The preparation of a novel fast response thremosensitive hydrogel was investigated by incorporating nanosized octavinyl polyhedral oligomeric silsesquioxane (OvPOSS) particles into inorganic clay-crosslinked poly(N-isopropylacrylamide) (PNIPA) nanocomposites hydrogels (NC gels).
The resulting hydrogels named as P-NC gels involving both the strategies of NC gels and double network gels (DN gels) were successfully synthesized via a two-step technique. The second PNIPA network crosslinked by OvPOSS were polymerized in the presence of the first clay-PNIPA network. The
P-NC gels were characterized by FTIR, X-ray, DSC, UV/vis spectra, SEM, mechanical properties and swelling behaviors measurements. The key factor for preparing homogenous P-NC gels with good transparency was the low concentration of OvPOSS (c
OvPOSS) dispersed uniformly in
polymer as a cross-linker. On the contrary, the high c
OvPOSS led to the significant aggregation of the OvPOSS particles and thus resulted in the heterogeneity of gels. The SEM images of freezedried P-NC gels exhibited a highly interconnected microporous network structure,
which could be adjusted by varying the amount of OvPOSS. The special porous morphology brought about an attractive faster swelling/deswelling rate than that of normal NC gels. All properties of P-NC gels displayed an obvious dependence on the concentration of incorporated OvPOSS. The excellent
mechanical properties, tunable LCST, especially the fast deswelling rate make these hydrogels potential candidates for applications in drug release and other biological fields.
Octavinyl polyhedral oligomeric sisesquioxane (OvPOSS) was synthesized via hydrolysis and condensation of vinyltriethoxysilane. The structure of OvPOSS was determined by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), 1 H nuclear magnetic resonance and 29 Si nuclear magnetic resonance. A novel hydroxyl functional polyacrylate latex (HPA) with core–shell structure modified by OvPOSS (OvPOSS/HPA) was successfully prepared via emulsion copolymerization. Consequently two-component waterborne polyurethane (2K-WPU) coatings were prepared by using the as-prepared latex as hydroxyl components and hydrophilic polyisocyanates as curing agents. The structure and properties of OvPOSS/HPA were marked by FTIR, XRD, differential scanning calorimetry and thermogravimetric analysis. The results of FTIR and XRD show that OvPOSS has been successfully embedded into HPA, and OvPOSS occupies a homogeneous distribution in the HPA matrix. The effect of OvPOSS on the properties of OvPOSS/HPA as well as the application performance of 2K-WPU coatings film were also investigated. The results show that OvPOSS/HPA possesses core–shell structure with the OvPOSS core and enhanced thermal stability. The glass transition temperature ( T g ) of OvPOSS/HPA with 2.0% OvPOSS content is 22.3°C, which is 8.4°C higher than that of pure HPA. The performance properties of the 2K-WPU coating films such as pencil hardness were also improved by incorporation of OvPOSS.
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