title: Volume phase transition mechanism of poly[oligo(ethylene glycol)methacrylate] based thermo-responsive microgels with poly(ionic liquid) cross-linkers.
abstract: Thermo-dynamic volume phase transition mechanisms of poly[oligo(ethylene glycol)methacrylate] (POEGMA) based microgels with poly(ionic liquid) (PIL) cross-linking moieties are investigated in detail on the basis of temperature-dependent Fourier transform infrared (FTIR) spectroscopy. The original FTIR data are further analysed by two-dimensional correlation spectroscopy (2Dcos) with the perturbation correlation moving window (PCMW) technique. It is observed that the content of hydrophilic PIL cross-linking structure strongly affects the temperature induced volume phase transition mechanism of microgels in which the less cross-linked microgel exhibits a sharp volume phase transition process while the highly cross-linked microgel presents a broad transition behavior. Peculiarly, the dehydration of C-H groups acts as the driving force for the whole phase transition process within the less cross-linked microgel network and cooperative response of chemical groups is identified. It is deduced that the hydrophilic PIL moieties develop polymer-water-polymer interactions with C=O groups as C=O···D2O-PIL hydrogen bonds emerge in the less cross-linked system. As regards the highly cross-linked microgel system, the phase transition process is driven by the disruption of hydrogen bonds between C=O groups and water molecules while the response of C-H groups becomes insensitive. PIL moieties passively dehydrate following the dehydration of C-H groups on oligo(ethylene glycol) side chains and no hydrogen bond between C=O group and IL-D2O association appears during the phase transition process.
authors.affiliation: State Key Laboratory of Molecular Engineering of Polymers, Collaborative Innovation Center of Polymers and Polymer Composite Materials, Department of Macromolecular Science and Laboratory of Advanced Materials, Fudan University, Shanghai, 200433, P. R. China. peiyiwu@fudan.edu.cn huitang@fudan.edu.cn.
authors.forename: Yuanyuan
authors.initials: Y
authors.lastname: Zhou
authors.forename: Hui
authors.initials: H
authors.lastname: Tang
authors.forename: Peiyi
authors.initials: P
authors.lastname: Wu
mesh_terms: D000067493:Dynamic Light Scattering; D005782:Gels / Q000737:chemistry; D006860:Hydrogen Bonding; D057927:Hydrophobic and Hydrophilic Interactions; D052578:Ionic Liquids / Q000737:chemistry*; D044367:Phase Transition; D011092:Polyethylene Glycols / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D013696:Temperature
chemical_list: D005782:Gels; D052578:Ionic Liquids; C450003:poly(ethylene glycol) methacrylate polymer; D011092:Polyethylene Glycols