Thermal properties of polyimides with main chain containing alicyclic units derived from 3,3 0 4,4 0 -oxydiphthalic anhydride (ODPA) and several alicycliccontaining diamine monomers, including 1,4-bis (4aminophenoxymethylene) cyclohexane (BAMC), 1,4-bis (3-aminophenoxymethylene) cyclohexane (mBAMC), 1,4-bis (4-aminobenzoyoloxymethyl) cyclohexane (BAZMC), and 1,4-bis (3-aminobenzoyoloxymethyl) cyclohexane (mBAZMC) were characterized in detail. The thermal stability, apparent activation energy, and evolved gas analysis of these polyimides were done using thermogravimetric analysis (TGA) coupled with Fourier transform infrared (FTIR) spectroscopy. Experimental results indicated that the resulting polyimides showed fairly high thermal stability, no weight loss was detected before a temperature of 4008C in nitrogen, and the values of glass-transition temperature of them were in the range of 134-1818C. Activation energy for the initial thermal degradation of polyimide derived from ODPA and mBAMC in nitrogen were 166 and 162 kJ/mol in two different methods. The TG-IR results represented that the major evolved products from the nonoxidative thermal degradation were detected to be hydrocarbons, CO, CO 2 , H 2 O, and aromatic compounds.

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Two polyimides with main chain containing cycloaliphatic units were synthesized by conventional two-step polycondensation of two diamines, 1,4-bis (4-aminophenoxymethylene) cyclohexane (BAMC) and 1,4-bis (4-aminobenzoyoloxymethyl) cyclohexane (BAZMC), with a dianhydride 3,3 0 , 4,4 0 -benzophenonetetracarboxylic dianhydride (BTDA), respectively. The resulting polyimides showed exceptional thermal properties with glass transition temperatures of 212 and 1788C, and temperature for 5% weight loss of 461 and 4218C in nitrogen, respectively. Meanwhile, thermogravimetry coupled to Fourier transform infrared spectrometry (TG/FT-IR) was used to study the thermal degradation behavior of the resulting polyimides. It was found that the thermal decomposition occurred by a double-stage process; the major evolved products from the nonoxidative thermal degradation were hydrocarbon, CO, CO 2 , H 2 O, and aromatic compounds.

Developing effective strategies to improve the hydrophilicity or aqueous solubility of hydrophobic molecular scaffolds is meaningful for both academic research and industrial applications. Herein, we demonstrate that stepwise and precise N/O heteroatoms doping on a polycyclic aromatic skeleton can gradually alter these structures from hydrophobic to hydrophilic, even resulting in excellent aqueous solubility. The Hansen solubility parameters (HSP) method shows that the three partial solubility parameters are closely related to N/O doping species, numbers and positions on the molecular panel. The hydrogen bonding solubility parameter indicates that the hydrogen bonding interactions between N/O doped molecules and water play a key role in enhancing hydrophilicity. Moreover, three optimized water-soluble molecules underwent a self-assembly process to form stable nanoparticles in water, thus facilitating better hydrogen bonding interactions disclosed by HSP calculations, NMR and single crystal X-ray analysis. These ensembles even show quasi-solid properties in water from NMR and luminescence perspectives.

Key indicators: single-crystal X-ray study; T = 298 K; mean (C-C) = 0.004 Å; R factor = 0.052; wR factor = 0.135; data-to-parameter ratio = 8.7.In the title crystal structure, C 11 H 13 NO 5 , molecules are linked through weak C-HÁ Á ÁO hydrogen bonds to form onedimensional chains in the c direction.