| Poly(aryl ether) (PAE) and polyimide (PI) are known as high performance polymers for their excellent thermo-oxidative, electrical and chemical properties. These advanced materials have been received considerable applications in aerospace, automobile, electronics and other high technology fields. However, the commercial products are hardly to be processed because of the structural regularity and rigidity. Various structural modification have been introduced in the standard poly(aryl ether) and polyimide resin to obtain different properties and applications.In this study, the bulky and coplanar naphthyl, tetramethyl or trifluoromethyl groups were introduced in the poly(aryl ether) and polyimide backbone for enhancing the solubility and thermal property. Further more, the fibers with high porosity and large surface-to-area ratio were prepared through electrospinning technique. The morphologies and surface properties of the fibers were also fully characterized and investigated in this work. The major contents are as follow:1. The synthesis of poly(aryl ether)(PAE). A bisphenol monomer containing naphthyl and tetramethyl pendant groups, bis(4-hydroxy-3,5-dimethylphenyl)-naphthylmethane (1), was synthesized via the condensation reaction of 2,6-dimethylphenol and 1-naphthaldehyde catalyzed by sulfuric acid. Two soluble poly(aryl ether)s were prepared conveniently from 1 and two activated dihalide monomers including 4,4'-difluorobenzophenone and bis(4-chlorophenyl)sulfone by an aromatic nucleophilic substitution. The polycondensation proceeded quantitatively in N,N-dimethylacetamide in the presence of anhydrous potassium carbonate and afford the polymers with inherent viscosities of 0.54 and 0.37 dL/g. The bulky naphthyl and tetramethyl pendant groups in the polymer backbone could decrease the packing density and intermolecular interactions of macromolecular chain, and make these poly(aryl ether)s show a good solubility in some polar and aprotic solvents. They all could be quickly soluble in CHCl3, CH2Cl2, and tetrahydrofuran at room temperature. Thermal analysis showed that these poly(aryl ether)s also had excellent thermal properties with the glass transition temperatures above 257℃and the temperatures of 10% weight loss all beyond 470℃in nitrogen atmosphere. Even under air condition, the range of 10% weight loss was 446-458℃. All the weight residue of polymers was above 46% at 800℃in nitrogen. The coating films exhibited good mechanical properties with tensile strengths of 64-78 MPa, elongations at break of 4.5-12.5% and initial modulus ranged of 2.2-2.4 GPa. Meanwhile, these films exhibited high optical transparency with the UV cutoff wavelength in the range of 305-315 nm, and the rate of optical transparency was above 80% after 400 nm.2. The synthesis of polyimide (PI). A new fluorinated diamine monomer containing naphthalene pendant group, bis(4-amino-3,5-difluorophenyl)naphthyl-methane (monomer 1), was synthesized from 1-naphthaldehyde and 2,6-difluoroaniline with thrifluoromethanesulfonic acid at reflux. The soluble poly(fluorinated imide)s (PFIs) were prepared via one-step polycondensation by monomer 1 and three aromatic dianhydrides including 4,4'-oxydiphthalic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride,3,3',4,4'-biphenyltetracarboxylic dianhydride in m-cresol, respectively. These polymers showed excellent thermal stability with glass-transition temperatures in the range of 326-352℃. In nitrogen and air condition, the 10% weight loss temperatures of polymers were 538-574℃and 525-547℃, respectively. The PFIs'weight residue was more than 57% at 800℃in nitrogen. The PFIs could be dissolved in a variety of organic solvents such as N-methyl-2- pyrrolidinone (NMP), N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), chloroform and tetrahydrofuran (THF) at room temperature. The PFI films had a tensile strength, elongation at break, and tensile modulus in the range of 84-102 MPa,8.7-12.8% and 2.2-2.8 GPa, respectively. The UV cutoff wavelength of these films was between 305 to 315 nm, and the rate of optical transparency was above 80% after 450 nm.3. The preparation of electrospun poly(aryl ether) (PAE) fiber membranes. The poly(aryl ether) fibers 3a and 3b were successfully prepared by electrospinning in CHC13 solution. SEM micrographs of the poly(aryl ether) membranes showed that the fibers were all the ribbon-shaped and the average diameters were all around 15μm. The porous surface structures with the pore size of 200-350 nm were exhibited in poly(aryl ether) fibers. The porous surface is probably produced by the rapid evaporation of the chloroform solvent and a subsequent rapid solidification of polymer during the electrospinning. The contact angles on the electrospun poly(aryl ether) membranes for water and glycerol were in the range of 142.2-143.3°and 141.4-144.8°, respectively. For the optical properties of electrospun membranes, three different colors blue, green and red could be seen after excited with different wavelength:333-380,450-490 and 510-560 nm, respectively. This phenomenon may be due to the conjugated effect of naphthalene unit in the macromolecular chain of polymer.4. The electrospinning of polyimide (PI) membranes. Polyimide electrospun fiber membranes were successfully prepared from 15 wt% CHCl3 solutions directly. The fiber diameters were in the range of 10-20 um. Approximately round shape nanopores(200 nm) were broadly distributed appeared on the fibers surface. Hydrophobic properties were characterized by contact angle (CA) measurement. The contact angles on the electrospun membrane for water and glycerol were in the range of 137.7-139.0°and 139.1-142.1°, respectively, it almost 40.0°higher than coating films. The results indicated that the rough surface were the main reasons of the different CA. The maximum UV-vis absorption spectrums of the PFI fibers were located at 300-340 nm. The photoluminescence spectra indicated that the PFI fibers exhibited the following luminescence characteristics (excitation wavelength (nm); color):330, blue; 450, olive green; 520, red. For the water repellency and fluorescence, these materials could be used in electronic and optical area.
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