Thermodynamics of Swelling of Poly(NIPAM-co-NTBA-co-HEAAm) Hydrogels

In the present study, poly(N-Isopropylacrylacrylamide-co-N-tertiarybutylacrylamide-co-hydroxyethylcrylamide) (NIPAM-co-NTBA-co-HEAAm) hydrogels are prepared with variation of molar ratio of hydrophilic HEAAm and hydrophobic NTBA. The prepared hydrogels are characterized with elemental analysis and Fourier transform infrared (FTIR) spectroscopy. The thermodynamics of swelling properties of poly(NIPAM-co-NTBA-co-HEAAm) hydrogels have also been discussed. The experimental C/N ratios are comparable with the theoretical value. The enthalpy change of mixing ∆H_mix, entropy change of mixing ∆S_mix, free energy change of mixing ∆G_mix are determined for swelling of hydrogels at 25 °C. The value of total free energy of hydrogel swelling is found to be negative which confirms the lower critical solution temperature (LCST) exhibited in all hydrogels and the volume change transition shows the thermoresponsive behavior. The values of ∆S_mix increase and ∆G_mix decrease with increasing amount of hydrophobic NTBA content in the hydrogels. The values of free energy change of elasticity (∆G_el) are found to be increased with increasing the hydrophobic NTBA content followed by decrease in swelling percentage. Also, the transition temperature of the hydrogel is found to be decreased with increasing the hydrophobic NTBA.     

Advances in the Chemistry of 2,4,6-Tri(thiophen-2-yl)-1,3,5-triazine

Heterocyclic systems are now considered to be an integral part of material chemistry. Thiophene, selenophene, furan, pyrrole, carbazole, triazine and others are some such examples worth mentioning. 2,4,6-Tri(thiophen-2-yl)-1,3,5-triazine is a C_3h-symmetric system with thiophene as the donor unit and s-triazine as the acceptor unit. This review gives an insight into the advances made in the thienyl-triazine chemistry over the past two to three decades. The synthetic pathways for arriving at this system and all its important derivatives are provided. The major focus is on the materials synthesized using the thienyl-triazine system, including star molecules, linear and hyperbranched polymers, porous materials and their diverse applications. This review will play a catalytic role for new dimensions to be explored in thienyl-triazine chemistry.