Synthesis and Thermal Analysis of Non-Covalent PS- b -SC- b -P2VP Triblock Terpolymers via Polylactide Stereocomplexation.

Polylactides (PLAs) are thermoplastic materials known for their wide range of applications. Moreover, the equimolar mixtures of poly(L-Lactide) (PLLA) and poly(D-Lactide) (PDLA) can form stereocomplexes (SCs), which leads to the formation of new non-covalent complex macromolecular architectures. In this work, we report the synthesis and characterization of non-covalent triblock terpolymers of polystyrene- b -stereocomplex PLA- b -poly(2-vinylpyridine) (PS- b -SC- b -P2VP). Well-defined ω -hydroxy-PS and P2VP were synthesized by "living" anionic polymerization high-vacuum techniques with sec -BuLi as initiator, followed by termination with ethylene oxide. The resulting PS-OH and P2VP-OH were used as macroinitiators for the ring-opening polymerization (ROP) of DLA and LLA with Sn(Oct) 2 as a catalyst to afford PS- b -PDLA and P2VP- b -PLLA, respectively. SC formation was achieved by mixing PS- b -PDLA and P2VP- b -PLLA chloroform solutions containing equimolar PLAs segments, followed by precipitation into n -hexane. The molecular characteristics of the resulting block copolymers (BCPs) were determined by 1 H NMR, size exclusion chromatography, and Fourier-transform infrared spectroscopy. The formation of PS- b -SC- b -P2VP and the effect of molecular weight variation of PLA blocks on the resulting polymers, were investigated by differential scanning calorimetry, X-ray powder diffraction, and circular dichroism spectroscopies.