Preparation of PHEMA/TiO2 nanocomposites by combination of in-situ polymerization/hydrothermal method and determination of their thermal, swelling, biological and dielectric properties

Poly(2-hydroxyethyl methacrylate) (PHEMA) and TiO 2 nanoparticles (NPs) containing polymeric nanocomposites (PNCs) in different mass ratios of TiO 2 (3, 5 and 7%) with respect to PHEMA were synthesized by using the in-situ polymerization/hydrothermal method. The prepared composite materials were characterized by SEM, FTIR, UV–Vis, TGA and XRD techniques. The results of the characterization experiments showed that the composite successfully synthesized and TiO 2 in the polymer matrix is well distributed, especially for the lowest TiO 2 contained composite (3% TiO 2 ). The thermal activation energies (E a ) of the PNCs were estimated by the Ozawa, Kissinger, and Kissinger–Akahira–Sunose methods by using non-isothermal TGA experiments. By increasing the amount of TiO 2 nanoparticles, the thermal stability and glass transition temperature (T g ) of PHEMA was increased. The water holding capacity of PNCs was determined by swelling experiments. As the amount of TiO 2 in the PNCs increased, the degree of swelling decreased. In addition, the swelling values ​​of both PHEMA and PNCs increased with increasing the temperature. The dielectric constant ( Ɛ′ ), the dielectric loss factor (Ɛ′′) and ac conductivity of neat PHEMA and PNCs were also measured for the frequency range of 100 Hz to 2 kHz and for the temperatures of 30 and 180 °C. It was obtained that the frequency dependence of the dielectric constant and dielectric loss factor decreased with increasing frequency. Finally, the biological activities of PNCs against gram-positive (S. aureus) and gram-negative (E. coli) bacteria were also tested and it was observed that this effect increased with the amount of TiO 2 .