IR investigation of hydrogen bonds in weakly hydrated films of poly(vinyl alcohol)

Bioinspired strategy for tuning thermal stability of PVA via hydrogen-bond crosslink

“…Poly (vinyl alcohol) (PVA) is a commercially important semi-crystalline, hydrophilic polymers due to many outstanding features including good biocompatibility, biodegradability, gas barrier and water-solubility [1,2]. These properties make PVA extensively used as membranes for proton-exchange, permeability and separation, drug delivery carriers and flexible packaging films.…”

“…These properties make PVA extensively used as membranes for proton-exchange, permeability and separation, drug delivery carriers and flexible packaging films. [1][2][3] However, PVA is extremely thermally unstable especially during melt, which is primarily attributed to its strong intermolecular interactions through hydroxyl groups, making the melting point (T m ) of PVA very close to the initial degradation temperature (T i ) [3,4]. Thus, creating thermally stable PVA is highly attractive and significant for its melt processing.…”

Effect of inorganic salts on the crystallinity of polyvinyl alcohol

“…We know that the weak crystallization of PVA from aqueous solutions is due to hydrogen bonds and hydrophobic interactions between the polymer and the water molecules [10]. The maximum amount of bound water is no greater than three H 2 O molecules per elementary unit of the PVA [11]. We also know that in aqueous solutions, the salt ions are surrounded by hydration shells [12,13].…”

“…It is of interest to compare the degree of crystallinity of PVA that can be achieved as a result of introducing a salt additive with the degree of crystallinity that can be achieved by high-temperature annealing of the polymer. The reason for such behavior involves the fact that PVA films cast from aqueous solutions at room temperature contain about 10% residual water [11]. Upon annealing of the films, the residual water has a plasticizing effect on the polymer chains, increasing their kinetic mobility, which accelerates crystallization.…”

“…Upon annealing of the films, the residual water has a plasticizing effect on the polymer chains, increasing their kinetic mobility, which accelerates crystallization. During annealing, the water is desorbed and the PVA-water hydrogen bonds are replaced by PVA-PVA hydrogen bonds [11], which reduces the mobility of the chains and hinders crystallization. (5).…”