Affiliation:
1. State Key Laboratory of Fine Chemicals, School of Chemical Engineering Dalian University of Technology Dalian China
2. Technology Innovation Center of High‐Performance Resin Materials, Liaoning Province Dalian China
Abstract
AbstractLimiting 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 Tg + 15°C, while the non‐grafted one was only 3.69%) and 20.70% (at Tg + 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 Tg 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.