Molecular weight effect Nanocomposites

A polymer electrolyte with acceptable conductivity, mechanical properties and electrochemical stability has yet to be developed and commercialized on a large scale. The main issues which are still to be resolved for a completely successful operation of these materials are the reactivity of their interface with the lithium metal electrode and the decay of their conductivity at temperatures below 70 °C. Croce et al. found an effective approach for reaching both of these goals by dispersing low particle size ceramic powders in the polymer electrolyte bulk. They claimed that this new nanocomposite polymer electrolytes had a very stable lithium electrode interface and an enhanced ionic conductivity at low temperature. combined with good mechanical properties. Fan et al. has also developed a new type of composite electrolyte by dispersing fumed silica into low to moderate molecular weight PEO. 

To understand the effect of the molecular weight of PLLA on the properties of nanocomposite, Chen et al. prepared different MWCNT-g-PLLA hybrids with varying molecular weights of PLLA, viz., 1000, 3000, 11000, and 15000. For detailed experimental conditions, refer to Chen et al. (64). The extent of PLLA grafting on MWCNTs was examined by both SEM and TEM (Figure 9.3 and Figure 9.4, respectively). TEM studies revealed that the degree... 

In this part of the chapter we discuss (a) the controlled thermolysis of thiolate solutions in polystyrene matrix at temperatures above the polymer glass transition temperature and (b) the reaction mechanism in the case of silver-polystyrene nanocomposite systems. However, the same reaction mechanism is probably involved in the thermolysis of other mercaptide-polystyrene systems. This technique has proven to be an excellent new preparative scheme for the generation of both metal and sulfide clusters in polymers. In particular, high-molecular-weight n-alkanethiolates have shown to be the most effective compound class since the low volatility of thermolysis by-products avoids film foaming during the annealing process. 

Wang, Y., Chen, F. -B., Wu, K. -C., and Wang, J. -C., Shear rheology and melt compounding of compatibilized-polypropylene nanocomposites effect of compatibilizer molecular weight, Polym. Eng. ScL, 46, 289-302 (2006a). 

Mariani, P.D.S.C., Allganer, K., Oliveira, F.B., Cardoso, E.J.B.N., Irmocentini-Mei, L.H. Effect of soy protein isolate on the thermal, mechanical and morphological properties of poly (epsilon-caprolactone) and com starch blends. Polym. Testing 28(8), 824—829 (2009) Fornes, T.D., Yoon, P.J., Keskkula, H., Paul, D.R. Nylon 6 nanocomposites the effect of matrix molecular weight Polymer 42(25), 09929-09940 (2001)... 

Recently, Tiwari and Paul (2011 a) carried out detailed studies on the effect of PP viscosity on the dispersed phase particle size, stability of dispersed phase morphology upon annealing, phase inversion behavior, and changes in the mechanical properties of PP/PP-g-MA/MMT/PS nanocomposites prepared with different molecular weight grades of PP. PP-g-MA was added to PP to facilitate dispersion of organoclay in the nonpolar PP moreover, it also provides better reinforcement effect when PP forms the continuous phase. 

The effect of MMT content and PP molecular weight on the elastomer morphology in PP/PP-g-MA/MMT/EOR nanocomposites is shown in Fig. 17.11. The elastomer particles are large with a mixture of spherical and elongated shapes in L-PP/EOR blend or mostly spherical shapes in the H-PP/EOR blend without MMT and become small and mostly elongated in the presence of MMT in both L-PP- and H-PP-based nanocomposites. The nonspherical nature of elastomer particles is... 

Fig. 17.10 The effect of elastomer MFI on MMT particle aspect ratio of PP/PP-g-MA/MMT/EOR nanocomposite prepared from various molecular weight PP. Gray- and black- filled symbol represents nanocomposites containing elastomers having 39 and 28 wt% octene content, respectively. The EOR and MMT content is based on the total nanocomposite weight (Tiwari and Paul 2011b)...

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