Polymer, Vol.79, 195-204, 2015
Instantaneous stereocomplex driven self-assembly of enantiomeric poly(vinyl alcohol)-graft-oligo(lactide) copolymers in DMSO and thin film formation thereof
The ability of enantiomeric graft copolymers composed of partially acetylated poly(vinyl alcohol) (PVA) as backbone and oligo(L-lactide) (OLLA) or oligo(D-lactide) (DP in lactate units = 20) as grafts to form stereocomplex in bulk and in solution is described. First, the copolymers are obtained by grafting onto the backbone through esterification, the oligomers that are priorly synthesized by ring-opening polymerization of the corresponding monomer and subsequently derived. By controlling the reaction time or the molar ratio between the reactants, this synthetic strategy makes it possible to tune the extent of modification of PVA for a given molecular weight of grafts. Then, racemic mixture of PVA-g-OLLA and PVA-g-ODLA is prepared in solution using DMSO as solvent: an Inter Polymer Complex is spontaneously and instantaneously formed, due to quantitative stereocomplexation-driven self assembly between the OLLA and ODLA grafts. This fastest ever reported stereocomplexation opens new perspectives in the design of PVA-based materials with biodegradable crosslinks, as demonstrated with the successive spin-coating of the racemic mixture on a flat substrate to readily form thin films that are not obtained when a homochiral graft copolymer-containing solution is used. (C) 2015 Elsevier Ltd. All rights reserved.
Keywords:Graft copolymers;Poly(vinyl alcohol);Poly(lactide);Stereocomplex;Thin films;Inter polymer complex;Crystallization-induced self-assembly