Optimized synthesis of hydroxypropyl cellulose-g-poly(ε-caprolactone) network

The objective of this study was the synthesis of copolymer networks based on poly (e-caprolactone) (PCL), hydroxypropyl cellulose (HPC) and hexamethylene diisocyanate (HDI) via bulk graft copolymerization followed by crosslinking (using routes I and II), and subsequent optimization of the process by response surface methodology (RSM). The studied reaction parameters were: (i) monomer content (weight ratio of CL/HPC), (ii) amount of catalyst, and (iii) amount of crosslinker. FT-IR and 1H NMR results confirmed that the grafting of PCL onto HPC and subsequent crosslinking through terminal hydroxyl groups of PCL grafts by HDI were performed successfully. Through differential scanning calorimetry (DSC) and X-ray diffraction analysis (XRD), it was found that the crystallinity of grafted polymers depended on the amount of grafted PCL and degree of crosslinking. In modeling of the process using RSM, the coefficient of determination (R2) for the models (97.3 and 93.3 % for two routes) as well as the probability (p < 0.0001) revealed high significance of the regression models. Also it was found that the obtained systems possessed T m s between 42.94 and 54.57 °C (route I) and 32.49–46.30 °C (route II) that were tunable by the monomer content, catalyst and crosslinker amounts. RSM provided a useful tool to select in a fast way the proper experimental conditions to synthesize crossinked HPC-g-PCL copolymer as a novel biocompatible and biodegradable shape memory polymer with adjustable switching temperature and potential biomedical applications, which would be further studied in the future.