Preparation, characterization, and properties of poly(thioether ether imide)s from isomeric bis(chlorophthalimide)s and bis(4-mercaptophenyl) ether

Abstract

A series of isomeric poly(thioether ether imide)s (PTEIs) containing both thioether and ether linkages were prepared by aromatic nucleophilic substitution reaction of isomeric bis(chlorophthalimide)s (BCPIs) with bis(4-mercaptophenyl) ether (BMPE). The inherent viscosities of synthesized polymers were found in the range of 0.41-0.86 dL g À1 in N-methyl-2-pyrrolidone at 30 C. The glass transition temperature (T g ) of the isomeric PTEIs were 210-242 C and increased by increasing the content of 3-substituted phthalimide unit in the polymer backbone. The 5% weight loss temperature values reached up to 525-539 C under nitrogen and 523-534 C in air atmospheres, respectively, which indicated this kind of polyimide possessed excellent thermal stability. Flexible films could be cast from the polymer solution. The PTEI films exhibited moderate mechanical properties with tensile strengths of 106-127 MPa, elongations at break of 8.6-11.5%, and tensile moduli of 2.2-2.8 GPa, respectively. Dynamic mechanical thermal analysis results illustrated that the storage moduli (E 0 ) of PTEI (a-e) almost completely maintained at about 2.3 GPa before reaching the corresponding T g . It is noted that the minimum melt viscosity of isomeric PTEIs (a 0 -e 0 ) decreased by increasing the content of unsymmetrical 3,4 0 -substituted phthalimide unit in the polymer main chain.

Preparation, characterization, and properties of poly(thioether imide)s from isomeric bis(chlorophthalimide)s and bisthiophenols

“…Higher T g values were caused by more difficult chain rotation of polymers, so this phenomenon could mainly be attributed to the rotational freedom around the carbon-sulfur bonds of 3substituted phthalimide, which is partially restricted by the steric effect of the ortho-carbonyl substituent. [23][24][25][26] These results suggested that the T g of isomeric PIs could be regulated by controlling the content of the isomeric units.…”

“…[29][30][31][32] In the second approach, PI can be synthesized directly by aromatic nucleophilic substitution reaction from isomeric BCPIs and bisphenols/bisthiophenols. [23][24][25][26] What's more, the nucleophilicity of thiophenoxide is 100 times higher than that of phenoxide, which was reported in the synthesis of poly(thiother ketone)s and poly(thioether sulfone)s. [33][34][35] Very recently, our group has been focused on isomeric poly(thioether imide)s (PTIs) obtained from the aromatic nucleophilic substitution of the isomeric BCPIs and bisthiophenols and found that the introduction of isomeric moieties and flexible thioether linkage into polymer main chain could be an effective way to obtain good solubility and melt processability without sacrificing other excellent properties. [23][24][25][26] Considering that the introduction of flexible -S-linkages and geometrically asymmetric isomeric moiety will improve the solubility and processability simultaneously, in this study, we synthesized and characterized a series of isomeric PTIs with a high content of -S-linkages in the polymer backbone based on the nucleophilic substitution of three isomeric BCPIs and bisthiophenols, bis(4-mercaptophenyl) sulfone, 4,4 0 -dimercaptobenzophenone, and 4,4 0 -thiobisbenzenethiol.…”

“…That's because twisted, noncoplanar and asymmetric 3,4 0 -substituted phthalimide units disturbed the regularity of molecular chain, which reduced the intermolecular interaction and hindered molecular chain close stacking. 12,24 Thermal property. The thermal decomposition and stability of the isomeric PTIs were evaluated by TGA, DSC, and DMTA curves.…”

“…As for the PTIs from three isomeric BCPIs with the same bisthiophenol, the T 5% values increased in the order of 3,3 0 -BCPI < 3,4 0 -BCPI < 4,4 0 -BCPI, which could be interpreted by the fact that the 3-phthalimide unit has lower thermal stability than 4-phthalimide unit. 23,24 In addition, the inferior thermal stability of the PTIs derived from 3,3 0 -BCPI may be ascribed to the structural stress caused by nonplanar configuration of the 3-substituted phthalimide moiety. 25,26 As shown in Figure 5, the T 5% values of the isomeric PTIs in air stayed in the range 472-520 C, which were slightly higher than that under nitrogen 441-508 C. This phenomenon has also been found in the other sulfur-containing polymers, which is ascribed to the different degradation mechanisms in various atmospheres.…”

“…12,13 There are two approaches to synthesize isomeric PIs; one is the polycondensation of isomeric tetracarboxylic dianhydrides and diamines [12][13][14][15][16][17][18][19][20][21][22] the other is the aromatic nucleophilic substitution reaction of isomeric bis(chlorophthalimide)s (BCPIs) with bisphenols or bisthiophenols. [23][24][25][26][27][28] In the first approach, isomeric tetracarboxylic dianhydrides and diamines firstly form soluble polyamic acid precursors, which are subsequently imidized by chemical or thermal treatment. However, the intermediate polyamic acids in solution are known to be notoriously unstable even at room temperature and tend to depolymerize in storage because hydrolytic cleavage reaction readily takes place.…”