The Fundamental Basis for Cyclopolymerization. X. A Systematic Study of the Cyclopolymerization of Methacrylic Anhydride

Abstract

Abstract The study of methacrylic anhydride has shown that the intramolecular propagation step has a higher energy of activation (2.6 ± 0.3 kcal/mole) than the intermolecular step. Steric factors have, however, been found to favor cyclization (A11/Ac = 0.0039 liter/mole). It has been concluded that the conditions which favor cyclization in methacrylic anhydride are high temperature, low monomer concentration, poor solvent system, and high conversion. The increase in cyclization caused by heterogeneous conditions, such as poor solvent or high conversion, appears to be due to tight coiling of the polymer chain and slow diffusion, thereby decreasing the value of k11 with respect to kc. Although methacrylic anhydride does cross-link to some extent, the number of cross-links was lower than expected due to anhydride interchange of pendent units. Also, even though some cross-links were present, the polymer could be dissolved due to interchange of the intermolecular cross-links to intramolecular anhydride units. ...