1998•Molecular crystals and liquid crystals science technology. Section A, Molecular crystals and liquid crystals/Molecular crystals and liquid crystals science and technology. Section A, Molecular crystals and liquid crystalsRequires access
Fluorescence Probe Studies of Thermosensitive N−Isopropylacrylamide Copolymers in Aqueous Solutions
Kaoru Iwai, Naomi Matsumoto, Makiko Niki, Masao Yamamoto
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Abstract
Temperature-induced phase transitions of some N−isopropylacrylamide (NIPAM) copolymers in aqueous solutions were studied with 9-(4-N,N− dimethylaminophenyl)phenanthrene (DP) as an intramolecular fluorescence probe. Lower critical solution temperature (LCST) of DP-labeled NIPAM copolymers depends on the properties and contents of comonomers incorporated in the NIPAM copolymers, i.e., a hydrophobic comonomer such as methyl methacrylate (MMA) lowers the LCST, and a hydrophilic comonomer such as methacrylic acid (MAA) raises it. The higher contents of comonomers, the bigger changes of the LCST. And the micro-environments of the NIPAM copolymers in aqueous solutions also depend on them. The temperature-induced phase transitions of NIPAM copolymers with N-n−propylacrylamide (NNPAM), and N−isopropylmethacrylamide (NIPMAM) appear to be very sharp as well as that of NIPAM homopolymer aqueous solution and their LCST values are good correlated with their copolymer compositions.