Surface Modification of Commercial Aromatic Polyamide Reverse Osmosis Membranes by Crosslinking Treatments

Crosslinking treatments for a commercially available aromatic polyamide reverse osmosis membrane were carried out to improve its chlorine resistance.The crosslinking agents including 1,6-hexanediol diglycidyl ether,adipoyl dichloride and hexamethylene diisocyanate ester with long flexible aliphatic chains and high reactivity with N-H groups were used in the experiments.Attenuated total reflective Fourier transform infrared spectra verified the successful preparation of highly crosslinked membranes by crosslinking treatments.It was suggested that the crosslinking agents were connected to membrane surface through the reactions with amine and amide Ⅱ groups,which is confirmed by surface charge measurements.Based on contact angle measurements,crosslinking treatments decreased membrane hydrophilicity by introducing methylene groups to membrane surface.With increasing amount of crosslinking agent molecules connected to membrane surface,the hydrolysis of unconnected functional groups of crosslinking agent produced polar groups and increased membrane hydrophilicity.The highly crosslinked membranes showed higher salt rejections and lower water fluxes as compared with the raw membrane.Since the active sites(N-H groups) vulnerable to free chlorine on membrane surface were eliminated by crosslinking treatments,the chlorine resistances of the highly crosslinked membranes were significantly improved by slighter changes in both water fluxes and salt rejections after chlorination.

KINETICS OF MESOPHASE FORMATION OF A LYOTROPIC AROMATIC POLYAMIDE

The kinetics of mesophase formation of a lyotropic aromatic polyamide from isotropic state has been studied by means of depolarized light intensity. Avrami type analysis of the data gives an exponent close to 1, which suggests the nucleation followed by one-dimensional growth. No influence of blending flexible chain from nylon 6 to the aromatic polyamide on the kinetics of mesophase formation was observed.

A novel hyperbranched aromatic polyamide containing bithiazole: Synthesis,metal complexation and magnetic properties

Based on the polycondensation of bifunctional 2,2′-diamino-4,4′-bithiazole(DABT) and trifunctional 1,3,5-benzenetricarbonyl trichloride (BTC),a novel hyperbranched aromatic polyamide PBD was synthesized with excellent solubility and good thermal stability.The structure of the polymer was confirmed by FT-IR and 1H NMR spectrum.The calculated degree of branching of our product was 52%.By exploring the influence of several different solvent systems,the yield of the polymer increased in the solvent system of DMAc/LiCl.Two kinds of metal complexes were obtained by chelation of the polyamide with Cu2+ and Ni2+,and the metal contents of the complexes were determined by complexometric titration.The magnetic behaviors of the complexes were examined as a function of magnetic field strength at 5 K,and as a function of temperature (5–300 K) at a magnetic field strength of 2.4 × 106 A/m.The results indicated that the complexes were soft ferromagnetic materials with Curie-Weiss temperature at 102 K and 53 K,respectively.

SYNTHESIS AND PROPERTIES OF SOLUBLE AROMATIC COPOLYAMIDES CONTAINING PHOSPHINE OXIDE MOIETY

Aromatic copolyamides were synthesized by the Yamazaki phosphorylation method starting from bis(4- carboxyphenyl) phenyl phosphine oxide,terephthalic acid and 4,4 -diaminodiphenyl methane.The copolymers with inherent viscosities of 0.52-0.99 dL/g were obtained.The structures of the copolyamides were characterized by elemental analysis, FTIR and NMR.The glass transition temperatures were measured by DSC and DMA,respectively,and the results showed that the T_gs of the polymers were higher than 287℃.Thermal de...

Improved Properties of Aromatic Polyamide Tape-casting Films

A convenient tape-casting method was applied to prepare high performance aromatic polyamide(PA)films based on Technora®.During the polycondensation,CaO was introduced to improve the solubility of the PA resin,and the generated halides were totally removed from the film via a simple water bath,without leaving any defects in PA films.The factors of processing temperature and immersion time had been systematically investigated,and the experimental results demonstrated that both of them had impressive impacts on aggregation state and comprehensive properties of the PA film.It was suggested that immersion in water for more than 1 min and baking below 300℃ for 10 min were the optimal conditions for the thermal,tensile,tear,and optical properties to be in the best equilibrium.The resultant PA films integrated outstanding film-forming ability and excellent general performance,especially the tensile property and tear resistance.

Synthesis, Characterization and Properties of Polymeric p-Benzoyl-4,4'-Diaminobenzoylaniline

An aromatic polyamide was synthesized by low-temperature poly-condensation reaction from terephthaloyl chloride and 4,4'-diaminobenzanilide (4,4'-DABA). The synthesized polyamide had a characteristic peak of carbon atoms in the amide group at 166 ppm, which was demonstrated by the solid nuclear magnetic resonance carbon spectrum. It was shown to be the stretching vibration absorption peak of the amide N-H bond at 3342 cm−1 by Fourier infrared (FT-IR) spectroscopy. It was obtained that the energy band near 1100 - 1276 cm−1 belongs to the absorption peak of the para-substituted benzene ring and the band near 2977 cm−1 was the C-H stretching vibration peak of the benzene ring by Raman spectroscopy. The molecular structure of the synthesized polyamide compound was confirmed by FT-IR, Raman, and solid 13C-NMR spectroscopies. It was proved that the polymer is stable up to 300˚C and has a relatively high stability by the thermogravimetric analysis. It was also confirmed by the fluorescence spectrum that it has a strong blue fluorescence near 420 nm. The morphological characteristics of the polymer were further demonstrated by electron scanning electron microscopy (SEM). The properties of polymeric p-benzoyl-4,4'-diaminobenzoyl-aniline were found to emit strong blue fluorescence and have good thermal stability, making it a promising functional material for fluorescence in the blue region with potential for large-scale applications.

Synthesis, Characterization and Properties of Polymeric p-Benzoyl-4,4'-Diaminobenzoylaniline

An aromatic polyamide was synthesized by low-temperature poly-condensation reaction from terephthaloyl chloride and 4,4'-diaminobenzanilide (4,4'-DABA). The synthesized polyamide had a characteristic peak of carbon atoms in the amide group at 166 ppm, which was demonstrated by the solid nuclear magnetic resonance carbon spectrum. It was shown to be the stretching vibration absorption peak of the amide N-H bond at 3342 cm−1 by Fourier infrared (FT-IR) spectroscopy. It was obtained that the energy band near 1100 - 1276 cm−1 belongs to the absorption peak of the para-substituted benzene ring and the band near 2977 cm−1 was the C-H stretching vibration peak of the benzene ring by Raman spectroscopy. The molecular structure of the synthesized polyamide compound was confirmed by FT-IR, Raman, and solid 13C-NMR spectroscopies. It was proved that the polymer is stable up to 300˚C and has a relatively high stability by the thermogravimetric analysis. It was also confirmed by the fluorescence spectrum that it has a strong blue fluorescence near 420 nm. The morphological characteristics of the polymer were further demonstrated by electron scanning electron microscopy (SEM). The properties of polymeric p-benzoyl-4,4'-diaminobenzoyl-aniline were found to emit strong blue fluorescence and have good thermal stability, making it a promising functional material for fluorescence in the blue region with potential for large-scale applications.

SYNTHESIS AND CHARACTERIZATION OF GRAFT COPOLYMERS BASED ON POLY(p-PHENYLENE TEREPHTHALAMIDE) BACKBONE AND WELL-DEFINED POLYSTYRENE SIDE CHAINS

A novel dualfunctional monomer, 2-（2＇,2＇,6＇,6＇-tetramethyl-piperidinyl-1＇-oxy）methylbenzene-1,4-dioyl chloride hydrochloride, with two acid chloride groups for step-growth polymerization and a nitroxide group for the mediation of living radical polymerization was synthesized. It was first copolymerized with terephthaloyl chloride and p- phenylenediamine at a feed molar ratio of 1：3：4 in N-methyl-2-pyrrolidone containing 10 wt% calcium chloride at -10℃ to yield a poly（p-phenylene terephthalamide） based macroinitiator, which initiated radical polymerization of styrene at 125℃ to obtain a series of poly（p-phenylene terephthalamide）-g-polystyrenes. A combinatory analysis of proton nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, elementary analysis, thermogravimetry and gel permeation chromatography indicated that the macroinitiator induced the radical polymerization of styrene to proceed in a well- controlled way. The molecular weight of side-chains increased with an increase of monomer conversion, and the molecular weight distribution index remained lower than 1.5. The graft copolymers showed a remarkably improved solubility in N- methyl-2-pyrrolidone and much depressed crystallinity in bulk.