Alkaline hydrolysis of homopolymers and copolymers of 2-hydroxypropyl methacrylate

✍ Scribed by Joseph Daly; Robert W. Lenz

• Publisher: John Wiley and Sons
• Year: 1992
• Tongue: English
• Weight: 662 KB
• Volume: 46
• Category: Article
• ISSN: 0021-8995
• DOI: 10.1002/app.1992.070460512

✦ Synopsis

Homopolymers of 2-hydroxypropyl methacrylate ( HPMA) and copolymers with acrylic acid (AA) were prepared in 1,4-dioxane. The reactivity ratios were determined to be rAA = 0.27 k 0.04 and rHkpMA = 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 watersoluble 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 energy E and frequency factor A , for the alkaline hydrolysis of HPMA monomer in water were found to be E = 10.3 kcal/mol and A = 1.5 X lo8 L/mol min, and those for the NaA-HPMA copolymers in water were found to be E = 24 kcallmol and A = 4 X 10'' L/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. 0 1992 John Wiley & Sons, Inc.