Ternary blends of polylactide (PLA, 90 wt.%) and poly(methyl methacrylate) (PMMA, 10 wt.%) with functionalized polysilsesquioxanes (LPSQ-R) were obtained by solution blending. R groups in LPSQ containing hydroxyethyl (LPSQ-OH), methylglycolic (LPSQ-COOMe) and pentafluorophenyl (LPSQ-F5) moieties of different chemical properties were designed to modify PLA blends with PMMA. The effect of the type of LPSQ-R and their content, 1–3 wt.%, on the structure of the blends was studied with scanning electron microscopy (SEM) combined with energy dispersive spectroscopy (SEM-EDS), dynamic mechanical thermal analysis (DMTA) and Raman spectroscopy. Differential scanning calorimetry (DSC) and tensile tests also showed various effects of LPSQ-R on the thermal and mechanical properties of the blends. Depth-sensing indentation was used to resolve spatially the micro- and nano-scale mechanical properties (hardness and elastic behaviour) of the blends. The results showed clearly that LPSQ-R modulate the structure and properties of the blends.

The influence of macromolecular architecture on shear-induced crystallization of poly(L-lactide) (PLLA) was studied. To this aim, three star PLLAs, 6-arm with M_w of 120 and 245 kg/mol, 4-arm with M_w of 123 kg/mol, and three linear PLLAs with M_w of 121, 240 and 339 kg/mol, were synthesized and examined. The PLLAs were sheared at 170 and 150 °C, at 5/s, 10/s and 20/s for 20 s, 10 s and 5 s, respectively, and then cooled at 10 or 30 °C/min. Shear-induced crystallization during cooling was followed by a light depolarization method, whereas the crystallized specimens were examined by DSC, 2D-WAXS, 2D-SAXS and SEM. The effect of shear depended on the shearing conditions, cooling rate and polymer molar mass but it was also affected by the macromolecular architecture. The shear-induced crystallization of linear PLLA with M_w of 240 kg/mol was more intense than that of the 6-arm polymer with similar M_w, most possibly due to its higher M_z. However, the influence of shear on the crystallization of the star polymers with M_w close to 120 kg/mol was stronger than on that of their linear analog. This was reflected in higher crystallization temperature, as well as crystallinity achieved during cooling.