Synthesis and self-assembly of AB2-type amphiphilic copolymers from biobased hydroxypropyl methyl cellulose and poly(L-lactide)

Abstract

AB₂-type amphiphilic (HPMC)₂-PLA copolymers with various hydrophilic block lengths were synthesized using a three step procedure: ring-opening polymerization of L-lactide initiated by propynol, amination reduction of the aldehyde endgroup of HPMC, and thiol-click reaction. The resulted copolymers were characterized by NMR, DOSY-NMR, SEC and FT-IR. The cloud point (CP) was determined by UV-vis spectrometer. Data show that the HPMC block length has little effect on the Cp of the copolymers which is lower than that of HPMC. The self-assembly behavior of the copolymers was investigated from DLS, TEM, and critical micelle concentration (CMC) measurements. Spherical micelles are obtained by self-assembly of copolymers in aqueous solution. The micelle size and the CMC of copolymers increase with increasing HPMC block length. It is concluded that biobased and biodegradable (HPMC)₂-PLA copolymers could be promising as nano-carrier of hydrophobic drugs.

Keywords: Hydroxypropyl methyl cellulose; Micelle; Poly(L-lactide); Self-assembly; Topology.