Allylic chain transfer agents

Abstract

A process for the free radical initiated polymerization of unsaturated species characterized by the use of compound of Formula (I) as chain transfer agents: ##STR1## wherein: X is selected from hydrogen; CN; optionally substituted aryl; COOH; COOR; C(O)NHR.sup.6 ; C(O)NR.sup.7 R.sup.8 ; and halogen;Q is selected from COOR.sup.1 ; CN; and C(O)NR.sup.7 R.sup.8 ;Y is selected from hydrogen; C.sub.1 to C.sub.6 alkyl; C.sub.1 to C.sub.6 alkyl substituted with one or more substituents selected from hydroxy, amino, C.sub.1 to C.sub.6 alkoxy, C.sub.1 to C.sub.6 alkoxycarbonyl, halogen, CN and optionally substituted aryl; C.sub.1 to C.sub.6 alkenyl; and C.sub.1 to C.sub.6 alkynyl;Z is selected from COOR.sup.2 ; CN; and optionally substituted aryl;R.sup.3 and R.sup.4 are the same or different and are selected from hydrogen C.sub.1 to C.sub.4 alkyl and halogen; or R.sup.3 and R.sup.4 together with carbon atom to which they are attached form part of a carbocyclic or heterocyclic ring structure; and the other substituents are as defined in the text.

Description

This invention relates to processes for radical-initiated polymerization of unsaturated species and for the control of molecular weight of the polymers produced from such processes. Polymers of low molecule weight, or oligomers, are important as precursors in producing other polymeric materials and such polymers have been found to be useful in a variety of products, for example, in the production of high solids (low VOC) surface coatings, in adhesives and as plasticizers in polymeric composites.

In conventional polymerization practice, the manufacture of oligomers requires the use of an initiator which acts as a free radical source, and of a chain transfer agent. The chain transfer agent controls the molecular weight of the polymer by reacting with the propagating polymer radical to terminate its growth. It then initiates a new polymer chain thus transferring the growth process from one discrete polymer molecule to another discrete polymer molecule.

The most commonly used chain transfer agents are alkanethiols, which normally are associated with an objectionable odour and lead to a wide distribution of molecular weight with certain monomers. Also, the residual thiols and the end thio-ether linkage of the polymers may have an adverse effect on the properties of the ultimate product from the polymer.

The present invention helps overcome the disadvantages of polymerizations regulated with thiols by using alternative polymerization regulators. These regulars 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 polymerization system of monomers and polymerization 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.

This invention provides a process for the free radical polygon of unsaturated species to provide polymers with lower molecular weight and narrower polydispersity characterised by the use of compounds of Formula (I) as chain transfer agents. ##STR2## wherein

X is selected from hydrogen; CN; optionally substituted aryl; COOH; COOR; C(O)NHR.sup.6 ; C(O)NR.sup.7 R.sup.8 ; and halogen;

Q is selected from COOR.sup.1 ; CN; and C(O)NR.sup.7 R.sup.8 ;

Y is selected from hydrogen; C.sub.1 to C.sub.6 alkyl; C.sub.1 to C.sub.6 alkyl substituted with one or more substituents selected from hydroxy, amino, C.sub.1 to C.sub.6 alkoxy, C.sub.1 to C.sub.6 alkoxycarbonyl, halogen, CN and optionally substituted aryl; C.sub.1 to C.sub.6 alkenyl; and C.sub.1 to C.sub.6 alkynyl;

Z is selected from COOR.sup.2 ; CN; and optionally substituted aryl;

R.sup.3 and R.sup.4 may be the same or different and are selected from hydrogen, C.sub.1 to C.sub.4 alkyl and halogen; or R.sup.3 and R.sup.4 together with the carbon atom to which they are attached form part of a carbocyclic or heterocyclic ring structure;

R is selected from C.sub.1 to C.sub.18 alkyl; C.sub.1 to C.sub.12 alkyl substituted with one or more substituents selected from hydroxy, amino, C.sub.1 to C.sub.6 alkoxy, phenyl halogen, NCO, CN, and COOR.sup.5 ;

R.sup.1 and R.sup.2 may be the same or different and are selected from C.sub.1 to C.sub.18 alkyl; C.sub.1 to C.sub.12 alkyl substituted with one or more substituents selected from hydroxy, C.sub.1 to C.sub.6 acyloxy, C.sub.1 to C.sub.6 alkoxy, amino, halogen, Si(R.sup.9).sub.3, Si(OR.sup.9).sub.3, optionally substituted aryl, CN and NCO;

R.sup.5 is selected from hydrogen and C.sub.1 to C.sub.6 alkyl;

R.sup.6 is selected from hydrogen and C.sub.1 to C.sub.18 alkyl;

R.sup.7 and R.sup.8 may be the same or different and are selected from C.sub.1 to C.sub.18 alkyl; and

R.sup.9 is selected from C.sub.1 to C.sub.18 alkyl; C.sub.1 to C.sub.18 cycloalkyl; and optionally substituted aryl.

A preferred group of compounds of Formula I are the malonates with Q=COOR.sup.1 and Z=COOR.sup.2 having the Formula (IA): ##STR3## wherein:

X is selected from hydrogen; CN; optionally substituted aryl; COOH; COOR; C(O)NHR.sup.6 ; C(O)NR.sup.7 R.sup.8 ; and halogen;

Y is selected from hydrogen; C.sub.1 to C.sub.6 alkyl; C.sub.1 to C.sub.6 alkyl substituted with one or more substituents selected from hydroxy, amino, C.sub.1 to C.sub.6 alkoxy, C.sub.1 to C.sub.6 alkoxycarbonyl, halogen, CN, optionally substituted aryl; C.sub.1 to C.sub.6 alkenyl; and C.sub.1 to C.sub.6 alkynyl;

R.sup.1 and R.sup.2 may be the same or different and are selected from C.sub.1 to C.sub.18 alkyl; C.sub.1 to C.sub.12 alkyl substituted with a substituent selected from hydroxy, C.sub.1 to C.sub.6 acyloxy, C.sub.1 to C.sub.6 alkoxy, amino, halogen, optionally substituted aryl, CN and NCO;

R.sup.3 and R.sup.4 may be the same or different and are selected from hydrogen; C.sub.1 to C.sub.4 alkyl; and halogen; and

R, R.sup.6, R.sup.7 and R.sup.8 are as defined above.

Another preferred group of compounds which possess high chain transfer activities are the compounds of Formula (IB) where Q=COOR.sup.1 and Z is optionally substituted aryl: ##STR4## wherein:

X Y, R.sup.1, R.sup.3 and R.sup.4 are as defined above; and

Z is optionally substituted aryl.

The term "optionally substituted aryl" is used herein to mean an aromatic carbocyclic group which may or may not be substituted with one or more substituents that do not interfere with the polymerization process. Such substituents include alkyl, hydroxyalkyl, aminoalkyl, carboxylic acid, ester, acyloxy, amide, nitrile, haloalkyl, alkoxy, phosphonate, sulfonate, silyl or silyloxy groups.

Preferred aryl groups are phenyl or naphthyl groups.

When X is halogen, chlorine or bromine are preferred.

When R.sup.3 or R.sup.4 is halogen, chlorine or fluorine are preferred.

The following compounds of Formula I are novel and form part of the invention:

ethyl 2,4-bis(ethoxycarbonyl)-2-methyl-4-pentenoate; ethyl 2,4-bis(ethoxycarbonyl)-2-ethyl-4-pentenoate; ethyl 2-benzyl-2,4-bis(ethoxycarbonyl)-4-pentenoate; ethyl 2-ethoxycarbonyl-2-methyl-phenyl-4-pentenoate; ethyl 2-ethoxycarbonyl-2,3-dimethyl-4-(t-butoxycarbonyl)-4-pentenoate; and ethyl 2-phenyl-4-(t-butoxycarbonyl)-4-pentenoate.

The process of this invention uses the compounds of Formula (I) as alternatives to thiols or other chain transfer agents for the control of molecular weight. The process of this invention may be operated in a similar manner to conventional processes using thiols. The compounds of Formula I can be prepared easily from inexpensive starting materials. Unlike thiols, they do not, in general, possess an objectionable odour.

The materials of this invention exhibit unexpectedly good chain transfer activities in general. For example, compound ethyl 2,4-bis(ethoxycarbonyl)-2-methyl-4-pentenoate (Ib) of this invention possesses significantly higher activity when compared with the methyl 4-methoxycarbonyl-2,2-dimethyl-4-pentenoate (MMA dimer or dimethyl 2,2-dimethyl-4-methylene glutarate) (refer to Table 5) in methyl methacrylate, acrylate and styrene polymerizations. The advantages of this invention will become more apparent by referring to the illustrative non-limiting examples shown below.

Preparation of Chain Transfer Agents

The allylic malonate derivatives �Formula (IA)! are synthesized in good to excellent yield in a one-step reaction between the corresponding allylic halides (II) and malonates (IIIA). The reaction is carried out in the presence of base and solvent. Acetonitrile, N,N-dimethylformamide (DMF), dried THF or diethyl ether are suitable solvents. Although many (inorganic and organic) bases are suitable, sodium hydride, sodium alkoxide, sodamide, potassium alkoxides are preferred bases. The use of sodium hydride is found to provide better results than sodium alkoxide for the synthesis of these types of compounds. ##STR5##

Similarly, the allylic compounds of Formula IB �e.g., compound (Ii)! can be synthesized in good yield in a one-step reaction between the corresponding allylic halide (II) and arylacetate (IIIB). The reaction is carried out in the presence of base and solvent. ##STR6##

Typical compounds (Ia & Ib) used in the process of this invention and their preparation are further illustrated by the following non-limiting preparative examples.

PREPARATIVE EXAMPLE 1

Ethyl 2,4-bis(ethoxycarbonyl)-4-pentenoate (Ia) �Formula (IA), X=COOCH.sub.2 CH.sub.3 ; Y=R.sup.3 =R.sup.4 =H; R.sup.1 =R.sup.2 =CH.sub.2 CH.sub.3 !. �Typical procedure!.

To a suspension of sodium hydride (80% dispersion in oil, 0.36 g, 12 mmol) in acetonitrile (10 mL), was added diethyl malonate (1.60 g, 10 mmol). The resulting suspension was allowed to stir at room temperature for 15 minutes. A solution of ethyl .alpha.-(bromomethyl)acrylate �obtained from a modified of S. E. Drewes, G. Loizou and G. H. P. Roos, Synthetic Communications, 1987, 17(3), 291-298! (1.93 g, 10 mmol) in acetonitrile (5 mL) was then added slowly to the above suspension. Stirring was maintained for 2 hours and then the reaction mixture was poured into water, and extracted (3x) with diethyl ether. The extracts were combined and dried over anhydrous Na.sub.2 SO.sub.4, filtered and evaporated to dryness. Distillation of the crude product under reduced pressure gave (Ia) as a colourless liquid (b.p. .about.140.degree. C./0.1 mmHg) (1.90 g, .about.70%). .sup.1 H-NMR (CDCl.sub.3) .delta.(ppm) 1.21 (t, 6H), 1.25 (t, 3H), 2.85 (d, 2H), 3.67 (t, 1H), 4.15 (q, 4H), 4.20 (q, 2H), 5.60 (br. s, 1H) and 6.18 (br. s, 1H). .sup.13 C-NMR (CDCl.sub.3) .delta.(ppm) 13.98, 31.34, 50.76, 60.81, 61.37, 127.56, 136.68, 166.38 and 168.67.

PREPARATIVE EXAMPLE 2

Ethyl 2,4-bis(ethoxycarbonyl)-2-methyl-4-pentenoate (Ib) �Formula (IA), X=COOCH.sub.2 CH.sub.3 ; Y=CH.sub.3 ; R.sup.3 =R.sup.4 =H; R.sup.1 =R.sup.2 =CH.sub.2 CH.sub.3 !.

This compound was prepared using a similar procedure to that described above. Pure ethyl 2,4-bis(ethoxycarbonyl)-2-methyl-4-pentenoate (Ib) was obtained (60% yield) after column chromatography on silica-gel (diethyl ether: n-hexane 1:4 as eluent). .sup.1 H-NMR (CDCl.sub.3) .delta.(ppm) 1.20 (t, 6H), 1.25 (t, 3H), 1.33 (s, 3H, 2.95 (s, 2H), 4.15 (m, 6H), 5.56 (br. s, 1H) and 6.22 (br. s, 1H). .sup.13 C-NMR (CDCl.sub.3) .delta.(ppm) 13.91, 14.06, 35.98, 53.88, 60.78, 61.23, 128.61, 136.29, 166.67 and 171.57.

PREPARATIVE EXAMPLE 3

Ethyl 2,4-bis(ethoxycarbonyl)-2-ethyl-4-pentenoate (Ic) �Formula (IA), X=COOCH.sub.2 CH.sub.3 ; Y=CH.sub.2 CH.sub.3 ; R.sup.3 =R.sup.4 =H; R.sup.1 =R.sup.2 =CH.sub.2 CH.sub.3 !.

This compound was prepared in .about.80% yield using a similar procedure to that described in Example 1. .sup.1 H-NMR (CDCl.sub.3) .delta.(ppm) 0.85 (t, 3H), 1.20 (t, 6H), 1.30 (t, 3H), 1.85 (q, 2H), 2.95 (s, 2H), 4.15 (m, 6H), 5.58 (br. s, 1H) and 6.25 (br. s, 1H). .sup.13 C-NMR (CDCl.sub.3) .delta.(ppm) 8.58, 14.06, 14.16, 25.46, 32.98, 58.32, 60.89, 61.15, 128.42, 136.53, 167.05 and 171.09.

PREPARATIVE EXAMPLE 4

Ethyl 2-benzyl-2,4-bis(ethoxycarbonyl)-4-pentenoate (Id) �Formula (IA), X=COOCH.sub.2 CH.sub.3 ; Y=CH.sub.2 C.sub.6 H.sub.5 ; R.sup.3 =R.sup.4 =H; R.sup.1 =R.sup.2 =CH.sub.2 CH.sub.3 !.

This compound was prepared by a procedure similar to Example 1, using diethyl benzylmalonate as the starting material; the product was isolated in 76% yield as a colourless syrup. .sup.1 H-NMR (CDCl.sub.3) .delta.(ppm) 1.20 (t, 6H), 1.30 (t, 3H), 2.95 (s, 2H), 3.25 (s, 2H), 4.15 (m, 6H), 5.65 (br. s, 1H), 6.25 (br. s, 1H) and 7.20 (m, 5H). .sup.13 C-NMR (CDCl.sub.3) .delta.(ppm) 13.82, 14.11, 30.40, 39.63, 43.30, 58.75, 60.84, 61.20, 126.87, 128.11, 128.55, 130.08, 167.40 and 170.56.

PREPARATIVE EXAMPLE 5

Ethyl 4-chloro-2-ethoxycarbonyl-2-methyl-4-pentenoate (Ie) �Formula (IA), X=Cl; Y=CH.sub.3 ; R.sup.3 =R.sup.4 =H; R.sup.1 =R.sup.2 =CH.sub.2 CH.sub.3 !.

To a suspension of sodium hydride (25.2 g, 0.84 moles, 80% dispersion in oil) and diethyl methylmalonate (104.5 g, 0.60 moles) in acetonitrile (500 mL), a solution of 2,3-dichloropropene (66.6 g, 0.60 moles) in acetonitrile (100 mL) was added slowly over 20 minutes with stirring at room temperature. The resulting mixture was allowed to stir at room temperature overnight. Water (250 mL) was added, and the mixture extracted three times with diethyl ether (200 mL.times.3). The combined organic layers were washed successively with water (200 mL) and brine (200 mL), they were then dried over anhydrous MgSO.sub.4. After removal of the organic solvent, distillation of the crude product under reduced pressure afforded the product (Ie) as a colourless liquid (91.6 g, 61.5% yield), b.p. 77.degree.-78.degree. C. (0.1 mmHg). .sup.1 H-NMR (CDCl.sub.3) .delta.(ppm) 1.22 (t, 6H), 1.42 (s, 3H), 3.00 (s, 2H), 4.18 (q, 4H), 5.20 (s, 1H) and 5.30 (s, 1H).

PREPARATIVE EXAMPLE 6

Ethyl 2-ethoxycarbonyl-4-phenyl-4-pentenoate (If) �Formula (IA), X=Phenyl; Y=R.sup.3 =R.sup.4 =H; R.sup.1 =R.sup.2 =CH.sub.2 CH.sub.3 !.

This compound was prepared in .about.20% yield (not optimized according to a similar procedure to that described in Example 1. The reaction was carried out between .alpha.-(bromomethyl)styrene �obtained from the reaction of .alpha.-methylstyrene and N-bromosuccinimide in carbon tetrachloride according to the published procedure by H. Pines, H. Alul and M. Kolobielski, J. Org. Chem., 1957, 22, 1113-1114! and diethyl malonate in the presence of sodium hydride (1 eq.). .sup.1 H-NMR (CDCl.sub.3) .delta.(ppm) 1.25 (t, 6H), 3.10 (d, 2H), 3.50 (t, 1H), 4.17 (q, 4H), 5.15 (br. s, 1H), 5.35 (br. s, 1H) and 7.35 (m, 5H).

PREPARATIVE EXAMPLE 7

Ethyl 2-ethoxycarbonyl-2-methyl-4-phenyl-4-pentenoate (Ig) �Formula (IA), X=Phenyl; Y=CH.sub.3 ; R.sup.3 =R.sup.4 =H; R.sup.1 =R.sup.2 =CH.sub.2 CH.sub.3 !.

This compound was prepared in .about.60% yield by reacting .alpha.-bromomethyl)styrene �obtained by method of H. Pines, H. Alui, M. Kolobielski, J. Org. Chem., p. 1113 (1957)! and diethyl methylmalonate in the presence of sodium hydride (2 eq.) in acetonitrile solvent. .sup.1 H-NMR (CDCl.sub.3) .delta.(ppm) 1.10 (t, 6H), 1.30 (s, 3H), 3.18 (s, 2H), 3.90 (m, 4H), 5.10 (br. s, 1H), 5.27 (br. s, 1H) and 7.30 (m, 5H).

PREPARATIVE EXAMPLE 8

Ethyl 2-ethoxycarbonyl-2,3-dimethyl-4-(t-butoxycarbonyl)-4-pentenoate (Ih) �Formula (IA), X=COOC(CH.sub.3).sub.3 ; Y=CH.sub.3 ; R.sup.3 =H; R.sup.4 =CH.sub.3 ; R.sup.1 =R.sup.2 =CH.sub.2 CH.sub.3 !.

The starting material, t-butyl (Z)-2-bromomethyl-2-butenoate, was prepared via literature procedures �H. Hoffman and J. Rabe, Helvetica Chimica. Acta, 67(2), p. 413 (1984)!.

A stirred solution of diethyl methylmalonate (1.5 g, 8.6 mmol) in distilled THF was cooled to -5.degree. C. and sodium hydride (0.52 g) added portionwise. The resultant suspension was stirred below 0.degree. C. for an hour, then t-butyl (Z)-2-bromomethyl-2-butenoate added dropwise. The mixture was stirred below 0.degree. C. for a further two hours before being allowed to warm to room temperature and stirred overnight Solvent was removed under reduced pressure, water added and the product extracted with ether (3.times.50 ml), and the combined organic layers dried over anhydrous magnesium sulphate. Upon removal of ether under reduced pressure, a pale yellow oil was obtained (2.02 g, 72%). .sup.1 H-NMR spectrum revealed the presence of two isomers in a ratio of 4:1, with the preferred isomer being the major product (Ih). Column chromatography on silica gel (9:1, pet. spirit 40.degree.-60.degree. C.: ethyl acetate) gave slight separation of the two isomers. The fraction containing the highest level of ethyl-2-ethoxycarbonyl-2,3-dimethyl-4-(t-butoxycarbonyl) pent-4-enoate (Ih) was used for the following spectroscopic data. .sup.1 H-NMR (CDCl.sub.3) .delta.(ppm): 6.25, s, 1H; 5.55, s, 1H; 4.2, m, 4H; 3.7, q, 1H; 1.2-1.6, m, 21H. .sup.13 C-NMR (CDCl.sub.3) .delta.(ppm): 171.7, 171.2, 166.6, 143.5, 125.2, 80.5, 61.1, 57.5, 36.7, 28.0, 17.5, 17.0, 14.0, 13.9.

PREPARATIVE EXAMPLE 9

Ethyl 2-phenyl-4-(t-butoxycarbonyl)-4-pentenoate (Ii) �Formula (IB), X=COOC(CH.sub.3).sub.3 ; Y=R.sup.3 =R.sup.4 =H; R.sup.1 =CH.sub.2 CH.sub.3 ; Z=phenyl!

The starting allylic bromide material, t-butyl 2-(bromomethyl)propenoate was prepared via a modified procedure of S. E. Drewes, G. Loizou and G. H. P. Roos, Synthetic Communication, 1987, 17(3), 291-298 using t-butyl acrylate.

Ethyl phenylacetate (6.66 g, 40.6 mmol) was dissolved in dry THF (20 mL) and sodium hydride (1.09 g, 36.5 mmol) added portionwise. The resulting suspension was stirred at room temperature for 30 minutes then cooled on ice while t-butyl 2-(bromomethyl)propenoate (4.49 g, 20.3 mmol) was added dropwise under nitrogen atmosphere. On completion of the addition, the reaction mixture was allowed to reach room temperature then heated under reflux for 8 hours. The THF solvent was removed under reduced pressure, water added and the product mixture extracted with diethyl ether (3.times.50 mL). After removal of organic solvent, the excess ethyl phenylacetate was removed by vacuum distillation and the residue was chromatographed on a silica-gel column using 5% ethyl acetate in petroleum spirit as eluent. The pure product (Ii) was obtained as a very pale yellowish liquid (2.5 g, 41%). .sup.1 H-NMR (CDCl.sub.3) .delta.(ppm): 1.10, t, 3H; 1.45, s, 9H; 2.65, dd, 1H; 3.00, dd, 1H; 3.85, dd, 1H; 4.10, m, 2H; 5.35, s, 1H; 6.00, s, 1H; 7.25, s, 5H.

Operation of the Process

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 compound of general Formula (1) for the thiol. The proportion of compound of Formula (I) used may be in the range of 0.01 to 30 mole percent based on total monomer, with a preferred range of 0.1 to 10 mole percent

The process may be operated at any of the reaction conditions appropriate to free radical polymerization, i.e., temperatures from -100.degree. C. to 200.degree. C. and pressures from below atmospheric to substantially above atmospheric.

The polymerization process can be carried out in bulk, solution, emulsion, mupon or other conventional polymerization modes Source of radicals for polymerizations are well known in the art and they include .alpha.,.alpha.'-azobisisobutyronitrile, 4,4'-bis(4-cyanovaleric acid), 2,2'-azobis(2,4-dimethylpentanenitrile), benzoyl peroxide, t-butyl peroxybenzoate, ammonium persulfate, potassium persulfate.

Any unsaturated monomers susceptible to free radical polymerization 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, vinyl esters, vinyl aromatics, unsaturated or polyunsaturated hydrocarbons, or mixtures of these. Examples of these monomers are methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, vinyl acetate, styrene, p-chloromethylstyrene, 2-vinylpyridine, 4-vinylpyridine, N-vinylpyrrolidone, vinyl halides of the formula CH.sub.2 =CHX where X is Cl or F, vinylidene halides of the formula CH.sub.2 =CX.sub.2 wherein X is independently Cl or F, vinyl ethers CH.sub.2 =CHOR where R is alkyl and allyl monomers such as allyl ethers, allyl carbonates or diallyl carbonates.

Compounds of general Formula (I) used in the process of this invention display an unexpected high activity in controlling molecular weight in polymerization 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 values of 1.0 for batch polymerizations and this activity is not as highly dependent as that of thiols on the structure of the propagating radical.

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, oligomers, macromonomers and functional polymers for a variety of applications such as high-solids surface coatings, paints, and adhesives. Furthermore, the process can be used to enable better control over the polymerization kinetics, e.g., delaying the onset of gelation in cross-linking systems.

The operation of this process is demonstrated by the following non-limiting examples. In these examples molecular weight measurements were performed on a Waters Associates liquid chromatograph equipped with differential refractometer and six .mu.-styragel columns of 10.sup.6, 10.sup.5, 10.sup.4, 10.sup.3, 500 and 100 .ANG. pore size. Tetrahydrofuran solvent was used at a flow rate of 1 mL/min. Results were derived by comparison with polystyrene standards using the Chromatix GPC-1 program.

The conversions were determined from the mass of the polymer isolated after precipitation in solvents where appropriate or after removal of all the volatiles in vacuo, and after subtracting the mass of the chain transfer agent.

EXAMPLE 1

Polymerization of Methyl Methacrylate

.alpha.,.alpha.'-Azobisisobutyronitrile (23.4 mg) was dissolved in freshly distilled inhibitor-free methyl methacrylate (MMA) (25 mL). Aliquots (4 mL) were removed and added to ampoules containing weighed amounts of the allylic chain transfer agent of Formula (I). The contents of the ampoule were either degassed by three freeze-evacuate-thaw cycles and sealed under vacuum or by bubbling nitrogen through the solution. The mixtures were then polymerized at 60.degree. C. for one hour. The contents of the ampoules were then added dropwise to methanol and the precipitated polymers were collected and dried in a vacuum oven to constant weight. A small portion of each polymer was examined by gel-permeation chromatography (GPC) to determine its molecular weight.

TABLE 1______________________________________Molecular Weight and Conversions forMethyl Methacrylate PolymerizationsCarried Out in the Presence of Chain Transfer Agents (CTA) Temp. Time 10.sup.3 �CTA!/ %Entry CTA (.degree.C.) (hr.) �Monomer! Conv. M.sub.n.sup.#______________________________________ 1 Ia 60 1.00 0.00 15.80 327160 2 Ia 60 1.00 10.20 14.70 287300 3 Ia 60 1.00 22.80 13.30 253630 4 Ib 60 1.00 0.00 14.95 159200 5 Ib 60 1.00 16.80 13.35 104100 6 Ib 60 1.00 31.30 12.80 89900 7 Ib 60 1.00 68.30 11.20 58700 8 Ic 60 1.00 0.00 16.30 254350 9 Ic 60 1.00 14.32 12.10 19590010 Ic 60 1.00 28.37 9.95 19015011 Ic 60 1.00 56.73 8.30 15315012 If 60 1.00 0.00 14.72 26680013 If 60 1.00 9.82 2.44 8900014 If 60 1.00 19.64 1.30 6487515 If 60 1.00 38.58 1.22 5080016 Ig 60 1.00 0.00 11.49 29900017 Ig 60 1.00 9.89 4.48 11340018 Ig 60 1.00 19.03 0.42 9199019 Ig 60 1.00 36.34 1.47 5753020 Ii 60 1.00 0.00 12.74 24886021 Ii 60 1.00 9.89 11.52 13102022 Ii 60 1.00 18.15 11.61 10090023 Ii 60 1.00 34.50 10.30 71120______________________________________ .sup.# Numberaverage molecular weight determined by GPC, calibrated with polystyrene standards.

EXAMPLE 2

Polymerization of Styrene

Polymerizations of styrene (Sty) were carried out similarly for three hours at 60.degree. C. .alpha.,.alpha.'-Azobisisobutyronitrile (21.6 mg) was dissolved in freshly distilled styrene (50 mL). Aliquots (10 mL) were removed and transferred to ampoules containing weighed amounts of chain transfer agent. After the degassing and polymerization, the contents of ampoules were poured into methanol and the precipitated polymers were collected, dried, and examined as before.

TABLE 2______________________________________Molecular Weight and Conversions for Styrene Polymerizations CarriedOut in the Presence of Allylic Malonate Chain Transfer Agents and MMADimer (Methyl 4-methoxycarbonyl-2,2-dimethyl-4-pentenoate) Temp. Time 10.sup.3 �CTA!/ %Entry CTA (.degree.C.) (hr.) �Monomer! Conv. M.sub.n.sup.#______________________________________ 1 Ia 60 3.00 0.00 9.80 130000 2 Ia 60 3.00 13.20 8.40 119250 3 Ia 60 3.00 26.20 9.30 114300 4 Ib 60 3.00 0.00 8.30 127000 5 Ib 60 3.00 14.86 4.20 20400 6 Ib 60 3.00 32.78 3.65 12500 7 Ib 60 3.00 43.11 3.20 11400 8 Ih 60 3.00 0.00 8.4 103995 9 Ih 60 3.00 8.75 6.3 4375510 Ih 60 3.00 16.90 5.8 2822211 Ih 60 3.00 30.40 5.2 1868212 Ii 60 3.00 0.00 9.0 11252513 Ii 60 3.00 9.01 8.3 10266014 Ii 60 3.00 18.35 7.4 8926015 Ii 60 3.00 38.69 6.5 8094016 MMA Dimer 60 3.00 0.00 10.5 12001017 MMA Dimer 60 3.00 12.50 7.0 5985518 MMA Dimer 60 3.00 25.00 5.8 4122019 MMA Dimer 60 3.00 49.88 5.7 27830______________________________________ .sup.# Numberaverage molecular weight determined by GPC, calibrated with polystyrene standards.

EXAMPLE 3

Polymerization of Acrylate Esters

Polymerizations of methyl acrylate (MA) (or ethyl acrylate, EA) were carried out using a stock solution prepared from .alpha.,.alpha.'-azobisisobutyronitrile (6.34 mg) and distilled thiophene-free benzene (25 mL). Aliquots (6 ml) were removed and added to ampoules containing freshly distilled methyl acrylate (4 mL), thiophene-free benzene (10 mL) and weighed amounts of the activated allylic malonate chain transfer agents. After degassing, the mixtures were polymerized at 60.degree. C. for one hour; or at 80.degree. C. for 30 minutes; or at 90.degree. C. for 30 minutes. The volatiles were then removed on rotary evaporator and the polymers were dried in vacuo to constant weight and examined by GPC.

TABLE 3______________________________________Molecular Weight and Conversions for Acrylate PolymerizationsCarried Out in the Presence of Chain Transfer Agents (CTA) Mono- Temp. Time 10.sup.3 �CTA!/ %Entry mer CTA (.degree.C.) (hr.) �Monomer! Conv. M.sub.n.sup.#______________________________________ 1 MA Ia 80 0.50 0.00 38.70 183900 2 MA Ia 80 0.50 10.00 36.60 137500 3 MA Ia 80 0.50 20.60 31.90 95750 4 MA Ia 80 0.50 39.75 25.60 67400 5 EA Ib 60 1.00 0.00 8.80 235,600 6 EA Ib 60 1.00 4.33 4.60 89400 7 EA Ib 60 1.00 5.87 3.85 53100 8 EA Ib 60 1.00 12.81 2.30 33500 9 MA Ie 60 1.00 0.00 26.3 49315010 MA Ie 60 1.00 3.73 25.3 46730011 MA Ie 60 1.00 14.67 21.8 36240012 MA If 60 1.00 0.00 28.2 38845013 MA If 60 1.00 9.43 .about.0.0 3145514 MA If 60 1.00 20.61 .about.0.0 814015 MA If 60 1.00 34.18 .about.0.0 581016 MA If 80 0.50 0.00 46.0 13330017 MA If 80 0.50 8.70 0.39 2263018 MA If 80 0.50 18.10 1.60 1154019 MA If 80 0.50 34.44 .about.0.0 437520 MA Ig 60 1.00 0.00 21.44 65780021 MA Ig 60 1.00 8.84 0.47 1326022 MA Ig 60 1.00 21.32 0.14 488523 MA Ig 60 1.00 37.33 0.0 349524 MA Ig 80 0.50 0.00 17.36 18750025 MA Ig 80 0.50 9.43 0.30 796026 MA Ig 80 0.50 20.73 0.21 386027 MA Ig 80 0.50 38.79 0.12 256028 MA Ih 60 1.00 0.00 20.5 92663229 MA Ih 60 1.00 6.54 22.6 6623130 MA Ih 60 1.00 13.30 27.5 3718031 MA Ih 60 1.00 26.50 12.9 2124332 MA Ih 80 0.50 0.00 40.6 17692533 MA Ih 80 0.50 6.91 38.3 4852534 MA Ih 80 0.50 13.30 32.1 2628535 MA Ih 80 0.50 26.50 28.4 1607436 MA Ii 60 1.00 0.00 23.4 73909037 MA Ii 60 1.00 7.49 3.2 15174038 MA Ii 60 1.00 14.29 1.7 9812039 MA Ii 60 1.00 29.24 0.2 5294040 MA Ii 90 0.50 0.00 55.6 8314541 MA Ii 90 0.50 6.93 20.9 4605542 MA Ii 90 0.50 14.91 16.4 2868043 MA Ii 90 0.50 28.99 14.9 18100______________________________________ .sup.# Numberaverage molecular weight determined by GPC, calibrated with polystyrene standards.

EXAMPLE 4

Polymerization of Vinyl Acetate

Polymerizations of vinyl acetate (VAc) were carried out in vacuo at 60.degree. C. for one hour or at 80.degree. C. for one hour using the following procedure. .alpha.,.alpha.'-Azobisisobutyronitrile (20.5 mg) was dissolved in freshly distilled vinyl acetate (25 mL). Aliquots (4 mL) were removed and added to ampoules containing weighed amounts of the chain transfer agents. After the polymerization, the volatiles were removed and the polymers were dried and examined as before.

TABLE 4______________________________________Molecular Weights and Conversions for Vinyl Acetate PolymerizationsCarried Out in the Presence of Chain Transfer Agents (CTA) Temp. Time 10.sup.3 �CTA!/ %Entry CTA (.degree.C.) (hr.) �Monomer! Conv. M.sub.n .sup.#______________________________________1 Ie 80 1.00 0.00 60.2 627002 Ie 80 1.00 1.87 29.9 547003 Ie 80 1.00 3.72 18.9 383004 Ie 80 1.00 7.43 12.6 259005 Ig 60 1.00 0.00 5.37 1935006 Ig 60 1.00 12.90 0.08 82007 Ig 60 1.00 23.90 0.02 57408 Ig 60 1.00 39.10 0.03 3260______________________________________ .sup.# Polystyrene standard equivalent numberaverage molecular weight.

Table 5 summarizes the results of chain transfer constants in polymerizations of common monomers using the allylic chain transfer agents �(Ia), (Ib), (Ic), (Ie), (If), (Ig) and (Ih)!.

TABLE 5______________________________________Chain Transfer Constants (C.sub.x) for Polymerizations of CommonMonomersin the Presence of Allylic Transfer Agents and MMA Dimer Chain Transfer ConstantsCTA Monomer Conditions (C.sub.x)______________________________________Ia MMA 60.degree. C. 0.004 MA 80.degree. C. 0.020 Sty 60.degree. C. 0.004Ib MMA 60.degree. C. 0.015 Sty 60.degree. C. 0.148 EA 60.degree. C. 0.203MMA EMA 60.degree. C. 0.007Dimer EA 60.degree. C. 0.120 Sty 60.degree. C. 0.057Ic MMA 60.degree. C. 0.004Ie VAc 80.degree. C. 0.274 MA 60.degree. C. 0.005If MMA 60.degree. C. 0.060 MA 60.degree. C. 0.450 MA 80.degree. C. 0.560Ig MMA 60.degree. C. 0.040 MA 60.degree. C. 0.670 MA 80.degree. C. 0.850 VAc 60.degree. C. 7.010Ih MA 60.degree. C. 0.150 MA 80.degree. C. 0.180 Sty 60.degree. C. 0.150Ii MMA 60.degree. C. 0.029 MA 60.degree. C. 0.053 MA 90.degree. C. 0.130 Sty 60.degree. C. 0.009______________________________________

EXAMPLE 5

Polymerization of Styrene

A multi-necked reactor was equipped with a stirrer, thermocouple, and condensor. The reactor was held under nitrogen positive pressure and the following ingredients were used.

______________________________________Part 1Styrene 2 mlMEK 4 mlTransfer agent (Ib) 370 mgPart 2Styrene 8 mlMEK 12 mlPart 3AIBN l4 mgMEK 2 mlPart 4MEK 2 ml______________________________________

Part 1 was charged to the reactor and heated to 80.degree. C. When the temperature stabilized at 80.degree. C., part 2 (the monomer feed) was charged to the reactor concurrently with part 3 (the initiator feed) over 90 minutes via a syringe pump. Then part 4 was charged to the reactor as a single shot feed to rinse the syringe pump and the reaction mixture was held at 80.degree. C. for further 120 minutes. The solvent and unreacted monomer were then distilled off. The result is summarized in Table 6.

TABLE 6______________________________________ CTA(Ib) M.sub.n M.sub.w Dispersity______________________________________Control 0 20400 39350 1.93Example 5 370 mg 14900 29600 1.94______________________________________

EXAMPLES 6-8

Polymerization of n-Butyl Methacrylate/Hydroxypropyl Acrylate

A multi-necked reactor was equipped with a stirrer, thermocouple, and condenser. The reactor was held under nitrogen positive pressure and following ingredients were used in three separate polymerizations.

______________________________________PART INGREDIENTS Example 6 Example 7 Example 8______________________________________I. Xylene 20.94 g 20.94 g 20.94 g Transfer Agent Ib 0.00 g 3.47 g 6.94 gII. n-BMA 51.17 g 47.70 g 44.23 g HPA 18.23 g 18.23 g 18.23 gIII. Xylene 9.07 g 9.07 g 9.07 g VAZO 67 0.60 g 0.60 g 0.60 g______________________________________

Part I was charged to the reactor and heated to 90.degree. C. When the temperature stabilized, Part II was charged to the reactor concurrently with Part III over 240 and 260 minutes, respectively. The reaction mixture was held for 60 minutes following the completion of the feeding of Part III. The monomer conversion was determined by solids analysis and molecular weight was determined by GPC. The results are summarized in Table 7.

TABLE 7______________________________________Example Wt %Number CTA(Ib) Mn Mw Dispersity Conversion______________________________________6 0 27180 65950 2.43 100% (control)7 5.0% 16410 37940 2.31 98%8 10.0% 12730 26750 2.10 100%______________________________________

Claims

1. A process for the free radical initiated polymerization of ethylenically unsaturated monomer species characterised by the use of compounds of Formula (I) as chain transfer agents. ##STR7## wherein X is selected from hydrogen; CN; optionally substituted aryl; COOH; COOR; C(O)NHR.sup.6 ; C(O)NR.sup.7 R.sup.8 ; and halogen;

Q is selected from COOR.sup.1 ; CN; and C(O)NR.sup.7 R.sup.8 ;

Y is selected from hydrogen; C.sub.1 to C.sub.6 alkyl; C.sub.1 to C.sub.6 alkyl substituted with one or more substituents selected from hydroxy, amino, C.sub.1 to C.sub.6 alkoxy, C.sub.1 to C.sub.6 alkoxycarbonyl, halogen, CN and optionally substituted aryl; C.sub.1 to C.sub.6 alkenyl; and C.sub.1 to C.sub.6 alkynyl;

Z is selected from COOR.sup.2 ; CN; and optionally substituted aryl;

R.sup.3 and R.sup.4 may be the same or different and are selected from hydrogen, C.sub.1 to C.sub.4 alkyl and halogen; or R.sup.3 and R.sup.4 together with the carbon atom to which they are attached form part of a carbocyclic or heterocyclic ring structure;

R is selected from C.sub.1 to C.sub.18 alkyl; C.sub.1 to C.sub.12 alkyl substituted with one or more substituents selected from hydroxy, amino, C.sub.1 to C.sub.6 alkoxy, phenyl, halogen, NCO, CN, and COOR.sup.5 ;

R.sup.1 and R.sup.2 may be the same or different and are selected from C.sub.1 to C.sub.18 alkyl; C.sub.1 to C.sub.12 alkyl substituted with one or more substituents selected from hydroxy, C.sub.1 to C.sub.6 acyloxy,

C.sub.1 to C.sub.6 alkoxy, amino, halogen, Si(R.sup.9).sub.3, Si(OR.sup.9).sub.3, optionally substituted aryl, CN and NCO;

R.sup.5 is selected from hydrogen and C.sub.1 to C.sub.6 alkyl;

R.sup.6 is selected from hydrogen and C.sub.1 to C.sub.18 alkyl;

R.sup.7 and R.sup.8 may be the same or different and are selected from C.sub.1 to C.sub.18 alkyl; and

R.sup.9 is selected from C.sub.1 to C.sub.18 alkyl; C.sub.1 to C.sub.18 cycloalkyl; and optionally substituted aryl.

2. The process of claim 1 wherein X is a phenyl, substituted phenyl, chloro or bromo group.

3. The process of claim 1 wherein Y is a phenyl or substituted phenyl.

4. The process of claim 1 wherein R.sup.3 and R.sup.4 may be the same or different and are a chloro or fluoro group.

5. The process of claim 1 wherein compounds of Formula (LA) are used as chain transfer agents. ##STR8## wherein Y, R, R.sup.6, R.sup.7 and R.sup.8 are as defined in claim 1;

X is selected from hydrogen; CN; optionally substituted aryl; COOH; COOR; C(O)NHR.sup.6 ; C(O)NR.sup.7 R.sup.8 ; and halogen;

Y is selected from hydrogen; C.sub.1 to C.sub.6 alkyl; C.sub.1 to C.sub.6 alkyl substituted with one or more substituents selected from hydroxy, amino, C.sub.1 to C.sub.6 alkoxy, C.sub.1 to C.sub.6 alkoxycarbonyl, halogen, CN, optionally substituted aryl; C.sub.1 to C.sub.6 alkenyl; and C.sub.1 to C.sub.6 alkynyl;

R.sup.1 and R.sup.2 may be the same or different and are selected from C.sub.1 to C.sub.18 alkyl; C.sub.1 to C.sub.12 alkyl substituted with a substituent selected from hydroxy, C.sub.1 to C.sub.6 acyloxy, C.sub.1 to C.sub.6 alkoxy, amino, halogen, optionally substituted aryl, CN and NCO; and

R.sup.3 and R.sup.4 may be the same or different and are selected from hydrogen; C.sub.1 to C.sub.4 alkyl; and halogen.

6. The process of claim 5 wherein X is a phenyl, substituted phenyl, chloro or bromo group.

7. The process of claim 5 wherein Y is a phenyl or substituted phenyl.

8. The process of claim 5 wherein R.sup.3 and R.sup.4 may be the same or different and are hydrogen, chloro or fluoro groups.

9. The process of claim 1 wherein compounds of Formula (IB) are used as chain transfer agents: ##STR9## wherein X, Y, R.sup.1, R.sup.3 and R.sup.4 are as defined in claim 1; and

Z is optionally substituted aryl.

10. The process of claim 1 where the polymerisation occurs in solution.

11. The process of claim 1 where the polymerisation occurs in an emulsified phase.

12. The process of claim 1 when the unsaturated species are added before the polymerisation commences.

13. The process of claim 1 when the unsaturated species are added during the reaction.

14. The process of claim 1 when part of the unsaturated species are added before the start of the reaction and the remainder of the unsaturated species are added during the reaction.

15. A compound of Formula (I) as defined in claim 1 which is selected from:

ethyl 2,4-bis(ethoxycarbonyl)-2-methyl-4-pentenoate;

ethyl 2,4-bis(ethoxycarbonyl)-2-ethyl-4-pentenoate;

ethyl 2-benzyl-2,4-bis(ethoxycarbonyl)-4-pentenoate;

ethyl 2-ethoxycarbonyl-2-methyl-4-phenyl-4-pentenoate;

ethyl 2-ethoxycarbonyl-2,3-dimethyl-4-(t-butoxycarbonyl)-4-pentenoate; and

ethyl 2-phenyl-4-(t-butoxycarbonyl)-4-pentenoate.

16. A compound of Formula (1) as defined in claim 1 for use as a chain transfer agent in the free radical initiated polymerisation of unsaturated species.

17. A chain transfer agent for use in the free radical initiated polymerisation of unsaturated species which comprises a compound of Formula (I) as defined in any one of claim 1.