Addition of methacryloil groups to poly(vinyl alcohol) in DMSO catalyzed by TEMED: Optimization through response surface methodology

The addition of methacryloil groups from glycidyl methacrylate (GMA) to poly(vinyl alcohol), PVA, was investigated in the former paper of this series. In this report, this reaction was optimized by response surface methodology (RSM). In the first step, the main and the interaction effects of reaction time, temperature, and environment (either room atmosphere or N2 bubbling) on the degree of substitution (DS) were investigated through a 23 factorial design and by keeping the feed solution molar ratio [-OH(PVA)/GMA] equal to 1/0.05. DS was calculated from the respective 1H NMR spectrum. The results showed that the reaction time and temperature inputs are significant (P<0.05) for the incorporation of methacryloil groups into PVA chains. In the second step, maximum DS was achieved by the use of RSM at 62 °C and reaction time of 6 h. In these optimized conditions, molar ratios [-OH(PVA)/GMA] equal to 1/0.10, 1/0.25, 1/0.50, 1/0.75, and 1/1 were investigated and the respective yield ranged from 91 to 93% when DS was up to 25 mol%. It is difficult to obtain more than 50 mol% substitution of PVA hydroxyl by methacryloil groups even in these optimized conditions due to increased steric hindrance by the large number of the methacryloil groups inserted into PVA. The response surface was based on the model DS=−19.70+6.09×10−1T+1.93t−3.89×10−3T2−5.21×10−2t2−2.14×10−2T∗t, where T is the temperature (°C) and t the reaction time (hours). This model explained 99.2 of the 99.6% explainable statistical data.