating controlled polymerisation reactions, the initiator comprising units of the formulae R(73SiO), (R72SiO3/2), and/or (SiO4/2) and has at least one group D-CR82X, wherein each R7 is independently an optionally substituted hydrocarbon group, D is a divalent straight chain or branched alkylene group containing an oxygen or nitrogen heteratom and/or substitued by a carbonyl group, each R8 is independently an alkyl group or a hydrogen atom and X' is a halogen atom. Preferably each R7 is a methyl group and the initiator comprises two terminal -D-CR82X groups wherein each R8 is a methyl group, X is bromine and D is a group CO-NR9R10 or a group CO- (OR10) wherein R9 is an alkyl group or a hydrogen atom and each R10 is independently a straight chain or branched alkylene group. The initiator is particularly useful for initiating controlled polymerisation of vinyl containing monomers.

Description

USE OF AN INITIATOR FOR CONTROLLED POLYMERISATION REACTIONS

The present invention relates to use of an initiator for controlled polymerisation reactions, in particular use of an initiator for controlled polymerisation of vinyl containing monomers to produce a polymer or copolymer.

Controlled polymerisation systems are of considerable importance in macromolecular chemistry since they allow for controlled preparation of polymers having a specific desired morphology. For example, by controlling the ratio of monomer to initiator concentration the molecular weight, molecular weight distribution, functionality, topology and/or dimensional structure of the resulting polymer can be controlled. For many years free radical polymerisation has been a commercially important process for the preparation of high molecular weight polymers . A wide variety of monomers may be polymerised or copolymerised by free radical polymerisation under relatively simple conditions in bulk, solution, emulsion, suspension or dispersion. However, a drawback of conventional free radical polymerisation is the lack of control of the morphology of the resulting polymer.

Processes for controlled radical polymerisation have been proposed. For example, WO 96/30421, WO 97/18247 and WO 98/01480 disclose polymerisation processes based on atom transfer radical polymerisation (ATRP) which provide for controlled radical polymerisation of styrene, (meth) acrylates, and other radically polymerisable monomers. The processes disclosed comprise the use of (i) an initiating system which comprises an initiator having a radically transferable atom or group, for example a 1-phenylethyl halide, alkyl 2-halopropionate, p-halomethylstyrene, or , α' -dihaloxylene, (ii) a transition metal compound, for example Cu(I)Cl, Cu(I)Br, Ni(0), FeCl₂, or RuCl₂, and (iii) a C- , N- , O- , S-, or P-containing ligand which can co-ordinate with the transition metal, for example bipyridine or (alkoxy)₃P. In Chem. Commun., 1999 99-100 Haddleton et al disclose solid supported copper catalysts, which are alleged to be easy to remove from polymer products for reuse, and their use in atom transfer polymerisation of methyl methacrylate using ethyl-2-bromoisobutyrate as an initiator.

WO 98/01480 further discloses the preparation and use of polydimethylsiloxane (PDMS) based macroinitiators; for example, benzyl chloride end groups are introduced to PDMS having silicon bonded hydrogen atoms by a platinum catalysed hydrosilylation reaction with vinylbenzylchloride . However, this route produces two isomers, α and β, having different activities. The β isomer which represents 65% of the product is totally inactive towards initiation of controlled polymerisation reactions of vinyl monomers, and use of the α isomer results in polymers or copolymers containing unacceptably high amounts of unreacted siloxane which is difficult to remove due to slow initiation of the reaction. We have prepared an alternative PDMS based macroinitiator by a condensation reaction which is capable of initiating a controlled polymerisation reaction of vinyl monomer and yielding a well defined polymer or copolymer, and which is more reactive than the aforementioned prior art PDMS based macroinitiator and leaves little or no unreacted siloxane remaining in the product.

The word "comprises" where used herein is used in its widest sense to mean and to encompass the notions of "includes", "comprehends" and "consists of".

According to the present invention there is provided use of an initiator for initiating controlled polymerisation reactions, the initiator having at least one group -D-CR⁸ ₂X' and comprising units of the formulae (R⁷ ₃Si0_1/2) , (R⁷ ₂Si0_2/2) , (R⁷Si0_3/2) , and/or (Si0_4/2) , wherein D is a divalent straight chain or branched alkylene group containing an oxygen or nitrogen heteroatom and/or substituted by a carbonyl group, each R⁸ is independently an alkyl group or a hydrogen atom, X' is a halogen atom, and each R⁷ is independently a group - D-CR⁸ ₂X' or an optionally substituted hydrocarbon group. The initiator may be a linear, branched, cyclic or resinous siloxane.

R⁷ may be an alkyl group, (e.g. a methyl, ethyl, propyl or butyl, pentyl or hexyl group) , a substituted alkyl group, (e.g. a fluoropropyl group), an alkenyl group, (e.g. a vinyl or hexenyl group) , an aryl group (e.g. a phenyl group) , an aralkyl group (e.g. a benzyl group) or an alkaryl group (e.g. a tolyl group), and is preferably a

alkyl group. Preferably, at least one group R⁸ in each group -D- CR⁸ ₂X' is an alkyl group, i.e. X' is preferably a secondary or tertiary halogen atom, more preferably both groups R⁸ in each group -D-CR⁸ ₂X' are alkyl groups, i.e. X' is more preferably a tertiary halogen atom. In a particularly preferred embodiment each R⁸ is a methyl group. X is preferably a bromine atom. Preferred examples of divalent group D include

wherein R⁹ is an alkyl group, for example a methyl group, or a hydrogen atom, each R¹⁰ is independently a straight chain or branched alkylene group, and r is an integer of from 1 to 4.

Preferred initiators used in the present invention have the formula R⁷ ₃SiO (SiR⁷ ₂0) _qSiR⁷ ₃ wherein R⁷ is as defined above and q is 0 or a positive integer, for example from 10 to 100.

Particularly preferred initiators have the general formula (VIII) :

(VIII)

wherein R⁷, R⁸, D, X' and q are as defined above. Examples of initiators of formula (VIII) are

and

wherein s is 0 or a positive integer, for example from 1 to 100, and t is a positive integer, for example from 1 to 10.

The initiator used in the present invention may be made by a method which comprises performing a condensation reaction between (i) a siloxane having at least one group R¹¹ and comprising units of the formulae (R^1:L ₃Si0_1/2) , (R^ι:L ₂Si0_2/2) , (R^1:1Si0_3/2) , and/or (Si0_4/2) wherein at least one group R¹¹ is an amino-, hydroxy- or alkoxy- group, or an amino- , hydroxy- or alkoxy-substituted alkyl group and the remaining groups R¹¹ are each independently a group R⁷ as previously defined, and (ii) a compound X'CR⁸ ₂-E wherein E is a group capable of participating in a condensation reaction with the amino-, hydroxy- or alkoxy- group, or an amino-, hydroxy- or alkoxy- substituted alkyl group to form a divalent straight chain or branched alkylene group containing an oxygen or nitrogen heteroatom and/or substituted by a carbonyl group, and R⁸ and X' are as previously defined.

The particular reagants (i) and (ii) defined above to be used in the method of making the initiator will of course depend upon the particular initiator to be made. For example, to make an initiator in which divalent group D previously defined comprises a peptide linkage, the condensation reaction may be performed between an aminoalkyl substituted siloxane and an acyl halide:

By way of further example, if divalent group D is to comprise a carboxy linkage then the condensation reaction may be performed between a hydroxyalkyl substituted siloxane and an acyl halide:

The condensation reaction may be performed at room temperature or above, for example from 50 to 100°C.

According to the present invention the initiator is used for initiating controlled polymerisation reactions, especially controlled polymerisation of vinyl containing monomers, such as those described in WO 96/30421, WO 97/18247, WO 98/01480 and Chem. Commun., 1999 99-100

(Haddleton et al) . The present initiator is capable of initiating a controlled polymerisation reaction of vinyl monomer to yield a well defined polymer or copolymer. It is more reactive than the aforementioned prior art PDMS based macroinitiators and leaves little or no unreacted siloxane remaining in the product .

We have found that the initiator is particularly effective for controlled polymerisation of vinyl monomers when used together with a particular catalyst composition which is solid at room temperature and comprises a transition metal or transition metal compound having on average more than one ligand co-ordinated thereto, each ligand being supported by a support via a divalent group R, wherein R is an optionally substituted C₁-C₂₀ straight chain, branched, or cyclic alkylene group, arylene, alkarylene or aralkylene group .

The transition metal may, for example, be selected from copper, iron, ruthenium, chromium, molybdenum, tungsten, rhodium, cobalt, rhenium, nickel, manganese, vanadium, zinc, gold and silver. Suitable transition metal compounds include those having the formula MY wherein M is a transition metal cation and Y is a counter anion. M is preferably selected from Cu(I), Fe(II), Co (II), Ru(II) and Ni(II), and is most preferably Cu(I) . Y may be, for example, Cl , Br, F, I, N0₃, PF₆, BF₄, S0₄, CN, SPh, SCN, SePh or triflate (CF₃S0₃) , and is most preferably Cl or Br.

The catalyst composition comprises on average greater than one ligand co-ordinated with the transition metal or transition metal compound, and preferably has at least two co-ordinated ligands. Suitable ligands include C- , N- , O- , P-, and S- containing ligands which can co-ordinate with the transition metal or transition metal compound. WO 97/47661, WO 96/30421, WO 97/18247 and WO 98/01480 disclose many examples of suitable ligands. Preferred ligands are those which contain an organodiimine group, in particular a 1, 4 -diaza-1, 3 -butadiene of formula (I),

a 2, 2 ' -bipyridine of formula (II)

(ID

a pyridine-2-carboxaldehyde imine of formula (III) ,

(III)

an oxazolidone of formula (IV)

or a quinoline carbaldehyde of formula (V) ,

(V)

wherein each R¹ is independently a hydrogen atom, an optionally substituted C^-C^ straight chain, branched, or cyclic alkyl group, aryl, alkaryl, aralkyl group or halogen atom. Preferably, R¹ is a hydrogen atom or an unsubstituted C₁-C₁₂ alkyl group. Each R² is independently an R¹ group, a C_j^-C_ao alkoxy group, N0₂-, CN- , or a carbonyl group.

One or more adjacent R¹ and R² groups, and R² and R² groups, may form C₅-C₈ cycloalkyl, cycloalkenyl, polycycloalkyl, polycycloalkenyl or cyclic aryl groups, for example cyclohexyl, cyclohexenyl or norbornyl groups. The 2-pyridinecarbaldehyde imine compounds of formula (III) may comprise fused rings on the pyridine group.

A preferred organodiimine containing group is of formula (III) wherein each R² is a hydrogen atom.

Divalent group R is preferably a

unsubstituted straight chain or branched alkylene group, for example a propylene group, or an aralkylene or alkarylene group, for example a benzylene or tolylene group. The support may be an inorganic or organic network or polymer. Suitable inorganic networks or polymers consist of oxides of Si, Zr, Al or Ti, including mixed oxides thereof, for example a zeolite. A preferred inorganic support is a siloxane polymer or network having units of the formula (R³ ₃Si0_1/2)_a(R³ ₂Si0_2/2)_b(R³Si0_3/2)_c(Si0_4/2)_d wherein each R³ is independently an alkyl group, preferably a methyl group, a hydroxyl group or alkoxy group, a, J , c and d are each independently 0 or a positive integer, and a+b+c+d is an integer of at least 10. The siloxane polymers and networks may be formed by polymerisation or cross-linking of silicon- containing monomers or oligomers, for example organofunctional silanes, silicas, and organocyclosiloxanes having the formula (R⁴ ₂SiO) _e wherein R⁴ is an alkyl group, for example a

alkyl group, most preferably a methyl group . Suitable organic network or polymer supports may comprise any organic material which will render the catalyst composition solid at room temperature and will not hinder any polymerisation reaction which the catalyst composition is to catalyse . Examples of suitable organic networks or polymers include polyolefins, polyolefin halides, oxides and glycols, polymethacrylates, polyarylenes and polyesters .

The ligands may be physically or chemically attached to the support via divalent group R; however, chemical bonding of the ligands to the support via divalent group R is preferred.

Particularly preferred catalyst compositions for catalysing controlled polymerisation reactions which are initiated according to the present invention are according to formula (VI) and (VII),

(VI) (VII) wherein the siloxane polymer or network has units of the formula (R³ ₃Si0_1/2) _a (R³ ₂Si0_2/2) _b (R³Si0_3/2) _c (Si0_4/2) _d, R³, a, J, c and d are as defined above and n is a positive integer.

The catalyst composition may be made by conventional methods known to those persons skilled in the art. The molar ratios of reagents to be used to make the catalyst composition must be such that in the catalyst composition the transition metal or transition metal compound has on average more than one ligand co-ordinated thereto.

By way of example, organodiimine containing groups which are diazabutadienes may be prepared by reaction of glyoxal with aniline derivatives:

wherein X is a leaving group, for example a hydroxy or alkoxy group or a halogen atom, which diazabutadienes may then react with a suitable support material and transition metal compound to form the catalyst composition, for example :

wherein n is as defined above.

By way of further example, organodiimine containing groups which are pyridine-2-carboxaldehyde imines of formula (III) above may be made by reaction of ethanolamine with pyridine-2-carboxaldehyde :

The pyridine-2-carboxaldehyde imine may then be reacted with a suitable support material Z and transition metal compound to form the catalyst composition, as illustrated above .

The catalyst composition hereinabove described in detail has an advantage over the aforementioned prior art controlled polymerisation methods in that the catalyst composition is a solid at room temperature and is thus recoverable from the polymer product and is reusable, and allows for a high degree of control over the polymerisation reaction. Particularly advantageous catalyst compositions are those which are a solid at room temperature but which have a melting point at a temperature lower than the temperature at which the polymerisation reaction occurs. Particularly effective polymerisation reactions may be performed in this way when the catalyst composition is a fluid in the reaction mixture at the reaction temperature and thus the transition metal compound may more easily blend into the reaction mixture to effect catalysis of the reaction. As the temperature of the product cools after the reaction has occurred to below the melting point of the catalyst composition the catalyst may solidify and be recovered from the reaction mixture. The vinyl containing monomer to be polymerised may be a methacrylate, an acrylate, a styrene, methacrylonitrile or diene . Examples of vinyl containing monomers include methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, and other alkyl methacrylates, and the corresponding acrylates, including organofunctional methacrylates and acrylates, including glycidyl methacrylate, trimethoxysilyl propyl methacrylate, allyl methacrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, dialkylaminoalkyl methacrylates, and fluoroalkyl (meth) acrylates . Other suitable vinyl containing monomers include methacrylic acid, acrylic acid, fumaric acid and esters, itaconic acid (and esters) , maleic anhydride, styrene, α-methylstyrene, vinyl halides, for example vinyl chloride and vinyl fluoride, acrylonitrile, methacrylonitrile, vinylidene halides of the formula CH₂=C (halogen) ₂ wherein the halogen may be Cl or F, optionally substituted butadienes of the formula CH₂=CR⁵-CR⁵=CH₂ wherein each R^s is independently H, a C^C^ alkyl group, Cl or F, acrylamide or derivatives thereof of the formula CH₂=CHCONR⁶ ₂ and methacrylamide or derivatives thereof of the formula CH₂=C (CH₃) CONR⁶ ₂ wherein R^s is H, a C-_L-C-_LO alkyl group or Cl . Mixtures of different monomers may also be used. Polymerisation may take place under an inert atmosphere, for example under argon or nitrogen.

The catalyst composition may be used in an amount of from 1 to 50%, preferably from 1 to 20%, more preferably from 5 to 10% by weight of the monomer. A variety of polymers and copolymers can be produced by controlled polymerisation reactions initiated according to the present invention. A large variety of monomers may be polymerised to afford homopolymers , random or gradient copolymers, periodic copolymers, block copolymers, functionalised polymers, hyperbranched and branched polymers, graft or comb polymers, and polysiloxane-organic copolymers. Polysiloxane-organic copolymers have a number of potential applications; for example, polysiloxane- polyhydroxyalkyl acrylate block and graft copolymers are used in soft contact lens applications, polysiloxane- aminoacrylate copolymers are usable as antifoam and anti-dye transfer agents, and polysiloxane-aminoacrylate copolymers having a short aminoacrylate block are usable as textile treating agents, polyalkoxysilylalkylacrylate-polysiloxane and polyepoxyglycidylacrylate-polysiloxane copolymers are usable as additives for epoxy resins, curable powder coatings and sealants, long alkyl methacrylate or acrylate- polysiloxane copolymers are usable as surface modifiers or additives for polyolefins and polyester-polyacrylate copolymers, and the ABA methacrylate or acrylate- polysiloxane block copolymer may be usable as a plasma crosslinkable oxygen barrier coating, and phosphobetaine or sulphobetaine-polysiloxane ionomers are biocompatible, for example for use in shampoos and other hair treating agents. The present invention will now be illustrated by way of example . Reference Example 1 - preparation of bromoisobutyrylamide end-capped polydimethylsiloxane (PDMS) macroinitiator

To a solution of 9. Og (62.9mmol) of tetramethylazasila- cyclopentane in 40ml of toluene under N₂ in a 250 ml flask equipped with a magnetic stirrer, condenser and addition funnel was added dropwise 100. Og of hydroxy terminated PDMS (degree of polymerisation (Dp) = 45) in 40ml toluene at room temperature. After heating for 2 hours at 50°C volatile materials were removed under vacuum to afford 93. Og of colourless liquid. Analysis by ¹³C, ²⁹Si NMR and FTIR confirmed the liquid to be amine end-capped PDMS (Dp=45) .

Then, to 30g of the amine end-capped PDMS in 50ml triethylamine in a 100ml flask equipped with a magnetic stirrer, condenser and addition funnel was added dropwise under N₂ 4.25g (18.5mmol) of bromoisobutyrylbromide in 20ml toluene at room temperature. The mixture was kept at 90°C for 1 hour with stirring prior to filtration of salts and evaporation of solvents under vacuum. The polymer was washed with toluene and water. The organic phase was dried with magnesium sulphate, filtered and volatiles removed to afford 27.8g (86% yield) of a pale yellow liquid. ¹H, ¹³C and ²⁹Si NMR characterisation of the liquid confirmed the formation of N-bromoisobutyryl, N-methylamino, 2-methyl propyl endblocked PDMS (Br (CH₃) ₂CCON (CH₃) CH₂CH (CH₃) CH₂) - ) . Reference Example 2 - preparation of first solid supported copper catalyst

20. Og (186.7mmol) of 2-pyridine carboxyaldehyde and 10.7g (74.6mmol) of CuBr were mixed in 62ml of tetrahydrofuran in a 100ml flask equipped with a magnetic stirrer and a condenser. Insoluble material was dissolved by addition of 33.5g (186.8mmol) of 3-aminopropyltrimethoxy- silane. The reaction was exothermic forming a deep red solution, which was allowed to cool to room temperature prior to the addition of 0.07g (1.9mmol) of NH₄F diluted in 1.7ml water. The solution was then heated under stirring at 60°C for 24 hours. Volatile materials were evaporated under vacuum and the resulting solid was ground, washed with ether and dried in vacuo at 80°C to afford 45.5g of brown-red powder (Cu (%m/m) =8.92%, insoluble in toluene, xylene and acetone) .

Example 1 - polymerisation of methylmethacrylate 5.39g (53.9mmol) of methylmethacrylate (MMA) in 11.5ml of anhydrous p-xylene was added to 0.66g of the catalyst prepared in Reference Example 2 above in a schlenk tube . The mixture was deoxygenated by a single freeze-pump-thaw cycle prior to addition of 1. Og of the macroinitiator prepared in Reference Example 1 above at room temperature. The solution was heated at 90°C for 6 hours under N₂ and samples were taken against time for ^XH NMR analysis. The final polymer and catalyst were separated by simple filtration on paper. The polymer was dried under vacuum to afford 3.9g of a pale yellow solid. The degree of conversion of the monomer observed by ¹H NMR was 59%. The catalyst was washed with toluene and ether and dried in vacuo to afford 0.51g of active copper catalyst, reusable for further polymerisations. The results are given in Table 1 below and show a very good correlation between theoretical and experimental molecular weight and hence controlled polymerisation:

Mn = number average molecular weight

Mn_th = theoretical number average molecular weight

Example 2 - polymerisation of MMA using recycled catalyst

4.01g (40.1mmol) of MMA in 8.6ml of anhydrous p-xylene was added to 0.49g of copper catalyst recycled from Example 1 above in a schlenk tube. The mixture was deoxygenated by a single freeze-pump-thaw cycle prior to addition of 0.744g of the macroinitiator prepared in Reference Example 1 above.

The solution was heated at 90°C for 24 hours under N₂ and samples were taken against time for ¹H NMR analysis. The results are given in Table 2 below and show a good correlation between theoretical and experimental molecular weight and hence controlled polymerisation:

capped PDMS macroinitiator

51g PDMS having -Si (CH₃) ₂- (CH₂) ₂-o- (CH₂) ₃CH₂OH terminal units and a number average molecular weight of 2084 (0.049 mole of OH) and 5.43g (0.053mol) of triethylamine were placed into a 100ml flask equipped with a magnetic stirrer a condenser and an addition funnel containing 20ml of toluene. 12.37g (0.053 mole) of bromobutyratebromide was added dropwise at room temperature and the reaction was allowed to react overnight at room temperature prior to filtration of salts and evaporation of solvents. The polymer was washed with toluene and water. The organic phase was dried with magnesium sulphate, filtrated and volatiles removed under reduced pressure. The ¹H NMR spectrum confirms the total disappearance of the carbinol function (δ=3.56ppm) and the appearance of -Si (CH₃) ₂- (CH₂) ₂-o- (CH₂) ₃CH₂OCOC (CH₃) ₂Br at 4.19ppm.

Reference Example 4 - preparation of second solid supported copper catalyst

100.4g (560.0mmol) of 3-aminopropyltrimethoxysilane and 63. Og (558.2mmol) of 2-pyridine carboxyaldehyde were mixed in a 11 flask equipped with a magnetic stirrer and a condenser. After stirring for 10 minutes 26.8g (186.8mmol) of CuBr, 170.4g (1119.4mmol) tetramethoxysilane, 45.2g (2511.1mmol) water and 0.6g (16.2mmol) NH₄F were successively added to the flask. A strong exotherm was observed affording an homogenous dark solution at room temperature. After 48 hours the solution gelled to a soft gel . The solids were aged for one week before removing volatiles by evaporation under vacuum. The resulting solid was ground, washed with ether and dried in vacuo at 80°C for 8 hours to afford 202.5g of a brown-red powder.

Example 3 - polymerisation of MMA

190g (1.9mol) of MMA in 300ml of anhydrous p-xylene was added to lOg of the catalyst prepared in Reference Example 4 above (previously extracted with p-xylene for 6 hours in a soxhlet) in a 500ml schlenk tube. The mixture was deoxygenated by a single freeze-pump-thaw cycle and heated at 90°C prior to addition of lOg of the macroinitiator prepared in Reference Example 3 above. The reaction was continued for 30 hours at 90°C. Samples were taken against time for ¹H NMR analysis. During polymerisation the solution became very viscous but remained clear and the catalyst remains visible in the polymer solution. After polymerisation the solid catalyst was filtered out. The degree of conversion of the monomer observed by H NMR was 44%, and the Mn as measured by 1H NMR was 20,900. The catalyst was extracted with p-xylene in a soxhlet for 6 hours, reusable for further polymerisations. GPC analysis of the polymer showed a narrower molecular weight distribution (Mn_th/Mn = 1.29) compared to the starting polysiloxane macroinitiator (Mn_ch/Mn = 1.5).

Example 4 - polymerisation of MMA using recycled catalyst

30g (0.3mol) of MMA in 30ml of anhydrous p-xylene was added to 2.3g of the catalyst collected from Example 3 above (previously extracted with p-xylene for 6 hours in a soxhlet) in a 100ml schlenk tube. The mixture was deoxygenated by a single freeze-pump-thaw cycle and heated at 90°C prior to addition of 3g of the macroinitiator prepared in Reference Example 3 above. The reaction was continued for 44 hours at 90°C. Samples were taken against time for ^XH NMR analysis. During polymerisation the solution becomes very viscous but remains clear and the catalyst remains visible in the polymer solution. After polymerisation the solid catalyst was filtered out. The results are shown in Table 3 below and show an excellent correlation between theoretical and experimental molecular weight and hence controlled polymerisation. :

Reference Example 5 - preparation of third solid supported copper catalyst

5g (0.01 mole -NH₂) of aminomethylpolystyrene and 1.2g (0.012 mole) of pyridinecarboxyaldehyde were added to a 100ml flask containing 50ml diethylether at room temperature and allowed to react overnight under nitrogen. After the reaction, a yellow powder was collected, washed with dichloromethane and toluene and dried at 65°C for 2 hours. 4.5g of the powder was mixed with 1.02g of CuBr in 50ml of acetone and agitated until all the powder turned black. The reaction was continued under acetone reflux for 3 hours. After the reaction, the powder was washed with water and extracted with methanol in a soxhlet for 7 hours. Solid state ¹³C NMR confirmed the presence of imine groups and the absence of amine groups .

Example 5 - polymerisation of MMA

20ml of anhydrous p-xylene and lOg (1.9mole) of MMA were added to a 100ml schlenk tube containing 5.3g of copper catalyst prepared according to Reference Example 5 above . The mixture was deoxygenated by a single freeze-pump-thaw cycle and then heated at 90°C prior to addition of l.Olg of PDMS macroinitiator prepared in Reference Example 3 above. The reaction was continued for 5 hours at 90°C and sampled against time. During polymerisation the solution became very viscous but remained clear. The catalyst particles are visible in the polymer solution. After 5 hours of polymerisation, ^XH NMR studies measured 33% monomer conversion and Mn=7100.

Example 6 - polymerisation of MMA

47.4g (0.47mol) of MMA in 50ml of anhydrous p-xylene was added to 19.4g of copper catalyst prepared according to Reference Example 4 above in a 250ml schlenk tube. The mixture was deoxygenated by a single freeze-pump-thaw cycle and heated at 90°C prior to addition of 5. Og of the macroinitiator prepared according to Reference Example 3 above. The reaction was continued for 4 hours at 90°C under N₂. Samples were taken against time for H¹ NMR analysis. During polymerisation the solution becomes very viscous and the catalyst remains visible in the polymer solution. The results are shown in Table 4 below and show a very good correlation between theoretical and experimental molecular weight and hence controlled polymerisation. :

Reference Example 6 - preparation of PDMS macroinitiator having pendant bromoisobutyrate groups. A 500 ml 3-neck reaction flask equipped with a dropping funnel, a thermometer and a magnetic stirrer was charged with 80.5 g of dimethylethoxy end-blocked dimethylmethyl (aminopropyl) siloxane having a degree of polymerisation of 100 and containing 0.018 mole NH₂, and 100 ml of p-xylene. After homogenisation, 3.35 ml (0.024 mole) of triethylamine was added and 5.53 g (0.024 mole) of bromo- isobutyryl bromide were injected slowly at room temperature. The reaction was allowed to proceed for 3 hours at 50° C under agitation. After reaction, p-xylene was evaporated prior the addition of 300 ml of n-hexane to precipitate the triethylammonium salt. This step was followed by filtration and evaporation of hexane . The product was a clear yellow and very viscous polymer. The disappearance of amine functionality was confirmed by ¹H NMR spectroscopy, the peak of CH₂CH₂NH₂ shifts from 3.99 ppm to 3.30 ppm and a new signal corresponding to -NH-COC (CH₃) ₂Br appears at 6.99 ppm. The bromination yield =100 % although some terminal ethoxy groups are hydrolysed .

Reference Example 7 - preparation of fourth solid supported copper catalyst A 2000 ml 3-neck reaction flask equipped with a dropping funnel, a thermometer and a reflux condenser was charged with 246 g (1.37 mole) of aminopropyltrimethoxy- silane and 300 ml of p-xylene. Then, 75 g (4.16 mole) of water was added over 60 minutes whilst distilling off methanol . After methanol removal, p-xylene is stripped off under reduced pressure to yield a white brittle solid. 84 g of the solid and 300 ml of p-xylene were then charged into a 1000 ml reaction flask and 70 g (1.0 mole) of 2-pyridine carboxyaldehyde was added slowly with cooling. After addition of the 2-pyridine carboxyaldehyde, 57 g of CuBr was added under strong agitation keeping the temperature below 30°C. The agitation was maintained until the total disappearance of the green colour characteristic of free Cu(I) . After the reaction, the solid was separated from the solvent, washed with toluene and used without further extraction. Theoretical CuBr w/w % = 29.

Example 7 - polymerisation of MMA A 250 ml Schlenk reaction flask was charged with 2.65 g (0.76 mole) of catalyst prepared in Reference Example 7 above and 4.85 g(1.2 mmole)of the macroinitiator prepared in Reference Example 6 above. The contents of the flask were vacuum dried at 80°C to remove oxygen and then covered by a nitrogen blanket. 28 g of MMA was then added under nitrogen. The mixture was deoxygenated by three freeze-thaw pump cycles in liquid nitrogen. The flask was then rapidly heated in an oil bath to the reaction temperature of 90°C. During the polymerisation reaction the viscosity increases and the solid particles of the catalyst remain in the polymer solution as a suspension. After polymerisation, the polymer solution is filtered, the residual monomer evaporated and the polymer analysed by ^XH NMR and/or by SEC to determine the average number molecular weight and the polydispersity . Based on a 100% monomer conversion and a total macroinitiator conversion, the theoretical degree of polymerisation is 233. From ^XH NMR calculation, the experimental degree of polymerisation is 113 after 4 hours.

Reference Example 8 - preparation of bromoisobutyrylamide functional MT resin macroinitiator

To a solution of 100. Og (1.45 mol) of MeSi0_3/2 resin containing 3.6 wt% of OH functionality in 200 ml of toluene under N₂ in a 500 ml flask equipped with a magnetic stirrer, condenser and addition funnel, was added dropwise 32.2g (225.2 mmol, in excess) of tetramethylazasilacyclopentane in 50 ml toluene at room temperature. After heating for 1 hour at 60°C volatile materials were removed under vacuum to afford 114. Og of colourless liquid. Analysis by ¹³C, ²⁹Si NMR and FTIR confirmed the liquid to be an amine functional MT resin containing 4.75 wt% of -NMeH functionality.

Then, to 112.7g of the amine functional MT resin in 200ml triethylamine in a 500ml flask equipped with a magnetic stirrer, condenser and addition funnel was added dropwise under N₂ 50. Og (217.5 mmol, in excess) of bromoisobutyrylbromide in 150ml toluene at room temperature. The mixture was kept at 60°C for 2 hours with stirring prior to filtration of salts and evaporation of solvents under vacuum. The functionalised MT resin was washed with toluene and water. The organic phase was dried with magnesium sulphate, filtered and volatiles were removed to afford 108.2g of a yellow viscous liquid. ¹H, ¹³C and ²⁹Si NMR characterisation of the liquid confirmed the formation of N- bromoisobutyryl, N-methylamino, 2-methylpropyl functional MT resin (Br (CH₃) ₂CCON (CH₃) CH₂CH (CH₃) CH₂) - ) containing 9.89 wt% of Br.

Reference Example 9 - preparation of fifth solid supported copper catalyst A 500 ml 3 -neck reaction flask equipped with a dropping funnel, a thermometer and a reflux condenser was charged with 50g (279.3 mmole) of aminopropyltrimethoxy silane and 200 ml of p-xylene. 18g (1.25 moles) of water was added over a period of 60 minutes whilst distilling off methanol. After methanol removal, p-xylene was removed under reduced pressure to yield a white solid. 200ml of toluene was then added to the solid, and the flask equipped with Dean & Stark apparatus . Water was azeotropically distilled from the reaction by heating at 120°C for 4 hours. Toluene was removed under reduced pressure to yield a white brittle solid, which was extracted for 4 hours with p-xylene in a Soxhlet extractor, followed by drying in a vacuum oven for 4 hours at 120°C. lOg of the white solid and 50 ml of p-xylene were charged into a 250ml reaction flask and 8.6g (69.9 mmole) of 2-pyridine carboxyaldehyde was added slowly and left overnight to react. An orange solid was recovered by filtration and washed with p-xylene.

8.6g of the orange solid, 3.5g CuBr (24.5 mmole), and 30ml of p-xylene were added to a 100ml flask and heated at 80°C for 4 hours. After cooling, the solvent was colourless, and absent of green colour characteristic of free CuBr. The reaction product was filtered to obtain a black solid which was extracted for 4 hours with p-xylene in a Soxhlet extractor and dried in a vacuum oven at 50°C for 6 hours. (Theoretical CuBr% ( w/w) = 35) .

Example 8 - polymerisation of MMA

2.7g (1.17 mmole) of macroinitiator prepared in Reference Example 8 and 3.55g of catalyst prepared in

Reference Example 9 were weighed into a Schlenk vessel and deoxygenated by exposure to a vacuum for 30 minutes. 23.6g (0.236 mole) of distilled methymethacrylate was added under nitrogen and degassed by three freeze-pump-thaw cycles. The solution was heated at 90°C for 195 minutes and samples removed. During polymerisation the solution became highly viscous, which prevented the removal of samples. After 195 minutes of polymerisation, 77% monomer conversion was measured by ^XH NMR.

Claims

1. Use of an initiator for initiating controlled polymerisation reactions, the initiator having at least one group -D-CR⁸ ₂X' and comprising units of the formulae

(R⁷ ₃Si0_1/2) , (R⁷ ₂Si0_2/2) , (R⁷Si0_3/2) , and/or (Si0_4/2) , wherein D is a divalent straight chain or branched alkylene group containing an oxygen or nitrogen heteroatom and/or substituted by a carbonyl group, each R⁸ is independently an alkyl group or a hydrogen atom, X' is a halogen atom, and each R⁷ is independently a group -D-CR⁸ ₂X' or an optionally substituted hydrocarbon group.

2. Use according to Claim 1 wherein at least one group R⁸ in each group -D-CR⁸ ₂X' is an alkyl group.

3. Use according to Claim 2 wherein both groups R⁸ in each group -D-CR⁸ ₂X' are alkyl groups.

4. Use according to any one of Claims 1 to 3 wherein the initiator has the formula R⁷ ₃SiO (SiR⁷ ₂0) _qSiR⁷ ₃ wherein R⁷ is as defined above and q is 0 or a positive integer.

5. Use according to Claim 4 wherein the initiator has the formula (VIII) :

(VIII) wherein R⁷, R⁸, X', D and q are as previously defined.

6. Use according to any preceding Claim wherein each R⁷ is a alkyl group and D is selected from the groups:

)_r

wherein R⁹ is an alkyl group or a hydrogen atom, each R¹⁰ is independently a straight chain or branched alkylene group, and r is an integer of from 1 to 4.

7. Use according to Claim 6 wherein the initiator is selected from

and

wherein s is from 40 to 45 and t is 4.

8. Use according to any preceding Claim for initiating controlled polymerisation of vinyl containing monomers.