EFFECTS OF POROSITY ON PROPERTIES OF MACROPOROUS POLY(VINYL FORMAL) HYDROGELS

The nonionic poly(vinyl formal) hydrogels with different porosities were synthesized by adding pore-forming agents, their swelling/deswelling behaviors and mechanical properties were measured in order to evaluate the effects of porosity. The swelling/deswelling behaviors of hydrogels are depended strongly on the pore diameter and quantities. Higher the porosity, more the absorbed water, faster the response rate. However, the mechanical properties, e.g. swelling pressure, compressive modulus and so on, decrease with the increase of porosity; furthermore, the sensitivity of mechanical behavior to water content decreases accordingly too. In the hydrogel-actuated intelligent material structure and system, selecting the hydrogels with optimum porosity as sensor and actuator is necessary to ensure the fast response rate and the satisfied mechanical behaviors.