Chemical–physical behavior of hydrogels of poly(vinyl alcohol) and poly(ethylene glycol)

Variation of t/W as a function of time for PEG/PVA hydrogels, at 25°C. [Display omitted] •New gels based on PEG and PVA of different degrees of hydrolysis were synthesized.•PVA degree of hydrolysis and PEG content of the network control the swelling capacity.•The pH influences the degree of swelling and the rate of hydrolysis of the hydrogel.•The degree of hydration decreases with temperature because their entropy is negative. New hydrogels based on polyethylene glycol (PEG) and poly(vinyl alcohol) (PVA) of different degrees of hydrolysis were synthesized. To form the network the PEG was modified at their ends with acyl chloride groups to be used as the crosslinking agent. The compositions of the hydrogels were between 50% and 90% by weight of PEG and PVA of various degrees of hydrolysis were used. It was found that the degree of hydrolysis of the PVA and the PEG content influence the equilibrium water content of the hydrogel. The process of swelling of all the hydrogels prepared followed a second-order kinetics. The pH of the medium influences the rate and degree of hydration of the hydrogel, this influence being less noticeable at lower pH values. At pH of 7.0 and above because the hydrolysis of the ester bonds which act as crosslinking points the swelling increases noticeably. The rate of hydrolysis of the hydrogels is greatly influenced by the degree of hydrolysis of the PVA used in their synthesis. The degree of hydration decreases with temperature because their entropy of mixing is negative; however, when the pH of the medium favors the process of hydrolysis, an increase in temperature accelerates this process, which causes a progressive increase in their degree of hydration.