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The dynamics of the sol–gel transition in aqueous solutions of poly(vinyl alcohol) was investigated by light scattering. The dynamical studies confirmed that this system has an upper critical solution temperature. In the phase diagram, the spinodal curve crosses the sol–gel transition curve. Essentially this is nothing but the situation predicted by Coniglio et al. as a result of the site‐bond correlated‐percolation problem. The gelation takes place both above and below the spinodal curve, suggesting two modes of gelation: one is accompanied by a spinodal decomposition and the other takes place without liquid–liquid phase separation. In the former case, the dynamics of phase separation at an early stage of gelation is well described within the framework of Cahn's linearized spinodal decomposition theory. The wavelength of the concentration fluctuation at the highest rate of phase separation is about 300 nm.

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