Nanocomposites of Polystyrene‑<i>b</i>‑Poly(isoprene)‑<i>b</i>‑Polystyrene Triblock Copolymer with Clay–Carbon Nanotube Hybrid Nanoadditives

Polystyrene-<i>b</i>-polyisoprene-<i>b</i>-polystyrene (PS-<i>b</i>-PI-<i>b</i>-PS), a widely used linear triblock copolymer of the glassy-rubbery-glassy type, was prepared in this study by anionic polymerization and was further used for the development of novel polymer nanocomposite materials. Hybrid nanoadditives were prepared by the catalytic chemical vapor deposition (CCVD) method through which carbon nanotubes were grown on the surface of smectite clay nanolayers. Side-wall chemical organo-functionalization of the nanotubes was performed in order to enhance the chemical compatibilization of the clay–CNT hybrid nanoadditives with the hydrophobic triblock copolymer. The hybrid clay–CNT nanoadditives were incorporated in the copolymer matrix by a simple solution-precipitation method at two nanoadditive to polymer loadings (one low, i.e., 1 wt %, and one high, i.e., 5 wt %). The resulting nanocomposites were characterized by a combination of techniques and compared with more classical nanocomposites prepared using organo-modified clays as nanoadditives. FT-IR and Raman spectroscopies verified the presence of the hybrid nanoadditives in the final nanocomposites, while X-ray diffraction and transmission electron microscopy proved the formation of fully exfoliated structures. Viscometry measurements were further used to show the successful incorporation and homogeneous dispersion of the hybrid nanoadditives in the polymer mass. The so prepared nanocomposites exhibited enhanced mechanical properties compared to the pristine polymer and the nanocomposites prepared by conventional organo-clays. Both tensile stress and strain at break were improved probably due to better interfacial adhesion of the clay–CNT hybrid of the flexible rubbery PI middle blocks of the triblock copolymer matrix

Effective Improvement of Water-Retention in Nanocomposite Membranes Using Novel Organo-Modified Clays as Fillers for High Temperature PEMFCs

Toward an enhanced water-retention of polymer electrolyte membranes at high temperatures, novel organo-modified clays were prepared and tested as fillers for the creation of hybrid Nafion nanocomposites. Two smectite clays (Laponite and montmorillonite), with different structural and physical parameters, were loaded with various cationic organic molecules bearing several hydrophilic functional groups (−NH2, −OH, −SO3H) and incorporated in Nafion by solution intercalation. The resulted hybrid membranes were characterized by a combination of powder X-ray diffraction, FTIR spectroscopy, and thermal analysis (DTA/TGA) showing that highly homogeneous exfoliated nanocomposites were created where the individual organoclay layers are uniformly dispersed in the continuous polymeric matrix. In this paper, water-transport properties were investigated by NMR spectroscopy, including pulsed-field-gradient spin–echo diffusion and spectral measurements conducted under variable temperature. Organo-montmorillonite nanofillers demonstrate a considerable effect on the Nafion polymer in terms both of water absorption/retention and water mobility with a remarkable behavior in the region of high temperatures (100–130 °C), denoting that the surface modifications of this clay with acid organic molecules significantly improve the performance of the final composite membrane. 1H NMR spectral analysis allowed a general description of the water distribution in the system and an estimation of the number of water molecules involved in the hydration shell of the sulfonic groups as well as that absorbed on the organoclay particles

Antibacterial and Algicidal Effects of Porous Carbon Cuboid Nanoparticles

Here, we have studied the antibacterial effects of a newly synthesized carbon structure with excellent properties, named porous carbon cuboid (PCC) nanoparticles, upon Gram-negative Escherichia coli and Gram-positive Corynebacterium glutamicum bacterial cells and its algicidal effects upon Chlamydomonas reinhardtii microalgal cells. More specifically, the antibacterial properties of PCCs enriched with acid treatment (PCC-ox) or metal encapsulation (PCC-Cu and PCC-Ag) were investigated under various concentrations of PCCs and their interaction times. Additionally, the impact of PCCs upon microalgal growth was estimated by measuring the total chlorophyll level during their cultivation. As a result, E. coli and C. glutamicum were shown to be substantially inhibited by PCCs, depending on their special characteristics, dose, and bacterial strain. Moreover, it has been proven that the antibacterial effect is time-dependent. Growth of C. reinhardtii was inhibited by PCCs in a material-dependent manner, whereas PCC-Ag had the highest registered effect. These results suggest that PCCs could be used as an effective antibacterial material, although consideration should be given to issues involving the disposal of PCCs after usage, given their level of toxic effect on the environment