New organosoluble and thermally stable poly(amide‐imide)s with benzoxazole or benzothiazole pendent groups: synthesis and characterization

Abstract

Two new benzoxazole or benzothiazole-containing diimide-dicarboxylic acid monomers, such as 2-[3,5-bis(Ntrimellitimidoyl)phenyl]benzoxazole (2 o ) or 2-[3,5-bis(N-trimellitimidoyl)phenyl]benzothiazole (2 s ) were synthesized from the condensation reaction between 3,5-diaminobenzoic acid and 2-aminophenol or 2-aminothiophenol in polyphosphoric acid (PPA) with subsequent reaction of trimellitic anhydride in the presence of glacial acetic acid, respectively, and two new series of modified aromatic poly(amide-imide)s were prepared. This preparation was done with pendent benzoxazole or benzothiazole units from the newly synthesized diimide-dicarboxylic acid and various aromatic diamines by triphenyl phosphite-activated polycondensation. In addition, the corresponding unsubstituted poly(amide-imide)s were prepared under identical experimental conditions for comparative purposes. Characterization of polymers was accomplished by inherent viscosity measurements, FT-IR, UV-visible, 1 H-NMR spectroscopy and thermogravimetry. The polymers were obtained in quantitative yields with inherent viscosities between 0.39 and 0.81 dl g S1 . The solubilities of modified poly(amide-imide)s in common organic solvents as well as their thermal stability were enhanced compared to those of the corresponding unmodified poly(amide-imide)s. The glass transition temperature, 10% weight loss temperature, and char yields at 800-C were, respectively, 7-26-C, 17-46-C and 2-5% higher than those of the unmodified polymers.

Modified poly(ether–imide–amide)s with pendent benzazole structures: Synthesis and characterization

“…1,3‐Phenylenediamine ( a ; Merck) was purified by sublimation before use. Aromatic diamines, including 5‐(2‐benzoxazole)‐1,3‐phenylenediamine ( b ; mp = 226–230°C),26 5‐(2‐benzothiazole)‐1,3‐phenylenediamine ( c ; mp = 167–171°C),26 5‐(2‐benzimidazole)‐1,3‐bis(4‐aminophenoxy)benzene (mp = 218–222°C),28 5‐(2‐benzoxazole)‐1,3‐bis(4‐aminophenoxy)benzene (mp = 168–171°C),28 and 5‐(2‐benzothiazole)‐1,3‐bis(4‐aminophenoxy)benzene (mp = 162–165°C),28 were synthesized according to our previous works. 1,3‐Bis(4‐aminophenoxy)benzene ( 6 ; mp 114–116°C) was prepared by the nucleophilic substitution reaction of the corresponding bisphenol precursor, resorcinol, and 4‐fluoronitrobenzene in the presence of potassium carbonate, followed by hydrazine catalytic reduction of the intermediate dinitro compound.…”

“…In previous work, we reported the synthesis and characterization of modified PAIs bearing benzazole pendent groups with better solubility and thermally stability than the corresponding unsubstituted PAIs 25, 26. It is important to note that when heterocyclic rings, such as benzimidazole, benzoxazole, or benzothiazole, were used as pendent groups, beneficial effects were observed, not only in the solubility but also in the thermal properties, because benzimidazole, benzoxazole, and benzothiazole are among the most heat‐resistant structures 27.…”

Organosoluble and Thermally Stable of Benzazole-Containing Poly(Imide-Urea)s: One-Pot Synthesis and Characterization

“…It displays characteristic absorption bands for Copyright © 2011 SciRes. OJPChem the imide ring at around 1779 and 1725 cm -1 (imide-I), which is indicative of the asymmetrical and symmetrical C=O stretching vibration, and at 1351 (imide-II), 1078 (imide-III) and 728 cm -1 (imide-IV) whereas the imide-I, -III, -IV bands were assigned to axial, transverse, and out-of-plane vibrations of the cyclic imide structure, respectively [22,28]. The N-H stretching band of the urea could be observed around 3200 -3350 cm -1 , and the C=O stretching band of urea groups at 1676 cm -1 , the C=N stretching band benzothiazole groups at 1619 cm -1 and the N-H bending and C-N stretching bands at 1557 cm -1 could also be observed.…”

“…Bis(imide-carboxylic acid) monomers such as 1 O , 1 S , and 1 N were synthesized by the condensation reaction between the appropriate aromatic diamine, 5-(2-benzoxazole)-1,3-phenylenediamine, and 5-(2-benzothiazole) -1,3-phenylenediamine, 5-(2-benzimidazole)-1,3-phenylenediamine, and two mole equivalents of trimellitic anhydride in glacial acetic acid, respectively. The details of this synthesis route and the characterization data were reported in our previous works [22,23].…”

“…So far, many efforts on chemical modifications of polyimides structure have been made to enhance their processability and solubility while other advantageous polymer properties are retained either by introducing flexible linkages, bulky groups, or molecular asymmetry into the polymer backbone [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. Among these approaches, the method of incorporating bulky, rigid benzazole hetero rings as pendent groups into the polymer backbone has become very attractive [20][21][22][23]. The advantages of this method include two main parts: (1) close chain packing and intermolecular interactions of the resulting polyimide are restricted, and this results in relatively high polymer solubility, and (2) the main chain rigidity of the polyimide can be maintained by restricting the segmental mobility, in addition, these benzazole hetero rings are thermally stable, and these allow the polyimide to have a high glass-transition temperature (T g ) and excellent thermal properties.…”