Facile Preparation of an Intrinsically Low Dielectric and High Thermal Conductivity Biobased (Magnolol) Polysiloxane Film

In response to the limitations imposed on the microelectronics industry by electronic crosstalk losses and signal delays, as well as the rapid accumulation of heat, intrinsically low dielectric and high thermal conductivity materials are in urgent demand. Here, a self-curable biobased silane precursor (M@KH590) with a biphenyl unit was synthesized. A series of films (magnolol polysiloxane films (MPSOs)) were prepared using simple sol–gel film conversion and annealing and modulated intermolecular forces and molecular structure. The red-shift of the UV–vis absorption indicated that a larger π–π conjugated system was established. As a result, the through-plane thermal conductivity of MPSO-140 was 0.601 W·m–1·K–1, which was more than three times that of the pure polysiloxane material. Meanwhile, MPSO-140 exhibited excellent intrinsic low dielectric properties (Dk = 2.52, Df = 0.000572, and f = 100 MHz). This was mainly attributed to the reduction of highly polar substances and groups as well as the difficulty in polarizing a π–π conjugated system. Based on rigid biphenyl units and high cross-link density, the tensile strength and modulus of MPSO-140 were 17.42 MPa and 2.61 GPa, respectively, showing prominent mechanical properties. In addition, MPSO-140 exhibited excellent water resistance (water contact angle and 72 h water absorption of 104.8° and 0.19%, respectively) and electrical insulation, showing great potential for practical applications. The study broadened the way toward overcoming the contradiction between low dielectric and high thermal conductivity by simultaneously introducing large free volume and modulating the intermolecular forces and molecular structure in a simple and effective way.