LAUSR

Polystyrene (PS) crosslinked with divinylbenzene is one of the most promising microwave (MW) transparent polymers for structural application. However, preparation of it has been always inhibited by severe thermal runaway. Under this background, novel technology referred to as “3D printing bulk polymerization” is innovated with great advantages on heat release control. Comparing to the multistage batch polymerization as previously reported, the products obtained in present work are also superior on both the thermal–mechanical properties and dielectric properties at MW band. The modulus is improved from 2.43 to 3.06 GPa, and Tg is increased to over 120 °C after crosslinking, while the ultralow dielectric loss feature of PS is well maintained with the loss factor to the order of 10−4. In-depth investigation about the effects of crosslinking on main-chain segments has found it extend to secondary relaxation originates from pendent phenyl groups and resulted in a dispersion shift toward higher band. Based on the Raman study, a possible mechanism is also proposed that the torsional relaxation of side groups is governed by a potential barrier arises from constraint by main-chain of several adjacent atoms through interaction between them. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44865.