Temperature-regulated ordered structure for synergistically enhanced thermal, mechanical, and thermal conductive in UV-cured liquid crystalline polymers

A liquid crystal monomer (BLMA-1) containing a biphenyl mesogenic unit and acrylate groups was designed and synthesized, and a temperature-regulated UV curing strategy was employed. The strategy is characterized by pre-aligning the liquid crystal monomer into an ordered template through the curing temperature, followed by photopolymerization. The photopolymerization process plays a dual role: on the one hand, it locks the mesoscopic ordered structure in situ, and on the other hand, it further enhances the ordering of the cross-linked network through polymerization-induced crystallization. The phase behavior and structural evolution of the monomer during the pre-curing stage were studied using polarized optical microscopy (POM) and variable-temperature X-ray diffraction (XRD). Subsequently, the properties of resins cured at different temperatures ranging from 140 °C to 180 °C were systematically characterized. The results demonstrate that photopolymerization not only preserves the mesoscopic order of the liquid crystal phase but also significantly enhances the ordering of the cross-linked network through the polymerization-induced crystallization mechanism, leading to the formation of a semi-crystalline cross-linked structure with relative crystallinity ranging from 14.98% to 22.79%. Importantly, the thermal conductivity (0.298–0.536 W·m −1 ·K −1 ), thermal stability (T 5%  = 294.7–380.1 °C), glass transition temperature (T g  = 126.3–131.1 °C), and mechanical properties of the material are closely related to the ordered structure formed during the curing process. By optimizing the curing temperature to 150 °C, an ideal balance between ordering (crystallinity = 22.79%) and cross-linking density (1.4105 × 10 4  mol·m −3 ) was achieved, resulting in a liquid crystal polymer network that combines high thermal conductivity (0.536 W·m −1 ·K −1 ), good mechanical strength (fracture strength 26.57 MPa), and excellent thermal stability. This work provides a theoretical and experimental framework for designing liquid-crystalline polymers with synergistically enhanced properties via photopolymerization, offering a promising strategy for developing advanced polymer thermal-management materials.