Polymerization of Methacrylic Acid in the Presence of Isotactic Poly(methyl Methacrylate) as Possible Template

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Abstract
Based on the stereoassociation ability between it-PMMA and st-polymethacrylic acid (PM acid) in DMF, methacrylic acid (M-acid) was polymerized in the presence of it-PMMA templates between 45 and -10°C. At temperatures between 0 and 45°C the polymerization rate and the radical lifetimes were identical with those of the corresponding blank polymerization, although gel formation took place. This could be explained by termination of growing PM acid radicals in the “free” solution before their association with it-PMMA could take place, in other words the association rate of the formed PMAA radicals with it-PMMA is too low. Only below ca. 0°C was a kinetic template effect observed; at -10°C the rate relative to that of the blank reaction (without it-PMMA) is vR = 1.5 ± 0.1. The decrease in ΔE‡ by the template is ascribed to mainly an increased hindrance of termination of associated PM acid radicals. The decrease in ΔS‡ may be caused by a sterically more stringent transition state of the propagation steps in which the template chain is involved. For the solvents, 2-methoxyethanol (2-ME) and EtOH/ H2O (volume ratio 83/17) in which complexation is moderate to strong, no template effect was observed, probably due to the bad solubility of it-PMMA. However, vR = 2.2 was found when a polymerization was performed at -10°C in a mixture of 30 vol % dioxane and 2-ME.