Managing of hydrogen bonding in aqueous poly(vinyl alcohol) solutions: new perspectives towards preparation of more homogeneous poly(vinyl butyral)

Abstract

This paper follows up investigations in the field of solution properties of poly(vinyl alcohol). Here we present a combined investigation based on both theoretical and various experimental methods focused on peculiarities in hydrogen bond reorganization in aqueous poly(vinyl alcohol) solutions discussed as a function of temperature. It was demonstrated that the specific polymeric effect takes place in binary poly(vinyl alcohol)/water systems. The effect is characterized by the delay in response of the polymer system on heating until the critical temperature is reached. It was demonstrated in this paper that hydrogen bond reorganization in binary aqueous systems may lead to an increase in the degree of undesirable intermolecular cross-linking reaction. This finding was in contrast to previously made proposition based on hydrogen bond reorganization in ternary poly(vinyl alcohol) solutions. This assumption based on the theoretical studies was confirmed experimentally. Thus, a series of poly(vinyl butyral) samples were synthesized in various solvents using traditional catalysts (HCl) as well as the modern thermosensitive polymeric catalyst. It was demonstrated by using GPC and viscometry experiments that poly(vinyl butyral) samples with a low degree of acetalization (<10%) prepared in water in the absence of co-solvent additives are characterized by large molecular weights and bimodal molecular weight distribution. On the contrary, polymers prepared in mixed (ternary) systems and in the presence of a thermosensitive polymeric catalyst demonstrate relatively narrow molecular weight distribution. This indicates the preparation of more homogeneous products which also facilitates mechanisms of hydrogen bond reorganizations observed in binary and ternary poly(vinyl alcohol) solutions.