Five porous ether-linked phthalazinone-based covalent triazine frameworks (PHCTFs) were successfully constructed via ionothermal polymerizations from flexible dicyano monomers containing asymmetric, twisted, and N-heterocyclic phthalazinone structure. All the building blocks could be easily prepared by simple and low-cost aromatic nucleophilic substitution reactions, showing the large-scale application potential of thermal stable phthalazinone structure in constructing porous materials. Generally, the flexible building blocks are avoided to prevent the networks from collapsing in constructing high surface area porous materials. Our experimental results revealed that the introduction of the substituents can effectively decrease the probability of the network interpenetration from the longer struts and the intermolecular/intramolecular intercalation from the increased degree of conformation freedom in the flexible ether-linkage, the BET surface areas of PHCTFs increasing from 676 to 1270 m g. Meanwhile, the effects of introducing different sizes (methyl or phenyl group) and amounts (one or two) of substituents on the porosities of the target polymer networks were also investigated in detail. The high CO adsorption capacity of 10.3 wt % (273 K, 1 bar) can be ascribed to the strong affinity of the electron-rich N,O-containing networks with CO. Excitingly, PHCTF-5 demonstrates the high CO/N selectivity up to 138 (273 K, 1 bar), according to the ideal adsorbed solution theory (IAST) for the higher proportion of V accompanied the electron-rich heteroatoms characteristic. Such high CO adsorption capacity and good separation properties are superior to those of many other microporous organic polymers. These properties along with easily up-scalable synthesis make porous PHCTFs promising candidates applied in gas sorption and separation field.
In this work, new classes of phthalazinone-based covalent triazine frameworks (PHCTFs) were prepared by ionothermal synthesis from two full rigid dicyano building blocks with rigid, thermostable and asymmetric N-heterocycle-containing structures.
High processing viscosity and poor solubility limit the application of heterocyclic polymers for fabricating organic wavetransparent composites for aerospace applications. In this paper, a novel resin, poly(phthalazinone ether bisphenol fluorene) encapped with phthalonitrile (PPEBF-Ph), was synthesized and used as the matrix. Biphenol-based phthalonitrile monomer BP-Ph was also synthesized and blended with PPEBF-Ph to further lower the processing viscosity. Solubility tests showed that the resin was soluble in dimethylformamide, N,N-dimethyl acetamide, N-methylpyrrolidone, dimethyl sulfoxide, chloroform, and other solvents. Differential scanning calorimetry and rheological studies revealed that the mixed resins exhibited low processing viscosity and a wide processing window below the gel temperature. Thermogravimetric analysis indicated that the cured resins were stable below 510-530 8C under nitrogen atmosphere after 6 h of curing (decreased by 40-60% compared with previous reports on phthalonitrile resin). In air, the char yields of the resins reached 20-30% when heated at 800 8C. The composites were reinforced by a quartz fiber cloth and exhibited a dielectric constant of 2.94-3.27 in an electromagnetic field with frequency ranging from 8 to 18 GHz. Retention of the bending modulus exceeded 70% at 400 8C according to dynamic mechanical analysis, indicating excellent mechanical stability was obtained.
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