Semicrystalline poly(vinyl alcohol) films and their blends with poly(acrylic acid) and poly(ethylene glycol) for drug delivery applications

Semicrystalline films of poly(vinyl alcohol) (PVA) were prepared by annealing amorphous PVA films at temperatures above the glass transition temperature of 85°C, thus allowing the macromolecules to form crystallites, which stabilized the films and made them behave as if they were chemically cross-linked. Films were prepared by casting a 15% aqueous PVA solution onto glass slides and annealing them at temperatures ranging from 90 to 120°C at 15 to 90 min. The degree of crystallinity of the dry films was measured by differential scanning calorimetry. As the annealing time increased, the degree of crystallinity increased up to a maximum value of about 48%. Swelling studies were performed by placing the films in deionized water at 37°C until they reached equilibrium, typically in 3 to 4 days. The water uptake was inversely proportional to the degree of crystallinity. Poly(acrylic acid) (PAA) and poly(ethylene glycol) (PEG) were blended with PVA in amounts of 15 and 25 wt% to add desirable properties to the ensuing films. Annealing studies showed that the addition of PAA decreased the crystallinity of the films while introducing pH sensitivity. Swelling studies of the PAA/PVA blends were performed in phosphate buffer solutions at varying pH levels. The studies showed that increasing pH from 3 to 6 caused an increase in the swelling of the films. Annealing studies also showed co-crystallization of PEG and PVA and molecular interactions between the molecules. These films exhibit excellent properties for drug delivery applications due to their stability, lack of toxic leachable compounds and high swellability.