The Difference in Molecular Orientation and Interphase Structure of SiO<sub>2</sub>/Shape Memory Polyurethane in Original, Programmed and Recovered States during Shape Memory Process
In order to further understand the shape memory mechanism of a silicon dioxide/shape memory polyurethane (SiO<sub>2</sub>/SMPU) composite, the thermodynamic properties and shape memory behaviors of prepared SiO<sub>2</sub>/SMPU were characterized. Dynamic changes in the molec...
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MDPI AG
2020-09-01
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| Series: | Polymers |
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| Online Access: | https://www.mdpi.com/2073-4360/12/9/1994 |
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| author | Shuang Shi Tao Xu Dawei Wang Markus Oeser |
| author_facet | Shuang Shi Tao Xu Dawei Wang Markus Oeser |
| author_sort | Shuang Shi |
| collection | DOAJ |
| description | In order to further understand the shape memory mechanism of a silicon dioxide/shape memory polyurethane (SiO<sub>2</sub>/SMPU) composite, the thermodynamic properties and shape memory behaviors of prepared SiO<sub>2</sub>/SMPU were characterized. Dynamic changes in the molecular orientation and interphase structures of SiO<sub>2</sub>/SMPU during a shape memory cycle were then discussed according to the small angle X-ray scattering theory, Guinier’s law, Porod approximation, and fractal dimension theorem. In this paper, a dynamic mechanical analyzer (DMA) helped to determine the glass transition start temperature (<i>T</i><sub>g</sub>) by taking the onset point of the sigmoidal change in the storage modulus, while transition temperature (<i>T</i><sub>trans</sub>) was defined by the peak of tan δ, then the test and the calculated results indicated that the <i>T</i><sub>g</sub> of SiO<sub>2</sub>/SMPU was 50.4 °C, and the <i>T</i><sub>trans</sub> of SiO<sub>2</sub>/SMPU was 72.18 °C. SiO<sub>2</sub>/SMPU showed good shape memory performance. The programmed SiO<sub>2</sub>/SMPU showed quite obvious microphase separation and molecular orientation. Large-size sheets and long-period structures were formed in the programmed SiO<sub>2</sub>/SMPU, which increases the electron density difference. Furthermore, some hard segments had been rearranged, and their gyration radii decreased. In addition, several defects formed at the interfaces of SiO<sub>2</sub>/SMPU, which caused the generation of space charges, thus leading to local electron density fluctuations. The blurred interphase structure and the intermediate layer formed in the programmed SiO<sub>2</sub>/SMPU and there was evident crystal damage and chemical bond breakage in the recovered SiO<sub>2</sub>/SMPU. Finally, the original and recovered SiO<sub>2</sub>/SMPU samples belong to the surface fractal system, but the programmed sample belongs to the mass fractal and reforms two-phase structures. This study provides an insight into the shape memory mechanism of the SiO<sub>2</sub>/SMPU composite. |
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| spelling | doaj.art-5c63fed32e2e460b850a3e73c7578b542023-11-20T12:16:08ZengMDPI AGPolymers2073-43602020-09-01129199410.3390/polym12091994The Difference in Molecular Orientation and Interphase Structure of SiO<sub>2</sub>/Shape Memory Polyurethane in Original, Programmed and Recovered States during Shape Memory ProcessShuang Shi0Tao Xu1Dawei Wang2Markus Oeser3College of Civil Engineering, Nanjing Forestry University, 159, Longpan Road, Nanjing 210037, ChinaCollege of Civil Engineering, Nanjing Forestry University, 159, Longpan Road, Nanjing 210037, ChinaInstitute of Highway Engineering, RWTH Aachen University, Mies-van-der-Rohe-Street 1, 52074 Aachen, GermanyInstitute of Highway Engineering, RWTH Aachen University, Mies-van-der-Rohe-Street 1, 52074 Aachen, GermanyIn order to further understand the shape memory mechanism of a silicon dioxide/shape memory polyurethane (SiO<sub>2</sub>/SMPU) composite, the thermodynamic properties and shape memory behaviors of prepared SiO<sub>2</sub>/SMPU were characterized. Dynamic changes in the molecular orientation and interphase structures of SiO<sub>2</sub>/SMPU during a shape memory cycle were then discussed according to the small angle X-ray scattering theory, Guinier’s law, Porod approximation, and fractal dimension theorem. In this paper, a dynamic mechanical analyzer (DMA) helped to determine the glass transition start temperature (<i>T</i><sub>g</sub>) by taking the onset point of the sigmoidal change in the storage modulus, while transition temperature (<i>T</i><sub>trans</sub>) was defined by the peak of tan δ, then the test and the calculated results indicated that the <i>T</i><sub>g</sub> of SiO<sub>2</sub>/SMPU was 50.4 °C, and the <i>T</i><sub>trans</sub> of SiO<sub>2</sub>/SMPU was 72.18 °C. SiO<sub>2</sub>/SMPU showed good shape memory performance. The programmed SiO<sub>2</sub>/SMPU showed quite obvious microphase separation and molecular orientation. Large-size sheets and long-period structures were formed in the programmed SiO<sub>2</sub>/SMPU, which increases the electron density difference. Furthermore, some hard segments had been rearranged, and their gyration radii decreased. In addition, several defects formed at the interfaces of SiO<sub>2</sub>/SMPU, which caused the generation of space charges, thus leading to local electron density fluctuations. The blurred interphase structure and the intermediate layer formed in the programmed SiO<sub>2</sub>/SMPU and there was evident crystal damage and chemical bond breakage in the recovered SiO<sub>2</sub>/SMPU. Finally, the original and recovered SiO<sub>2</sub>/SMPU samples belong to the surface fractal system, but the programmed sample belongs to the mass fractal and reforms two-phase structures. This study provides an insight into the shape memory mechanism of the SiO<sub>2</sub>/SMPU composite.https://www.mdpi.com/2073-4360/12/9/1994shape memory polyurethaneSiO<sub>2</sub> particlesmolecular orientationinterphase structure |
| spellingShingle | Shuang Shi Tao Xu Dawei Wang Markus Oeser The Difference in Molecular Orientation and Interphase Structure of SiO<sub>2</sub>/Shape Memory Polyurethane in Original, Programmed and Recovered States during Shape Memory Process Polymers shape memory polyurethane SiO<sub>2</sub> particles molecular orientation interphase structure |
| title | The Difference in Molecular Orientation and Interphase Structure of SiO<sub>2</sub>/Shape Memory Polyurethane in Original, Programmed and Recovered States during Shape Memory Process |
| title_full | The Difference in Molecular Orientation and Interphase Structure of SiO<sub>2</sub>/Shape Memory Polyurethane in Original, Programmed and Recovered States during Shape Memory Process |
| title_fullStr | The Difference in Molecular Orientation and Interphase Structure of SiO<sub>2</sub>/Shape Memory Polyurethane in Original, Programmed and Recovered States during Shape Memory Process |
| title_full_unstemmed | The Difference in Molecular Orientation and Interphase Structure of SiO<sub>2</sub>/Shape Memory Polyurethane in Original, Programmed and Recovered States during Shape Memory Process |
| title_short | The Difference in Molecular Orientation and Interphase Structure of SiO<sub>2</sub>/Shape Memory Polyurethane in Original, Programmed and Recovered States during Shape Memory Process |
| title_sort | difference in molecular orientation and interphase structure of sio sub 2 sub shape memory polyurethane in original programmed and recovered states during shape memory process |
| topic | shape memory polyurethane SiO<sub>2</sub> particles molecular orientation interphase structure |
| url | https://www.mdpi.com/2073-4360/12/9/1994 |
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