PREPARATION AND CHARACTERIZATION OF OPTICALLY ACTIVE AMPHIPHILIC BLOCK COPOLYMER

Nowadays, synthetic optically active polymers are of great interests, since they might mimic the fascinating functions of naturally occurring polymers, such as nucleic acid, protein, and polysaccharide, and leading extensive studies being conducted on their synthesis, conformations and functions. In this publication, Optically active diblock copolymers poly (ethylene golycol) monomethyl ether-b-poly (N-methacryloyl L-leucine methyl ester) s (MPEG-b-PMALM) s, with different mole ratios for the two blocks and narrow molecular weight distribution, were synthesized via atom transfer radical polymerization (ATRP), using Bromine terminated poly(ethylene glycol) monomethyl ether (MPEG-Br) as macroinitiator and tris[(2-dimethylamino) ethyl] amine (Me6TREN)/CuBr as catalytic system. The chemical structure and the mole ratio of the two blocks were verified by H-1-NMR. The molecular polydispersity,as evaluated from SEC,as well as the bromine content in the prepared block copolymer,as analyzed from anion chromatography, indicate that the reaction is followed the mechanism of ATRP. Thermogravimetry analysis (TGA),and differential scanning calorimetry (DSC) were used to evaluate the thermal properties of the prepared polymers. The specific rotation of the prepared polymers reversed against that of the monomer, and its absolute value was obviously larger than that of the monomer. It was found that the absolute value increased with the increase of weight ratio of PMALM blocks in the prepared polymers. The random conformation of the copolymer was verified by CD spectra, and it was found that the optical activity of the block copolymer was promoted with the increase of the ratio of PMALM block to MPEG block in the block copolymers.