Three novel dianhydride monomers involving amide groups were synthesized and further polymerized with various diamines to afford a series of colorless polyimides (cPI). The resultant cPI films present outstanding optical performance, exceedingly good dimensional stability at high temperature, great film ductility and solution-processability. In particular, chemically imidized AMDA/TFDB has an ultra-low coefficient of thermal expansion value of 5.2 ppm K−A, a relatively high Tg value of 333 °C and large elongation at break of 29%, resulting from its rigid-rod backbone and the formation of hydrogen bonding (–CO⋯NH–) between adjacent molecular chains. Concurrently, it exhibits a high optical transmittance of 87% at a wavelength of 550 nm, a small haze value of 0.71 and low yellow index of 4.29 by reason that the incorporation of bulky trifluoromethyl and cyclohexyl preclude the formation of a charge transfer complex effectively. The high overall performance of the amide-containing cPI films suggests its potential application in the field of flexible OLED displays.
An azobenzenediamide bridged bis(β-cyclodextrin) chiral stationary phase (AZCDP) was prepared, and its high-performance liquid chromatography performance in reversed-phase and polar organic modes was evaluated by chiral probes, including triazoles, flavanones, amino acids and β-blockers. The results showed that AZCDP had strong chiral separation ability and the 40 chiral compounds were successfully resolved, of which 32 were completely separated (Rs ≥ 1.5) and the best enantioresolution was up to 3.93 within 20 min under a wide range of pH value and temperature. The separation ability of AZCDP with double cavities was significantly better than common CD-CSPs with single cavity, which was related to the synergistic inclusion effect. Compared with the previously reported stilbene (C=C)-bridged CSP, AZCDP with azobenzene (N=N)-bridged had a wider resolution range. For example, it could resolve myclobutanil, pindolol, carteolol, betaxolol, bevanolol and bitertanol, which could not be resolved before, and should be related to the fact that the flexible N=N was more compatible with the synergistic inclusion between cavities than the rigid C=C bridge group. The azobenzenediamide bridging group could also provide hydrogen bond, π–π and other sites, which was conducive to chiral separations.
A stilbene diamido-bridged bis (β-cyclodextrin) was synthesized via the reaction between 4,4′-stilbene dicarboxylic acid and 6- deoxy -6-amino-β-cyclodextrin. Then it was bonded onto the surface of an ordered mesoporous SBA-15 to obtain a novel bridged bis (β-cyclodextrin)-bonded chiral stationary phase (SBCDP). The structures of the bridged bis (β-cyclodextrin) and SBCDP were characterized by the mass spectrometry, nuclear magnetic resonance, infrared spectroscopy, elemental analysis and thermogravimetric analysis. The chromatographic performance of SBCDP was systematically evaluated by separating 23 racemic drugs and pesticides, including trimeprazine, praziquantel, flavanones, β-blockers and triazole pesticides in the reversed-phase chromatography or the polar organic mode. The chromatographic conditions that affect the enantioselectivity or diasterioselectivity of SBCDP were investigated in detail, including the mobile phase composition, pH value and column temperature. As a result, all tested analytes were resolved on SBCDP with high resolutions (1.51∼5.15) within about 25 min, and the enantioseparation resolutions of flavanone and imazalil were up to 5.15 and 4.38, respectively. Compared with the native β-cyclodextrin stationary phase (CDCSP), the SBCDP had a better chromatographic performance in enantioselectivity and diasterioselectivity. For example, enantiomers of trimeprazine, praziquantel, flavanone and imazalil those could not be separated by CDCSP, were separated by SBCDP with high resolutions. Unlike the small cavity (0.65 nm) of native CD, the bridging linker of the bridged bis (β-CD) supplied a well-organized “ pseudo-cavity” , and combined two native CDs as an organic whole, which could synergistically encapsulate and complex some bulky analytes, making the chiral discrimination of SBCDP more precise. Moreover, we also found that SBCDP possessed high enantioselectivity and diastereoselectivity over a wide range of temperature (30∼60 °C), which made the fast analysis possible. As a new chiral separation material, SBCDP may have wider applications in analysis of chiral compounds.
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