Effects of alkyl polyglucoside on the self-assembly behavior and foam properties of the thermoresponsive triblock copolymer (EO)100(PO)65(EO)100

Abstract

Thermoresponsive liquid foams stabilized with the triblock copolymer (EO)100(PO)65(EO)100 (PF127) have been proved to be effective in suppressing pool fire. Understanding how the low-molecular-weight surfactants affect the properties of thermoresponsive foam stabilized by PF127 is important in the development of fluorine-free firefighting foam. In this work, the effects of the non-ionic surfactant alkyl polyglucoside (APG) on the properties of the foam stabilized by the triblock copolymer PF127 were studied. The relationships among molecular self-assembly, interfacial properties, and foam properties were investigated by conducting scattering experiments and foam aging tests. The results demonstrated that the APG molecules participated in the organization of the mixed micelles with PF127 molecules and the competition of both components in the mixed micelles affected the foaming properties. For the systems containing APG and 20 wt% PF127, APG acted as a foam inhibitor, suppressing foam generation at low concentrations. In contrast, APG acted as the foam booster at high concentrations since the mixed micelles were relatively unstable, allowing more unimers to diffuse to the interfacial region. In the absence of APG, the liquid foam from PF127 exhibited high stability and elasticity under heat due to the ordered structure formed by PF127 micelles inside the foam. As the APG concentration increased, the transition of orderly packed PF127-rich mixed micelles into disordered APG-rich mixed micelles caused the originally inhibited liquid drainage to restart rapidly, making the foams unstable upon heating. The results of this work can give theoretical guidance for the development of thermoresponsive firefighting foams.