Die Angewandte Makromolekulare Chemie 258 (1998) 5–9 (Nr. 4484) 5 Synthesis and characterization of poly(amide imide)s containing cyclohexylidene moieties with bulky substituents Mi Hie Yi 1 , Wenxi Huang 2 , Kil-Yeong Choi 1, * 1 Advanced Materials Division, Korea Research Institute of Chemical Technology, P.O. Box 107, Yusong, Taejon, 305– 600, Korea 2 Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, 130022, P. R. China (Received 11 August 1997) SUMMARY: Novel poly(amide imide)s (PAI) containing alkyl-substituted cyclohexylidene moieties were synthesized by conventional polycondensation of trimellitic anhydride chloride with novel aromatic diamines followed by chemical imidization using acetic anhydride and pyridine. The inherent viscosities of the resul- ting PAIs are relatively high and range from 71 to 112 mL g –1 . The prepared PAIs show excellent thermal stability and good solubility. The glass transition temperatures (T g ) measured by DSC are observed in the range of 312 – 342 8C. Furthermore, all the polymers are readily soluble in less hygroscopic organic solvents like cyclohexanone, c-butyrolactone as well as aprotic polar solvents. ZUSAMMENFASSUNG: Durch konventionelle Polykondensation von Trimellitsa ¨ureanhydridchlorid mit neuen aromatischen Diaminen und anschließender chemischer Imidisierung mit Acetanhydrid und Pyridin wurden neuartige Polyamidimide (PAI) mit alkylsubstituierten Cyclohexylidengruppen hergestellt. Die inha ¨- renten Viskosita ¨ten der resultierenden PAI sind relativ hoch. Sie liegen im Bereich von 71 bis 112 mL g –1 . Die synthetisierten PAI zeigen eine exzellente thermische Stabilita ¨t und gute Lo ¨slichkeit. Die mittels DSC bestimmten Glasu ¨bergangstemperaturen (T g ) liegen zwischen 312 und 342 8C. Ferner sind alle diese Polyme- ren leicht in wenig hygroskopischen organischen Lo ¨sungsmitteln, wie Cyclohexanon oder c-Butyrolacton, sowie aprotischen polaren Lo ¨sungsmitteln lo ¨slich. Introduction Aromatic polyimides (PI) have been known for excellent electrical, thermomechanical properties and chemical resistance 1, 2) . However, the strong interaction and the rigidity of the polymer chains make them insoluble and infusible, which limits its application area. Therefore, various approaches have been conducted to improve the processability by the incorporation of flexible linkages into the polymer backbone. As the results, several kinds of processable PIs have been developed and the most representative one is poly(amide imide) (PAI). However, drawbacks against wide applications of PAI are relatively low thermal stability, limited solubility and high melt viscosity for injection molding. It is well known, that the solubility and melt viscosity of PAI are strongly related to hydrogen bonding between amide groups and intermole- cular interaction of rigid aromatic groups. To reduce the intermolecular interaction, several methods such as copo- lymerization with a diamine mixture, using aliphatic dia- mines instead of aromatic diamines and introduction of alkyl- or aryl-substituents in aromatic diamines were reported 3, 4) . In our previous work, it was possible to synthesize PAIs with good solubility as well as thermal stability by introduction of an alicyclic diamine (isophor- onediamine, IPDA) containing the 3,3,5-trimethylcyclo- hexane structure 5, 6) . From that research, it was realized that the free volume of the resulting polymers was increased by the introduction of the 3,3,5-trimethylcyclo- hexane structure, bringing about good solubility of the polymers. However, we could not obtain PAIs with high molecular weight by polycondensation reaction of trimel- litic anhydride chloride (TMAC) and IPDA, which was due to the aliphatic character of IPDA. That is, the nucleophilicity of the amine end group was decreased due to salt formation of the amine groups with the carb- oxylic group of polyamic acid, which resulted in low molecular weight. Therefore, the present work was under- taken to synthesize novel PAIs with high molecular weight from aromatic diamines containing cyclohexyli- dene moieties with bulky substituents, and the general properties of these polymers have been compared to those of polymers prepared in previous works. Experimental Materials and instruments Trimellitic anhydride chloride was distilled under reduced pressure. N,N-dimethylacetamide (DMA, Aldrich Co.) was distilled under reduced pressure over CaH 2 . Pyridine, acetic * Correspondence author. Die Angewandte Makromolekulare Chemie 258 i WILEY-VCH Verlag GmbH,D-69451 Weinheim 1998 0003-3146/98/0808–0005$17.50+.50/0