A dynamic light scattering study of hydrogels based on telechelic poly(vinyl alcohol)

Chemical hydrogels based on poly(vinyl alcohol), PVA, were obtained by reacting telechelic PVA bearing aldehydic groups at both ends of the chain with the hydroxylic moiety of the polymer. These networks were studied by dynamic light scattering around the sol-gel transition threshold. The auto-correlation function, g((2))(q,t), displays nonergodic behavior when the system enters the gel phase. Appropriate ensemble averaging of the g((2))(q,t) yields the dynamic structure factor f(q,t). To extract from the f(q,t) the characteristic parameters of the network, we adopted a model originally proposed for colloidal gels. A correct description of the f(q,t) was obtained. The results were compared with those obtained independently on the same type of hydrogels by equilibrium swelling and compression modulus measurements. A link to macroscopic properties of the gels is also shown.