Phthalonitrile resins are renowned for their outstanding heat resistance, withstanding temperatures exceeding 350 °C. This makes them highly sought after in industries such as aerospace, automotive, electronics, and renewable energy. To improve the sustainability of these materials, bio-derived phenols have been employed for the synthesis of the monomer in this research field. Thermosets derived from these partially bio-based monomers have demonstrated performance on par with their fossil-based counterparts, emphasizing the potential of sustainable phthalonitrile resins for advanced applications. Herein, the furan chemical platform is utilized to design and synthesize phthalonitrile monomers. Starting with furfural and its derivatives, novel low-melting (50-75 °C) Schiff-base monomers are synthesized and subsequently cured into thermosets. The resulting thermosets exhibit remarkable properties, including degradation temperatures (T5%, determined by thermogravimetric analysis) above 450 °C (after curing at 350 °C), char yields (Yc, at 900 °C) determined between 74 and 78%, and glass transition temperatures (Tg) surpassing 400 °C after curing at 350 °C and exceeding 300 °C after curing at only 250 °C. These findings underscore the versatility of furan chemistry in producing more sustainable phthalonitrile resins. The chemical design of these monomers enables the optimization of processability and material properties, broadening their application potential and advancing sustainability across multiple industries.

A hybrid diluent containing both phthalonitrile and benzonitrile functions was tested for improvement of phthalonitrile resin processability. The composites were obtained by the solvent-free prepreg technique and characterized by thermal and mechanical tests (a11+ = 640 MPa at room temperature with 100% retention at 400 degrees C) and preserved 50% of the strength after 1000 h aging at 350 degrees C.

Phthalontirile resins are renowned as the most heat-resistant polymeric materials and exhibit exceptional performance under harsh conditions. Consequently, phthalonitrile thermosets offer the potential to substitute metals in hot parts, thereby broadening the operational limits of plastic materials in high-tech applications. Given their unique combination of properties, phthalonitriles have garnered significant demand across sectors such as aerospace, automotive, electronics, and renewable energy. With industrial production and application of phthalonitriles recently initiated in several countries, questions regarding the sustainability of these materials have naturally arisen. Thermosetting materials, owing to their highly cross-linked architecture, cannot be recycled, necessitating the adoption of synthetic methods utilizing bio-feedstock raw materials and green protocols to mitigate their environmental impact. The present prospective review summarizes and analyzes the current state-of-the-art in bio-based phthalonitrile resins and discusses potential directions for research and development of new application areas, with a focus on the challenge of maintaining high-performance levels during the transition to bio-based raw materials. Partially bio-based phthalonitrile resins, originally developed as heat-resistant materials like their fossil-based counterparts, can be explored for broader applications due to their attractive performance characteristics. While challenges remain, particularly in processability and thermal performance, recent advancements in molecular design and green synthesis suggest a promising development. Overcoming these challenges will require multidisciplinary collaboration and thorough research into structure-property relationships. image

The process of thermal oxidation decomposition of phthalonitrile resins which had been post-cured at various temperatures (603 K, 623 K and 648 K) was studied using dynamic and isothermal measurement modes. It was shown that the degradation process is a complex branched four-stage process. We have concluded that the first stage is an nth order reaction with autocatalysis. The second stage is described with the expanded Prout-Tompkins equation which corresponds to an autocatalytic solid-state reaction caused by the formation of im-perfections at the reaction surface. The third and fourth stages are also reactions of the nth order. The phtha-lonitrile resin post-cured at 603 K exhibited better thermal stability than the resins post-cured at 623 K and 648 K based on the activation energies of the 1st stage - 132 kJ/mol, 104 kJ/mol, and 106 kJ/mol respectively. These data were confirmed by comparable experimental activation energy values (111 kJ/mol, 87 kJ/mol, 86 kJ/mol respectively) and changes in mass loss and flexural strength values determined during long-term thermal aging in the temperature range of 553-623 K. It was shown that the phthalonitrile resin post-cured at 603 K with the initial flexural strength of 107 MPa is suitable for long-term application at temperatures up to 573 K.

Bucky gel electrodes are composed of morphology-determining polyvinylidene difluoride (PVDF) filled with carbon nanotubes (CNT). The electrodes are commonly fabricated via the casting of a CNT dispersion containing PVDF and ionic liquid. In this study, several pore-forming additives such as polyethylene glycol (PEG), dibutyl phthalate (DBP), and the common ionic liquid BMIMBF4 were used to control the morphology of the bucky gel electrodes. The crystalline phase type and content of PVDF in the electrodes were determined by FT-IR and DSC, respectively. SEM revealed a sponge-like structure in the case of the use of BMIMBF4 and a spherulite structure if PEG and DBP were used as additives. A strong influence of morphology on the anisotropic increase in the volume of electrodes upon impregnation with electrolyte was observed. The PEG-based electrode elongated more than the others, while the BMIMBF4-based electrode thickened to a greater extent. Ionic actuators were fabricated to experimentally reveal the effect of electrode morphology on their electromechanical efficiency. A high-precision vat photopolymerization technique was used to fabricate identical ionic membranes and minimize their influence on the properties of the actuators. The electrodes were characterized by the same porosity and electrical capacitance, while the actuators differ significantly in performance. As a result, a simple method of using pore-forming additives made it possible to increase the maximum deformation of bucky gel ionic actuators by 1.5 times by changing the morphology of the electrodes.

Carbon–carbon composites (C/C) were produced from carbon fiber reinforced phthalonitrile (CFRP) matrix composites in a two-step impregnation–carbonization procedure. After graphitization at 1800 °C, the obtained C/C composites demonstrated highly crystalline structure and properties characteristic of composites derived from phenolic matrix CFRP by the industrial procedure: d = 1.73 g cm −3 , interlaminar shear strength was 14.1 MPa, compression strength was 139.8 MPa, and coefficient of friction was in the range 0.32–0.34.

Two types of poly(5-phenyl-2-norbornene) were synthesized via ring opening metathesis and addition polymerization. The polymers sulfonation reaction under homogeneous conditions resulted in ionomer with high sulfonation degree up to 79% (IEC 3.36 meq/g). The prepared ionomer was characterized by DSC, GPC, 1H NMR and FT-IR. Polymers for electromechanical applications soluble in common polar organic solvents were obtained by replacing proton of sulfonic group with imidazolium and 1-methylimidazlium. Membranes were prepared using the above-mentioned polymers and 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF4), as well as mixtures with polyvinylidene fluoride (PVDF). Mechanical, morphological, and conductive properties of the membranes were examined by tensile testing, SEM, and impedance spectroscopy, respectively. Dry and air-stable actuators with electrodes based on SWCNT were fabricated via hot-pressing. Actuators with membranes based on methylimidazolium containing ionomers outperformed classical bucky gel actuator and demonstrated high strain (up to 1.14%) and generated stress (up to 1.21 MPa) under low voltage of 2 V.

Phthalonitrile modified novolac (PNN) was synthesized in aim to develop a fast-curing resin for hot-pressing processing and characterized by NMR to confirm a full substitution of hydroxyl groups with phthalonitrile. PNN blended with high amounts (10–50 wt%) of the amine curing agents have been investigated by DSC, FT-IR spectroscopy and TGA, which revealed T5% = 420 °C. Curing times for the compositions were 4–16 min at 240 °C. The 50 min post-curing cycle for FRPs was selected based on DMA. Composites were fabricated via hot-pressing of prepregs including post-curing at 280 °C (providing Tg > 340 °C) in total of 60 min, which is the fastest curing cycle for thermosetting resins developed for applications up to 300 °C. Carbon and glass fabric reinforced polymers (CFRP and GFRP) were obtained by the developed program yielding integral composites with high mechanical properties and great heat resistance. Interlaminar shear strengths of the CFRP were up to 31 MPa and up to 70 MPa for GFRP. The latter which demonstrated retention of 75% of initial ILLS values after dwelling for 200 h at 300 °C. Thus, a new fast-processing phthalonitrile resin was developed for application in electric transport, aerospace and heat-resistant insulation.

Easy-pmcessable phthalonitrile resins were prepared from tris-phthalonitrile phosphate monomer TPP (tris(3-(3,4-dicyanophenoxy)phenyl)phosphate), bis-phthalonitrile RP (bis (3,4-dicyanophenoxy)benzene) and novel viscosity reducing comonomer CPN (4-(4-cyanophenoxy)benzene-1,2-dicarbonitrile). It was shown that TPP is more resistant to hydrolysis than reported phosphate based phthalonitriles (k =8.2.10(-4) s(-1) at 65 degrees C and pH 10). Two different type of curing agents: aromatic diamine DDS and 4-(4-aminophenoxy) phthalonitrile APN were used to study their effect on properties of the obtained resins and composites. Carbon fabric composites with APN-cured matrix fabricated by vacuum infusion demonstrated compression strength up to 633 MPa and 100% retention of ILSS after oxidative aging for 200 h at 300 degrees C. Post-curing of the matrix at 375 degrees C resulted in growth of Tg but at the same time micmcracking occurrence in the composite leading to decrease in mechanical properties and thermal aging sustainability.

Novel dual-functional phthalonitrile monomers containing a maleimide group were synthesized and characterized. Ortho, meta, and para isomers were obtained and only the meta-isomer can be considered as a low melting phthalonitrile monomer with a melting point of 107.4 degrees C. Analysis of the dual-curing behavior of monomers showed radical homopolymerization of maleimides followed by phthalonitrile polymerization with the formation of isoindoline, triazine, and phthalocyanine ring structures. Two alternative copolymerization processes of maleimide groups via ene reaction and ring-opening amidation were investigated. The approach of dual-curing maleimide and phthalonitrile fragments in a single molecule allowed combining the excellent inherent mechanical properties of bismaleimide resins and the outstanding thermo-oxidative stability of phthalonitriles. After curing of both functional groups impact strength was as high as 11.81 kJ m(-2), flexural strength was 108 MPa, Young's modulus was 4.38 GPa. On the contrary, T-g of this polymeric system was above 370 degrees C and T-5% was higher than 450 degrees C in air.

Objectives . Determination of target products and byproducts is necessary for the quality control of phthalonitrile monomer synthesis as well as production scaling and performing related kinetic studies. High-performance liquid chromatography (HPLC) is a simple and affordable method for quantitative chemical analysis, which also verifies the quality of raw materials. The objective of this study was to develop an HPLC technique for determining the composition of the reaction mixture in the synthesis of 1,3-bis(3,4-dicyanophenoxy)benzene (DPB). Methods . Reversed-phase HPLC was used to quantitatively analyze the reaction mixture. Results . A simple and rapid method for the quantitative HPLC analysis of phthalonitrile monomers and their mixtures with reagents was developed. Reaction times and the accumulation of byproducts were also studied. Conclusions . The successful performance of the developed technique allows us to recommend it for practical applications. The results obtained for reactors of different sizes have good convergence, and DPB synthesis was successfully scaled up to intermediate scale equipment.

This review focuses on the processes involved in producing heat-resistant matrices for fiber reinforced plastics (FRP) by polymerization of the resins consisting of phthalonitrile monomers and comonomers, and the specifics of fiber reinforced plastics fabrication technologies. Polymerization behaviors observed in the presence of various types of initiators and in different temperature modes are reviewed. Fabrication methods and mechanical properties of FRPs based on phthalonitrile resins with various reinforcing materials are discussed. Properties of glass fiber reinforced plastics (GFRP) and carbon fiber reinforced plastics (CFRP) obtained through curing of different phthalonitriles are compared.

A new low melting highly hydrolytically stable phthalonitrile monomer containing silane fragment was synthesized by a three-step procedure and cured to obtain a highly heatresistant thermoset. The polymer demonstrated the glass transition temperature of 485°C and the decomposition onset temperature over 500°C. Stiffness of the obtained thermoset appeared to be the highest among those of the reported silicon-containing phthalonitrile thermosets.

The microporous polyvinylidene fluoride (PVDF) membranes were prepared by the solvent evaporation method using 50 wt.% of different pore-forming additives: poly(1-ethyl-3-vinylimidazolium tetrafluoroborate) (PIL-BF4), polyethylene glycol 3000 (PEG-3K) and 40000 (PEG-40K), dibutyl phthalate (DBP). The influence of used additive on morphology, porosity, degree of crystallinity, tensile properties, electrolyte uptake and ionic conductivity of the membranes were investigated. The maximum electrolyte uptake of 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF4) was 184 wt.% for the membrane prepared with PEG-40K, however, the membrane was fragile and unsuitable for practical use. The remaining membranes showed approximately the same porosity (45‒48%) and electrolyte uptakes (169‒175%). At the same time, the membranes significantly differed in mechanical properties and ionic conductivity. The membrane prepared with PIL-BF4, unlike others, has a sponge-like structure and demonstrated high mechanical properties, namely tensile strength is 17.7 MPa and fracture strain is 132.5%. Bucky gel actuators were fabricated using membranes prepared with different additives. The blocking force of the actuators based on membranes with different additives decreased in the sequence of PIL-BF4, DBP and PEG. The actuator based on the membrane prepared with PIL-BF4 demonstrates a blocking force of 5.7 mN and a deformation of 1.35 % at 3 V DC.

Fluorinated phthalonitrile monomers exhibit low activity in polymerization initiated by a wide range of curing agents of various nature. On the contrary, the use of fluorinated diamines as hardeners for common non-fluorinated phthalonitrile monomer allows one to obtain thermosets with high glass transition temperature (Tg > 426 °C) and improved thermal oxidation stability (T5% = 520 °C in air).

Composites consisting of propargyl- and allyl/propargyl- modified novolac resins and carbon fabric were obtained by the vacuum infusion molding process. It was established that the presence of potassium cations remaining after the synthesis increase the resin melt viscosity, and acid washing is needed to obtain resins suitable for cost-effective injection techniques of composite fabrication. The mechanical properties of all composites such as compressive strength, tensile strength, in plane shear strength, and interlaminar shear strength were determined at 25, 200 and 230 °С. The carbon fiber reinforced plastics (CFRPs) retained their mechanical properties at temperatures up to 200 °C. It was shown that the use of the obtained allyl-containing polymer matrices improved mechanical properties and increased the thermal stability of the CFRPs in comparison with the propargylated novolac matrices. The composite material with novolac matrices modified by 18% propargyl and 23% allyl groups retains only up to 70% of the initial interlaminar shear strength values at 230 °C which corresponds to the data of the dynamic mechanical analysis of neat cured resins.

A new monomer containing thermosetting groups of two types, namely, propargyl ether and phthalonitrile, in the structure of the molecule was synthesized and studied. It was found that thermal polymerization was accompanied by the degradation of the monomer with propargyl ether decomposition. This problem can be solved using catalysts based on Cu(i) favoring the polymerization at both the propargyl group and phthalonitrile fragments. The cured monomer has a non-porous structure and high thermal properties (Vicat softening temperature 395 °C, T5% 451 °C). The low viscosity of the melt (<200 mPa s at 120 °C) and low glass-transition temperature (9 °C) of the monomer make it possible to use it for the formation of composite materials by vacuum infusion or injection into a mold.