New Developments in Cationic and Anionic Aldehyde Polymerization

Abstract

Abstract—Aldehydes polymerize readily with cationic and anionic initiators to polyacetals. Higher aliphatic aldehydes are conveniently polymerized with anionic initiators at low temperatures, frequently to isotactic polyaldehydes. The range of known polyaldehydes has recently been extended to poly(n-dodecaldehyde). Polymers with side chains longer than C3 possess the characteristics of the crystallization of the aliphatiç side chain separate and in addition to the crystallization of the main chain. An NMR investigation of the rate of polymerization and copolymerization of chloral showed that the polymerization becomes diffusion controlled above approximately 40 % conversion. At that conversion small molecules are entrapped in the polymer matrix and individual parts of these molecules have different mobility as may be detected by NMR. Bromal has recently been polymerized at low temperatures where its crystallization was avoided by judicious selection of solvent and temperature of polymerization. The tribromomethylgroup of bromalis the largest side group of any monomer which has ever been polymerized. Dichlorobromoacetaldehyde and chiorodibromoacetaldehyde were synthesized and polymerized to what are completely insoluble and apparently isotactic polymers. Fluorodich-loroacetaldehyde and difluorochloracetaldehyde were also synthesized and polymerized. Fluorodichloroacetaldehyde gives only insoluble and apparently isotactic polymers. Difluorochioroacetaldehyde gave soluble amorphous polymers