Organic solvent-free gelation of syndiotactic-rich poly(vinyl alcohol)

Abstract

Poly(vinyl alcohol) (PVA) is commonly used in a wide variety of applications due to its desirable characteristics. However, limitations exist regarding its solubility and mechanical properties. To address this, the gelation of syndiotactic-rich polyvinyl alcohol (sPVA) with a regular three-dimensional structure was performed using an organic solvent-free approach. The obtained sPVA exhibited a higher crystallinity than the commonly used atactic PVA (aPVA). However, both systems exhibit low solubilities in solvents such as water and dimethyl sulfoxide due to their high crystallinities, thereby rendering it impossible to exploit their properties. However, since the hot pressing method does not require the dissolution of PVA in a solvent, it is possible to perform gelation even using sparingly soluble materials such as sPVA. Consequently, a hydrogel was formed by applying the hot pressing method to water-swollen sPVA. The obtained sPVA hydrogel (sPVA-H) was subsequently dried and heat-treated at different temperatures to compare its crystallinity and thermal and mechanical properties with those of the aPVA hydrogel (aPVA-H). It was found that sPVA-H exhibited comparable properties to the original sPVA-H following heat treatment at higher temperatures, and also when heat-treated at a temperatures lower than those required for aPVA-H. The obtained results indicated that sPVA-H exhibits excellent mechanical properties, suggesting its potential for incorporation in materials for long-term loading applications, such as artificial cartilage.