## 2 Nanocomposite Materials
### Synthetic approaches to nanocomposite materials
Oleic acid capped CdS NCs have been synthesized by thermal decomposition in the presence of surfactants and have been embedded in optically transparent PS and PMMA [98]. The optical properties of the CdS NCs have been preserved after the incorporation in the polymers. A capping exchange of the NC coordinating surfactants has been carried out to investigate the role of the surface ligands in the interaction with the polymer matrix. Quenching of the band edge emission and high defect state emission band have occurred in octylamine capped CdS NC based nanocomposites, thus indicating the effective interaction between oleic acid and polymeric chains. Aqueous CdTe NCs have been either transferred in solution of styrene and methyl methacrylate monomer [99] or dispersed in hydrophilic polymer nanofibers [100] in order to obtain NC-polymer bulk composites and highly fluorescent 1D materials, respectively, in which emission properties of the inorganic nanostructures have been preserved. [PERSON] _et al._ prepared metal NPs-conjugated polymer nanocomposites by two different preparative strategies, namely by (i) mixing Au NP solution with polymer and (ii) _in situ_ metal ions reduction in the presence of the polymer solution [101]. Authors have found that the morphology and optical properties of Au NPs and molecular structure of the polymer in the nanocomposite depend on the preparative method and conditions. The _ex situ_ formation of nanocomposite materials has resulted in an uniform distribution of NPs in the matrix. On the contrary, the _in situ_ formation of Au NPs in the matrix has caused the particle aggregation and the partial damage of the polymer molecular structure. Nevertheless, due to the high surface energy of nanoscale materials, the incorporation methods based on the use of a common solvent often causes the occurrence of phase segregation or NC aggregation, which lead to detrimental weakening of the mechanical, optical and electrical properties of the final nanocomposite material. In order to overcome these disadvantages, the proper chemical functionalization of NP surface can be carried out by the introduction of functional groups supporting the interaction between the NC surface and polymeric matrix. Surface modification of NPs with surfactants or coupling agents not only stabilize the NPs during the nanocomposite formation process [6, 102], but can also improve their compatibility with the surrounding media and enhance the mechanical, optical and electronic properties of the final nanocomposite material [103]. Recent research activity has been devoted to the preparation of nanocomposite materials by using NP modified surface-initiated polymerization method. This method utilizes the physicochemical adsorption of a initiator onto the NP surface for promoting monomer polymerization in the component solution. This approach has been used by [PERSON] _et al._ to prepare surface modified Fe\({}_{2}\)O\({}_{3}\) NPs for the  
Figure 4: Strategies for homogeneous dispersion of NCs in polymer matrix: part a represent the polymers and part b the prepared nanocomposites. 1 Use of a common solvent; 2 Presence of initiator groups on NC surface to induce the binding to polymer matrix; 3 Functional chemical groups on the polymer chains, able to coordinate NC surface. polymerization of urethane in tetrahydrofuran [104]. High refractive index with excellent transparency have been successfully prepared by the UV-curing of surface modified ZnS NPs in N,N-dimethylformamide (DMF) solution in the presence of commercial UV-curable OROMOCOMP(r)[105]. The resulting nanocomposite material has shown tunable refractive index and has been exploited in the replication of microchannels with submicron features by micromolding in capillaries (MIMIC).