Caixia Zhao,Sheng Yang,Tian Fu,Wang Qin,Yaqi Yang,Guoxiang Zou
In order to compare the effect of the monophenyl ring terephthalic acid (TPA) and biphenyl rings 4,4′-oxybisbenzoic acid (OBBA) with ether bond on poly(butylene adipate) (PBA)-based copolyesters properties, two copolyester series poly(butylene adipate- co -butylene terephthalate)s (PBATs) and poly(butylene adipate- co -butylene oxybisbenzoate)s (PBAOs) were synthesized, and comparatively investigated. All the synthesized copolyesters had satisfactory number-average molecular weights in the range of 26,500–73,000 g/mol. For PBATs copolyesters, the crystalline structure gradually transitioned from the monoclinic crystal structure of poly(butylene adipate) to poly(butylene terephthalate) (PBT) with increasing TPA because of the crystalline segments transformation from butylene adipate to butylene terephthalate, while PBAO copolyesters progressively shifted from the crystalline structure of PBA to the amorphous structure of poly(butylene oxybisbenzoate) (PBO) as increasing content of OBBA. The incorporation of either TPA or OBBA comonomers with rigid cyclic structure into PBA chain noticeably increased the glass transition temperature ( T g ). With the same monomer molar ratio, PBAOs because of incorporation of the bicyclic comonomers presented higher T g (range from −24.2 to 49.5°C) than that of PBATs (range from −56.5 to 22.4°C). It was found that copolyesters with bicyclic and ether bond OBBA comonomers exhibited a better flexibility in property than that with monocyclic TPA comonomers.
Lina Zhang,Xinbing Chen,Fengqi Zhao,Xuezhong Fan,Pei Chen,Zhongwei An
Three series of 2-(4′-alkoxybiphenyl-4-yl)-1H-benzimidazole derivatives (nM-x), which possessed 5-nitrobenzimidazole (nM-N series), benzimidazole (nM-H series) or 5-methylbenzimidazole (nM-M series) units at the end of the molecule, were synthesised and characterised by infrared, 1H- and 13C-nuclear magnetic resonance spectra, electrospray ionisation-mass spectrometry and elemental analysis. Their phase transition behaviour was investigated by differential scanning calorimetry, polarising optical microscopy and X-ray diffraction. All the compounds exhibited enantiotropic smectic mesophases with wide temperature domains for a carbon number in the alkoxy chain from 6 to 16, where the mesophase ranges were 14–91°C and 17–99°C during heating and cooling processes for the nM-N compounds, 7–25°C and 8–49°C for the nM-H compounds and 48–81°C and 52–85°C for the nM-M compounds, respectively. The effect of the length of alkoxy chain on mesomorphic properties was discussed. The nM-N and nM-M exhibited a much wider mesophase range whether during heating or cooling process than the corresponding nM-H series, especially for the longer terminal chain (n > 8), which indicated that the substituent in the benzimidazole moiety was helpful in increasing the mesophase stability.
There is a lack of systematic research on the use of liquid crystal-modified graphene in the production of thermally conductive composites. In this work, we utilized covalent and non-covalent interactions between 4′-allyloxy-biphenyl-4-ol (AOBPO) and graphene oxide (GO), reduced graphene oxide (rGO), and high-temperature reduced graphene oxide (GNS) to improve the compatibility and dispersion of the fillers with the silicone-cycloaliphatic epoxy resin. The thermal conductivity of GNS-AOBPO composite material significantly increases when a shear force field is applied, even at a lower filler content of 7 wt%, reaching 0.828 W/(m·K), which is 1.8 times higher than that without the field. At 9 wt% filler content, the thermal conductivity further increases to 1.161 W/(m·K), which is 10 times higher than epoxy resin. Concurrently, the electrical resistivity decreased by half. This provides a method for preparing thermal conductive composite materials by inducing the orientation of graphene through the application of a shear force field.
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