Wenbo Shen,Ling Wang,Gang Chen,Chunxin Li,Lanying Zhang,Zhou Yang,Huai Yang
A liquid crystalline epoxide was synthesized and its curing reactivity was compared with that of the conventional epoxy monomers . By utilizing the difference in curing reactivity between the liquid crystalline epoxide and non-liquid crystalline epoxy monomers, a coexistent system of polymer-dispersed and polymer-stabilized liquid crystal (LC) in the intelligent films can be obtained by two-step thermal curing method. If the later curing process was undertaken under an external electric field , the ordered microstructure of liquid crystalline epoxy polymer (LCEP) network can be implanted into the conventional epoxy resin. The competition of the anchoring effect on the LC molecules from the LCEP network and the conventional epoxy resin matrix was crucial to the electro-optical performance of the films. Moreover, the performance of the films can be adjusted by controlling the content of liquid crystalline epoxide and the external electric field applied during later curing. This approach can provide a facile route to regulate the electric-optical performance of polymer-dispersed liquid crystal films for practical applications.
Graphene has been widely studied for its excellent properties of outstanding conductivity, strength , and flexibility. However, interlayer defects formed during the macroscopic assembly of graphene nanosheets will severely degrade the performance of graphene films. Herein, a strategy combined with trace carboxyl graphene oxide (GO), mild reduction, and chemical crosslinking is employed to minimize the interlayer defects for enhancing both the conductivity and mechanical strength of graphene films. The trace carboxyl feature of GO allows nanosheets to assemble orderly into highly oriented GO films . Subsequently, the mild chemical reduction preserves the highly oriented and packed microstructure. Coupling with further crosslinking by introducing conjugated molecules with pyrene terminal groups (1-pyrene butyric acid-1,6-hexane diamine, PHD) to provide extra π-π bonds, both the mechanical strength and conductivity of graphene films are improved to 548.4 MPa and 1.7 × 10 5 S m −1 , respectively. In addition, the graphene film with only ∼2 μm in thickness possesses an excellent electromagnetic interference shielding effectiveness (EMI SE) of ∼40 dB and a specific shielding effectiveness of up to 74 278 dB cm 2 g −1 in a wide frequency range of 8.2–40.0 GHz. Thus, this study provides an energy-saving fabrication route for mechanically strong, effective thermal management and EMI shielding films.
Xiangli Gao,Gaoyi Han,Yunzhen Chang,Ying Zhang,Honggang Li
To enhance the reduced graphene oxide hydrogels' capacitive performance, many modifiers are used to add doped element into the materials and improve the structure. The isomers of aminophenol which contain amino and hydroxyl groups on the benzene ring are employed as structure regulator and modifier to synthesize high-performance reduced graphene oxide hydrogels. The influences of preparation conditions including ratios of graphene oxide to aminophenol isomers, temperature, reaction times on the samples’ structure and properties have been investigated. The results show that the oligomer of o-aminophenol is formed on reduced graphene oxide sheets while the molecules of p, m-aminophenol are bound to the sheets; and that the hydrogel prepared in the presence of p-aminophenol has larger specific surface area, total pore volume , specific capacitance and good rate capability (74.0% of 427.0 F g −1 retains at 100 mV s −1 ) than other. The cells assembled by the optimized hydrogels exhibit the energy density of 14.07 Wh kg −1 at power density of 124.3 W kg −1 , and 4.96 Wh kg −1 at 6.78 kW kg −1 . Furthermore, 92.2% of initial capacitance can be retained after 20,000 cycles for the cells assembled by the optimal hydrogel. This kind of material may be found its use in energy storage field.
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