The solubility parameters of pure poly(2-hydroxyethyl methacrylate) (PHEMA) and poly(2-hydroxyethyl methacrylate/itaconic acid) [P(HEMA/IA)] hydrogels were determined by 20 solvents with various solubility parameters in swelling experiments. The solubility parameter of pure PHEMA was 26.93 Ϯ 0.46 (MPa) 1/2 . The effect of mole percentages of itaconic acid (IA) in P(HEMA/IA) hydrogels on the solubility parameter was investigated. The measured values were compared to literature and solubility values theoretically determined by group contribution values of van Krevelen and Hoy. The incorporation of IA into the hydrogel system slightly increased the solubility parameter.

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The thermal behavior of poly(2-hydroxyethyl methacrylate) [PHEMA] homopolymer and poly(2-hydroxyethyl methacrylate-co-itaconic acid) [P(HEMA/IA)] copolymeric networks synthesized using a radiationinduced polymerization technique was investigated by differential scanning calorimetry, thermogravimetric analysis, and Fourier transform infrared spectroscopy. The glasstransition temperature (T g ) of the PHEMA homopolymer was found to be 878C. On the other hand, the T g of the P(HEMA/IA) networks increased from 888C to 1178C with an increasing amount of IA in the network system. The thermal degradation reaction mechanism of the P(HEMA/ IA) networks was determined to be different from the PHEMA homopolymer, as confirmed by thermogravimetric analysis. It was observed that the initial thermal degradation temperature of these copolymeric networks increased from 2718C to 3008C with IA content.

In the crystal structure of the title compound, C8H8N2S, the molecules form centrosymmetric dimers via N—H...S hydrogen bonds.

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