A powerful strategy to enhance the thermal conductivity of liquid crystalline epoxy resin (LCER) by simply replacing the conventional amine cross-linker with a cationic initiator was developed. The cationic initiator linearly wove the epoxy groups tethered on the microscopically aligned liquid crystal mesogens, resulting in freezing of the ordered LC microstructures even after curing. Owing to the reduced phonon scattering during heat transport through the ordered LC structure, a dramatic improvement in the thermal conductivity of neat cation-cured LCER was achieved to give a value ∼141% (i.e., 0.48 W/mK) higher than that of the amorphous amine-cured LCER. In addition, at the same composite volume fraction in the presence of a 2-D boron nitride filler, an approximately 130% higher thermal conductivity (maximum ∼23 W/mK at 60 vol %) was observed. The nanoarchitecture effect of the ordered LCER on the thermal conductivity was then examined by a systematic investigation using differential scanning calorimetry, polarized optical microscopy, X-ray diffraction, and thermal conductivity measurements. The linear polymerization of LCER can therefore be considered a practical strategy to enable the cost-efficient mass production of heat-dissipating materials, due to its high efficiency and simple process without the requirement for complex equipment.

Flame retardant epoxy is closely related to the safety of a human's life against the surrounding fire threat. Flame retardant properties can be obtained by supplementing with additives, such as phosphorus compounds and nanomaterials, or synthesizing flame retardant monomers. The principle of improving flame retardancy is based on the capture of oxygen radicals and the formation of a char layer, which blocks flammable gases. This paper focuses on a flame retardant epoxy resin using naturally occurring tannic acid (TA) as a hardener, which is both an oxygen-radical quencher and a charring agent. TA is reacted with the commercially available diglycidyl ether of bisphenol A (DGEBA). The reaction between the epoxy ring of the DGEBA and multiple functional groups in TA is empirically demonstrated using dynamic scanning calorimetry (DSC) and Brillouin spectra. The most effective flameretardant TA-DGEBA (TD) thermoset had an limiting oxygen index (LOI) value 46% higher than the control sample. This result suggests that TA-based epoxy resins could be promising flame-retardant polymers.

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Liquid crystalline epoxy resins with a wide temperature range exhibit a high thermal conductivity of 0.4 W m−1 K−1.

Light-harvesting antennae (LHA) were demonstrated using polyfluorenes (PFs) modified with borondipyrromethene (BODIPY) dyes tethered to the cardo structures. PFs work as a light absorber and an energy donor to the BODIPY units. The series of BODIPY-tethering PFs via the cardo carbon including homocardo PFs and alternative polymers with fluorene and the cardo fluorene were synthesized, and their optical properties were investigated. Initially, highly efficient energy transferring was observed from the PF main chains to the BODIPY unit (99%). It was found that PFs can work as an efficient light absorber because of the large molar extinction coefficient and cause the rapid energy transfer through the cardo structure. Next, from the comparison with the emission efficiency of the BODIPY units in the series of the synthetic polymers, the favorable position of the BODIPY units was obtained to avoid the concentration quenching: The alternative polymer with cardo fluorene and dialkyl-substituted fluorene showed the largest emission efficiency in this study. Finally, we received the effective LHA with the 9 times larger amplification efficiency compared to that of the unimolar BODIPY unit. The results from the computer modeling suggest that the positions of the BODIPY units via the cardo structure could play a significant role in the inhibition of aggregation and electronic coupling with the BODIPY units, leading to the suppression of concentration quenching. Here is presented the feasibility of the cardo structure in fluorene as a scaffold for designing advanced optical materials.