Synthesis and crosslinking behavior of a soluble, crosslinkable, and high young modulus poly(arylene ether nitriles) with pendant phthalonitriles

Preparation and characterization of phthalonitrile resin within hyperbranched structure

In this article, a kind of polyester-type phthalonitrile cyano resin (2,2-bis (((3-((4-(3,4-dicyanophenoxy) benzoyl)oxy)-2-(hydroxymethyl)-2-methylpropanoyl)oxy)methyl) propane-1,3-diyl)bis(oxy)) bis (2-(hydroxymethyl)-2-methyl-3-oxopropane-3, 1-diyl) bis (4-(3,4-dicyanophenoxy) benzoate (hbppn)) with branched structure was introduced. The molecular structure and relative molecular mass of hbppn were characterized by nuclear magnetic resonance, Fourier transform infrared spectroscopy, and the matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF). The results showed that the synthesized HBPPN contained both polyester and hyperbranched structures. The thermal and rheological properties of HBPPN were characterized by differential scanning calorimetry and rheometer, and the results showed that HBPPN would be cured at about 322°C and the viscosity of the resin showed good processability. The results of dynamic mechanical analysis and thermogravimetric analysis showed that the synthesized resin had good heat resistance. The glass transition temperature was above 329°C, the residual weight ( C y) at 900°C was as high as 66.2% in the nitrogen atmosphere, and the temperature at which the resin lost 5 wt% of heat in air atmosphere was about 423.3°C. The synthesized HBPPN had good comprehensive properties, which could be applied to high-temperature resistant and thermal protection materials.

Interface conjugation enhances the interface adhesion performance of carbon fiber-reinforced phthalonitrile composites by π-π stacking

There has been little research focus on the interface problems of phthalonitrile (PN) resin and carbon fiber. However, interface performance is related to the overall mechanical properties of composites and is very important. This study focused on the interfacial performance and adhesion mechanism of a carbon fiber C_f/PN composite. Micro-composites of C_f/PN and C_f/epoxy resins were prepared, and their interfacial shear strengths (IFSS) were tested by micro-droplet testing. The result showed that the IFSS of C_f/PN was higher than that of C_f/epoxy resin, indicating that the interfacial adhesion of the PN matrix composite must be more effective. To explain the obtained results, a number of tests, including SEM, SEM-EDS, FTIR, and TGA, were carried out. From the SEM analyses, cured PN polymer films were found on the surface of de-bonded carbon fibers. With the aid of SEM-EDS, the elements on the de-bonded carbon fiber surface of the C_f/PN composite were detected in situ. An interesting synchronous relationship was observed in the IFSS and SEM-EDS results. Through the FTIR spectra, the chemical structures of the PN polymers were identified. From the detailed analyses and discussion in this work, the effective interfacial bond function in the C_f/PN composite appears to be a complex result for all relative functions. The functional advantage of the PN composite may be the interface conjugation between the PN polymers and the graphene layer on the surface of the carbon fiber.

Novel cardo poly(arylene ether nitrile sulfone) copolymers bearing xanthene moiety in the main chain

A series of cardo poly(arylene ether nitrile sulfone) (PENS) copolymers containing xanthene moiety were prepared by the nucleophilic substitution reaction of 9,9-bis(4-hydroxyphenyl)xanthene with 2,6-difluorobenzonitrile (DFBN) and 4,4′-dichlorodiphenylsulfone (DCDPS) by varying stoichiometric ratio of DFBN to DCDPS (90/10–40/60) using N, N-dimethylacetamide (DMAc) as solvent in the presence of anhydrous potassium carbonate. The copolymers having number-average molecular weights of 17,100–18,300 g mol−1 with the polydispersity index from 1.79 to 2.11 were amorphous and were easily soluble in polar solvents such as N-methyl-2-pyrrolidone and DMAc, and even in tetrahydrofuran and chloroform at room temperature. The resulting PENS copolymers showed glass transition temperature ( Tg) between 253.3°C and 260.4°C, and the Tg values were found to increase with increasing sulfone content in the copolymers. Thermogravimetric studies showed that all the polymers were stable up to 450°C, with 10% weight loss temperatures ranging from 500°C to 524°C and char yields of 56–63% at 700°C under nitrogen atmosphere. All new polymers could be cast into strong and flexible films with tensile strengths of 56.7–78.8 MPa, elongations at break of 7.8–9.1%, and tensile moduli of 2.1–3.2 GPa.

Sulfonated copoly(arylene ether nitriles) as proton exchange membrane with excellent mechanical and thermal properties

A series of sulfonated biphenol poly(arylene ether nitriles) (BP-SPEN) copolymers were synthesized by the nucleophilic aromatic substitution polymerization of 2,6-difluorobenzonitrile with different ratios of hydroquinonesulfonic acid potassium salt and biphenol in the presence of potassium carbonate. The composition and structures of the BP-SPEN copolymers were characterized by Fourier transform infrared spectroscopy. Thermal properties, mechanical properties, proton conductivity, and water uptake of copolymer membranes were also investigated. The results showed that they present high glass transition temperature ranging from 131°C to 180°C and good thermal stability with the 5% weight loss temperatures in the range of 284–287°C under nitrogen atmosphere. They also exhibited good mechanical property with the tensile strength in the range of 68–109 MPa in the dry state and 31–72 MPa in the wet state. Furthermore, these copolymer membranes exhibited good water uptake ranging from 8.8% to 39.9%. Thus, the membranes had good proton conductivities in the range of 1.09 × 10−5–1.54 × 10−3 S cm−1 at room temperature and 100% relative humidity. The influence of temperature on water uptakes, tensile strength, and proton conductivity was also investigated.

Thermally stable phthalonitrile resins based on multiple oligo (aryl ether)s with phenyl-s-triazine moieties in backbones

Phenyl-s-triazine segments in the polymer backbones endowed phthalonitrile networks with enhanced thermal stability, which could also be tuned by the main-chain lengths of the aromatic ether.