Polyimide–polydimethylsiloxane copolymers containing nitrile groups

Thermal and oxidative behavior of a tetraphenylsilane-containing phthalonitrile polymer

Phthalonitrile polymers have potential for high-temperature applications in polymer matrix composites as electronic encapsulation compounds. To investigate the effect of inclusion of an organosilicon moiety, a tetraphenylsilane-containing phthalonitrile monomer was synthesized in high yields. The monomer possessed a high melting point of 222–223°C, while no hydrolytic sensitivity was observed. Cured polymers exhibited glass transitions in the range of 290–325°C and coefficients of thermal expansion of 73–77 µm/(m °C). In thermogravimetric analysis (TGA), 5 wt% loss was observed at 482–497°C and 519–526°C, under air and nitrogen, respectively. Infrared (IR)-TGA of evolved gases revealed multiple degradations in both nitrogen and air. The material possessed good thermo-oxidative stability (TOS) when aged in air at 250°C. After aging for 5000 h, oxidative degradation was characterized using Fourier transform IR microscopy, energy dispersive spectroscopy, optical microscopy, and Knoop hardness testing. Four zones were identified in aged samples. The cleavage of Si-phenyl bonds and the formation of Si–O phases and carbonyl groups were observed.

Phthalonitrile resin bearing cyanate ester groups: synthesis and characterization

Cyanato–phthalonitrile thermosets formed by independent curing of the two groups showed increased processability but marginally reduced water repellency and thermal stability.

Preparation and characterization of poly(imide siloxane) block copolymers based on diphenylthioether dianhydride isomer mixtures

A series of poly(imide siloxane) block copolymers were prepared based on diphenylthioether dianhydride isomer mixtures (m-TDPA), 4,4′-oxydianiline (ODA) and bis(γ-aminopropyl)polydimethylsiloxane (APPS). The ODA and m-TDPA composed the hard segment, while the APPS and m-TDPA composed the soft segment. The hard segment length was kept constant, while the soft segment lengths were varied with varying the APPS contents. The copolymers had inherent viscosities range from 0.37 to 0.51 dL g−1, and their weight-average molecular weights and number-average molecular weights were in the range of 45 000–52 600 and 21 300–27 000, respectively. All copolymers were readily soluble in many organic solvents, and could afford flexible films via solution casting. The cast films exhibited mechanical properties with tensile strengths at break of 26.7–86.2 MPa, elongations at break of 9.9–112.2%, and tensile moduli of 0.12–2.15 GPa, depending on the soft segment length. The films also exhibited low water uptakes in the range of 0.18–0.68 wt.%. Furthermore, the copolymers showed high glass transition temperatures derived from the hard segments in the range of 196–225 °C, and good thermal stability with almost no weight loss up to 350 °C under nitrogen atmosphere and 335 °C under air atmosphere.

Hybrid Films Based on a Polyimide Containing Nitrile Groups and Barium and Titanium Oxides

Hybrid polyimide films based on barium and titanium oxides were obtained by sol-gel technique using a poly(amic acid) containing nitrile groups and a soluble precursor of barium and titanium oxides. The poly(amic acid) was synthesized by solution polycondensation reaction of 4,4'-oxydiphthalic anhydride with 2,6-bis(3-aminophenoxy)benzonitrile. Hybrid polymer films were investigated by atomic force microscopy, scanning electron microscopy, thermogravimetric analysis and dynamic mechanical analyses. The nanoactuation properties of some hybrid polyimide films were also investigated.