Novel Amphiphilic Diblock Copolymer of Low Molecular Weight Poly(<i>N</i>-vinylpyrrolidone)-<i>b</i><i>lock</i>-poly(<scp>d</scp>,<scp>l</scp>-lactide): Synthesis, Characterization, and Micellization

Abstract

Low molecular weight poly( N -vinylpyrrolidone) (PVP) with a hydroxyl group at one end was successfully synthesized by free radical polymerization of N -vinyl-2-pyrrolidone (NVP). Using isopropyl alcohol as solvent and 2-mercaptoethanol as chain transfer agent, a control over molecular weight (MW) profile of PVP was obtained, leading to average-number MW as low as 2500 Da and polydispersity indexes close to 1.5. MALDI−TOF mass spectrometry indicated that the insertion of hydroxyl group on one chain end was quantitative. Hydroxyl-terminated PVP was used as macroinitiator in ring-opening polymerization of d, l -lactide yielding amphiphilic poly( N -vinylpyrrolidone)- block -poly( d, l -lactide) (PVP- b -PDLLA) diblock copolymer with polydispersity indexes as low as 1.14. PDLLA contents could be tuned according to the feed ratio of DLLA, leading to molar percents up to 47%. The well-defined diblock copolymer self-assembles into micelles in aqueous solution. Polymeric micelles, composed of PVP- b -PDLLA with PVP M n of 2500 and PDLLA molar content of 45%, displayed monodispersed size distribution of about 40 nm. The critical association concentration of micelles was determined to be around 6 mg/L.