Optically transparent and organosoluble poly(ether imide)s based on a bis(ether anhydride) with bulky 3,3′,5,5′-tetramethylbiphenyl moiety and various fluorinated bis(ether amine)s

Novel optically transparent and organosoluble poly(ether imide)s (PEIs) were prepared from 4,4′-bis(3,4-dicarboxyphenoxy)-3,3′,5,5′-tetramethylbiphenyl dianhydride and various fluorinated bis(ether amine)s via chemical or thermal imidization. The effects of fluorinated groups and the imidization method on the properties of PEIs were investigated. Fluorinated PEIs prepared by the chemical imidization method exhibited essentially colorless characteristic with cutoff wavelengths lower than 380 nm, and yellowness index (b* values) ranging from 5.2 to 7.3, which are close to that of transparent polyarylate polymer (b* = 3.3). In addition, all fluorinated PEIs showed excellent solubility in common organic solvents. The thermal decomposition temperature at 10% weight loss is higher than 490°C, and the glass transition temperatures are in the range of 245–315°C. The fluorinated PEI series also exhibited low dielectric constants of 2.95–3.29 (1 MHz) and low moisture absorption in the range of 0.17–0.86 wt%, which are lower than the analogous nonfluorinated series.

Synthesis and properties of (A2+B4)-type hyperbranched polyimides with different terminal groups

To investigate the effect of terminal groups on the properties of hyperbranched polyimides (HBPIs) for potential optical applications, a series of HBPIs bearing different terminal groups have been synthesized through a novel aromatic CF3-containing tetra-amine, 4,4′-di[3,5-di(2-trifluoromethyl-4-aminophenoxy)phenoxy] sulfone, and a long chain dianhydride, 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]hexafluoropropane, via a two-step polycondensation procedure. The synthesized HBPIs could form flexible and tough polyimide (PI) films, which exhibit good thermal stability with the glass transition temperatures of 191–234°C for differential scanning calorimetry measurement, the 5% weight loss temperatures of 533–610°C, and residual weights of 45.8–58.6% at 800°C under nitrogen atmosphere. The PI films have favorable mechanical properties with tensile strengths of 77–92 MPa, elongation at break of 3.55–7.99%, and initial modulus of 2.05–2.86 GPa. The films also exhibit the good transmittance of higher than 80% at 800 nm. The average refractive indices ( nav) and in-plane/out-of-plane birefringence (Δ n) measured at 632.8 nm are in the range of 1.5539–1.6022 and 0.0065–0.0077, respectively. The good transmittance in the visible region, tunable nav, and low Δ n are very suitable for optical applications.

Structural Characterization and Properties of Organo-soluble Polyimides, Bismaleimide and Polyaspartimides Based on 4,4′-Dichloro-3,3′-Diamino Benzophenone

A novel chlorinated diamine monomer with keto group, 4,4′-dichloro-3,3′-diamino benzophenone (DADCB) was prepared through the nitration of dichloro benzophenone (DNDCB) followed by catalytic reduction with SnCl4 and HCl. Chlorinated polyimides (IVa-e) were synthesized from the above diamine with various commercially available dianhydrides via one-step and two-step methods. Polyimides IVa-e have inherent viscosity in the range 0.98–1.42 dL g° 1 in the one-step method and 0.70–0.95 dL g° 1 (thermal imidization) and 0.84–1.33 dL g° 1(chemical imidization) in the two-step method. The polyimidesprepared by the one-step method and chemical imidization method exhibited excellent solubility, but those prepared via thermal imidization exhibited limited solubility. Polyimide° lms exhibited tensile strength 95–121MPa, percentage elongation 8–13% and tensile modulus 1.6–2.4 GPa. The T g of the polyimides are in the range 272–297° C and T10 values are in the range 510–542° C in N2 and 460–498° C in air with more than 40% char yield at 800° C in N2 atmosphere. The prepared polyimides have cutoff wavelength in the range of 360–398 nm and percentage transmittance at 500 nm is in the range 80.9–94.2%. The dielectric constant of the polyimide films are in the range of 2.90–3.82 at 1 kHz and 2.85–3.68 at 10 kHz with moisture absorption in the range 0.38–0.88%. Bismaleimide (BMCB) was also synthesized using the synthesized diamine and maleic anhydride and further treated with various diamines to form linear polyaspartimides and their properties such as viscosity, solubility and thermal properties were also studied.

Organo-Soluble Fluorinated Polyimides Derived from Bis-Trifluoromethyl-Substituted Aromatic Diamines and Various Aromatic Dianhydrides

A new diamine monomer with bis-trifluoromethyl-substituted phenyl in the side chain, α,α-bis (4-amino-3,5-dimethylphenyl)-3′,5′-bis(trifluoromethyl)phenyl methane (6FMA) was successfully synthesized. A series of fluorinated polyimides (PI-IIa-d) were prepared by reacting the diamine with various aromatic dianhydrides. For comparison, another series of polyimides (PI-Ia-d) derived from another diamine with single-trifluoromethyl-substituted phenyl in the side chain, α,α-bis(4-amino-3,5-dimethylphenyl)-3′-trifluoromethyl phenyl methane and the same dianhydrides were also synthesized. The polymers were characterized by inherent viscosity, elemental analysis, Fourier transform-infrared, X-ray, ultraviolet-visible analysis, moisture absorption, thermogravimetric analysis, and differential scanning calorimetry measurements. It was shown that PI-II polyimides exhibited good film formability, enhanced solubility, good thermal stability, superior optical transparency, and acceptable mechanical properties. In addition, the polyimides derived from 3,3′,4,4′-benzophenone tetracarboxylic dianhydride and 6FMA showed high sensitivity to i-line (365 nm) of a high-pressure mercury lamp. The combined properties of the polyimides make them good candidates for microelectronic fabrications.

Structure–property studies on fluorinated polyimide isomers containing biphenyl moieties

Aimed at clarifying the structure–property relationships of fluorinated high-performance polymers, two series of polyimides were synthesized via a two-step thermal imidization derived from isomeric diamine monomers. Furthermore, comparative studies on their properties including solubility, thermal properties, contact angles, refractive indices, dielectric constants and gas permeability were thoroughly performed. Some property differences of the isomers caused by the sequence changes were found.

Thermoset polyimide matrix resins with improved toughness and high Tg for high temperature carbon fiber composites

Thermoset polyimide matrix resins with high melt processability for high-temperature carbon fiber composites were prepared from the diethyl ester of 3,3′,4,4′-benzophenonetetracarboxylic acid (BTDE) and the aromatic diamine mixtures consisting of 4,4′-bis(4-amino-2-trifluoromethylphenoxy)biphenyl (6FBAB) and p-phenylenediamine ( p-PDA) with the monoethyl ester of 5-norbornene-2,3-dicarboxylic acid (NE) as the molecular-weight-controlling and reactive endcapping agent. The effects of diamine mixture compositions on the melt processability of the B-staged oligoimides and the thermal and mechanical properties of the thermally cured polyimide resins were systematically investigated. Experimental results indicated that the polyimide matrix resins with p-PDA concentration of ≤ 40% in 6FBAB + p-PDA showed lower melt viscosities, corresponding to a higher melt processability, than the conventional thermoset polyimide (PMR-15). After thermal curing, the thermoset polyimides exhibited a very good combination of thermal and mechanical properties with the glass transition temperature (Tg) of as high as 353 °C determined by differential scanning calorimetry and impact strength of 15.2 kJ m−2. Carbon fiber-reinforced composite derived from the representative polyimide resin showed good mechanical properties at temperatures of as high as 288 °C.

Fluorinated PMR polyimides with improved melt processability and impact toughness

Fluorinated in situ polymerization of monomeric reactants (PMR) polyimide resins with improved melt processability and impact toughness were prepared from the diethyl ester of 3,3',4,4 '-benzophenonetetracarboxylic acid and the aromatic diamine 4,4 '-bis(4-amino-2-trifluoromethylphenoxy)biphenyl (6FBAB) with the monoethyl ester of 5-norbornene-2, 3-dicarboxylic acid as the molecular-weight-controlling and reactive endcapping agent. Effects of the calculated molecular weights (calc’d Mn values) on the resin melt processability and the thermal and mechanical properties of the thermally cured polyimides were systematically investigated. It was found that the fluorinated PMR resins with calc’d Mn of ≤ 2500 g mol-1 exhibited higher melt processability than the conventional PMR-15. After thermally cured, the thermoset polyimides displayed high thermal stability with the decomposition temperature at 5% weight loss ( T5) of > 62; 450°C, the glass transition temperature ( Tg) of 273—326° C, and good mechanical properties. Carbon-fiber-reinforced composites fabricated from the representative polyimide showed outstanding mechanical properties both at ambient and elevated temperatures as well as high impact toughness at room temperature.