The Synthesis of Polycaprolactone-based Polyurethane Crosslinked by Polyrotaxanes with Exceptional Mechanical and Hydrolytic Properties

Abstract

Polyurethane has been considered as one of the most versatile polymers with a wide range of applications such as elastomers, thermoplastic polymers, foams, and smart coatings by simply combining various polyols and polyisocyanates. In our recent work, polycaprolactone-based polyurethane (PCL-based PU) was, for the first time, crosslinked by half-methylated polyrotaxanes (PRXs) with filling ratios of 37 and 79 %. Besides examining crosslinking extents of PUs through gel fraction and swelling degree, other analyses of PUs were also measured such as differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), dynamic mechanical thermal analysis (DMTA), and hydrolytic tests to evaluate general properties of PUs. The results show that PCL-based PU-PRX acts as an elastic material with low elastic modulus, very high tensile strength, and elongation at break (~ 1200%). The hydrolytic degradation was also achieved when the weight of samples reduced by 21.6 % after 28 days, and the deformation of three-dimensional crosslinking network was shown via the sharp reduction of elongation at break and the stress at break. These results demonstrated that PCL-based PU-PRX is a potential candidate to be used in alkaline and/or acid environment such as human’s body, and also used externally to protect our environment and ecological system.