Highly soluble polyimides from sterically hindered diamines

• Published in: Polymer (Guilford) 1999-07, Vol.40 (15), p.4279-4288
• Main Authors: Grubb, Tina L, Ulery, Victoria L, Smith, Tara J, Tullos, Gordon L, Yagci, Havva, Mathias, Lon J, Langsam, Michael
• Format: Article
• Language: English
• Subjects: Applied sciences; Exact sciences and technology; Glass transition temperature; Organic polymers; Physicochemistry of polymers; Polyimide; Polymers with particular properties; Preparation, kinetics, thermodynamics, mechanism and catalysts; Steric hindrance
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/S0032-3861(98)00663-6

Polyimides with enhanced solubility have been synthesized from various aromatic tetracarboxylic dianhydrides and sterically hindered diamines. Intrinsic viscosities in 1-methyl-2-pyrrolidinone (NMP) ranged from 0.28 to 1.05 dL/g. Most of the polyimides were soluble in common solvents such as N,N-dimethylacetamide, NMP, chloroform and tetrahydrofuran. Polyimides derived from thianthrene-2,3,7,8-tetracarboxylic dianhydride (TDAN) and diamino mesitylene (DAM) or diethyltoluene diamine (DETDA) were insoluble in all solvents indicating that polyimide solubility decreased as anhydride rigidity increased. Glass transition temperatures ranged from 252 to 398°C and above with the polymers showing little or no weight loss by TGA up to 400°C in both air and nitrogen. The glass transition temperatures of the polyimides increased 15 to 98°C (compared to unhindered polyimide analogs) when one or more methyl group was placed ortho to the imide nitrogen, hindering backbone rotation, chain packing and flexibility. Tough, transparent films of the soluble polyimides were cast from solution.