Synthesis and Characterization of Grafted Copolymers of Aromatic Polyimides and e-Caprolactam Tat’yana V. Volkova, Yakov S. Vygodskii, Olesya N. Zabegaeva, Yan V. Zubavichus, Marina N. Il’ina, Alexander P. Krasnov, Ol’ga V. Afonicheva, Elena I. Lozinskaya, Irina A. Garbuzova, Alexander S. Shaplov A.N. Nesmeyanov Institute of Organoelement Compounds Russian Academy of Sciences (INEOS RAS), 119991, GSP-1, 28 Vavilov str., Moscow, Russia Received 15 August 2008; accepted 3 April 2009 DOI 10.1002/app.30543 Published online 8 June 2009 in Wiley InterScience (www.interscience.wiley.com). ABSTRACT: Anionic polymerization of e-caprolactam was performed in the presence of only 5 wt % of aromatic polyimides having five- and six-membered imide cycles and bearing hexafluoroisopropylidene, ether, fluorene, si- loxane, phthalide, or SO 3 HA groups, both in the polymer backbone and as side moieties. The synthesized new copolymers were fully characterized by IR spectroscopy, thermomechanical analysis, dilatometry, and X-ray diffrac- tion. Tough and frictional properties of the obtained copolymers were estimated as well. It was found that on the selection of polyimide activator it is possible to gain the desirable control over the polymer properties, namely the gel-fraction content, phase composition, compression mod- ulus, notched Izod impact strength, temperature of fric- tional contact, friction coefficient, etc. These investigations will facilitate the choice of the optimum macromolecular activator for the modification of both the synthetic method and the properties of the commercial polycaproamide. V V C 2009 Wiley Periodicals, Inc. J Appl Polym Sci 114: 577–586, 2009 Key words: e-caprolactam; anionic polymerization; macro- molecular activators; aromatic polyimides INTRODUCTION One of the important problems in lactam-based polyamide synthesis, namely the decrease in the reaction temperature, was solved more than 50 years ago by the use of special polymerization activators. Among the modern suggested activators for lactam anionic polymerization are macromolecular activa- tors, which allow not only the decrease in the pro- cess temperature, but also the preparation of block and grafted copolymers. 1 Usually, the role of such macromolecular activators is carried out by the spe- cially synthesized polymers having grafted acyllac- tam groups. In contrast to that, for the first time we had demonstrated 2–4 the principle possibility of the utilization of common (without any grafted acyllac- tam side chains) aromatic polyimides (PI) as excel- lent activators for lactam anionic polymerization. Thus, a set of aromatic PIs, soluble in lactams melt, was successfully used in the polymerization of e- caprolactam. It was proved 2–4 that polymerization activation occurred at 150–180  C due to the opening of the imide cycles in PI backbone under the action of lactam anionic polymerization catalyst, namely e- caprolactam magnesium bromide. Along with this, it is necessary to mention that on the utilization of Na- e-caprolactam as another popular catalyst the ani- onic polymerization of e-caprolactam (APC) with mentioned PIs did not proceed at elevated temperature. The activating ability of PI was also studied by differential isothermal calorimetry method using various aromatic diimides as model compounds. 3 It was found 3 that the diimide activating ability is strongly dependent on the nature of the spacer between two five-membered imide cycles. These dii- mides containing hexafluoropropylidene or ketone groups proved themselves as best activating agents imparting the highest reaction rate. On the contrary, diimides based on aliphatic diamines do not activate the reaction. Later on Youlee 5 used the same technique and synthesized copolymers based on polycaproamide (PCA) and PIs of the other type. However, copoly- mers prepared during this investigation and in Refs. 2–4 differ from those obtained in Ref. 5 by the presence of crosslinked structure, which greatly improves their operating characteristics as construc- tional materials. To gain the desirable control over the obtained co- polymer properties, we enlarged the set of PIs in the suggested study and carried out the detailed investi- gation of their influence on the APC. The most strik- ing advantage of the suggested method concludes in Journal of Applied Polymer Science, Vol. 114, 577–586 (2009) V V C 2009 Wiley Periodicals, Inc. Correspondence to: A. S. Shaplov (zipper@ineos.ac.ru).