Supramolecular interactions involving fluoroaryl groups in hybrid blends of polylactide and ladder polysilsesquioxanes

Abstract

Linear ladder polysilsesquioxanes (LPSQ-R) bearing fluoroaryl groups [R: p-fluorophenyl (F), p-trifluoromethylphenyl (F3) or pentafluorophenyl (F5)] were used to modify polylactide (PLA). Vibrational spectroscopy analysis suggested specific, non-covalent interactions between CO of PLA and fluoroaryl groups of LPSQ-R while quantum-chemical modelling performed for representative models indicated that the pattern of possible preferred contacts differs for LPSQ-F3 in respect to LPSQ-F and LPSQ-F5 (H····F hydrogen bonding against n→π* attractive interactions). It may affect interface phenomena in PLA/LPSQ-R systems. Thermal characteristics of PLA/LPSQ-R depended on the type of R and LPSQ-R content. Dielectric relaxation spectroscopy (DRS) studies revealed one relaxation process present in PLA and related to the glass transition. However, for PLA/LPSQ-R blends two processes were identified: glass transition and normal–mode relaxation. The modification with fluorinated macromolecules increased hydrophobicity of amorphous PLA and improved its mechanical and gas barrier properties, which can be of importance for packaging applications.