Incorporation of titanate nanosheets to enhance mechanical properties of water-soluble polyamic acid

Pyromeliticdianhydride (PMDA) and 4’,4’-oxydianiline (ODA) were used asmonomers of polyimide. To synthesise a water soluble polyimide precursor (polyamic acidsalt), triethylamine (TEA) was added to polyamic acid with a TEA/COOH mole ratio of 1:1.Titanate nanosheets were synthesised by solid-state reaction, ion-exchanged with acid, andexfoliated by TEA. Exfoliated titanate nanosheets were mixed with water soluble polyamicacid salt as reinforcing filler. Drop casting was deployed to synthesise polyamic acid/titanatenanosheet nanocomposite films. Scanning electron microscopy (SEM) and transmissionelectron microscopy (TEM) were employed to study the morphology and dispersion ofnanosheets in the colloidal dispersion and the solid film composite. Modulus and hardness ofnanocomposites was provided by nanoindentation. Hardness increased by 90% with addition of2% TiNS while modulus increased by 103% compared to pure polymer. This behaviour agreeswell with Halpin-Tsai theoretical predictions up to 2 wt% filler loading; agglomeration occursat higher concentrations.

Carbon molecular sieve membrane from a microporous spirobisindane-based polyimide precursor with enhanced ethylene/ethane mixed-gas selectivity

A highly selective carbon molecular sieve (CMS) membrane derived from a novel spirobisindane-based polyimide was synthesized. The mixed-gas ethylene/ethane selectivity of 15.6 at 20 bar is the highest reported value for CMS-type membranes to date.

Synthesis and characterization of low-CTE polyimide films containing trifluoromethyl groups with water-repellant characteristics

A novel fluorinated ester-bridged aromatic diamine, bis(2-trifluoromethyl-4-aminophenyl)terephthalate (CF3-BPTP) was synthesized, which was employed to prepare a series of fluorinated ester-bridged polyimide (PFEI) films with controlled ester-bridged segments and fluorine contents in the polymer backbone. The PFEI films were prepared by copolymerization of biphenyl tetracarboxylic dianhydride as aromatic dianhydride monomer and the aromatic diamine monomer mixture consisting of p-phenylenediamine and different amounts of CF3-BPTP. Experimental results indicated that the films’ water uptakes (Wus) reduced with increasing of the CF3 groups loadings in the ester-bridged polyimide backbones while keeping the films with low enough coefficient of thermal expansion (CTE). By controlling CF3 group loadings, polyimide films with desirable combination of thermal, mechanical, and dielectric properties for application in high density and thinner flexible printed circuits (FPCs) have been obtained. Thus, polyimide films with CTE of ≤20 × 10−6 1/K (ppm/K) at 50–200°C, glass transition temperature of ≥310°C, Young’s modulus of ≥6.0 GPa, Wu of as low as 0.7 wt%, dielectric constant ( ε) of 3.3 have been obtained. The two-layer flexible copper clad laminate prepared by coating the polyimide precursor resin poly(amid acid) solution on the surface of copper foil followed by thermal imidization at elevated temperature did not show apparent curling due to its closed CTE value.