Polymer blends nanoparticles

Fig. 51 Preparation of the pristine polymer and polymer-polymer blend nanoparticles is presented. Step 1 a by ultrasonication a polymer solution and water/surfactant solution are blended to a miniemulsion and transformed by solvent evaporation to an aqueous polymer-in-water nanoparticle dispersion. Step 2 b Films are spin cast from the dispersion. (Reprinted with permission from [239], 2003, Macmillan Publishers Ltd)...

In a research study conducted by van Vlerken et al, pH responsiveness was utilized for targeting breast cancer with the use of a polymer-blend nanoparticle system of 30% by weight pH-responsive polymer poly(beta-amino ester) and 70% by weight poly(D,L-lactide-co-glycolide) to administer paclitaxel and Cg-ceramide, an apoptotic signaling molecule, respectively [39]. The polymer blend allowed for a delay in the release of Cg-ceramide, which based on preliminary results improved therapeutic efficacy in this specific combination therapy scheme for multidrug-resistant breast and ovarian cancer. Expected conclusions were generated for the accumulation of particles based on the enhanced... 

Raezkowska, J., Montenegro, R., Budkowski, A., Landfester, K., Bemasik, A., Rysz, J., Czuba, P. (2007) Structure evolution in layers of polymer blend nanoparticles. Langmuir, 23,7235-7240. 

L. E. van Vlerken et ah, Biodistribution and pharmacokinetic analysis of paclitaxel and ceramide administered in multifunctional polymer-blend nanoparticles in drug resistant breast cancer model. Mol. Pharm. (2008). 

Figure 25.14 (a) Concentration-dependent fluorescence spectra of polymer blend nanoparticles under 375 nm excitation (b) Variation of the fluorescence intensity of PFO and dopant polymers in each pair with the dopant... 

Moreover, the development of new strategies for surface modifications of nanoparticles with compounds having FR activity could provide a new field of research on FR systems. The use of novel phosphorus-, nitrogen-, or halogen-containing modifiers, instead of alkylammonium ions, for layered silicates seems promising. FR action conferred by the surface modifier can be combined with action due to composite morphology, particularly when the host polymer is a polymer blend instead of a pure polymer. 

It was also noticed by the same authors19 that the incorporation of the OMMT in EVA instead of PA6, keeping constant the global composition, led to a strong decrease in heat released, but with a different evolution of HRR as a function of time. This was ascribed to different morphologies of clays (mixed intercalated/exfoliated versus completely exfoliated) for the polymer blend. Consequently, the formulation process of complex FR systems involving polymer blends and made up of nanoparticles in combination with FRs seems crucial. 

Nanoparticles are solid species of nanoscale size usually composed of an insoluble and biodegradable polymer or polymer blend (Figure 47. IB). Generally, the methods of preparation of such nanoparticles are simple and easy to scale-up. The drug is captured within the particle upon its preparation and is released upon degradation of the polymer in the body. The use of nanoparticles as carriers for drug and gene delivery has been... 

Kietzke, T. Neher, D. Landfester, K. Montenegro, R. Guntner, R. Scherf, U. Novel approaches to polymer blends based on polymer nanoparticles. Nature Mater. 2003, 2, 408 12. 

One extensively studied material system among the nanocrystal-polymer blends is zinc oxide (ZnO) in combination with MDMO-PPV or P3HT [273-282]. Beek et al. presented the first polymer solar cells containing ZnO nanoparticles, reaching power conversion efficiencies of 1.6% [273]. In this case the nanoparticles were prepared separately and then intermixed with MDMO-PPV in solution. Shortly after this study the Janssen group presented another route to ZnO-polymer hybrid solar cells by forming the nanocrystals in situ inside the film by applying a precursor [274]. Here, diethylzinc served as the precursor and was spin cast in blends with MDMO-PPV. Process-... 

Walther A, Matussek K, Muller AHE (2008) Engineering nanostructured polymer blends with controlled nanoparticle location using Janus particles. Acs Nano 2(6) 1167-1178... 

Finally, shear viscosity is strongly affected by the clay in the blends, especially at high PEN contents. A lubricating effect rather than a filler effect reveals the possibility that the clay is not well dispersed in the polymer blend, and migration of particles in the flow to the wall region can explain the observed reduction in shear viscosity. When MMT clay is mixed with crystallizable polymers such as polyesters, some processing problems arise because the crystallization process is modifled by nucleation effects induced by the nanoparticles. Moreover, these particles also influence the kinetics of transesteriflcation between PET and PEN, besides other factors such as the reaction time and extruder processing temperature. In Reference 72, a quaternary alkyl ammonium compound (Cl8) and MAH were used to modify the surface properties of the clay... 

The combination of experimental evidence and computational modeling show conclusively that stable, homogeneously blended (bulk-immiscible) mixed-polymer composites can be formed in a single microparticle of variable size. To our knowledge, this represents a new method for suppressing phase-separation in polymer-blend systems without compatibilizers that allows formation of polymer composite micro- and nanoparticles with tunable properties such as dielectric constant. Conditions of rapid solvent evaporation (e.g. small (<10 pm) droplets or high vapor pressure solvents) and low polymer mobility must be satisfied in order to form homogeneous particles. While this work was obviously focused on polymeric systems, it should be pointed out that the... 

Immiscible polymer blends normally have a sea-island stmcture, where one polymer is dispersed as (normally spherical) particles in the other polymer, which forms the matrix, or a co-continuous structure, where both polymers are equally distributed in the blend without one polymer forming a continuous phase. For the blends to have good mechanical properties, it is also important that there is good interaction between the different components in the blend. To ensure this, researchers have tried a variety of methods to compatibilize the polymers in blends. The most used method is to add a third polymer, which interacts well with the other two polymers, into the blend. Reactive blending is another well-used method, and recently, a lot of investigation went into the use of (especially clay) nanoparticles to improve the interaction between the polymer components by locating themselves on the interfaces between the polymers. 

---