Effect of Polymer Composition on Rheological and Degradation Properties of Temperature-Responsive Gelling Systems Composed of Acyl-Capped PCLA-PEG-PCLA

In this study, the ability to modulate the rheological and degradation properties of temperature-responsive gelling systems composed of acyl-capped poly(e-caprolactone-co-lactide)-b-poly(ethylene glycol)-b-poly(e-caprolactone-co-lactide) (PCLA-PEG-PCLA) triblock copolymers was investigated. Eight polymers with varying molecular weight of PCLA, caproyl/lactoyl ratio (CL/LA) and capped with either acetyl- or propionyl-groups were synthesized by ring-opening polymerization of l-lactide and e-caprolactone in toluene using PEG as initiator and tin(II) 2-ethylhexanoate as catalyst, and subsequently reacted in solution with an excess of acyl chloride to yield fully acyl-capped PCLA-PEG-PCLA. The microstructure of the polymers was determined by 1H NMR, and the thermal properties and crystallinity of the polymers in dry state and in 25 wt % aqueous systems were studied by differential scanning calorimetry and X-ray diffraction. Rheological and degradation/dissolution properties of aqueous systems composed of the p...