title: Swelling-induced optical anisotropy of thermoresponsive hydrogels based on poly(2-(2-methoxyethoxy)ethyl methacrylate): deswelling kinetics probed by quantitative Mueller matrix polarimetry.
abstract: Thermodynamically favored polymer-water interactions below the lower critical solution temperature (LCST) caused swelling-induced optical anisotropy (linear retardance) of thermoresponsive hydrogels based on poly(2-(2-methoxyethoxy)ethyl methacrylate). This was exploited to study the macroscopic deswelling kinetics quantitatively by a generalized polarimetry analysis method, based on measurement of the Mueller matrix and its subsequent inverse analysis via the polar decomposition approach. The derived medium polarization parameters, namely, linear retardance (δ), diattenuation (d), and depolarization coefficient (Δ), of the hydrogels showed interesting differences between the gels prepared by conventional free radical polymerization (FRP) and reversible addition-fragmentation chain transfer polymerization (RAFT) and also between dry and swollen state. The effect of temperature, cross-linking density, and polymerization technique employed to synthesize hydrogel on deswelling kinetics was systematically studied via conventional gravimetry and corroborated further with the corresponding Mueller matrix derived quantitative polarimetry characteristics (δ, d, and Δ). The RAFT gels exhibited higher swelling ratio and swelling-induced optical anisotropy compared to FRP gels and also deswelled faster at 30 °C. On the contrary, at 45 °C, deswelling was significantly retarded for the RAFT gels due to formation of a skin layer, which was confirmed and quantified via the enhanced diattenuation and depolarization parameters.
authors.affiliation: Polymer Research Centre, Department of Chemical Sciences, Indian Institute of Science Education and Research, Kolkata, PO: BCKV Campus Main Office, Mohanpur-741252, Nadia, West Bengal, India.
authors.forename: Nagaraj
authors.initials: N
authors.lastname: Patil
authors.forename: Jalpa
authors.initials: J
authors.lastname: Soni
authors.forename: Nirmalya
authors.initials: N
authors.lastname: Ghosh
authors.forename: Priyadarsi
authors.initials: P
authors.lastname: De
mesh_terms: D016880:Anisotropy; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate / Q000737:chemistry*; D007700:Kinetics; D008689:Methacrylates / Q000138:chemical synthesis / Q000737:chemistry*; D055620:Optical Phenomena; D011108:Polymers / Q000138:chemical synthesis / Q000737:chemistry*; D013696:Temperature
chemical_list: D008689:Methacrylates; D011108:Polymers; C581192:poly(2-(2-methoxyethoxy)ethyl methacrylate); D020136:Hydrogel, Polyethylene Glycol Dimethacrylate