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The shear orientation of the hexagonal liquid crystal phase of nonionic surfactant/water mixtures was investigated by means of different techniques, namely, microscopy, small-angle light and neutron scattering, (SALS, SANS), birefringence, and nuclear magnetic resonance (NMR). On a microscopic length scale probed by NMR, SANS, and birefringence, the shear flow results in an alignment of rodlike micelles along the flow direction. The 10 plane was parallel to the shear plane. On a mesoscopic length scale, studied by microscopy and SALS, a stripe texture was observed. This is due to an undulation of the director which is on average aligned in flow direction. The corresponding SALS pattern shows a better orientation correlation perpendicular to the flow direction.

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Unique combinations of hard and soft components found in biological tissues have inspired researchers to design and develop synthetic nanocomposite gels and hydrogels with elastomeric properties. These elastic materials can potentially be used as synthetic mimics for diverse tissue engineering applications. Here we present a set of elastomeric nanocomposite hydrogels made from poly(ethylene glycol) (PEG) and hydroxyapatite nanoparticles (nHAp). The aqueous nanocomposite PEG-nHAp precursor solutions can be injected and then covalently cross-linked via photopolymerization. The resulting PEG-nHAp hydrogels have interconnected pore sizes ranging from 100 to 300 nm. They have higher extensibilities, fracture stresses, compressive strengths, and toughness when compared with conventional PEO hydrogels. The enhanced mechanical properties are a result of polymer nanoparticle interactions that interfere with the permanent cross-linking of PEG during photopolymerization. The effect of nHAp concentration and temperature on hydrogel swelling kinetics was evaluated under physiological conditions. An increase in nHAp concentration decreased the hydrogel saturated swelling degree. The combination of PEG and nHAp nanoparticles significantly improved the physical and chemical hydrogel properties as well as some biological characteristics such as osteoblast cell adhesion. Further development of these elastomeric materials can potentially lead to use as a matrix for drug delivery and tissue repair especially for orthopedic applications.

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