Alkaline hydrolysis of homopolymers and copolymers of 2‐hydroxypropyl methacrylate

摘要

AbstractHomopolymers of 2‐hydroxypropyl methacrylate (HPMA) and copolymers with acrylic acid (AA) were prepared in 1,4‐dioxane. The reactivity ratios were determined to berAA= 0.27 ± 0.04 andrHPMA= 2.2 ± 0.2. The alkaline hydrolysis by sodium hydroxide of the HPMA monomer and polymers showed that while the HPMA monomer hydrolyzed readily as expected for a low‐molecular‐weight carboxylic ester the HPMA homopolymer and water‐soluble sodium acrylate (NaA) copolymers were extremely resistant to alkaline hydrolysis. The saponification reaction followed a second‐order rate equation, being first order with respect to both HPMA and hydroxide ion concentration. The Arrhenius parameters, activation energyEand frequency factorA, for the alkaline hydrolysis of HPMA monomer in water were found to beE= 10.3 Kcal/mol and A = 1.5 × 108L/mol min, and those for the NaA–HPMA copolymers in water were found to beE= 24 kcal/mol andA= 4 × 1012L/mol min. The NaA–HPMA copolymers had a limiting extent of hydrolysis, ranging from 9–90 ester conversion. A sharp rate decrease at low conversion was noted during the HPMA homopolymer hydrolysis in 58/42 dimethyl sulfoxide/water, allowing the calculation of two distinct reaction rates. © 199