Synthesis And Characterization Of Polynaphthalimides Contained Six-membered Imide Ring

Major:Chemistry of fine chemicalsAdviser:Professor Chunhai ChenIn late 1950's, after the patenting of the polyimide materials, a number of developments have been made. Development of new PI structures and high performance PI enhance their applications tremendously. Unique structural properties of PI give rise to its higher thermostability, and strength properties makes it best suit material for aerospace, automotive, microelectronics and others fields as well.So far, the thermoplastic polyimides like Kapton, Upilex have been widely used, the thermo setting materials like PMR-15 also used in aerospace. By comparing these two polymers, it can be seen that these all contain five-membered imide ring, both are extensively applied polyimides. In the polyimides family, there is a class of polyimides contained six-membered imide ring,and which give them higher themostabilites, mechanical peoperties and chemical resistance, etc., the most important feature of six-membered ring polyimides are small angle tension as compared to five-membered ring polyimides. The prominent feature of 6-membered ring PI seems to produce more stability especially in hydrostability.Although polynaphthalimides possess excellent performance, the most research works also stay in the laboratory stage about proton exchange membrane fuel cells. The performance is closely related to the structures, the six-membered imide ring is a large rigid groups, it gives high glass transition temperature, better mechanical properties, excellent hydrolysis stability and chemical stability, which makes them suffer from more processability problem, inasmuch as they are more insoluble and infusible. These properties make them difficult to fabricate by means of conventional techniques.Adoption of the polymer structural modification to change its solubility is a better method to improve the polymer processibility. Due to the rigid structure of six-membered imide, it cooperate the inter molecular main chain, which hinder its solubility, in order to increase the solubility, we would like to proceed from molecular design, to increase the distance of rigid imide ring to get good soluble polynaphthalimides.In our experiment, we design to prepare dianhydrides monomers, we hope to enlarge the distance between two imide ring with flexible group to get good soluble polymers, for another purpose, the dianhydrides can improve the diversity of polymers. The introduction of distorted structure is a viable option to improve the solubility. So we designed and prepared a binaphthyl dianhydride monomer. The most applied is from Ni(0)-catalytic coupling reaction, the drawback is low yield. So we use a simple Pd/C catalytic coupling method. In this study, we selected carbon monoxide (CO) as the reducing agent, When the velocity of CO flow was kept lower than 5 ml/min, dehalogenation-coupling reaction occurred as dominant step and BNTDA was obtained. However, KBNTDA was the major product when CO flow was increased above 40ml/min. Because at higher CO flow (>30 ml/min), insertion reaction dominated over dehalogenation-coupling reaction. In the preparation of KBNTDA, CO was not only reducing reagent but also acted as inserting reactant. Polymerizations of the dianhydrides BNTDA and KBNTDA with aromatic diamines were carried out via a one-step method in m-cresol. All polyimides remained fully soluble during the course of the polymerization. Fibrous high molecular weight polyimides could be isolated upon precipitation into methanol. The intrinsic viscosity (η) value of these polyimides ranged from 0.83 to 1.17 dL/g, it showed that these polyimides had high molecular weights, all the polyimides studied were soluble in m-cresol and concentrated H2SO4,Ⅱc seems to be more soluble than other polyimides, the possible reason is the more flexible chain structure caused by the ether band and carbonyl of p-TPEQ and KBNTDA, and the bulky side group of p-TPEQ reduced the intermolecular interaction and chain packing. PolyimidesⅡa-c showed transitions on DSC thermo grams above 326℃. The temperatures of 5%weight loss were all above 545℃in N2, the char yields reported at 800℃in N2 are above 55%. Hydrolytic stability testing shows that polyimides contained six-membered ring proved to be more hydrolytic stable than polyimides contained five-membered ring.From the previous work, we find that the longer flexible structure would be introduced between two imide rings, the better soluble can be obtained. Therefore, we designed and prepared two dinanhydride containing longer flexible structures, and then polymerisized with three common diamine. The viscosity test showed that the polymer have high molecular weight, the XRD showed that it is amorphous structure. All the polymer can dissolved in H2SO4, m-cresol, NMP and chloroform, and partially in DMAc, and DMF, insoluble in THF. At the same time, the thermal properties and hydrolysis stability were tested, they showed polymer also have good thermal properties and hydrolytic stability.The traditional method to get polynaphthalimides is one step method, the advantage of using phenolic solvent is that they are high boiling point solvent, it can provide high reaction temperature, because that they have good solubility for polynaphthalimides,this can guarantee the polymer in the reaction system to get high molecular weight polymer. However, the phenolic solvent is toxicity, in order to product scale and application, we need to find a workable method. In our study, firstly we prepared a dichioro-monomer 4,4'-bis (N-phenyl-4-chloro-1,8-naphthalimide) ether (BCNPI), and we synthesized novel polyethernaphthalimide (PENI) derived from BCNPI and Bisphenol A salt in the present of sulfolane. The test of Intrinsic viscosity showed that the polymer possess high Molecular Weight. From the Differential scanning calorimetry, it showed high Tg. According to the Thermogravimetric analysis we can see that the polyetherimide exhibited excellent thermal and thermooxidative stabilities, and from the test of the mechanical properties, it showed high Modulus, Strength and Elongation. At the same time, the hydrolytic sability test showed that it have good hydrolytic stability.