A Study On Novel Aromatic Polyamides And Sulfonated Aromatic Polyamides

Wholly aromatic polyamides (aramids) are considered to be high-performance organic materials due to their outstanding thermal and mechanical resistance. In the last few decades, in the industry such as automobile, aerospace, micro-electronics, there is an increasing demand for the material of high heat resistant, so as to replace the metal and ceramics. Their properties arise from their aromatic structure and amide linkages, which result in stiff rod-like macromolecular chains that interact with each other via strong and highly directional hydrogen bonds. Owing to their chemical structure, they exhibit extremely high transition temperatures that lie above their decomposition temperatures, are sparingly soluble in common organic solvents and, accordingly, the aromatic polyamides have so poor a processability that their application are limited. Research efforts are therefore underway to incorporate new flexible chemical functionalities (e.g. ether linkage, methylene, oxyethidene group), and bulky pendant groups (e.g. phenyl group, aryl group, tert.-butyl) in the polyamide, so that their solubility can be improved, processability increased, applicability expanded and then let polyamide remain on the forefront of scientific research.Sulfonated polymers are giving more and more attention because of its promising application in the fields of polymer electrolyte fuel cell, permeation membrane, hydrogel, and so on. Generally, there are two ways to prepare sulfonated polymers, one is post-sulfonation, of which polymers are sulfonated by sulfonating agents, this method is simple, but the sulfonation degree is low and the polymers tend to decompose; and the other is direct polymerization of sulfonated monomers, this method is relatively complex, but the sulfonation degree can be controlled by choosing proper monomers, and high molecular polymers can be obtained.In chapter 2, a series of aromatic diacids have been synthesized, i.e. 1,3-bis(3-carboxyphenoxy) benzene (BCPOBCOOH-1), 1,4-bis(4-carboxyphenoxy) benzene (BCPOBCOOH-2), 1,4-bis(3-carboxyphenoxy) benzene (BCPOBCOOH-3), 1,2-bis(4-carboxyphenoxy) benzene (BCPOBCOOH-4), following a procedure of a previously reported synthesis. These diacids were condensed directly with aromatic diamines 4,4'-oxydianiline (ODA), via the Yamazaki–Higashi phosphorylation method in the presence of triphenylphosphite (TPP), pyridine (Py) and halide salts to give high molecular aromatic polyamides (PAs). The structures and properties of the obtained PAs were characterized by Fourier transform infrared (FT-IR) spectra, Nuclear Magnetic Resonance (NMR), Thermogravimetric analysis (TGA), Polarizing Optical Microscope (POM), and so on. In addition, the inherent viscosities, solubility, film forming ability and mechanical properties were also researched. The measurements showed that four kinds of novel aromatic polyamides were synthesized successfully with high molecular via Yamazaki–Higashi phosphorylation method. Four polyamides all showed good solubility in polar solvents, such as dimethylsulfoxide (DMSO), N,N-dimethylacetamide (DMAc), N-dimethylformamide (DMF), N-methylpyrrolidone (NMP), and so on. The obtained polymers showed high thermal stability with decomposition temperature around 400°C. The polyamide membranes manifest excellent mechanical properties, with Young's modulus of 2.5~5.5 GPa. Interestingly, the films of PA-1, PA-2 and PA-3 are completely transparent in the visible range, while PA-4 film is opaque. By POM, crystallization was observed in PA-4 film, although the molecular structure of PA-4 is not as symmetrical as PA-2.In chapter 3, a new kind of sulfonated aromatic dicarboxylic acid monomer, sodium 1,4-bis(4-carboxyphenoxy) benzene-2-sulfonate (BCPOBS-Na), in addition, one kind of sulfonated aromatic diamine monomer, 4,4'-diaminodiphenyl ether-2,2'-disulfonic acid (ODADS), was synthesized following a procedure of a previously reported synthesis. These two sulfonated monomers were reacted with 1,3-bis(3-carboxyphenoxy) benzene (BCPOBCOOH-1) and 4,4'-oxydianiline (ODA) respectively, which were used as non-sulfonated monomer, via the Yamazaki–Higashi phosphorylation method in the presence of triphenylphosphite (TPP), pyridine (Py) and halide salts to give high molecular sulfonated aromatic polyamides (SPAs). They showed good solubility in polar solvents, such as DMSO, DMF, DMAc, NMP, and so on. As well, they possess excellent thermal stability with decomposition temperatures higher than 370°C.In chapter 4, with two sufonated monomers synthesized in chapter 3, i.e. sodium 1,4-bis(4-carboxyphenoxy) benzene-2-sulfonate (BCPOBS-Na) and 4,4'-diaminodiphenyl ether-2,2'-disulfonic acid (ODADS), high molecular sufonated aromatic polyamide was synthesized via the Yamazaki–Higashi phosphorylation method in the presence of triphenylphosphite (TPP), pyridine (Py) and halide salts. The structure and properties were characterized in detail and the result suggested that the aqueous solution of sulonated polyamide was sensitive to temperature and pH.