Reducing the dielectric loss of poly(aryl ether)s by grafting
Limiting molecules' polarized motion effectively reduces the dielectric loss of materials. This article synthesized side chains with different lengths using p-ethoxyphenol, p-hydroxybenzoic acid, and long-chain halohydrins through a two-step process. These chains' movement was almost unaffected by the main chain of polymers, so they can fill up the free volume of polymers under certain conditions. 1,2-dihydro-4-(4-hydroxyphenyl)phthalazine-1-(2H)-one(DHPZ), 4,4'-Difluorophenyl sulfone(DFS), and 4,4-Bis(4-hydroxyphenyl) valeric acid(HPV) obtained three polymers with different carboxyl groups (10%, 30%, and 50%) through nucleophilic substitution. They were then grafted and treated with hot-pressing. The introduction of side chains could reduce the free volume of polymers under hot-pressing conditions, so further reducing the dielectric loss of materials. Polymer with the shortest and least (10%) side chains showed the most obvious dielectric loss tangent, the reduction rate of the film's dielectric loss tangent was 13.11% (at T g + 15°C, while the non-grafted one was only 3.69%) and 20.70% (at T g + 80°C, while the non-grafted one was only 8.35%), respectively. In addition, WXRD and DMA tests showed that films' intermolecular chain spacing (“ d ”) and T g changed after the hot-pressing process, respectively. The change law of both was consistent with that of dielectric loss tangent. Confirm that grafting high-motility side chains can significantly reduce polymer's dielectric loss by enhancing the free volume reduction effect after hot-pressing.
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