Thermal behavior of ethylene copolymers with di- and tri-alkenylsilsesquioxane comonomers synthesized by post-metallocen
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Thermal behavior of ethylene copolymers with di‑ and tri‑alkenylsilsesquioxane comonomers synthesized by post‑metallocene catalysts Paweł Groch1 · Katarzyna Dziubek1 · Krystyna Czaja1 · Beata Sacher‑Majewska1 Received: 30 August 2019 / Accepted: 24 February 2020 © The Author(s) 2020
Abstract This paper reported thermal properties of ethylene copolymers with di- and tri-alkenylsilsesquioxanes (POSS) synthesized by bis(phenoxy-imine) Ti, Zr, V, and V salen-type complexes. Ethylene copolymers with multi-alkenyl POSS obtained by such complexes contain multi-alkenyl POSS incorporated into the polymer chain as a side group. They were characterized by different thermal behavior depending on the kind of multi-alkenyl POSS comonomer, and type of the catalyst used, as well as polymerization conditions and thus the structure of the copolymer chain. Ethylene/POSS copolymers differed in incorporation of POSS into the polymer chain, content of specific unsaturation groups, and molecular weight, as well as heterogeneity of polymer chain compositions. The incorporation of multi-alkenyl POSS into the polymer chain affected melting and crystallization processes of copolymers in different ways. The POSS units could act as a nucleating agent of macromolecules. The increasing POSS content in E/POSS copolymers resulted in increasing thermal stability of obtained products, regardless of the kind of multi-alkenylsilsesquioxanes used. Thermal stability of such copolymers increased with decreasing content of trisubstituted vinylene groups (internal saturations) as well. The highest improvement of thermal stability over 85 °C in comparison with PE was observed in case of E/POSS copolymers synthesized by bis(phenoxy-imine) zirconium catalyst. The composition heterogeneity of E/POSS copolymers was found to affect markedly thermal stability of E/POSS copolymers. Keywords Ethylene · Multi-alkenyl polyhedral oligomeric silsesquioxanes (POSS) · Copolymers · Thermal stability · Melting and crystallization process
Introduction One of the most promising methods for improving thermal stability of polyolefins is development of new materials containing polyhedral oligomeric silsesquioxanes (POSS) [1, 2]. POSS are a class of interesting nano-scale units for the synthesis of organic–inorganic hybrid materials [3–9]. Indeed, incorporation of POSS into polymer chain results in improvement of physicochemical properties, such as mechanical properties [10], thermal stability [1], thermooxidative resistance [1], and flammability [11, 12] in comparison with unmodified polymers.
* Paweł Groch [email protected] 1
Faculty of Chemistry, Opole University, Oleska 48, 45‑052 Opole, Poland
A typical POSS molecule is composed of a Si–O cage and several reactive or unreactive organic groups attached to Si atoms. POSS compounds containing at least one reactive substituent can be introduced into the polymer chain via polymerization or reactive grafting methods. Monofunctional POSS macromonomers can be incorporated into the polymer chain as pendant side group
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