BL8S3

実験番号：202103018（4 シフト）

Microstructure study of carbon nanotubes nanocomposites witharomatic polyamides
Rodolfo Cruz-Silva, Hiroyuki Matsuda, Kazunori Fujizawa,
Hiroyuki Muramatsu, Kenjji Takeuchi, and Morinobu Endo
Research Initiative for Supra-Materials and COI Aqua Innovation Center, Faculty of Engineering,
Shinshu University
Key words：membranes，polymer microstructure，reverse osmosis，nanocomposites.
1．Background and research purpose
In the last 10 years, there has been great interest in nanocomposite reverse osmosis (RO) membranes. These
membranes have great potential to replace the traditional polymeric RO membranes because of their higher
chlorine resistance and better antifouling behavior. [1] In addition, these membranes often show higher
permeability compared to the polymeric membranes without decreasing the salt rejection. However, the influenceof these nanomaterials on the microstructure of these membranes is still poorly understood. We have found thatcarbon nanotubes (CNTs) [2] and cellulose nanofibers (CNFs) [3] modify the topology of the fully aromaticpolyamide. These changes in the polymer microstructure might have important effect on pore size distribution andwater diffusion. In addition, the presence of nanomaterials within the polyamide active layer has increased theirchlorine resistance compared to the plain membranes.[4] While the resistance has been attributed to electronic
withdrawing effect in the case of CNTs it is less clear how the CNF can provide such chlorine protection topolyamide. It is possible that changes in polyamide topology might be in part responsible of the different chemicalreactivity. In this work we analyze several nanocomposite membranes by using wide angle and small angle X-ray
scatter in order to understand their microstructure, focusing mainly on the CNT-MPD structure which is the bestwell-known among them. We aim to develop a general model of how the nanomaterials con modify the polyamidestructure.
2．Experiment contents
Four different polymeric nanocomposites used to prepare RO membranes were synthesized in bulk quantity
using the typical interfacial condensation reaction. The studied nanomaterials were CNTs, CNFs and graphene
oxide (GO). The membrane polymers were prepared as previously reported[4] by reaction of trimesoylchloride
dissolved in organic solvent and either m-phenylendiamine or piperazine dissolved in the aqueous phase. Bothphases were mixed vigorously in a shaker where the crosslinking polymerization rapidly took place. For thenanocomposite materials, a certain amount of the nanomaterial was dispersed in the aqueous phase prior to thepolymerization reaction. The resulting polymer powders were washed with methanol three times and finally withwater, before drying at 80 oC for 2h. These materials were analyzed with Fourier transformed infrared
spectroscopy, X-ray photoelectron spectroscopy, and wide angle and small angle X-ray scattering. For the wide(WAXS) and small (SAXS) angle X-ray scattering studies, the nanocomposite polyamide powders were loaded inaluminum sample holders and analyzed in the BL8S3 line (0.92 Å) at the Aichi synchrothron radiation centerusing two sample to detector distance configurations: 208 mm and 2134 mm for the WAXS and SAXS
measurements.
3．Results and discussion
In figure 1 the D-spacing of the radially integrated WAXS pattern of CNTs is shown compared to a graphitestandard. The most prominent peak of the CNTs corresponds to the 002 peak of the concentric graphitic layers.
Compared to the standard is slightly shifted to a higher D-spacing value and is broader due to the crystalline
defects and stress induced by the concentric arrangement. The 004 peak is very weak in comparison to that shownby the graphite and it is the result of the reduced order in the z direction of the concentric graphitic layers. There
are very weak peaks in the areas corresponding to the d-spacings of iron oxide that suggest the catalyst wasremoved after synthesis by the heat treatment. These CNTs were used as the main material to prepare a series ofcrosslinked aromatic polyamide powders containing increasing amount of CNTs by interfacial polymerization.

Figure 1. D-spacings plot from the radially integrated WAXS pattern of CNTs.
Figure 2 shows the Wide-angle X-ray scattering patterns of these nanocomposite polymers. These patterns arecharacterized by a sharp peak at 3.97 nm-1 and a broad peak at 16.9 nm-1, which correspond to d spacings of 1.6
nm and 0.37 nm, respectively. The first one can be assigned to intermolecular spacing of the aromatic rings of thepolymer, while the second one might correspond to the intramolecular packing of the chains. When theconcentration of the nanotubes increases, the peak at 16.9 nm-1 decreases its intensity and a shoulder at 18.7 nm-1
appears, probably due to the graphitic d-spacing of the nanotubes at 0.336 nm. The lower scattering of the samples
also suggests the densification of the nanocomposite structure. Additional analysis by FTIR would help to confirm
the packing by correlation between the molecular vibrational intensity and the proposed polymer packing.

Figure 2. WAXS pattern from a series of aromatic polyamide samples with increasing amount of CNTs.

4．References
1．Jeong, B. H.; Hoek, E. M. V.; Yan, Y. S.; Subramani, A.; Huang, X. F.; Hurwitz, G.; Ghosh, A. K.;
Jawor, A., Interfacial polymerization of thin film nanocomposites: A new concept for reverse osmosis membranes.
Journal of Membrane Science 2007, 294 (1-2), 1-7.
2. Araki, T.; Cruz-Silva, R.; Tejima, S.; Takeuchi, K.; Hayashi, T.; Inukai, S.; Noguchi, T.; Tanioka,A.; Kawaguchi, T.; Terrones, M.; Endo, M., Molecular Dynamics Study of Carbon Nanotubes/Polyamide
Reverse Osmosis Membranes: Polymerization, Structure, and Hydration. Acs Applied Materials & Interfaces 2015,
7 (44), 24566-24575.
3．Cruz-Silva, R.; Izu, K.; Maeda, J.; Saito, S.; Morelos-Gomez, A.; Aguilar, C.; Takizawa, Y.;
Yamanaka, A.; Tejiima, S.; Fujisawa, K.; Takeuchi, K.; Hayashi, T.; Noguchi, T.; Isogai, A.; Endo, M.,
Nanocomposite desalination membranes made of aromatic polyamide with cellulose nanofibers: synthesis,performance, and water diffusion study. Nanoscale 2020, 12 (38), 19628-19637.
4. Ortiz-Medina, J.; Inukai, S.; Araki, T.; Morelos-Gomez, A.; Cruz-Silva, R.; Takeuchi, K.; Noguchi, T.;
Kawaguchi, T.; Terrones, M.; Endo, M. Robust water desalination membranes against degradation using highloads of carbon nanotubes. Scientific Reports 2018, 8. DOI: 10.1038/s41598-018-21192-5.