Structural levels of supermolecular organization in aqueous solutions of poly (vinyl alcohol)

The isothermal rise in supermolecular order (SMO) in aqueous solutions of poly (vinyl alcohol) (PVA) over a wide range of temperature and concentration and also under shear has been studied. SMO was characterized by the equivalent average radius of super‐molecular particles (SMP) r Λ , estimated by the turbidity spectrum τ = τ(Λ). The methods of gradient dependence of viscosity electron and polarize‐optical microscopy, and light scattering according to Debye‐Zimm have also been used. It is shown that the process of isothermal rising of SMP over a wide range of temperature and solution concentration consists of two distinct stages: a relatively rapid rise and then a slow rise of SMP. In aqueous PVA solutions SMO represents, generally, the hierarchy of some its levels. The first level is considered to be the supermolecular particles, which form after the dissolution of the whole polymer mass. The character of this level is determined by the microstructure of the sample in the condensed state and dissolution conditions. The particles of the first level are the heterogeneous formation nuclei of the second level–particles of the fibril type. Fibrils, which have risen from the solution at high temperature ( T ≥ 80°C) have shown the ability to aggregate into anisodiametric structures as the solution cools. These aggregates, determined to be the third level, are very sensitive to temperature. In turbulent shear the rising rate of SMO increases greatly as the characteristic concentration is made smaller. The results obtained give us reason to conclude that the rise in SMO in aqueous PVA solutions is due to the crystallization of macromolecules when the low molecular weight component is available.