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The thermal conductivity of bulk polymers is usually very low, which is due to the amorphous domains where chains are randomly entangled, improving the degree of the chain alignment and forming a continuous thermal conduction network are expected to enhance the thermal conductivity. A series of liquid crystalline monomer-poly (vinyl alcohol) dispersion (MDLC) films with high thermal conductivity containing microscopic-ordered structure were prepared by introducing a highly ordered liquid crystalline monomer (LCM) exhibiting Smectic phase. The thermal conductivity of MDLC films was strongly related to the amount of LCM, which firstly increased and then decreased with the increase of LCM content. The thermal conductivity of MDLC film reached up to 1.20 W m −1 K −1 when the content of LCM was 15 wt% and rapidly decreased to 0.85 W m −1 K −1 as the content of LCM further increased to 25 wt%. LCM with low content (1-15 wt%) showed good fluidity, dispersity and interfacial compatibility in PVA molecular chains, which further increases the regularity of molecular chains alignment.

Flexible epoxy‐dispersed liquid crystal membranes (EDLC‐v membranes) with high thermal conductivity were successfully prepared by using of high voltage orientation molding. Liquid crystal monomer (LCM) was uniformly dispersed into flexible epoxy polymers cured by trimethylolpropane tris(3‐mercaptopropionate) (TTMP) or pentaerythritol tetra(3‐mercaptopropionate) (PETMP). In‐plane thermal conductivity (TC//) of EDLC‐v membranes reached to 1.47 W m−1 K−1 with LCM content of 30 wt%, which was 5.65 times higher than that of epoxy polymers without LCM (0.26 W m−1 K−1). In addition, the tensile strength and elongation at break of EDLC‐v membranes were up to 27.9 MPa and 92.8%, respectively. The main reasons for high TC// and flexibility of EDLC‐v membranes are molecular chains' ordered arrangement, crosslinking in epoxy polymers, hydrogen bond interaction, and high voltage orientation molding. This work provided a new and feasible way to prepare intrinsic high thermal conductive polymer materials, as well as flexible epoxy polymers.

In view of the problem of heat accumulation in electronic devices, the development of new composites with high thermal conductivity (TC) is the current research focus. Nowadays, improving TC often lead to inevitable deterioration of the mechanical properties of materials. In this work, the E‐functionalized boron nitride nanosheets (f‐BNNS)/liquid crystal monomer (LCM)/Epoxy‐thiol films with high TC were prepared by using flexible epoxy‐thiol polymer as matrix and LCM and f‐BNNS as thermal fillers via high voltage orientation molding. The epoxy‐thiol polymer possessed high intrinsic TC due to the regular arrangement of molecular chains and the f‐BNNS showed favorable dispersibility because of the modification by isopropyl tri(dioctylpyrophosphate) titanate (ITDPT). The results show that TC of E‐f‐BNNS/LCM/Epoxy‐thiol films with 30 wt% f‐BNNS content achieves 1.65 W/m·K and is 511.11% higher than that of pure epoxy‐thiol polymer (0.27 W/m·K). The tensile strength and elongation at break increase to 24.9 MPa and 47.41%, respectively. The favorable results are attributed to the ordered arrangement of f‐BNNS and molecular chains, resulting from the hydrogen‐bonding interaction between OH group in f‐BNNS, LCM and epoxy‐thiol polymer. This research provides a simple and feasible method for preparing flexible epoxy polymer films with high TC.Highlights The functional BNNS was achieved by isopropyl tri(dioctylpyrophosphate) titanate. Effects of matrix thermal conductivity on films thermal conductivity are probed. High voltage orientation molding are used for preparing epoxy composite films. The films demonstrate excellent thermal conductivity and favorable tensile strength.