Synthesis, characterization and properties of telechelic hybrid biodegradable polymers containing polyhedral oligomeric silsesquioxane (POSS)

In this work, telechelic POSS-containing inorganic-organic hybrid poly(L-lactic acid) (POSS-PLLA) and ditelechelic POSS-containing hybrid poly(epsilon-caprolactone) (POSS-PCL-POSS) were synthesized by click coupling between alkyne moiety-functionalized POSS and azide end-functionalized PLLA and bis-azide end-functionalized PCL. Characterization of the POSS-containing hybrid polymers was performed using FTIR, H-1 and C-13 NMR spectroscopy. The study of the effects of covalent POSS incorporation on the polymer thermal and surface properties was undertaken using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and water contact angle measurement. In all synthesized hybrids, the glass transition temperature (T-g) increased and crystallization was retarded with the incorporation of a POSS moiety at the chain ends of PLLA and PCL compared to that of neat homopolymers. Covalent end-capping by POSS disrupted the crystallization of PCL and PLLA. POSS moieties, attached to both ends of PCL, crystallized in the polymer matrix prior to PCL crystallization from the melt. The thermal and thermal oxidative stability of the polymers enhanced significantly after incorporation of the POSS moiety. Static contact angle measurements revealed that the POSS-containing polymers displayed a significant enhancement in surface hydrophobicity.