Dual Roles of Alkyl Alcohols as Syndiotactic-Specificity Inducers and Accelerators in the Radical Polymerization of N-Isopropylacrylamide and Some Properties of Syndiotactic Poly(N-isopropylacrylamide)

Effect of simple alkyl alcohol on radical polymerization of N-isopropylacrylamide (NIPAAm) in toluene at low temperatures was investigated. We succeeded in induction of syndiotactic-specificity and acceleration of polymerization reaction at the same time by adding simple alkyl alcohols such as 3-methyl-3-pentanol (3Me3PenOH) into NIPAAm polymerization. The diad syndiotacticity increased with a decrease in temperature and an increase in bulkiness of the added alcohol, and reached up to 71% at –60°C in the presence of 3Me3PenOH. With the aide of NMR analysis, it was revealed that alcohol compounds play dual roles in this polymerization system; alcohol compound coordinating to N-H proton induces the syndiotactic-specificity and that hydrogen-bonded to C=O oxygen accelerates the polymerization reaction. The effect of syndiotacticity on properties of poly(NIPAAm)s was also discussed in some detail.