| Autor: |
Seto, Ryosuke, Kanamura, Kiyoshi, Yoshida, Satoshi, Kajihara, Koichi |
| Předmět: |
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| Zdroj: |
Dalton Transactions: An International Journal of Inorganic Chemistry; 2/28/2020, Vol. 49 Issue 8, p2487-2495, 9p |
| Abstrakt: |
Thermoplastic poly(phenylsilsesquioxane) [poly(Ph-SQ)] and its copolymers with R-SQ units of linear aliphatic R groups [poly(Ph-co-R-SQ) (R = Me, Et, Pr, and Vi)] were synthesised by cosolvent-free hydrolytic polycondensation from acid-catalysed water–organotrimethoxysilane binary systems. These compounds became transparent glasses with coefficents of linear thermal expansion of ∼1 × 10−4 K−1 and Vickers hardnesses of 50–110 MPa when thermally treated at or above 100 °C. Poly(Ph-SQ) formed a fragile melt with kinetic fragility (F1/2 ≳ 0.8) as high as that of molecular glasses. The low melting temperature and high fragility probably arise from weak attractive π interactions between phenyl groups that readily dissociate on heating, disordered Si–O frameworks, and low average molar mass (∼103 g mol−1). Proton NMR measurements confirmed other weak attractive CH/π interactions between phenyl and R groups in poly(Ph-co-R-SQ). Poly(Ph-SQ) and poly(Ph-co-R-SQ) glasses were hydrophilic and strongly bonded to a glass plate because of the presence of residual SiOH groups, while thermosetting by polycondensation was insignificant at or below 140 °C. The poly(Ph-SQ) glass was brittle, and macroscopic cracks were formed when melted on a glass plate as a result of a thermal expansion coefficient mismatch. Such crack formation was suppressed by incorporating Et-SQ, Pr-SQ, or Vi-SQ units and enhancing structural relaxation. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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