AbstractThe activation energies of flowEAof methacrylate–styrene copolymers containingn‐butyl,n‐hexyl,n‐heptyl,n‐octyl,n‐decyl,n‐dodecyl,n‐tridecyl,n‐octadecyl, and cyclohexyl methacrylate have been investigated as a function of molecular weight, composition, and methacrylate monomer. Below a critical pendent group molar volume per chain unit (120 ± 10 ml Le Bas units),EAwas found to increase with molar volume; and above this value, a decrease inEAwas observed, reflecting a decrease in copolymer density. Copolymers with pendent group molar volumes per average chain unit of between 96 and 140 ml (Le Bas units) were found to exhibit sufficiently highEAvalues to render them suitable for use in thermoplastic and photothermoplastic devices with superior development and erasure rates, at temperatures which enabled the attainment of the development and erasure viscosities with a low expenditure of heat energy. Methacrylate–styrene copolymers with long‐chain ester methacrylates (viz.,n‐decyl andn‐dodecyl methacrylate) were found to exhibit critical molecular weightsMcbelow 3000; andMcwas found to decrease with increasing methacrylate tail length and methacrylate concentration. TheseMcvalues correspond to critical chain lengthsZcbelow 45. SimilarZcvalues have been previously reported for acrylonitrile–methyl methacrylate copolymers30and eth
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