Colorless and transparent poly(amide imide) nanocomposites containing organically modified hectorite

Polyamic acid (PAA) was synthesized using the diamine monomer N,N'-[2,2'-bis(trifluoromethyl)-4,4'-biphenylene]bis(4-aminobenzamide) and dianhydride monomer 4,4'-oxydiphthalic anhydride. Colorless and transparent poly(amide imide) (CPAI) hybrid films were prepared via multi-step thermal imidization of PAA in which various contents of nano-filler were dispersed. The CPAI hybrid films were prepared by dispersing organoclay STN, which was obtained by organically modifying hectorite, in CPAI by solution intercalation with various contents ranging from 1 to 7 wt%. The thermomechanical properties, morphologies, and optical transparencies of the obtained CPAI hybrid films were investigated based on the dispersed STN content, and the results were compared. Some of the clay in the CPAI hybrid film were agglomerated, which was observed using a transmission electron microscope; however, most clays were well-dispersed, with a nano-size of less than 10 nm. The best thermomechanical properties of the CPAI hybrid film were exhibited with an STN content of 3 wt%, but these properties decreased above the critical content. The coefficients of thermal expansion of all the hybrid films were below 20 ppm per °C regardless of the amount of STN, and the yellow index was 1-2 even when the STN content increased to 7 wt%.

Biomass materials derived from anethole: conversion and application

Renewable biomass has attracted much attention because of its advantages over fossil fuels. Of these biomasses, anethole has been developed as a reliable monomer or precursor for diverse materials with potential applications.

Polyimides containing cycloaliphatic segments for low dielectric material

New polyimides have been synthesized by the reaction of 3,3′,4,4′-benzophenone tetracarboxylic dianhydride (BTDA) or/and 5-[2,5-(dioxotetrahydrofuryl)]-3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride (DOCDA) with 4,4′-methylene dianiline (DDM). Polycondensation reactions were carried out in N, N-dimethylformamide solution and the resulting polyimides gave flexible free-standing films. The introduction of alicyclic moieties in the polyimide backbone improved the solubility of the resulting polymers and facilitated their processing while maintaining a high thermal stability. The dielectric constant values (measured at 106 Hz at room temperature), were found in the range of 3.14–2.83 and decreased with increasing of the alicyclic units content.

Dendronized polyimides bearing long-chain alkyl groups and their application for vertically aligned nematic liquid crystal displays

Polyimides having dendritic side chains were investigated. The terphenylene diamine monomer having a first-generation monodendron, 3,4,5-tris(n-dodecyloxy)-benzoate and the monomer having a second-generation monodendron, 3,4,5-tris[-3’,4’,5’-tri(n-dodecyloxy)benzyloxy]benzoate were successfully synthesized and the corresponding soluble dendritic polyimides were obtained by polycondensation with conventional tetracarboxylic dianhydride monomers such as benzophenone tertracarboxylic dianhydride (BTDA). The two-step polymerizations in NMP that is a general method for the synthesis of soluble polyimides is difficult; however, the expected dendritic polyimides can be obtained in aromatic polar solvents such as m-cresol and pyridine. The solubility of these dendoronized polyimides is characteristic; soluble in common organic solvents such as dichloromethane, chloroform, toluene and THF. These dendronized polyimides exhibited high glass transition temperatures and good thermal stability in both air and under nitrogen. Their application as alignment layers for LCDs was investigated, and it was found that these polyimides having dendritic side chains were applicable for the vertically aligned nematic liquid crystal displays (VAN-LCDs).