Gelling behavior of PVA or its blends with other polymers such as polyvinyl pyrrolidone (PVP), polyethylene oxide (PEO), hydroxyl propyl cellulose (HPC), agar and gelatin A has been studied as a function of borax concentration from viscosity measurements. The pH of the borax cross linked hydrogels of PVA or its blends showed an interesting behavior with temperature - it initially increases with temperature up to a maximum and then decreases with further increase in the temperature. Such temperature sensitive transparent hydrogels when embedded with a suitable acid-base indicator like phenolphthalein showed reversible thermochromism. However, thermochromism was not observed in the hydrogels of polymer blends if the amount of PVA in the blend was less than 60%. The results suggest that thermochromism in dye embedded borax cross-linked hydrogels is due to the formation of didiol cross-links between hydroxyl groups in PVA and the borax, which is governed by change in temperature. The effect of the addition of an anionic (SDS), or a non ionic (TX-100) surfactant on the thermochromic behavior of the hydrogels has also been studied.