SYNTHESIS AND CHARACTERIZATION OF AN OPTICAL ACTIVE TRIBLOCK COPOLYMER via ATOM TRANSFER RADICAL POLYMERIZATION
一种光学活性三嵌段共聚物的ATRP合成及表征

An optical active triblock copolymer poly(N-methacryloyl-L-leucine methyl ester)-b-polysulfone-b-poly-(N-methacryloyl-L-leucine methey ester)(PMALM-b-PSF-b-PMALM)with predetermined structure and narrow molecular weight distribution was synthesized via atom transfer radical polymerization(ATRP)using polysulfone macroinitiator and CuBr/Me_6TREN complex system.The structure was verified by 1H-NMR,GPC and end group titration techniques.DSC,thermogravimetry analysis(TGA)and circular dichroism(CD)were used to study the thermal and optical properties.The mole ratio of PMALM block to PSF block calculated from TGA has a good agreement with the result calculated from 1H-NMR.Both a reversion and an increase of the absolute value of specific rotation in the transformation from MALM to PMALM-b-PSF-b-PMALM were observed,which were probably caused by some kind of stereostructure of the main chain formed during the polymerization due to the intermolecular hydrogen-bonding.The random conformation of PMALM blocks was verified by CD spectra and the linear relationship between the specific rotation and the polarity of CH_3OH/CCl_4 mixed solvent.