Polymerization of Heterocycles Related to Biomedical Polymers

Abstract

Abstract Preparation, properties, and some of the applications of heterochain polymers, related to biologically active or medical materials, are discussed. Various examples of the polymerization processes of the monomers containing 0, S-, N- a.o. heteroatoms in the ring are considered together with some peculiarities of the resulting polymers. The presence of the heteroatoms in the polymer chains makes the latter in many cases related to the native polymers (polysaccharides, polypeptides) if the hydrophilicity (water-solubility), biocompatibility, resolution, destruction ability, and elimination are considered. On the other hand, these polymers may reveal (depending on the nature of the backbone, presence and position of the functional side groups) physiological activity themselves or induce biocompatibility of the materials formed from them (medical fibres, films etc.). The use of hetero-chain polymers with functional groups as a base for addition of physiological (therapeutical) active substances permits to obtain water-soluble polymers with pharmaceutical properties. The detailed study of the polymerization mechanism of the heterocyclic monomers permitted to find conditions for the regulation of the molecular parameters and structure of the polymers used for (or investigated as) plasma substituents, alloplastic materials, crioprotectors, drugs, pharmaceutical species etc. Some examples of the polymerization reactions of the heterocyclic monomers (cyclic oxides, lactones, lactolides, N-carboxyanhydrides, anhydrosugars), leading to the biomedical polymers, are discussed in more detail. The presence of functional groups in a heterocyclic derivative leads in many cases to significant increase of the proportion of the side or parasite reactions, and, eventually, to the formation of products with relatively low molecular weight. The synthesis of high molecular weight heterochain polymers containing active functional side groups became possible by using of the reactions in polymer chains. As an example the experimental data for the copolymerization of ethylene oxide with epichlorohydrin, glycidole a.o. are given together with the data concerning the corresponding chemical reactions of these copolymers leading to the biologically active polymers. Some of their properties, including the medical-biological characteristics of the high molecular weight derivatives are also discussed.