Influence of chain interaction and ordered structures in polymer dispersed liquid crystalline membranes on thermal conductivity

Polymer dispersed liquid crystalline (PDLC) membrane with intrinsic thermal conductivity was prepared by dispersing liquid crystalline polysiloxane containing crosslinked structure (liquid crystalline polysiloxane elastomer (LCPE)) into polyvinyl alcohol (PVA). Chemical structures were characterized by Fourier transform infrared (FT-IR) and 1H-NMR, and microscopic structures were analyzed by polarizing optical microscope (POM), scanning electron microscope (SEM) and X-ray diffraction (XRD). The thermal conductivity of PDLC membrane was characterized by hot disk thermal constants analyzer, and the tensile properties were measured by tensile testing machine. Thermal properties were characterized by differential scanning calorimeter (DSC) and thermal gravimetric analyzer (TGA). The results show that LCPE was dispersed in PVA uniformly, and the mesogenic monomer of LCPE formed microscopic ordered structures in PDLC membrane. Meanwhile, hydrogen-bond interaction was formed between LCPE and PVA chain. Both microscopic-ordered structure and the hydrogen-bond interaction improved the phonon transmission path, and the thermal conductivity of PDLC membrane was up to 0.74 W/m⋅K, which was 6 times higher than that of pure PVA film. PDLC membrane possessed proper tensile strength and elongation at break, respectively 5.18 MPa and 338%. As a result, PDLC membrane can be used as thermal conductive membrane in electronic packaging and other related fields.