Synthesis, Thermal, and Dielectric Properties of Polysulfone-Calix[4]Arene Crosslinked Networks (VPSU-VC4As)

With the rapid development of communication technologies, there is an urgent need for materials that simultaneously possess excellent dielectric properties and high thermal stability to ensure efficient signal transmission. In this study, a molecular-level microphase structure modulation strategy is proposed, in which vinyl-functionalized calix[4]arene-modified polysulfone oligomers are used to prepare a series of novel polysulfone-based crosslinked networks (VPSU-VC4As). This method demonstrates remarkable efficiency in enhancing the thermal stability and dielectric properties of the materials. After incorporating 4-tert-Butylcalix[4]arene, the glass transition temperature (T_g) of the thermosets increases from 193°C to 231°C, with T_d5 exceeding 350°C and an increased char yield. Meanwhile, the dielectric constant (D_k) and dielectric loss (D_f) of the thermosets are significantly reduced (D_k = 2.61 and D_f = 4.6 × 10^-3 at 1 GHz). Studies reveal that this improvement is attributed to the nanoporous structure of VC4A and the presence of bulky tert-butyl groups, which increase the free volume of the polymer, reduce its density, and enhance hydrophobicity. The material also exhibits a dielectric breakdown strength of 6.97-7.77 kV/mm and a tensile strength of 27-64 MPa. This work not only confirms the unique advantages of calix[4]arene in developing low-k materials but also further optimizes the dielectric properties of polysulfone through molecular design, providing a new strategy for the development of low-dielectric materials.