Synthesis And Characterization Of Novel Aromatic Polyamides Containing Pyridine Unit And Trifluoromethyl Pendant Groups

In this dissertation, the recent progress on the research of aromatic polyamideswas investigated. The main skeleton contains two parts:1. Firstly, treatment of4-trifluoromethylbenzaldehyde with4-nitroacetophenonethrough a modified Chichibabin reaction afforded4-（4-trifluoromethyl）phenyl-2,6-bis[4-（4-nitrophenoxy）phenyl]pyridine （MPNPP）, which was reduced into a new kindof pyridine-containing aromatic diamine monomer,4-（4-trifluoromethyl）phenyl-2,6-bis（4-aminophenyl）pyridine （MPAPP） with Pd/C and hydrazine monohydrate. Thediamine monomer （MPAPP） was soluble in methylene chloride, chloroform,anhydrous alcohol or ether. An ideal single crystal with convex polyhedral shapes wasobtained through solvent volatilization. The MPAPP was employed to synthesize aseries of new polyamides containing pyridine by the conventional solutionpolycondensation reaction with various aromatic diacids containing Cardo units, etherbonds or nonplanar-twisted units, etc. The inherent viscosities of the resultingpolyamides were in the ranged of0.54–1.30dL/g, and their glass transitiontemperatures （Tg） were between277–346°C. The decomposition temperatures at5%and at10%weight loss were in the ranged of350–469°C and444–545°C, and theresidual weight ranged from47.3%to63.9%in nitrogen atmosphere at800°C. Themechanical properties of these polymers with tensile strengths of43.7–89.5MPa andmodulus of elasticity of0.96–1.98GPa and elongations at break of9.7–43.0%werealso obtained. The aromatic polyamide films exhibited good optical transparency,which are more than75%of transmittance at ranged of500–800nm light-wavelength,and all the aromatic polyamides had cutoff wavelength （UV–λ₀） less than390nm, andmost of them were soluble in aprotic organic solvents in room temperature, such asN,N-dimethylacetamide （DMAc）, N-methyl-2-pyrrolidone （NMP） or Dimethyl sulfox- ide （DMSO）, as well as in common solvents such as tetrahydrofuran （THF）, pyridine（Py）, etc. Moreover, all of them showed good hydrophobic and insulativity.2. Similarly,4-（4-trifluoromethyl）phenyl-2,6-bis（4-hydroxypendyl）pyridine（MPHPP） was synthesized by a modified Chichibabin reaction of4-trifluoromethyl-benzaldehyde with4-hydroxyaceophenone, which then was reacted with2-choro-5-nitro-trifluorotoluene forming dinitro compounds4-（4-trifluoromethyl）phenyl-2,6-bis[4-（2-trifluoromethyl-4-nitro）phenoxyphenyl]pyridine（MPNPOPP）,follwed by the reduction reaction in the presence of Pd/C and hydrazine monohydrateto obtain4-（4-trifluoromethyl）phenyl-2,6-bis[4-（2-trifluoromethyl-4-amino）phenoxyl-phenyl]pyridine （MPMAPOPP）. The single crystal of the pyridine-containingaromatic diamine monomer MPMAPOPP with onvex polyhedral shapes wassuccessfully obtained by the method of evaporating solvents step by step. Thearomatic diamine monomer MPMAPOPP was employed to synthesize a series of newaromatic polyamides containing pyridine and trifluoromethyl pendant groups by thepolycondensation reaction with various aromatic diacids, which containtrifluoromethyl pendant groups, Cardo units, ether bonds or nonplanar-twisted units,etc. The inherent viscosities of the resulting polyamides were in the range of0.50–0.95dL/g, and the glass transition temperatures （Tg） of236.6–283.9°C, and thedecomposition temperature at5%and at10%weight loss was in the ranged of431–470°C and493–515°C, and the residual weight range of52.7–62.4%innitrogen atmosphere at800°C, as well as outstanding mechanical properties withtensile strengths of53.7–90.0MPa and modulus of elasticity of1.08–1.98GPa andelongations at break of8.43–16.75%. The polymer films exhibited good opticaltransparency more than84%of transmittance at500–800nm of light-wavelength,and all of their cutoff wavelength （UV–λ₀） were shorter than370nm. Most of themwere soluble both in aprotic organic solvents, such as N,N-dimethylacetamide（DMAc）, N-methyl-2-pyrrolidone （NMP） and Dimethyl sulfoxide （DMSO）, and incommon solvents such as tetrahydrofuran （THF）, pyridine （Py） etc. Moreover, all ofthe aromatic polyamide films illustrated good hydrophobic and insulativity.