## 2 Polymer Nanocomposites for Membranes Applications
The following inorganic fillers were used in the composites: natural montmorillonite intercalated with quaternary aliphatic amine; commercial product Cloisite 15A (Southern Clay Products, Inc., Gonzales, TX 78629 USA); and SNT of Mg3 Si2O5(OH)4 with a chrysotile structure. These SNTs were produced by hydrothermal synthesis [137; 138] and have a cylindrical morphology and various dimensions: (a) outer diameter d\({}_{\text{o}}\) = 10-15 nm, inner diameter d\({}_{\text{i}}\) = 2-3 nm, and length L = 100-250 nm (SNT-I); (b) d\({}_{\text{o}}\) = 20-25 nm, d\({}_{\text{i}}\) = 4 nm, and L = 500-1000 nm (SNT-II); and (c) d\({}_{\text{o}}\) = 50-110 nm, d\({}_{\text{i}}\) = 5-6 nm, and L = 300-700 nm (SNT-III) (Figure 22a-c). The photomicrographs of the film's surfaces showed that the surface relief of PAI-1-SNT is similar to the corresponding reliefs of homogeneous film of PAI-1 (Figure 23). Both composite and PAI-1 homogeneous films are characterized by a smooth upper surface and finely granular lower one, on which are viewed clearly expressed bands, not related to the presence of an inorganic component in the composite. Figure 4.8 Micrographs of Mg\({}_{3}\)Si\({}_{2}\)O\({}_{5}\)(OH)\({}_{4}\) SNTs with a cylindrical morphology and various dimensions: (**a**) SNT-I; (**b**) SNT-II; and (**c**) SNT-III [112]. A study of the transport properties of the corresponding films (homogeneous membranes) in pervaporation demonstrated the following. Introduction into the polymeric matrix NTs of the SNT-I-III types without their additional treatment (chemical or orienting) leads to an increase in the flux of water across the corresponding film membrane (Table 2 sample nos. 2-4 [112]), which is the most pronounced for SNT-II in the case of a good compatibility of components of the composite material (Table 2, sample N 3). Table 3 [112] compares the results of tests of PAI-1 and PAI-1-SNT-II(20) (20 min of ultrasonic agitation, 2 wt %) films, and of a composite PAI-1-MMT-15A (2 wt %) film obtained under the conditions in which PAI-1-SNT-II(20) was formed, in dehydration of an aqueous solution of ethanol (48 wt % ethanol) in the course of pervaporation at 40 \({}^{\circ}\)C. As the content of NTs in the composite increases from 2 to 10 wt % (Table 3, sample N 5 and Table 2, sample N 3, respectively), the permeability of the material to polar liquids, such as water and ethanol, grows. A possible explanation of this effect is that the permeability is affected by the appearance of microscopic inhomogeneities or defects (on the nanosize level or coarser) in the nonporous matrix of the composite film upon introduction of the inorganic component. However, this assumption is easily refuted by analysis of the data in Table 3, because introduction of 2 wt % SNT-II into a PAI-1 film yields a composite for which the separation factor of the water/ethanol mixture not only does not decrease, but even somewhat increases as compared with that for the homogeneous PAI-1 film. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Sample No.** & **Sample** & **c, wt \%** & \(I\)*, \(\mu\)m & \(P_{w}\), \(\mathbf{kg\;m^{-2}\;h^{-1}}\) & \(P_{w}\)\(I\)*, \(\mathbf{kg\;m^{-2}\;h^{-1}\;\mu m}\) \\ \hline
1 & PAI & 0 & 15 & 0.043 & 0.645 \\
2 & PAI-SNT I & 2 & 15 & 0.044 & 0.660 \\
3 & PAI-SNT II & 10 & 15 & 0.084 & 1.260 \\
4 & PAI-SNT III & 2 & 15 & 0.056 & 0.672 \\ \hline \hline \end{tabular}
* \(I\) is the sample thickness, and \(P_{w}\)\(I\) is sample flux normalized to thickness.  
\end{table} 
Table 2: Permeate flux for water, \(P_{w}\), and flux normalized to thickness for non-porous composite films in comparison with a nonporous PAI film (sample No. 1) in pervaporation at 40 \({}^{\circ}\)C [112]. Figure 23: SEM micrographs of (**a**,**b**,**e**) upper and (**c**,**d**,**f**) lower surfaces of (**a**–**d**) PAI-NTII(10) and (**e**,**f**) PAI-NTII(20) of thickness 20 \(\mu\)m [112].