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Thoms E, Napolitano S. Enthalpy-entropy compensation in the slow Arrhenius process. J Chem Phys 2023; 159:161103. [PMID: 37888759 DOI: 10.1063/5.0174213] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2023] [Accepted: 10/02/2023] [Indexed: 10/28/2023] Open
Abstract
The Meyer-Neldel compensation law, observed in a wide variety of chemical reactions and other thermally activated processes, provides a proportionality between the entropic and the enthalpic components of an energy barrier. By analyzing 31 different polymer systems, we show that such an intriguing behavior is encountered also in the slow Arrhenius process, a recently discovered microscopic relaxation mode, responsible for several equilibration mechanisms both in the liquid and the glassy state. We interpret this behavior in terms of the multiexcitation entropy model, indicating that overcoming large energy barriers can require a high number of low-energy local excitations, providing a multiphonon relaxation process.
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Affiliation(s)
- Erik Thoms
- Laboratory of Polymer and Soft Matter Dynamics, Experimental Soft Matter and Thermal Physics (EST), Université libre de Bruxelles (ULB), Brussels 1050, Belgium
| | - Simone Napolitano
- Laboratory of Polymer and Soft Matter Dynamics, Experimental Soft Matter and Thermal Physics (EST), Université libre de Bruxelles (ULB), Brussels 1050, Belgium
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Suzuki Y, Kano T, Tomii T, Tsuji N, Matsumoto A. Relaxation and Amorphous Structure of Polymers Containing Rigid Fumarate Segments. Polymers (Basel) 2022; 14:polym14224876. [PMID: 36433003 PMCID: PMC9692691 DOI: 10.3390/polym14224876] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2022] [Revised: 11/08/2022] [Accepted: 11/09/2022] [Indexed: 11/16/2022] Open
Abstract
The physical properties of polymers are significantly affected by relaxation processes. Recently, we reported that poly(diethyl fumarate) (PDEF) shows two thermal anomalies on DSC measurement, despite the fact that it is a homopolymer. We attribute these two relaxations α relaxation and β relaxation, respectively. In this study, we investigate the two relaxations of fumarate-containing polymers by DSC, solid-state NMR, and X-ray scattering. The two relaxations are present even in a copolymer of diethyl fumarate and ethyl acrylate with fumarate segments of 30%. We used poly(methyl methacrylate) (PMMA) as a model polymer for comparison, since there are detailed investigations of its dynamics and physical properties. Solid-state NMR indicates that the very local relaxation of poly(fumarate)s is not significantly different from that of PMMA. The tensile test showed that PDEF is still brittle at above β relaxation temperature and below α relaxation temperature. It was revealed that a structural anisotropy appeared when PDEF was extended at around α relaxation temperature. We discuss the effect of the glassy packing of the rigid polymer chain including the DEF segments on the strong β relaxation behavior. Our data provide insight into the microscopic mechanism of β relaxation of vinyl polymers.
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Affiliation(s)
- Yasuhito Suzuki
- Department of Applied Chemistry, Graduate School of Engineering, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai 599-8531, Osaka, Japan
- Department of Applied Chemistry, Graduate School of Engineering, Osaka Metropolitan University, 1-1 Gakuen-cho, Naka-ku, Sakai 599-8531, Osaka, Japan
- Correspondence: (Y.S.); (A.M.)
| | - Takahito Kano
- Department of Applied Chemistry, Graduate School of Engineering, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai 599-8531, Osaka, Japan
| | - Tsuyoshi Tomii
- Department of Applied Chemistry, Graduate School of Engineering, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai 599-8531, Osaka, Japan
| | - Nagisa Tsuji
- Department of Applied Chemistry, Graduate School of Engineering, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai 599-8531, Osaka, Japan
| | - Akikazu Matsumoto
- Department of Applied Chemistry, Graduate School of Engineering, Osaka Prefecture University, 1-1 Gakuen-cho, Naka-ku, Sakai 599-8531, Osaka, Japan
- Department of Applied Chemistry, Graduate School of Engineering, Osaka Metropolitan University, 1-1 Gakuen-cho, Naka-ku, Sakai 599-8531, Osaka, Japan
- Correspondence: (Y.S.); (A.M.)
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