Solvent induced shape recovery of shape memorypolymer based on chemically cross-linked poly(vinyl alcohol)

Abstract

A shape memory polymer based on poly(vinyl alcohol) (SM-PVA) chemically cross-linked with glutaraldehyde exhibits good temperature responsive shape memory behavior. In the present investigation, solvent-induced shape memory behavior is observed by immersing this kind of SM-PVA in good or poor solvents (including water, DMF, and EG etc.) for PVA. A significant indication of shape memory is the decrease of the glass transition temperature (T_g), which is caused by PVA swelling in certain solvents. Differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), swelling equilibrium and bending tests are carried out to find the mechanism behind this interesting phenomenon. Factors that influence the permeation of solvents in the polymer depend on the rate and degree of swelling and whether swelling will occur, which determines the shape recovery ratio in different solvents. Water can induce shape recovery in a shorter time than organic solvents. The structure of water and PVA, and the interaction between them, contribute to the shorter recovery time. SM-PVA has an excellent shape recovery ratio even after several test cycles. Using solvents as a stimulus for shape memory behavior will extend applications of SMPs, especially in the field of medical devices, where stimulus instead of heat is highly desired.