Synthesis of Poly(methyl/amino)silsesquioxane Microsphere as an Efficient Compatibilizer for Enhanced PHB/PCL Blend Properties

To enhance the compatibility of polyhydroxybutyrate/polycaprolactone (PHB/PCL) binary blend system, a novel covalent compatibilizer, poly(methyl/amino)silsesquioxane (PMASQ) was synthesized via the base-catalyzed sol-gel method using Methyltrimethoxysilane (MTMS) and γ-Aminopropyl trimethoxysilane (APTMS). The films were prepared through the solution casting method with the blend of PHB/PCL (25:75, w/w) incorporating with various content of PMASQ (1   wt%, 3   wt%, 5   wt%). As a result, ATR-FTIR analysis confirmed the successful synthesis of PMASQ and the subsequent grafting of PHB and PCL segments onto the PMASQ. At 3   wt% PMASQ, the blend exhibited optimal mechanical enhancement, with tensile strength and elongation at break increasing by 1.23-fold and 6.17-fold, respectively, compared to uncompatibilized blends. Furthermore, the incorporation of PMASQ resulted in a reduction in crystallinity while enhancing thermal stability within the PHB/PCL blend system. An improvement in continuity was also observed in the PHB/PCL/PMASQ blends, characterized by a reduction in the size of the dispersed phase and an emergence of a homogeneous morphology. These results demonstrate PMASQ’s dual role as a reactive compatibilizer and thermal stabilizer, mitigating inherent brittleness and phase incompatibility in PHB/PCL systems. The improved physicochemical properties and processability of the blend highlight PMASQ’s potential to expand the utility of biodegradable PHB/PCL composites in packaging, biomedical, and environmentally sustainable industrial applications.