Lactones copolymerization with cyclic ethers

When lactones copolymerize with cyclic ethers, such as j -ptopiolactone with tetrahydrofiiran, in the early steps of the reaction the cyclic ethers polymerize almost exclusively. This is due to the greater basicity of the ethers. When the concentration of the cyclic ethers depletes to the equilibrium value, their consumption decreases markedly. Polymerizations of the lactams com-mence. The products are block copolymer. 

Polyesters contain the ester group —COO— in the main chain. Many methods are suitable for their synthesis self-condensation of a,o>-hydroxy acids, ring-opening polymerization of lactones, the polycondensation of dicarboxylic acids with diols, transesterification, the polycondensation of diacyl chlorides with diols, polymerization of O-carboxy anhydrides of a- and jS-hydroxycarboxylic acids, and the copolymerization of acid anhydrides with cyclic ethers. The last reaction is commercially used in the curing of epoxides with anhydrides. 

Lactones can polymerize with cyclic ethers such as epoxides, tetrahydrofuran, oxetans and trloxane as well as Imines. The copolymerization of lactones with epoxides, for example, should lead to the formation of copolymers containing ether and ester links in the chain. 

Epoxides readily undergo anionic copolymerization with lactones and cyclic anhydrides because the propagating centers are similar—alkoxide and carboxylate [Aida et al., 1985 Cherdron and Ohse, 1966 Inoue and Aida, 1989 Luston and Vass, 1984]. Most of the polymerizations show alternating behavior, with the formation of polyester, but the mechanism for alternation is unclear. There are few reports of cationic copolymerizations of lactones and cyclic ethers other than the copolymerizations of [5-propiolactone with tetrahydrofuran and... 

A large number of copolymers of cyclic ethers, cyclic sulphides and cyclic formals have been prepared. Many cyclic compounds that will not homopolymerize do copolymerize readily [7, 146,147]. Some cyclic compounds will copolymerize with lactones, cyclic anhydrides, or vinyl monomers. Very many commercially important materials have resulted from these copolymerizations. 

Yamashita et al. [146] point out some features of the basicity of cyclic ethers. The basicity is affected by chemical structure, ring size, and substituents. The ring size affects basicity in the order 4 > 5 > 6 > 3. In 5-membered rings the basicity order is ether > lactone > formal. Methyl substitution increases the basicity and chloromethyl substitution decreases basicity. The relative basicities of the monomers are broadly in agreement with their reactivity in copolymerization experiments [58, 122]. 

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