Polymerization of Methyl Methacrylate Initiated by Sex Hormones

Abstract

The polymerization of methyl methacrylate (MMA) in itiated by several sex hormones (Fig.1) and its analogous compounds was studied as an example of radical rea ction of physiologically active substances in vitro. Although the polymerization was not initiated by these compounds alone, it was found that progesterone (Pro), testosterone (Test), and 11-ketoprogesterone (Kpro) were able to show the initiating activity of polymerization by adding small amounts of FeCl₃ (the polymerization was retarded in above a certain quantity; Table 1). The overall activation energies for the polymerization were estimated to be 48.9 kJ·mol^-1 (for Pro system), 57.3 kJ·mol^-1 (for Test system), and 47.7 kJ·mol^-1(for Kpro system), respectively. The polymerization of MMA by Pro or Kpro system was kinetically studied in methanol, keeping the ratio of hormone to FeCl₃ constant ([Hormone]/[FeCl₃]=50; Table 2, Figs.4 and 5), to give the following equation of polymerization rate (R_p):
R_p=k[MMA] [Pro or Kpro+FeCl₃]^0.5
The initiating radical was assumed to be produced through the redox reaction between the hydrogen at 17-position of steroid ring and Fe³⁺. Follicular hormones having phenolic hydroxyl group acted as a terminator for the radical polymerization.