MWCNT nanocomposites

Shakir, h, et ah, Mo03-MWCNTs nanocomposites photocatalyst with control of lightharvesting under visible and natural sunlight irradiation. Journal of Materials Chemistry,... 

Li, H. Zhang, X. Cui, X. Lin, Y., Ti02 nanotubes/MWCNTs nanocomposite photocatalysts synthesis, characterization and photocatalytic hydrogen evolution under UV-vis light illumination./. Nanoscience andNanotechn. 2012,12 1806-1811. 

Polymer-linked MWCNT nanocomposites were prepared by reversible addition fragmentation chain transfer (RAFT). The RAFT reagent was successfully grafted on to the surface of MWCNTs and PS chains were grafted from MWCNTs via RAFT polymerization [192], By covalently linking acyl chloride functions of functionalized MWCNTs with living polystyryllithium, Huang et al. succeeded in the preparation of polystyrene-functionalized MWCNTs (Scheme 1.32) [193],... 

Figure 3.16. STEM image performed in SEM on cryo-ultramicrotomed sections of P(S-ABu)/MWCNT nanocomposites films in annular dark-field conditions at 30 kV the contrast between the fillers and the matrix is important. Scale bar 500 nm.

Another important property - wettability was followed by SEM analysis on PS/MWCNTs nanocomposite prepared by in-situ bulk-suspension polymerization (54). Figure 8.7 presents a micrograph of fracture surface of the prepared nanocomposite. The picture very clearly evidences that the nanotubes are covered by a thick layer of polystyrene. Parts of original nanotubes can be identified at the end of the fracture noteworthy is also the smaller diameter at the end of tubes. 

Figure 8.7. Evidence of wettability of polystyrene matrix on the surface of MWCNT nanocomposite prepared by in- situ polymerization with assistance of sonication (54).

Chen et al. used a "grafting to" technique to synthesize PLLA-MWCNT nanocomposites (64). In this study, MWCNTs were first treated with acid to yield the carboxylic-acid-functionalized MWCNTs (MWCNT-COOH), which subsequently reacted with... 

Zhang et al. (65) prepared PLLA-MWCNT nanocomposites by solution-mixing and precipitation method. First, 50g MWCNTs were suspended in lmL DMF. This suspension was stirred overnight in a round-bottom flask along with purified PLLA at 110 °C under N2. The resultant mix was poured into excess methanol, filtered, washed with methanol, and dried at 100 °C under vacuum overnight, which yielded a fluffy black solid (226 mg, 90% yield). SEM and TEM (Figure 9.5) were used to visually examine the degree of dispersion and the extent of absorption of PLLA on the surface of... 

Figure 9.6. A representative image of microcellular PLA-MWCNT nanocomposite produced via microcellular injection-molding.

Figure 9.7. TEM Images of (a) Solid PLA-MWCNT Nanocomposite at 500 nm (Inset-a magnified view of agglomerated MWCNTs at 100 nm) (b) Microcellular PLA-MWCNT Nanocomposite at 500 nm (arrow indicates micro cell formed during microcellular injection-molding) (c) Solid PLA-MWCNT Nanocomposite at 100 nm and (d) Microcellular PLA-MWCNT Nanocomposite at 100 nm. Reprinted with permission from S. Pilla et al.. International Polymer Processing, XXII, p. 418,2007, 2007, Polymer Processing Society.

Wu and Liao (75) also used melt-compounding to process PLA-MWCNT nanocomposites similar to other studies listed above ... 

Wu et al. (73) studied the viscoelastic properties, viz. storage modulus (GO and complex viscosity (r 0 with respect to frequency (co) of PLA-carboxylic-acid-functionalized MWCNTs nanocomposites using a rheometer (HAAKE RS600, Thermo Electron Co., USA). The dynamic frequency sweep measurements were carried out at the pre-strain level of 1%. They observed that the addition of carboxylic-acid-functionalized MWCNTs weakened the dependence of G on go, especially at higher loading levels (Figure 9.12). This indicates... 

Figure 9.12. (a) Dynamic storage modulus (GO and (b) complex viscosity (r) ) for pure PLA and PLA- carboxylic-acid-functionalized MWCNTs nanocomposites obtained in dynamic frequency sweep. Reprinted with permission from D. Wu et al., Polymer Degradation and Stability, Vol. 93, p. 1577,2008, 2008, Elsevier Science Ltd. 

Figure 9.13. (a) Young s modulus and (b) elongation at break of PLLA-MWCNTs nanocomposites plotted versus the MWCNTs contents. Reprinted with permission from S. Moon et al., Macromolecular Symposia, Vol. 224, p. 287,2005, 2005, Wiley InterScience Ltd. 

Table 9.2. Specific mechanical properties of solid and microcellular PLA and PLA-MWCNT nanocomposites (35)... 

Moon et al. (61) showed from the mass loss curves for the degradation of PLLA and PLLA-MWCNT nanocomposites that PLLA degraded without forming any residue, but the nanocomposites left a residue of about 3-10% (Figure 9.14). Additionally, the decomposition temperature (Td), at 10% weight loss, was found to increase with the MWCNT loading by 10-20%. Rapid weight loss also took place at around 300 °C in both PLA and PLA nanocomposites. Similar results were also obtained by (64,73,75,76). 

Figure 9.15. Effect of MWCNTs contents on the surface resistance of PLA-MWCNTs nanocomposites. Reprinted with permission from C-F. Kuan et al.. Journal of Physics and Chemistry of Solids, Vol. 69, p. 1395,2008, 2008, Elsevier Science Ltd.

The novel SERS-active substrates were prepared by electrodeposition of Ag nanoparticles in the MWCNTs-based nanocomposites. The formation of Ag-MWCNTs nanocomposite was characterized by scanning electron microscopy and energy dispersive X-ray spectroscopy. The application of the Ag-MWCNTs nanocomposite in SERS was investigated by using rhodamine 6G (R6G). The present methodology demonstrates that the Ag-MWCNTs nanocomposite is suitable for SERS sensor. 

In conclusion, it has been shown that the SERS techniques offer a means of sensitive detection of probe molecules. An efficient and simple SERS-active substrate prepared by electrodeposition of Ag on MWCNTs has been developed. The prepared Ag-MWCNT nanocomposites exhibited good SERS performance and also featured a simple application process. The technique may have a potential use for in situ determination of analytes. Therefore, such a work will lead to a very promising future for applications in SERS chemical sensors. 

Generally, PLA nanocomposites exhibit moderate improvement in modulus, strength and thermal stability, decreased gas permeability, and rate of degradation. Lee et al. [128] reported that the modulus of the PLLA nanocomposites systematically increased with increasing montmorillonite [MMT] loading. They also claimed that the crystallinity and the Tg of PLLA nanocomposites were lower than neat PLLA. In the case of PLLA/multi-walled carbon nanotube (MWCNT) nanocomposites, it was observed... 

Other nano-fillers have also investigated. Cao et al. [253] reported the utilization of multiwalled carbon nanotubes (MWCNTs) as filler-reinforcement to improve the performance of plasticized starch (PS). The PS/MWCNTs nanocomposites were prepared by a simple method of solution casting and evaporation. The results indicated that the MWCNTs dispersed homogeneously in the PS matrix and formed strong hydrogen bonding with PS molecules. Besides the improvement of mechanical properties, the incorporation of MWCNTs into the PS matrix also led to a decrease in the water sensitivity of the PS-based materials. 

Baek and co-workers grafted hyperbranched poly(ether ketone)s (HPEKs) on to MWCNTs through an in situ polycondensation of A3 (trimesic acid) and B2 (phenyl ether) monomers in the presence of poly(phosphoric acid) and P2O5. Due to the globular molecular architecture of HPs, the morphology of the nanocomposites resembled mushroom-like clusters on MWCNT stalks . The HPEK-g-MWCNT nanocomposites were soluble in polar aprotic... 

P. Saini, V. Choudhary, B. P. Singh, R. B. Mathur, S. K. Dhawan, Polyaniline-MWCNT Nanocomposites for Microwave Absorption and EMI Shielding. Materials Chemistry and Physics 2009,113,919-926. 

Figure 9.23 Frequency dependence of losses due to reflection (SEj ) and absorption (SE ) for MWCNT-loaded PANl nanocomposites having different loadings of MWCNT relative to aniline monomer viz. PCNTO (0.0 wt.%), PCNT5 (5.0 wt.%), PCNTIO (10 wt.%), PCNT20 (20 wt.%), and PCNT25 (25 wt.%). Loss tangent (tan 6) of in-situ synthesized PANl-MWCNT nanocomposites as a function of MWCNT loading. Reprinted from Ref [4] with permission from Elsevier.

---