Preparation And Studies On The Structure And Properties Of Novel Soluble And Functional Aromatic Polyamides

Polymaides have achieved a remarkable position among other polymers because of their unique combination of thermooxidative stability, electrical performance, flame retardancy and retention of physical properties at high temperatures. So they have been successfully applied in many fields such as aviation, spaceflight, nuclear energy, communication, telecom, petroleum etc. At the same time, this kind of polymer, usually processed at high temperature was considered as a disadvantage for processing. So a great deal of research has been made on improving the solubility of these polamides by introduction of pendent fluorine substitution and bulky side groups onto aromatic polyamides. The aim of this dissertation was concentrated on synthesis of new polyamides containing trifluoromethyl, methyl and cyclohexane by Yamazaki Phosphorylation to improve the solubility of resultant polyamides. In addition, other functions such as optical behavior, dielectric performance, and thermal stability were supplied to these polyamides.1. Novel fluorinated poly(ether ketone amide)s (PEKAs) were prepared from an unsymmetrical aromatic diamine, (4'-(4"-amino-2"-trifluoromethylphenoxy)-3',5'-dimethylphenyl)(4-aminophenyl)-met hanone synthesized in our lab, with various aromatic dicarboxylic acids by means of the phosphorylation polycondensation technique. The PEKAs displayed inherent viscosities ranging from 0.43 to 0.65 dl/g. All the fluorinated PEKAs could be soluble in many polar organic solvents such as N-methyl-2-pyrrolidinone (NMP), N,N'-dimethylacetamide (DMAc), N,N'-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and tetrahydrofuran (THF). Flexible and tough polyamide films were prepared by casting from DMAc solvent. The PEKA films exhibited good mechanical properties with tensile strengths of 78-98 MPa and elongations at break of 11.5-18.5%. The obatanined PEKAs showed glass-transition temperatures in the range of 288-323℃and the 10% decomposition temperatures in the range of 431-447℃in nitrogen atmosphere. Meanwhile, the PEKA films possessed low dielectric constants less than 3 at 1 MHz.2. A series of novel fluorinated poly(aryl ether amide)s were prepared from an aromatic diamine made in our laboratory, with various aromatic dicarboxylic acids through the phosphorylation polycondensation. The fluorinated polymaides (PA1-PA7) were obtained in almost quantitative yields with inherent viscosities ranging from 0.55 to 0.78 dl/g. All the polyamides revealed good solubility in many polar organic solvents such as N-methyl-2-pyrrolidinone (NMP), dimethyl sulfoxide (DMSO) and tetrahydrofuran (THF) and so on. Flexible and tough polymer films could be easily prepared by casting from DMAc solvent. The PA1-PA7 films exhibited high optical transparency with a cutoff wavelength of 331-364 nm and good mechanical properties with tensile strengths of 78.4-104.8 MPa and elongations at break of 5.4-10.3%. They showed high glass transition temperatures in the range of 227-244℃. They also exhibited good thermal stability, the 10% weight loss temperatures ranged from 453 to 464℃in nitrogen atmosphere. Meanwhile, the obtained poyamide films possessed low dielectric constants of 2.43-2.98 at 1 MHz. These polyamides based on ortho diamine exhibited better solubility and optical properties.3. New aromatic diamines with trifluoromethyl pendent groups, 1,4-Bis((4-amino-2-(trifluoromethyl)phenoxy)methyl)cyclohexane and 4,4'-(cyclohexane-1,4-diylbis(oxy))bis(3-(trifluoromethyl)aniline), were successfully synthesized in two steps from 1,4-cyclohexanedimethanol, 1,4-cyclohexanediol and 2-chloro-5-nitrobenzotrifluoride as starting materials. And the newly obtained diamines with various aromatic dicarboxylic acids, including isophthalic acid(IPA), 2,2-bis(4-carboxy-phenyl)hexafluoropropane(6FA) and 4,4'-oxydibenzoic acid(OBA), were polymerized respectively via the usual Yamazaki reaction to prepare series of fluorinated polyamides (2a-2d and 4b-4d). The resulting polymers were characterized by FT-IR, DSC, TGA and WAXD. The prepared polymaides showed inherent viscosities ranging from 1.85 to 2.36 dL/g. All the polymers presented excellent solubility and could be easily dissolved in amide-type polar aprotic solvents (e.g., N-methyl-2-pyrrolidone (NMP), DMAc, and DMF) and even dissolved in less polar solvents (e.g., pyridine, and tetrahydrofuran). These polymers could also be easily cast into transparent, tough and flexible films. In addition, these polyamide films exhibited low dielectric constants of 2.15-2.88 at 1MHz, high transparency with an ultraviolet-visible absorption cut-off wavelength in the 332-357 nm range, and the transmittance more than 85% at 500 nm. Furthermore these polyamides still retained good thermal stability.