Novel poly(vinyl alcohol)/chondroitin sulfate (PVA/CS) composite hydrogels containing hydroxyapatite (HA) or Sr‐doped HA (HASr) particles were synthesized by a freeze/thaw method and characterized aiming towards biomedical applications. HA and HASr were synthesized by a wet‐precipitation method and added to the composite hydrogels in fractions up to 15 wt%. Physical–chemical characterizations of particles and hydrogels included scanning electron microscopy, energy‐dispersive spectroscopy, Fourier‐transform infrared spectroscopy, X‐ray diffraction, thermogravimetry, porosity, compressive strength/elastic modulus, swelling degree, and cell viability. Particles were irregular in shape and appeared to have narrow size variation. The thermal behavior of composite hydrogels was altered compared to the control (bare) hydrogel. All hydrogels exhibited high porosity. HA/HASr particles reduced total porosity without reducing pore size. The mechanical strength was improved as the fraction of HA or HASr was increased. HASr particles led to a faster water uptake but did not interfere with the total hydrogel swelling capacity. In cell viability essay, increased cell growth (above 120%) was observed in all groups including the control hydrogel, suggesting a bioactive effect. In conclusion, PVA/CS hydrogels containing HA or HASr particles were successfully synthesized and showed promising morphological, mechanical, and swelling properties, which are particularly required for scaffolding.

The goal of this work was to measure the solubility of terephthalic acid (TA) in six pure solvents (2-ethyl-1-hexanol (2EH), dimethyl sulfoxide, 1-methyl-2-pyrrolidinone, N,N-dimethylformamide, N,N-dimethylacetamide, and pyridine) and five binary mixtures (composed of 2EH and 5 or 10% w/w another solvent) from 313.15 to 363.15 K at atmospheric pressure 101.3 kPa. Experiments were performed by an isothermal method employing an in situ filter to sample only the homogeneous liquid phase, and samples were analyzed by liquid chromatography. Solubility of TA in 2EH is 100-fold lower when compared to the other studied solvents, but a binary mixture composed of 2EH and 5 or 10% w/w (solute-free basis) dimethyl sulfoxide could increase solubility up to 61 and 165%, respectively. Furthermore, the parameters of λh, Apelblat, Wilson, and NRTL models were estimated. All of the models fitted the experimental data with good agreement, but the nonrandom two-liquid (NRTL) model was the most suitable to represent experimental data.

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