Hydrophilic nanocomposites based on polyurethane/poly(2‐hydroxyethyl methacrylate) semi‐IPNs and modified/unmodified nanosilica for biomedical applications

Abstract

Nanocomposites based on sequential semiinterpenetrating polymer network (semi-IPN) of cross-linked polyurethane and linear poly(2-hydroxyethyl methacrylate) with 0.25 and 3 wt % of nanosilica filler were prepared and investigated. The unmodified silica, carboxyl-modified, and amino-modified silica were used in an attempt to control the microphase separation of the polymer matrix by polymer-filler interactions. A variety of experimental techniques were used to study morphology, thermal transitions, mechanical properties, and polymer dynamics of the nanocomposites. Special attention was paid to the investigation of the hydration properties of the nanocomposites in the perspective of biomedical appli-cations. The results show that the good hydration properties of the semi-IPN matrix are preserved in the nanocomposites. Effects of water on polymer dynamics were found to be particularly pronounced for the secondary b sw , PHEMA and the b PU relaxations, in agreement with interpretations in terms of hydrogen bonding interactions with specific groups in the structure of the two polymers.

Structure–properties investigations in hydrophilic nanocomposites based on polyurethane/poly(2–hydroxyethyl methacrylate) semi‐interpenetrating polymer networks and nanofiller densil for biomedical application

“…Finally, in a previous study of ours on same PU–PHEMA matrix filled with different nanosilicas (initial and surface modified A–300) the existence of both polymer–filler and polymer–polymer interactions were also manifested in water immersion experiments. After long stay (6–130 days) of the samples in distilled water it was found that neat PU network was decomposed (hydrolyzed) by ∼50–90%.…”

“…All the measured and calculated parameters for the semi‐IPNs and for the nanocomposites are shown in Table . For both the unfilled matrices and for the nanocompo‐sites two well separated endothermic steps at around −58 and 100°C were recorded (Figure ), representing the glass transition of PU and PHEMA, respectively.…”

“…In Figure , γ PHEMA relaxation is assigned to rotation of hydroxyethyl groups in the side chain of PHEMA . β sw,PHEMA is a local secondary relaxation assigned to crankshaft motion of the PHEMA side groups with attached water molecules .…”

“…The diffusion coefficient of water, D , was calculated, employing the following equation where (Δ m ) t is the change (increase or decrease) in the water mass on the sample after a time period t from the beginning of the measurement, (Δ m ) ∞ is the respective value at equilibrium and l is the thickness of the sample. D was calculated by fitting the above equation to experimental data, assuming (a) Fickian behavior, (b) water diffusion in one direction through a certain surface of the sample (which is a thin film in the present study), and (c) unchanged thickness of the sample during the experiment …”

“…The modification of silica has been obtained by the mechanochemical activation (MCA) of initial fumed oxides and resulted in surface's changes and significantly higher porosity of nanofiller . The materials have been prepared and investigated having in mind biomedical applications, on the basis of biocompatibility of the PU and biocompatibility combined with strong hydrophilicity of PHEMA and silica . To that aim we employ a combination of structure (Small Angle X–ray Scattering, SAXS), surface morfology (AFM), mechanical (stress–strain), calorimetric (DSC), and thermo–dielectric (broadband dielectric relaxation spectroscopy, DRS, and Thermally stimulated depolarization currents, TSDC) techniques.…”