956 ISSN 0965-545X, Polymer Science, Series A, 2016, Vol. 58, No. 6, pp. 956–967. © Pleiades Publishing, Ltd., 2016. Original Russian Text © N.V. Afanas’eva, G.N. Gubanova, K.A. Romashkova, D.A. Sapegin, S.V. Kononova, 2016, published in Vysokomolekulyarnye Soedineniya, Seriya A, 2016, Vol. 58, No. 6, pp. 639–651. Relaxation Processes in an Aromatic Polyamide-Imide and Composites on Its Basis with Hydrosilicate Nanoparticles N. V. Afanas’eva, G. N. Gubanova, K. A. Romashkova, D. A. Sapegin, and S. V. Kononova Institute of Macromolecular Compounds, Russian Academy of Sciences, Bolshoi pr. 31, St. Petersburg, 199004 Russia email: afann@mail.ru Received December 28, 2015; Revised Manuscript Received March 26, 2016 Abstract―Features of the relaxation behavior of an aromatic polyamide-imide and a composite with nano- tubes of magnesium silicate with the structure of chrysotile have been studied by dynamic mechanical anal- ysis, dielectric spectroscopy, and differential scanning calorimetry. Two secondary relaxation (β 1 and β 2 ) transitions have been found, the activation energies of these processes have been determined, and the solvent effect on the cooperativeness degree has been studied. Changes in the value of the apparent activation energy of the β 1 -process caused by the subsequent heating of polymeric and composite samples have been analyzed according to the Starkweather procedure. It has been shown that, as the solvent is released from the polyam- ide-imide film, the polymer exhibits increasing local mobility, which are predetermined by the structure of the molecular unit. Using the GAMESS software, we have assumed the most probable dimer conformations that correspond to two repeating units of the polyamide-imide molecule. DOI: 10.1134/S0965545X16060018 INTRODUCTION Polyamide-imides (PAIs), which are contained in the main chain both the amide and imide groups, are promising material for various applications including microelectronics, optical devices, isolators, and mem- brane technology [1‒9]. PAI samples prepared by the low-temperature condensation in solution possessing high MW and narrow MWD meet the requirements of chemical and thermal stability and high mechanical characteristics needed for the formation of flexible and strong self-supported films. The condensation conditions have been optimized in the Institute of Macromolecular Compounds of the Russian Acad- emy of Sciences [10]. The formation of membrane- purpose materials is one of the most successful appli- cations of these polymers [11‒13]. Particular attention in this application is given to PAI containing diphenyloxide fragments in the diamine component of the molecular unit. Based on this PAI synthesized from dicarboxyphenyl phthalim- ide dichloranhydride and diaminodiphenyl ether, high diffusion membranes of varying morphology, includ- ing a multilayer membrane with PAI microporous support layers (substrates) and solid nonporous PAI films [14‒17], were developed in order to separate gases or liquids (pervaporation). Organic-inorganic composites for pervaporate membranes containing nanotubes of magnesium sili- cate Mg 3 Si 2 O 5 (OH) 4 with the structure of chrysotile were obtained based on PAIs for the first time in [18]. The morphology, structure, and dynamic mechanical properties of these composites were studied [19, 20]. The problem of the desired permeability changes and selective diffusion properties of membranes with PAI layers is related with studies on relaxation properties of this polymer and its composites, which affect the nature of the diffusion of penetrants through corre- sponding nonporous films [21]. Typically, three relaxation transitions are observed in polymers with increasing temperature, namely γ, β, and α, which are recorded by various methods, including dielectric spectroscopy and dynamic mechanical analysis (DMA). It is known that the α-transition corresponds to the glass transition tem- perature of polymers, while molecular mechanisms of the secondary β- and γ-processes are the subject of intense debate, in particular for polyimides [22‒29]. Many researchers believe that the low-temperature γ- process results from the relaxation of water molecules associated with polar groups of the polymer [22, 23]. The correlation between the water content and the intensity of the transition were found in [25]. In con- trast, the γ-process was associated with the vibrational motion of the phenyl rings [26] or the vibrational mobility of phenoxy groups in the diamine moiety [27]. In polyimides, at temperatures higher than room temperature, the secondary β relaxation transition is observed, which is localized in a wide temperature range of 100‒200°C (1 Hz) and is explained by molec- ular mobility in the diamine moiety of the macromol- ecule [28], and some authors assumed that it results 1 1 STRUCTURE AND PROPERTIES