ABSTRACT:60 Co-gamma-radiation and ceric ammonium nitrate (CAN) redox-induced graft polymerization of acrylic monomers (acrylonitrile, acrylic acid, and methyl acrylate) to starch was performed to produce drug-delivery systems. The grafted starches obtained mainly by redox-induced polymerization were characterized by chemical and physicochemical methods, and the nature and size of the polyacrylic moiety grafted to the starch were determined. Although the choice of grafting method depended in part on the particular monomer, only copolymers obtained by gamma radiation proved to be satisfactory drug delivery systems. Changes of parameters in the gamma radiation-induced polymerization, such as radiation times and changes in the amount of starch and/or acrylic monomers, were tested in terms of the release rate of model drug compounds.

'fC\ll-trans" alkyds (unsaturated polyesters) were prepared by lipase-catalyzed polytransesterifications of diesters of fumaric acid and 1,4-butane diol. Industrially prepared alkyds, however, contain aromaticity in their backbone, which is introduced by phthalic acid derivatives and/or isomers. Thus, in this study, the specificity of lipases toward aromatic esters, diesters, and diols was investigated in order to find a means of introducing aromaticity in the lipase-catalyzed synthesis of "all-trans" alkyds. It was found that lipases from Pseudomonas and Mucor efficiently catalyzed the polytransesterification of dichloroethyl fumarate with aromatic diols such as benzene dimethanol. Crystallinity was found in the "alltrans" alkyds synthesized in acetonitrile. In order to determine whether this property was due to the nature of diol or the frequency of the double bond in the backbone of the polyester, other alkyds were prepared in which the length of the diol was changed as well as the number of carbons (odd or even) in the diol and the chemical nature of the diol (primary or secondary). In all cases crystallinity was found. It thus seems that the stereochemistry of the double bond is responsible for this property. Molecular weights, which were determined by gel permeation chromatography (GPC) analyses, were comparable with those of the industrially prepared alkyds.

The synthesis of unsaturated polyesters (UP) by high‐temperature polycondensation is accompanied by isomerization of the double bond from the cis to the trans configuration. The presence of the trans double bonds facilitates crosslinking and may have an important influence on rheological and mechanical properties of the UP and the cured end product. All‐trans polyesters are not available on the market. A study of “all‐trans” low‐temperature polycondensation based on chemical and enzymatic lipase catalysis was recently reported. This paper presents the characteristics of lipase‐synthesized UP vs. general‐purpose UP, as obtained by X‐ray, differential scanning calorimetry (DSC), and other methods. In contrast to the commercial amorphous UP, crystallinity was found in the “alltrans” enzymatically and chemically synthesized UP. The crystallinity of the enzymatically and chemically synthesized UP. The crystallinity of the enzymatically synthesized UP was confirmed by higher values of elasticity. DSC analyses complemented the results obtained by other methodologies.

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