| Polyarylene ether nitriles (PEN) were studied since 80 decade of past century, and the first generation of PEN (PEN-ID300) was introduced by Idemitsu Kosan Co., Ltd. Japan in 1986. However, because the high precipitation from crystallization in the synthesis of polyarylene ether nitrile homopolymers makes it difficult to obtain high molecular weight polymer, Idemitsu Kosan Company reported the related products and their performance, and then never report again. The domestic studies of polyarylene ether nitriles are mainly limited to laboratory synthesis, and it is difficult to steadily-synthesize and evaluate the overall performance. Also, there is less study on dispersibility and compatibility of functional PEN composites. In this paper, the research of fabrication modifying and the relationship between the structure and properties of PEN polymers were studied on the basis of copolymerization-synthesis, from the angle of view of industrialization and application for PEN. It will lay the foundations for scalization-synthesis and applications of PEN. On this basis, the thesis focuses on the dielectric properties and dielectric-functionalization of PEN. Through the study on composition of the polymer and functionalized fillers, dielectric composites with high performance were obtained and a different technical approach for functionalization of special engineering plastic was developed.In this work, a series of polyarylene ether nitriles with different structure and function were synthesized based on nucleophilic substitution, using 2, 6-dichlorobenzonitrile, hydroquinone, resorcinol, bisphenol A and phenolphthalein as raw materials. The relationship between their structures and properties was systematic studied, and the paper mainly researches the dielectric and fluorescent properties of the resins. It was found that the copolymerization is beneficial to increasing the molecular weight of the resin. High molecular weight PEN resins possess excellent mechanical properties and the resins with different molecular structure show different physical characteristics. PEN resins possess a relatively high dielectric constant, which is due to the double effect of dipole polarization and electronic polarization. Meanwhile, their dielectric properties have low frequency-dependence and good temperature stability, so they have stable performance below the glass transition temperature. The PEN copolymers synthesized from phenolphthalein and phenolphthalin show some fluorescence, and when the copolymers are in solution state, the phenomenon of fluorescence is more significant due to the solvent effect. Besides, the copolymers with equimolar phenolphthalein and phenolphthalin units show the best fluorescence.The high molecular weight PEN resins possess excellent performances. However, the increase in molecular weight has also brought the problem of deterioration of liquidity, which will enable their applications be limited and is detrimental to preparation of high performance composites. In this paper, the binary blends were prepared with phthalonitrile prepolymers and polyphenylene sulfide as plasticizers, and the compatibility, processing fluidity, mechanical properties and thermal stability of binary blends were studied in detail by rheological analysis, dynamic mechanical analysis, and so on. The glass fiber composites were prepared on this basis, and the effect of heat treatment on performance of composites was mainly studied. It was found that the processing fluidity of PEN was improved by adding phthalonitrile prepolymers and polyphenylene sulfide, which is attributed to their high fluidity. The mechanical and thermal properties of PEN remain stable after modification. Phthalonitrile prepolymers and polyarylene ether nitriles have good compatibility due to the similarity of their structures. However, there is microphase separation between polyphenylene sulfide and polyarylene ether nitriles, which is due to the big difference in cooling rate. This microphase separation increased the crack propagation paths; thereby the energy could be dissipated, which played a role in toughening. Because it can generate crosslinking reaction between phthalonitrile prepolymers and polyarylene ether nitriles under heat treatment, and the hydrogen bond can be formed between phthalonitrile prepolymers and glass fiber surface hydroxyl groups to improve the resin-filler interface force, the performance of PEN/glass fiber composites containing phthalonitrile prepolymers can be significantly improved by heat treatment.On the basis of synthesis and processing of PEN, the thesis developed a series of technical approach for functionalization of PEN, with PEN as matrix and fullerenes, carbon nanotubes and barium titanate as nano-fillers, aiming at resolving the dispersivity and compatibility of nano-fillers in PEN matrix. First, we prepared PEN/fullerenes composite films with low dielectric constant by a controllable solvent evaporation method, and the effect of the controllable solvent evaporation method on the dispersion of fullerenes and films performance is analyzed emphatically. It was found that the controllable solvent evaporation method can help the fillers achieve excellent dispersion for preparation of composites containing soluble nano-fillers, by the principle of entanglement between polymer chains and particle fillers. The as-prepared composite films not only possessed low dielectric constant of less than 2.0, but also their thermal and mechanical properties were both improved.For most non-soluble nano-fillers, we developed a continuous ultrasonic dispersion fabrication process, and prepared PEN/barium titanate (BT) nanocomposite films. It was found that the process can well solve the problem about dispersion of the nano-fillers in resin matrix. The PEN/BT nanocomposite films possess good dielectric properties (energy density 1.388 J/cm3, dielectric loss 0.021), mechanical properties (tensile strength > 100 MPa) and high thermal stability (initial decomposition temperature >450℃). However, this method can not resolve the problem about compatibility between the organic phase and the inorganic phase in composites. Therefore, the BT nanoparticles surfaces were chemically grafted by a single-layer and a double-layer, respectively. It was found that the interfacial compatibility between the inorganic fillers and the polymer matrix was greatly improved by surface grafting of BT particles, and both temperature-stability and frequency-stability on dielectric properties of the composite films were not affected. However, because the surface grafting modification of BT nanoparticles hindered the formation of dielectric channels and weakened the interfacial polarization, the dielectric constant of composite films decreased slightly.To prepare nanocomposite films with high dielectric constant, another way is adding conductive fillers into polymer matrix by using the percolation theory, except the way of adding fillers with high dielectric constant into polymer matrix. The thesis combines the solution process, the continuous ultrasonic dispersion fabrication process and surface grafting modification based on the above research. In the basis of the design thought that the introduction of insulated interfacial layers between the conductive particles can restrain high dielectric loss caused by the DC leakage conductivity, PEN/MWNT nanocomposite films were prepared by MWNT surface grafting method and in-situ polymerization, respectively. Through the study on structure and properties of composite films, it was found that: (1) The MWNT can be dissolved after being surface grafted by high 4-aminophenoxy phthalonitrile content, this greatly reduces the difficulty of dispersion. The surface grafting of MWNT is beneficial to improving the dispersion and compatibility of MWNT in PEN matrix. (2) The MWNT had an insulating layer on the surface after surface grafting, which blocked the leakage channel between MWNT. Therefore, the PEN/MWNT-CN composite films not only possess relatively high dielectric constant, but also have relatively low dielectric loss. (3) Another effective way to resolve the dispersity and compatibility of MWNT in resin matrix is acylchlorination on MWNT surface to achieve in-situ polymerization of PEN and MWNT. The PEN/MWNT composites prepared by in-situ polymerization have better dispersion and interfacial compatibility, compared with those prepared by surface grafting. Furthermore, the PEN/MWNT composites prepared by in-situ polymerization have the advantage that they can be processed by melting blend, so in-situ polymerization is one of the best ways to prepare such composite materials. |
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