Silica-nanocomposites of photo-crosslinkable poly(urethane)s based on poly(ε-caprolactone) and coumarin

Abstract

Photo-reversible nanocomposites of polyurethanes (PUs) based on coumarin (CD) and poly(ε-caprolactone) (PCL), with different molecular weights (PCL530, PCL2000) were developed. High molecular weight PUs were loaded with three different amounts of fumed silica nanoparticles (SiNPs) (1, 3 and 5wt%) to improve their physical, mechanical, thermal and photo-chemical properties. The incorporation of SiNPs and the interaction with the PU matrix was confirmed by FTIR, while their dispersion was observed by Field Emission Scanning Electron Microscopy (FE-SEM). The thermal stability of PU nanocomposites was improved due to the positive interaction of SiNPs with PU matrix. The incorporation of SiNPs leads to the formation of more thermal stable semicrystalline structure. Stress-strain experiments showed an increase on Young‘s modulus. Surprisingly, the photo-reversible ability of nanocomposites measured by UV–vis exhibited faster photo-dimerization process in PCL2000-PUs based nanocomposites than in PCL530-PUs ones, contrarily to the behavior of PUs without SiNPs. These nanocomposites are promising systems to design versatile and sustainable coatings with improved thermal stability and tunable mechanical performance.