Citation

Lan Ma, Hui Tang, and Peiyi Wu*. Volume Phase Transition Mechanism of Poly[Di(Ethylene Glycol)Ethyl Ether Acrylate] Based Microgels Involving Thermosensitive Poly(Ionic Liquid). Langmuir 2017, 33, 12326-12335.

Abstract

Microdynamic volume phase transition mechanism of poly[di(ethylene glycol)ethyl ether acrylate] (PDEGA) based microgels with newly developed thermo-responsive poly (ionic liquid) (PIL) (poly(tetrabutylphosphonium styrenesulfonate), P[P4,4,4,4][SS]) moieties was studied by applying temperature-variable Fourier transform infrared (FTIR) spectroscopy in combination with two-dimensional correlation spectroscopy (2Dcos) and perturbation correlation moving window (PCMW) technique. It can be found that the content of hydrophilic PIL moieties plays a significant role in the thermally induced phase transition behavior of microgel system, namely, the microgels containing less PIL moieties present a sharp transition behavior and a gel-like state (10%, w/v) in water while the microgels with more PIL moieties exhibit a slightly broad phase transition process and a flowable solution state. Herein, the C=O···D2O-PIL hydrogen bonds as the interaction between PDEGA and P[P4,4,4,4][SS] moieties result in a complete dehydration process for the microgels with less PIL moieties and the dehydrated behavior of SO3- groups acts as the driving force during the phase transition. As for the microgels with more PIL moieties, the whole transition process is dominated by the hydrophobic interaction of C-H groups. Even though the intermolecular hydrogen bonds (C=O···D2O-PIL) appear as well, the more remarkable effect of coulombic repulsive force of PIL restrain the water molecules from breaking away, thus causes a gradual and incomplete dehydration process during heating.