SANS study on the solvated structure and molecular interactions of a thermo-responsive polymer in a room temperature ionic liquid

Kazu Hirosawa; Kenta Fujii; Takeshi Ueki; Yuzo Kitazawa; Kenneth C. Littrell; Masayoshi Watanabe; Mitsuhiro Shibayama

doi:10.1039/c6cp02254e

SANS study on the solvated structure and molecular interactions of a thermo-responsive polymer in a room temperature ionic liquid

Kazu Hirosawa, Kenta Fujii, Takeshi Ueki, Yuzo Kitazawa, Kenneth C. Littrell, Masayoshi Watanabe, Mitsuhiro Shibayama

Instrument Development Group

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Abstract

We have utilized small-angle neutron scattering (SANS) to quantitatively characterize the LCST-type phase behavior of the poly(benzyl methacrylate) (PBnMA) derivative poly(2-phenylethyl methacrylate) (PPhEtMA) in the deuterated ionic liquid (IL) d₈-1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide (d₈-[C₂mIm⁺][TFSA^-]). The SANS curves showed a discontinuous change from those characteristics of dispersed polymer chains to those of large aggregates of PPhEtMA chains suspended in the IL solution, indicating that phase separation occurs discontinuously at T_c. Furthermore, we evaluated the enthalpic and entropic contributions to the effective interaction parameter χ_eff of PPhEtMA in [C₂mIm⁺][TFSA^-] and compared them with those of PBnMA. The absolute value of the enthalpic contribution observed for PPhEtMA was smaller than that for PBnMA. This difference in the enthalpic term can be attributed to the unfavorable interaction between the IL and the alkyl group in the side chain of PPhEtMA. In addition, the temperature dependence of χ_eff was smaller than the previously reported value for a thermo-responsive polymer in an aqueous system. It was found out that the strong dependence of T_c on the chemical structure in IL systems originated from the relatively smaller temperature dependence of χ_eff.

Original language	English
Pages (from-to)	17881-17889
Number of pages	9
Journal	Physical Chemistry Chemical Physics
Volume	18
Issue number	27
DOIs	https://doi.org/10.1039/c6cp02254e
State	Published - 2016

Funding

This work has been financially supported by Grants-in-Aid for Scientific Research from the Ministry of Education, Culture, Sports, Science, and Technology (No. 22245018 to M. S.). The experiment (IPTS12408.1) using the General-Purpose SANS (CG-2) at Oak Ridge National Laboratory was supported by the US-Japan Cooperative Program on Neutron Scattering. Travel expenses for the experiment were also supported by General User Program for Neutron Scattering Experiments, Institute for Solid State Physics, The University of Tokyo (proposal no. 14906), at JRR-3, Japan Atomic Energy Agency, Tokai, Japan. The High Flux Isotope Reactor and beamline CG2 of ORNL was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy. K. H. was supported by Japan Society for the Promotion of Science through Program for Leading Graduate Schools (MERIT).

Funders	Funder number
General-Purpose SANS	CG-2
Japan Atomic Energy Agency, Tokai, Japan
Scientific User Facilities Division
US-Japan
U.S. Department of Energy
Basic Energy Sciences
Japan Society for the Promotion of Science	26620164, 15H05495, 15H05758, 16H02277
Ministry of Education, Culture, Sports, Science and Technology	22245018, IPTS12408.1
University of Tokyo	14906

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title = "SANS study on the solvated structure and molecular interactions of a thermo-responsive polymer in a room temperature ionic liquid",

abstract = "We have utilized small-angle neutron scattering (SANS) to quantitatively characterize the LCST-type phase behavior of the poly(benzyl methacrylate) (PBnMA) derivative poly(2-phenylethyl methacrylate) (PPhEtMA) in the deuterated ionic liquid (IL) d8-1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide (d8-[C2mIm+][TFSA-]). The SANS curves showed a discontinuous change from those characteristics of dispersed polymer chains to those of large aggregates of PPhEtMA chains suspended in the IL solution, indicating that phase separation occurs discontinuously at Tc. Furthermore, we evaluated the enthalpic and entropic contributions to the effective interaction parameter χeff of PPhEtMA in [C2mIm+][TFSA-] and compared them with those of PBnMA. The absolute value of the enthalpic contribution observed for PPhEtMA was smaller than that for PBnMA. This difference in the enthalpic term can be attributed to the unfavorable interaction between the IL and the alkyl group in the side chain of PPhEtMA. In addition, the temperature dependence of χeff was smaller than the previously reported value for a thermo-responsive polymer in an aqueous system. It was found out that the strong dependence of Tc on the chemical structure in IL systems originated from the relatively smaller temperature dependence of χeff.",

author = "Kazu Hirosawa and Kenta Fujii and Takeshi Ueki and Yuzo Kitazawa and Littrell, {Kenneth C.} and Masayoshi Watanabe and Mitsuhiro Shibayama",

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year = "2016",

doi = "10.1039/c6cp02254e",

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T1 - SANS study on the solvated structure and molecular interactions of a thermo-responsive polymer in a room temperature ionic liquid

AU - Hirosawa, Kazu

AU - Fujii, Kenta

AU - Ueki, Takeshi

AU - Kitazawa, Yuzo

AU - Littrell, Kenneth C.

AU - Watanabe, Masayoshi

AU - Shibayama, Mitsuhiro

PY - 2016

Y1 - 2016

N2 - We have utilized small-angle neutron scattering (SANS) to quantitatively characterize the LCST-type phase behavior of the poly(benzyl methacrylate) (PBnMA) derivative poly(2-phenylethyl methacrylate) (PPhEtMA) in the deuterated ionic liquid (IL) d8-1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide (d8-[C2mIm+][TFSA-]). The SANS curves showed a discontinuous change from those characteristics of dispersed polymer chains to those of large aggregates of PPhEtMA chains suspended in the IL solution, indicating that phase separation occurs discontinuously at Tc. Furthermore, we evaluated the enthalpic and entropic contributions to the effective interaction parameter χeff of PPhEtMA in [C2mIm+][TFSA-] and compared them with those of PBnMA. The absolute value of the enthalpic contribution observed for PPhEtMA was smaller than that for PBnMA. This difference in the enthalpic term can be attributed to the unfavorable interaction between the IL and the alkyl group in the side chain of PPhEtMA. In addition, the temperature dependence of χeff was smaller than the previously reported value for a thermo-responsive polymer in an aqueous system. It was found out that the strong dependence of Tc on the chemical structure in IL systems originated from the relatively smaller temperature dependence of χeff.

AB - We have utilized small-angle neutron scattering (SANS) to quantitatively characterize the LCST-type phase behavior of the poly(benzyl methacrylate) (PBnMA) derivative poly(2-phenylethyl methacrylate) (PPhEtMA) in the deuterated ionic liquid (IL) d8-1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide (d8-[C2mIm+][TFSA-]). The SANS curves showed a discontinuous change from those characteristics of dispersed polymer chains to those of large aggregates of PPhEtMA chains suspended in the IL solution, indicating that phase separation occurs discontinuously at Tc. Furthermore, we evaluated the enthalpic and entropic contributions to the effective interaction parameter χeff of PPhEtMA in [C2mIm+][TFSA-] and compared them with those of PBnMA. The absolute value of the enthalpic contribution observed for PPhEtMA was smaller than that for PBnMA. This difference in the enthalpic term can be attributed to the unfavorable interaction between the IL and the alkyl group in the side chain of PPhEtMA. In addition, the temperature dependence of χeff was smaller than the previously reported value for a thermo-responsive polymer in an aqueous system. It was found out that the strong dependence of Tc on the chemical structure in IL systems originated from the relatively smaller temperature dependence of χeff.

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ER -

SANS study on the solvated structure and molecular interactions of a thermo-responsive polymer in a room temperature ionic liquid

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