Crosslinked polyurethane-based gels

Abstract

Crosslinked polyurethanes (CPUs) were synthesized by reaction of (ethylene oxide-propyleneoxide-ethyleneoxide) (EO-PO-EO) triblock copolymer with diisocyanate and a low molecular weight triol as a crosslinking agent. The short diol was used as a chain extender. The effect of some factors such as the nature and content of PAOs, short diol chain extender and triol crosslinking agent on the phase separation of CPUs was studied by infrared spectroscopy (IR) and differential scanning calorimetry (DSC). The presence of amine group-containing compounds favors the phase separation of CPUs. The swelling behavior of CPUs in the different media such as aqueous solution and ethanol (EtOH)-water mixture has been investigated. The CPUs show the negatively thermosensitive swelling behavior. The collapsing swelling process in response to the change in environmental temperature was observed in CPUs prepared from EO-PO-EO triblock copolymer having a commercial code L92. In a EtOH-water mixture, CPUs reached the maximum swelling degree at the ratio EtOH/water congruent to 80/20 at the whole range of the environmental temperature due to the coupling effect.