Synthesis and Properties of Aromatic Polyimides Based on Ether-Sulfone-Diamines

ISSN： 1022-9760

Source： Journal of Polymer Research, Vol.5, Iss.3, 1998-07, pp. : 193-198

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Abstract

Two diamine monomers, 4,4′-[sulfonylbis(1,4-phenyleneoxy)]dianiline (III_a) and 4,4′-[sulfonylbis(2,6-dimethyl-1,4-phenyleneoxy)]dianiline (III_b), were prepared by an aromatic nucleophilic substitution of 4,4′-sulfonyldiphenol (I_a) and 4,4′-sulfonylbis(2,6-dimethylphenol) (I_b) with p-chloronitrobenzene in the presence of potassium carbonate, followed by hydrazine catalytic reduction of the intermediate dinitro compounds. The diamines III_aand IIII_b were used as monomers with various aromatic tetracarboxylic dianhydrides (IV_a-f) to synthesize polyimides. The polymerization was conducted in two steps via the formation of a poly(amic acid) precursor followed by thermal cyclodehydration. The poly(amic acid)s had inherent viscosities above 0.87 and up to 2.56 dL/g. Most poly(amic acid)s could be coated and thermodehydrated into flexible and transparent polyimide films. The polyimides derived from the dianhydrides containing -O- and -SO₂- or -C(CF₃)₂- bridging groups between the phthalic anhydride units were soluble in some organic solvents such as N,N-dimethylacetamide (DMAc) and N, N-dimethylformamide (DMF). The glass transition temperatures (T_g) of the polyimides were in the range from 254 to 300 &°C. The methyl-substituted polyimides exhibited slightly higher solubility and higher T_g compared to the corresponding unsubstituted polyimides. Thermogravimetric analysis (TG) showed that the polyimides containing methyl substitutents started to lose weight around 450 &°C and the unsubstituted ones started to lose weight around 550 &°C.