Synthesis of Functionally-Terminated Oligomers by Free Radical Ring-Opening Polymerization

Abstract

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...

Ring-opening polymerization of heterocycles bearing substituted and unsubstituted exo-methylene groups - a review

“…This may be due to the fact, that the parent compound 2-methylene-pyrane 72 was found to be an unsuitable monomer for ring-opening reactions. Reference like [1,3,4,11], report only 4 -8% ring-opening at 120 8C (DtBPO) combined with the statement, that generally the radically induced ring-opening of cyclic ethers should be less extensive than those of comparable ketene acetals possessing the same ring size. Unfortunately no further information is enclosed so that the overall situation remains somewhat unclear.…”

“…In contradiction cationic initiators like BF 3 , AlCl 3 and I 2 produce mixed structures without any remarkable dependence on conditions [45]. The following mechanism was established and repeatedly proved [1,3,7,8] (Eq. (11)).…”

“…Although they only have 3 poten- (1) (2) (3) tial positions available for substitution, a wide variety of compounds is synthetically accessible. As expected fivemembered cycles should exhibit a less complicated polymerization mechanism that is easier to study than those of e. g. spiroortho monomers.…”

Synthesis of heterotelechelic polymers by free radical addition-fragmentation chain transfer

“…Some end-groups obtained by such a system may be useful for further modification (e. g., quaternization of amine to give a hydrophilic head-group) or may be the basis of ionic association with polymers containing acid groups [29]. Bailey et al, who pioneered elsewhere the radical ring-opening polymerization technique [8], proposed the use of open-chain ketene acetals [30] as addition-fragmentation regulators to yield x-(alkoxycarbonylmethyl) oligomers P14 (Fig. 7, Table 2) with a variety of end-groups.…”

“…The introduction of a phenyl group on one (or both) of the carbons a to an oxygen atom was used to stabilize the eliminated radical and to promote the quantitative cleavage of the transfer agent during copolymerization. The access to a,x-dihydroxytelechelic oligomers P14 (Table 2) was done in the same manner by the use of a linear ketene acetal bearing p-hydroxymethylbenzyl groups on both acetalic oxygens [30].…”