Material characterisation1H NMR relaxometry and X-ray study of PCL/nevirapine hybrids

Polycaprolactone (PCL) hybrids containing layered silicates, silica and dioxide titanium were developed and used as matrixes for the incorporation of nevirapine. These systems were characterized by X-ray diffraction (XRD) and proton nuclear magnetic resonance (NMR) relaxometry. The XRD showed that the PCL crystallization is hindered with higher amounts of nevirapine and that the drug has an amorphous distribution in the PCL matrix. The NMR showed that the hybrids present three distinct environments: crystallites, rigid-amorphous and flexible-amorphous regions, with three distinct spin-lattice relaxation times, T11, T12, T13. The proton relaxometry showed that the PCL chains have more restricted motions in the presence of Viscogel organoclay S7 comparing to TiO2 and SiO2. The presence of nevirapine and nanoparticles together decreased the polymer chain mobility, especially in the amorphous regions. Both T12 and T13 dispersions could be interpreted in terms of power laws T12, T13 ∼ νp. In the case of T12, the exponent obtained was around 0.73, which in the frame of the renormalized Rouse model could be associated with a type I mesophase region, indicating some constraint in the amorphous part.