Organic-ICP Composite Particles

Since then, a number of composite particles have been developed [66-70], Lu et al. have demonstrated the effect of surfactants on the morphology of ICP-coated polystyrene (PS) or poly(styrene-co-butyl acrylate) [PST-co-BuA] particles [71]. These authors showed that when the core particles are stabilized with ionic surfactants, a raspberry-type of morphology is obtained, whereas a homogeneous coreshell morphology is achieved in the case of nonionic surfactant-stabilized particles. 

It was also shown that the core materials influence the conductivity of the composite particles. Nano-sized PS-PPy composites have been reported by Xu et aL [72], who also noted that when the cationic, nonpolymerizable surfactant cetyl-triemethylammonium bromide (CTAB) was used as stabilizer, the latex particles prepared showed poor colloidal stability and low electrical conductivity (Fig. 6.13) compared to that of latexes stabiHzed by nonionic polymerizable surfactant (o-methoxy[poly(ethylene oxide)4Q] undecyl a-methacrylate (PEO-R-MA-40) and cationic polymerizable surfactant (o-acryloyloxyundecyltrimethylammonium bromide (AUTMAB). These authors also proposed that the poor colloidal stability and low conductivity of the composite particles were due to the desorption of CTAB 

Sapurina et al. have reported the synthesis of PANI-coated waterborne polyurethane latexes in the presence of a polymeric stabihzer, polyvinylpyrrolidone (PVP). The composite particles showed a conductivity of 10 S cm i, with good colloidal and mechanical properties [73]. Recently, Huang et al. synthesized a series of PPy-coated styrene-butyl acrylate (SBA) core-shell latex particles [74], The Tg of the composite particles was shown to be determined mainly by the core material. It was reported that the conductivity of the hybrid particles could be tuned by varying the butyl acrylate content in the SBA copolymer. The composite particles showed a conductivity of 0.17 S cm Composite particles having a photochromic dye as the core and ICP as shell, and possessing properties of photoluminescence, have been studied by Jang etal. [75]. Thin PEDOT-coated PS particles (Fig. 6.14) were reported for self-assembled crystalline coUoidal arrays with a stop band in the visible regime by Han and coworkers [76]. 

Currently, carbon nanotubes (CNT) are of major interest for their apphcations in nanomaterials and nano devices, and composite particles based on a CNT core and ICP shell have been reported recently [77,78]. Yu and coworkers successfully synthesized multi-waUed carbon nanotubes (MWNT) coated with a PPy shell with core-shell morphology [78] the composite particles obtained showed an improvement of conductivity and the redox behavior of PPy. 

Another strategy that allows the combination of electronic, electrical and optical properties of ICP with tunable properties of the matrix has also been explored. Nanostructure materials with an ICP core and an insulating polymer shell have also been reported [79-81]. Highly transparent conductive coatings with core-shell nanoparticles have been reported by Jang et al. [82]. Poly(methyl methacrylate) 

---