1474 Grafting of x-Functionalized PVP Oligomers onto Dextran: A Novel Route to Biodegradable and Biocompatible Polymers Carl F. Brunius, Elisabetta Ranucci* a Department of Polymer Technology, Royal Institute of Technology, Teknikringen 58, 10044 Stockholm, Sweden Keywords: biocompatibility; biodegradable; chain-transfer agents; dextran; graft copolymers; x-hydroxy-terminated poly- vinylpyrrolidone; Introduction Growing attention has currently been devoted to the design of new bioactive and biocompatible polymers cap- able of temporary therapeutic functions, using different macromolecular engineering approaches. Among the cur- rently available biocompatible polymers, dextran and poly(N-vinyl-2-pyrrolidinone) (PVP) certainly belong to the most popular and widely investigated ones. Dextran is a bacterially produced, highly linear poly- saccharide, used in the biomedical field e.g., for plasma expansion, [1] anemia therapy of dialysis patients [2, 3] and in the preparation of imaging contrast agents. [4] Further- more, dextran and its derivatives find use in drug-release formulations [5–8] and soluble polymeric drug carriers. [9–12] Grafting dextran with amphiphilic biocompatible poly- mers, such as poly(ethylene glycol) (PEG), [13, 14] has been proposed as to increase its biocompatibility and expand its potential in the pharmaceutical and biomedical field. PVP is a synthetic amphiphilic polymer [15, 16] with a unique combination of properties: solubility in both water and a range of organic liquids, complexing ability towards several organic and inorganic compounds (used as detoxifying agent [17] ) and physiological acceptability. PVP is widely used in pharmaceutical formulations, e. g., as a color dispersant [18] or tablet disintegrator, [19] and has also been used as a plasma expander. [20] Due to problems with metabolism and excretion that use was later aban- doned. PVP has also been proposed for the modification of therapeutically useful enzymes [21] and as a soluble drug carrier. [22, 23] Communication: x-Hydroxy-functionalized oligo(N- vinyl-2-pyrrolidinone) (PVPOH) was prepared by chain- transfer radical polymerization in the presence of 2-iso- propoxyethanol as the chain-transfer agent, and grafted onto dextran. Two PVP-Dex graft copolymers were obtained starting from different PVPOH/dextran weight ratios in the feed, namely 2:1 and 5:1. The variation of molecular weight distributions, combined with the results of solubility tests and of selective extractions in organic solvents, irrefutably confirmed the successful grafting reactions and the efficacy of the purification procedures applied. Macromol. Rapid Commun. 2001, 22, No. 18 i WILEY-VCH Verlag GmbH, D-69451 Weinheim 2001 1022-1336/2001/1812–1474$17.50+.50/0 a Present address: Dipartimento di Chimica Organica e Indus- triale, via Venezian 21, 20133 Milano, Italy; E-mail: ranuccie@libero.it. Macromol. Rapid Commun. 2001, 22, 1474–1480