Molecular interactions, nanocomposite morphology

Katti, K. S., Sikdar, D., Katti, D. R., Ghosh, P. Verma. D. (2006). Molecular interactions in intercalated organically modified clay andclay-polycaprolactam nanocomposites Experiments and modeling. Polymer, Vol. 47, No. 1, pp. 403-414 Kister, G., Cassanas, G. Vert, M. (1998). Structure and morphology of solid lactide-glycolide copolymers from n.m.r., infra-red and Raman spectroscopy. Polymer, Vol. 39, No. 15, pp. 3335-3340... 

In this review, recent advances in polymer/(nano)HAp composites and nanocomposites for bone tissue regeneration are presented, including specific subjects associated with polymer/HAp composition, molecular orientation and morphology, surface modification, and interactions between components and the biological environment. 

The reinforcement largely depends on the interactions between the particles and the polymer. It has been reported that there exists an interaction zone (interfacial region) around the particles, within which the molecular dynamics and morphology of polymers are different from those in bulk [1], Once the dimensions of the particles decrease to the nanometer scale and the fraction of interfacial areas reaches a sufficiently high level, the interfacial properties dominate the overall composite properties. Earlier studies on polystyrene (PS)-carbon nanotubes (CNT)/carbon nanofibers (CNF) nanocomposites revealed strong physical interactions between the particles and the polymer. 

PANI has a strong affinity to GNs due to n electron interactions and therefore the morphology of PANI transforms from twist structure to extended structure after the GNs are introduced [13] as shown in Figure 6.7. Similar with CNT/PANI nanocomposites, the ordered or extended PANI molecular structure in GO (or GNs)/PANI contribute to the increase of carrier mobility of PANI and therefore enhance the TE properties. 

As in the case of other material systems, the macroscopic properties of nanocomposites are driven by their micro-/nanoscopic structure. From an electrical insulation perspective, polyethylene (PE) and epoxy resins constitute two technologically important material systems, each of which embodies in very different ways, a great deal of structural complexity. In the case of PE, the constituent molecules are the result of the inherently statistical polymerisation process, which can ultimately result in the formation of a hierarchical morphology in which different molecular fractions become segregated to specific morphological locations. In an epoxy resin, the epoxy monomer chemistry, the hardener and the stoichiometry can all be varied, to affect the network structure that evolves. In the case of nanocomposites, another layer of structural hierarchy is then overlaid upon and interacts with the inherent characteristics of the host matrix. 

Due to the structure filler hierarchical morphology and surrounding polymer matrix at nanometer length scale, the well-defined concepts in conventional two-phase composites should not be directly applied to polymer nanocomposites. Polymer molecules and nanofillers have equivalent size and the polymer-filer interactions are highly dependent on the local molecular structure and bonding at the interface. Therefore, nanofillers and polymer chains structures cannot be considered as continuous phase at these length scales, and the bulk mechanical properties caimot be determined, for that reason, using traditional continuum-based micromechanical approaches [47,48]. 

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