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ABSTRACT A diamine containing heterocyclic pyridine and unsymmetrical carbazole substituents, 4-(9-ethyl-3-carbazole)-2,6-bis(4-aminophenyl)pyridine ( CBAPP), was prepared for use in the synthesis of poly(pyridine-imide)s PI-1-8 by direct polycondensation with dianhydrides in N,N-dimethylacetamide (DMAc). The poly(pyridine-imide)s derived from the diamine are highly soluble in solvents such as N-Methyl-2-pyrrolidone (NMP) and DMAc at room temperature. Noncoplanar polyimide (PI-1) showed excellent solubility, high transparency, and high-performance mechanical properties. These polymers had relatively high glass transition temperatures and exhibited good thermal stability in both nitrogen ( Td10 > 470 °C) and air ( Td10 > 450 °C). The PI-3∼5 cannot form flexible and tough films due to the unsymmetrical carbazole moiety, rigid structure, and polar-polar interaction. However, through copolymerization technique these polymers (PI-6∼8) could be enhanced through the solubility, mechanical, and thermal properties. The optical properties included a strong orange fluorescence (540 nm) after protonation with acid. When the HCl concentration was increased, a new absorption band at approximately 350 nm appeared, and the intensity of the fluorescent peak at 380 nm observed in the neutral polymer solution decreased, along with the appearance of the new fluorescent peak at 540 nm. The poly(pyridine-imide)s presented here showed only slight fluorescence quenching in the presence of methanol. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 405-412 [ABSTRACT FROM AUTHOR]

Abstract: Polyimides rank among the most heat-resistant polymers and are widely used in high temperature plastics, adhesives, dielectrics, photoresists, nonlinear optical materials, membrane materials for separation, and Langmuir–Blodgett (LB) films, among others. Additionally, polyimides are used in a diverse range of applications, including the fields of aerospace, defense, and opto-electronics; they are also used in liquid crystal alignments, composites, electroluminescent devices, electrochromic materials, polymer electrolyte fuel cells, polymer memories, fiber optics, etc. Polyimides derived from monomers with noncoplanar (kink, spiro, and cardo structures), cyclic aliphatic, bulky, fluorinated, hetero, carbazole, perylene, chiral, non-linear optical and unsymmetrical structures have been described. The syntheses of various monomers, including diamines and dianhydrides that have been used to make novel polyimides with unique properties, are reported in this review. Polyimides, with tailored functional groups and dendritic structures have allowed researchers to tune the properties and applications of this important family of high-temperature polymers. The synthesis, physical properties and applications of advanced polyimide materials are described. [Copyright &y& Elsevier]

• Preparation of regular through-pore polyimide membranes on filter paper using the breath-figure technique. • Regular through-pore membranes with high water permeance and high yeast and mud rejection. • Surface cleaning or backwash easy restore the fouled membrane. Regular through-pore membranes exhibit extremely high productivity and size-selective capabilities. Previous studies have demonstrated that the use of a polymer alone on a solid substrate surface hinders the formation of regular through-pore membranes. In this study, amphiphilic dendrons were used as surfactants to concentrate the functional groups and strengthen the weak bonding forces between the molecules, which is conducive to the formation of regular through-pores in the membrane. The amphiphilic dendrons were mixed with commercial-grade polyimide (PI) using chloroform as the solvent, and the solution was evenly coated on the surface of the filter paper. Using the breath-figure method, an ultrathin regular through-pore PI layer was formed directly on the surface of the filter paper. The SEM image shows that regular through-pores were formed only on the surface of the substrate. The preparation process used in this study eliminates the need to transfer ultrathin and weak membranes to the substrate surface, which simplifies the membrane-making process. Pure water and yeast solution filtration tests were conducted on the composite membrane prepared with a 5 mg/ml dendron solution. A pure water permeance of 118,826 L m-2h−1 bar−1 (LMH/bar) was obtained, the yeast solution permeance and rejection are 17,410 LMH/bar and 92.85 %, respectively. The yellow, turbid, muddy water was successfully purified to clean water. The original performance of the fouled membrane was restored after only 30 s of water flushing. This study proposes a new approach to fabricate high-efficiency regular through-pore PI composite microfiltration membranes. [ABSTRACT FROM AUTHOR]