Synthesis of High-Performance and Biodegradable Polymer Blends Based on Poly(butylene succinate) and Grafted Polyrotaxane via Controlled Reactive Processing

In this study, novel, high-strength polymer blends were synthesized using poly(butylene succinate) (PBS) modified with grafted polyrotaxane (GPR). Then, their mechanical properties and morphologies were evaluated. A unique, two-step, reactive kneading method was developed to substantially improve the mechanical properties of PBS, which promoted transesterification reaction using an organo-titanium catalyst (Ti) in the first step and a urethanization reaction using hexamethylene diisocyanate (HDI) in the second step. The optimized blend material, [PBS/GPR10/Ti]-HDI, achieved remarkable toughening, and its Izod impact strength increased approximately seven-fold compared with that of unmodified PBS. Scanning electron microscopy (SEM) of the fracture surfaces confirmed a transition from brittle to ductile fracture, attributed to the controlled reaction sequence. First, strong chemical bonds formed at the PBS/GPR interface via Ti-catalyzed transesterification. Then, HDI induced simultaneous internal crosslinking (gelation) of the GPR domains and chain extension of the PBS matrix. This modification strategy maintained the excellent inherent soil biodegradability of PBS while improving its degradability in marine environments. This study presents a new guideline for designing materials that can considerably enhance the mechanical properties of biodegradable plastics.