Nanoparticle miniemulsion method

Nanoparticles of the conjugated polymers Me-LPPP and MEH-PPV were produced with the miniemulsion method. Monolayer of the particles on glass with ITO coating was prepared by spin-coating. The content of components in Me-LPPP MEH PPV blend is 2 1. 

The formation of structured polymeric nanoparticles is of great importance for many appUcadons. In general, polymer nanoparticles can be prepared from several heterophase methods. One of the most known methods, developed extensively by Landfester et al. during the last decade, is the so-called miniemulsion method (Landfester 2001, 2009 Kietzke et al. 2007). 

Fig. 6.2 Atomic Force Microscopy (AFM) topography image of polystyrene (PS) nanoparticles prepared by the miniemulsion method after spin casting the miniemulsion on a silicon wafer. The starting material is the bulk polymer...

PDLLA (NatureWorks, PLA 2002D, D-content 4.25%, p= 2A g/cm ) nanoparticles can be prepared either by the miniemulsion method or the reprecipitation method. In the present case, for the miniemulsion method PDLLA was dissolved in chloroform (CHCI3), at a 0.2 wt% concentration. The polymer solution was added to a 1 wt% aqueous surfactant solution of sodium dodecyl sulfate (SDS). Pre-emulsification was obtained by stirring at room temperature for... 

Fig. 6.6 AFM topography images and size distribution of PDLLA nanoparticles prepared by the miniemulsion method (a, c) and reprecipitation method (b, d). Size distribution was quantified on the AFM images by measuring the nanoparticles diameters. Continuous black line represents a Gaussian fit to the distribution...

WAXS results in the previous section showed that polymer nanoparticles of PDLLA were able to crystallize when heated above certain temperatures. The diffraction patterns also show that nanoparticles prepared via the miniemulsion protocol showed a crystallization behavior quite similar to the bulk polymer. Based on these results, we have evaluated the morphological change of PDLLA nanoparticles prepared by the miniemulsion method, when subjected to thermal treatments. 

More recently, Priego-Capote et al. reported on the production of MIP nanoparticles with monoclonal behaviour by miniemulsion polymerisation [63]. In the synthetic method that they employed, they devised to use a polymerisable surfactant that was also able to act as a functional monomer by interacting with the template (Fig. 4). The crosslinker content was optimised at 81% mol/mol (higher or lower contents leading to unstable emulsions). In this way, the authors were able not only to produce rather small particles (80-120 nm in the dry state) but also to locate the imprinted sites on the outer particle surface. The resulting MIP nanobeads were very effective as pseudostationary phases in the analysis of (/ ,S)-propranolol by CEC. 

Novel applications in science and technology require highly efficient and, if possible, environmentally friendly methods and techniques for the generation of functional nanocomposite materials. Serving the environmental aspect, water-based formulation techniques that avoid the use of organic solvents are the focus of attention. Besides the well-known water-based emulsion and mlcroemul-sion polymerization processes, the miniemulsion polymerization technique is a highly versatile heterophase system that is suitable for the preparation of complex nanoparticles. 

Yang et al. used the same method to prepare particles from noncrosslinked LC polymers [101]. The shape of the obtained nanoparticles was found to deviate from spherical. Such shape-anisotropic colloids are usually very difficult to produce by miniemulsion techniques. 

Figure 6.6a, b show AFM topography images of the PDLLA nanoparticles prepared by the miniemulsion and reprecipitation method, respectively. In both cases, the nanoparticles consist of polymer nanospheres, without signs of... 

In the first section, various kinds of functional polymer, in particular the most used conductive polymer, conjugated polymer (CP), redox polymer, metallopolymer. Selection of the correct functional polymer depends on the desired properties of the resulting nanocomposites. The second part of the chapter focuses on the basic approaches used in the preparation of polymeric nanoparticles. As mentioned earlier, there are two basic approaches in the recent literature to synthesize the polymeric nanoparticles. In this section, we focus on the discussion of the common and widely used preparation methods for various kinds of polymeric nanoparticles. The polymerization method is based on the encapsulation of nanoparticles through heterogeneous polymerization in dispersion media. This method can be further classified into emulsion, microemulsion and miniemulsion. Polymer encapsulated nanoparticles can also be prepared directly from preformed polymer, where this approach is based on the specific interactions between nanoparticles and the preformed polymer, such as electrostatic interactions, hydrophobic interactions and secondary molecular interactions or self-assembly method. 

Shulai Lu prepared magnetic polymeric composite particles by miniemulsion polymerization of styrene in the presence of hydrophobic magnetic nanoparticles with hexadecane (HD] as hydrophobe, 2,2 -azobisisobutyronitrile (AIBN], and sodium dodecyl sulfate (SDS] as an emulsifier or sodium p-styrenesulfonate (NaSS] as an ionic comonomer [151], The results showed that miniemulsion polymerization is an effective method for encapsulation of magnetite into a hydrophobic polymer. 

---