Effect of precise and non-precise linker length, backbone polarity, and dispersity on crystallization and rheological properties of dynamic ethylene networks

Precise placement of ionic and non-ionic side groups has been shown to have a strong impact on the crystallization of polyolefins and polyacetals, resulting in unique temperature-dependent crystal phases and enhanced proton conduction. A series of dynamic ethylene networks were synthesized with 8-18 carbons between dynamic bonds to study the effect of precise and non-precise linker length, backbone polarity and dispersity on crystallization and rheological properties of these networks. Precise and non-precise linkers show negligible differences in the rubbery plateau modulus and have similar glass transition temperatures (T_g), but the induction period for crystallization in the non-precise networks is longer than a precise network with the same average crosslink density. Comparison of the (T_g) normalized relaxation times of dynamic ethylene oxide vs dynamic ethylene networks suggests that for the same precise linker length the backbone polarity doesn’t influence relaxation behavior. Odd vs even numbered carbon linker lengths have been reported to show a periodic up-down trend in T_g, T_m, and ion conductivity in permanent networks, highlighting the importance of precise chemistry on network properties. In contrast, odd-even effect is not observed in our dynamic ethylene networks.