Inorganic-Organic Hybrids Based on Poly (ε-Caprolactone) and Silica Oxide and Characterization by Relaxometry Applying Low-field NMR

Poly (epsilon-caprolactone) (PCL) based hybrids containing different amounts of modified (Aerosil (R) R972) and unmodified (Aerosil (R) A200) silica oxide were prepared employing the solution method, using chloroform. The relationships of the amount of nanofillers, organic coating, molecular structure and intermolecular interaction of the hybrid materials were investigated mainly using low-field nuclear magnetic resonance (NMR). The NMR analyses involved the hydrogen spin-lattice relaxation time (T1H) and hydrogen spin-lattice relaxation time in the rotating frame (T-1 rho H). The spin-lattice relaxation time measurements revealed that the PCL/silica oxide hybrids were heterogeneous, meaning their components were well dispersed. X-ray diffraction (XRD), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were also employed. The DSC data showed that all the materials had lower crystallization temperature (Tc) and melting temperature (Tm), so the crystallinity degree of the PCL decreased in the hybrids. The TGA analysis demonstrated that the addition of modified and unmodified silica oxide does not cause considerable changes to PCL's thermal stability, since no significant variations in the maximum temperature (Tmax) were observed in relation to the neat polymer.