Soft polymer nanocomposites

In this chapter, we present an overview of the development of novel soft, nanohybrid materials (e.g., nanocomposite gels [19, 21, 28-30] and soft polymer nanocomposites [31-33]) with unique organic-inorganic network structures that overcome the previous limitations and exhibit excellent optical and mechanical properties in addition to outstanding new characteristics. 

Metal-polymer nanocomposites can be obtained by two different approaches, namely, in situ and ex situ techniques. In the in situ methods, metal particles are generated inside a polymer matrix by decomposition (e.g., thermolysis, photolysis, radiolysis, etc.) or chemical reduction of a metallic precursor dissolved into the polymer. In the ex situ approach, nanoparticles are first produced by soft-chemistry routes and then dispersed into polymeric matrices. Usually, the preparative scheme allows us to obtain metal nanoparticles whose surface has been passivated by a monolayer of -alkanethiol molecules (i.e., Crfiin+i-SH). Surface passivation has a fundamental role since it avoids aggregation and surface oxidation/contamination phenomena. In addition, passivated metal particles are hydrophobic and therefore can be easily mixed with polymers. The ex-situ techniques for the synthesis of metal/polymer nanocomposites are frequently preferred to the in situ methods because of the high optical quality that can be achieved in the final product. 

Coupling of highly conductive CNT network with a soft polymer matrix with large coefficient of thermal expansion (CTE) leads to a new class of electrothermal CNT-polymer composite actuators,which generates significant strains reversibly at applied electric fields at least two orders of magnitude lower than those reported for electrostrictive polymer nanocomposites. 

Due to the excellent redox properties and high conductivity of the conducting polymer nanocomposites, researchers have been extensively investigating them as electrode materials for batteries and supercapacitors [29,30]. Further, the soft porous conductive polymer matrix can efficiently buffer the severe volume changes of active electrode material during the ion intercalation and extraction process, hence improving cyclability of the electrode material and also acts as a conductive binder, decreasing the contact resistance between particles of active material [31]. In this section... 

Oberdisse J, El Hariak A, Carrot G, Jestin J, Boue F (2005) Structure and rheological properties of soft-hard nanocomposites influence of aggregation and interfacial modification. Polymer 46(17) 6695-6705... 

By extending the synthetic technology of NC gels, novel nanohybrid materials such as new stimuli-responsive NC gels (non-PNlPA systems), zwitterionic NC gels, aqueous dispersions of polymer-clay nanocomposite microspheres, Pt-NC gels with clay-mediated platinum nanoparticles, and soft hydrophobic polymer nanocomposites have been developed, as described below. 

Cangialosi, D., Boucher, V.M., Alegria, A., Colmenero, J. Physical aging in polymtas and polymer nanocomposites Recent results and open questions. Soft Matter 9, 8619 (2013)... 

Wong, M., Tsuji, R., Nutt, S., Sue, H.J. Glass transition temperature changes of melt-blended polymer nanocomposites containing finely dispersed zno quantum dots. Soft Matter 6, 4482-4490 (2010)... 

Recent demands for polymeric materials request them to be multifunctional and high performance. Therefore, the research and development of composite materials have become more important because single-polymeric materials can never satisfy such requests. Especially, nanocomposite materials where nanoscale fillers are incorporated with polymeric materials draw much more attention, which accelerates the development of evaluation techniques that have nanometer-scale resolution." To date, transmission electron microscopy (TEM) has been widely used for this purpose, while the technique never catches mechanical information of such materials in general. The realization of much-higher-performance materials requires the evaluation technique that enables us to investigate morphological and mechanical properties at the same time. AFM must be an appropriate candidate because it has almost comparable resolution with TEM. Furthermore, mechanical properties can be readily obtained by AFM due to the fact that the sharp probe tip attached to soft cantilever directly touches the surface of materials in question. Therefore, many of polymer researchers have started to use this novel technique." In this section, we introduce the results using the method described in Section 21.3.3 on CB-reinforced NR. 

Historically, polysiloxane elastomers have been reinforced with micron scale particles such as amorphous inorganic silica to form polysiloxane microcomposites. However, with the continued growth of new fields such as soft nanolithography, flexible polymer electronics and biomedical implant technology, there is an ever increasing demand for polysiloxane materials with better defined, improved and novel physical, chemical and mechanical properties. In line with these trends, researchers have turned towards the development of polysiloxane nanocomposites systems which incorporate a heterogeneous second phase on the nanometer scale. Over the last decade, there has been much interest in polymeric nanocomposite materials and the reader is directed towards the reviews by Alexandre and Dubois (4) or Joshi and Bhupendra (5) on the subject. 

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