2‐Methylene‐1,3‐dioxepane 6 polymerized with a quantitative ring opening to form poly‐ϵ‐caprolactone via a free radical mechanism. On the other hand, 2‐methylene‐1,3‐dioxolane (ethylene ketene acetal) 4 and 2‐methylene‐1,3‐dioxane 5, under the same conditions, generated polymers with mixed ring‐opened and nonring‐opened structures. In copolymerization monomer 6 also showed a high tendency toward ring opening by which the ester functionality could be conveniently introduced into the backbone of the addition polymers.

The cyclic ketene acetal, 2-methylene-4-phenyl-1,3-dioxolane (3), was shown to undergo free radical ring-opening polymerization to produce the polyester, poly[y-(8-phenyl)butyrolactone].The monomer 3 was synthesized by an acetal exchange reaction of chloroacetaldehyde dimethyl acetal with styrene glycol in an 87% yield followed by dehydrochlorination of the resulting cisand trans-2-chloromethyl-4-phenyl-1,3-dioxolane (2) with potassium tert-butoxide in tert-butyl alcohol in a 70% yield. 3 was shown to undergo essentially quantitative free radical ring-opening at all temperatures from 60 -150 "C and also nearly complete regioselective ring-opening with cleavage to give the more highly stable secondary benzyl free radical. Even in free radical copolymerization with styrene, methyl methacrylate, vinyl acetate, or 4-vinylpyridine, 3 gives essentially complete ring opening to introduce an ester groups into the backbone of the addition copolymer. The structures of the polymers were established by elemental analysis and 'H and l3C NMR spectroscopy.

S i n c e f r e e radical ring-opening polymerization made p o s s i b l e t o introduce f u n c t i o n a l groups, such as esters, bonates, t h i o e s t e r s , and amides, i n t o t h e backbone of an t cara d d i t i o n polymer, it w a s reasoned t h a t simple h y d r o l y s i s of t h e s e copolymers would produce t h e d e s i r e d oligollbers t h a t could be terminated w i t h various caubinations of hydroxyl, amino, t h i o l , and carboxylgroups. Thus t h e copolymerization of Z-methylene-1,3-dioxepane and s t y r e n e (rl=0.021 and r2=22.6) gave a copolymer containing 10 mole-percent of an e s t e r -c o n t a i n i n g u n i t w i t h 100% r i n g opening a t 120OC. Hydrolysis of t h i s copolymer gave an oligomer terminated w i t h a hydroxyl group and a carboxylic a c i d group. l a r l y t h e copolymerization of 2-methylene-1,3-dioxepane and e t h y l e n e gave a series of biodegradable polyethylene copolymers c o n t a i n i n g 2.1 t o 10.4% e s t e r c o n t a i n i n g u n i t s . Hydrolysis of t h e s e copolymers gave a series of ethylene oligomers w i t h nine t o forty-seven e t h y l e n e u n i t s and terminated w i t h a hydroxyl group and a carboxylic a c i d group. By t h e same g e n e r a l method oligomers of various monomers t h a t are terminated with a methylamino S i m iCopyright 0 1984 by Marcel Dekker, Inc.979 0022-2331(l84l21084919~3 .solo Downloaded by [Michigan State University] at 22:40 25 December 2014 980 BAILEY ET AL. group and a carboxylic a c i d group from N-methyl-Z-methylene-1,3-o x a z o l i d i n e and with a t h i o l group and a carboxyl group f r o m Z-methylene-1,3-oxathiolane.When 3,9-dimethylene-l,5,7,1l-tetraoxaspiro[5.5]undecane was copolymerized w i t h a wide v a r i e t y of monomers, copolymers cont a i n i n g t h e carbonate group i n t h e backbone of t h e polymers by double r i n g opening were obtained. When s t y r e n e w a s used a s t h e ccmonomer, s t y r e n e copolymers containing 4 t o 10% carbonatec o n t a i n i n g u n i t s were obtained. Hydrolysis w i t h base gave a s e r i e s of s t y r e n e oligomers t h a t were terminated w i t h hydroxyl groups , A restudy of t h e copolymerization of d i e t h y l ketene a c e t a l w i t h s t y r e n e gave a s t y r e n e co-oligmer c o n t a i n i n g some ketene a c e t a l u n i t s but terminated w i t h an e t h y l group and a carboethoxy group. Thus p a r t of t h e ketene a c e t a l was a c t i n g as a chaint r a n s f e r agent, f u n c t i o n i n g by a n addition-elimination mechanism.When t h i s process w a s extended t o benzyl methyl ketene acetal and s t y r e n e , a s t y r e n e oligomer t h a t is terminated by a benzyl group and a carbomethoxy group r e s u l t e d .Apparently t h e high s t a b i l i t y of t h e benzyl f r e e r a d i c a l promotes complete e l i m i n a t i o n and 100% c h a i n t r a n s f e r . A t 120a, s t y r e n e and benzyl methyl ketene a c e t a l( 1 : l ) i n t h e presence of d i -m -b u t y l peroxide gave a 25% conv e...

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Abstract-Since a carbon-oxygen double bond i s considerably more s t a b l e a n a carbon-carbon double bond, i t has been possible to use t h i s d r i v i n g force to promote free r a d i c a l ring-opening polymerization o f unsaturated heterocyclic compounds. This process, f o r the f i r s t time, has permitted the i n t r o d u c t