Radical methyl methacrylate—methacrylic acid copolymerization in isopropyl alcohol, acetone, and their mixtures. Application of the copolymer products for microencapsulation of ampicylline trihydrate

Abstract

The copolymerization ratios of radical methyl methacrylate (MMA)-methacrylic acid (MA) copolymerization in mixtures of isopropyl alcohol (IPA) with acetone (A), xylene (X), and water (W) are determined. Their values and those in IPA are smaller than unity. The established alternating tendency of the monomer parts in the obtained copolymers is somewhat larger than the theoretically expected one and this is explained by the donor-acceptor interaction either between comonomers or between them and the propagating radicals. It is suggested that the reason for this tendency is the difference in H-bond formation between comonomers and solvents used. The dependencies of the apparent mass average molecular weight of the copolymers (M_{w, ap}) on their composition are also determined as well as the θ-composition of the A-heptane (H) mixture for these copolymers. These data are used for ampicyl line trihydrate (AT) microencapsulation by phase separation of the AT suspension in copolymer solutions in A after H addition. The AT microencapsulation characteristics (yield, degree and efficiency) as dependent on the copolymer composition as well as the influence of this composition on the solution kinetics of the microencapsulated AT at pH=4.5 and 6.5 and temperature of 37°C are established.