## 2 Polymer Nanocomposites for Membranes Applications
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Sample No.** & **Sample** & **c, wt \%** & \(l\), \(\mu\)m & **P, kg m\({}^{-2}\) h\({}^{-1}\)** & \(F_{w}\)** \\ \hline
1 & PAI & 0 & 15 & 3.20 & 5.5 \\
5 & PAI-NT II & 2 & 15 & 3.75 & 7.9 \\
6 & PAI-MMT-15A & 2 & 15 & 2.35 & 5.8 \\ \hline \hline \end{tabular}  
* \(l\) is the sample thickness, and \(\Gamma\)\(l\), sample permeability normalized to thickness.  
\end{table} 
Table 3: Permeability to water of nonporous films of PAI-SNT I-III composites, in comparison with the nonporous PAI film, in pervaporation at 40 \({}^{\circ}\)C [112]. PAI-2 being more of a hydrophilic polymer is two times more permeable by water than PAI-1, like in the case of PAI-1-SNT, compared to PAI-1. The introduction of NTs in the PAI-2 enhances the ability of the film to pass water more than two-fold, which makes the material five-fold more permeable for water than PAI-1-SNT. It should be noted that the permeability of PAI-2-SNT by a low polar penetrant cyclohexane remain as low as the permeability of PAI-2, in contrast to PAI-1, for which the introduction of NTs reduces the permeability of cyclohexane significantly (Figure 24). Most important is the fact that the composites PAI-1-SNT and PAI-2-SNT are obtained under similar conditions and containing NTs in equal amounts, they are similar by the trend of permeability of polar and weakly polar liquids, but differ by their degree. The effect obtained requires attention and explanation. It is obviously associated with the appearance of a channel with facilitated transfer of the dipoles of water molecules or polar alcohols in the moderately swelling matrix of the composite film. The nature of interaction of the polymer matrix with the nanoparticles, which determines distribution of the latter in the nanocomposite film, affects the transport channel formation. In other words, the difference in the structure of the films on the nano-scale level leads to a difference in their transport properties. Figure 25 shows ultrafine cross-sections of PAI-1-SNT and PAI-2-SNT films, allowing us to judge about the nature of NTs and their agglomerates distribution in the inner layers of membranes. The image analysis shows that unlike the PAI-1-SNT film, which is characterized by aggregates of 10 NTs randomly placed throughout the thickness of the sample, in the PAI-2-NT the aggregates are observed of 2-3 NTs that are uniformly distributed in the inner layers of the film. Aggregates containing the same numbers of NTs were also observed by AFM methods [139]. These morphological features correlate well with the data on pervaporation presented in this paper. Selective increase in permeability, instead of barrier properties, for cases of introduction of SNT into the polymer, but simultaneous decrease in permeability of PAI-1-SNT--these data indicate the possible realization of the sieving effect due to the structural features of nano-fillers, as it was well shown above on the example of zeolite-polymer systems. However, an increase in water permeability and a decrease in cyclohexane permeability may be due to sieving (in terms of the size of the molecules) or to physical interactions between the nanoparticles and the penetrant, and thus influencing the transport of liquid penetrants by the sorption-diffusion mechanism (Figure 26). In the latter case, the presence of OH groups in NT should influence the transport of water. It should be noted that these groups are absent in the inner channel of the NT and are in the upper surface and interlayer space of the tube-roll (Figure 16[130]). In the MMT structure there are also OH groups available for interactions, but in a smaller amount. However, water permeability only decreases when passing from non-porous  
Figure 24: The composite PAI-2-SNT-II: SEM of (**a**) Upper; (**b**) Button surfaces [121]. PAI-1 films to PAI-1-MMT composite films, as is typical for many polymer-MMT systems and was discussed in detail above.