Recent advances in nanostructures polymer blend systems

In recent years, several strategies have been developed to form well defined and predictable multicomponent polymer structures with phase separation at the nanoscale. Nanostructured polymer morphologies have been prepared by reactive blending by Hu et al. and Pernot et al. have developed the concept of in situ polymerization and in situ compatibilization to obtain stabilized nanoblends and have shown the feasibility of their approach by using PP and PA6. Their method consists of polymerizing a monomer of PA6, e-caprolactam (eCL), in a matrix of PP. A fraction of the PP bears 3-isopropenyl-a,a-dimethyl benzene isocyanate (TMI), which acts as a growing center to initiate PA6 chain growth. In fact, the polymerization of PA6 and the grafting reaction between PA6 and PP took place simultaneously in the matrix of PP, leading to the formation of compatibilized nanoblends. The size of the dispersed phase was between 10 and 100 nm, as shown in Figure1.

Figure 1 Morphology of PP-g-TMI/eCL/NaCL microactivator system.
Pernot et al. also adopted a similar methodology to produce a cocontinuous nanoscale product. In this approach, one component bears reactive groups along the backbone and the second component possesses complementary reactive moieties only at the end. Even though this novel strategy is expected to be versatile, it has yet to be applied to a wide range of polymers including semiconducting or fluorescent materials and to thin layer applications. Kietzke et al. developed two new approaches to synthesize nanoscale polymer blend systems. In both cases, thin spin coated layers are used. In the first approach, two dispersions of single component nanospheres are mixed and processed into thin layers. In the second approach, the nanospheres are prepared from a mixture of two polymers in a suitable solvent. In this case, both polymers are contained in individual nanoparticles, where the particle size determines the upper limit to the dimension of the phase separation.
Nanostructures can also be developed by the thermal treatment of initially miscible polymer blends. The concept of forming structures by combining phase separation and crystallization is becoming increasingly more important. The crystallization, phase structure, and semicrystalline morphology of phase separated nanostructured binary blends of PEO and poly(ether sulphone) (PES) have been reported by Dreezen et al. The authors have shown that 75:25 and 50:50 PEO/PES blends show a clear cocontinuous structure with a characteristic dimension of approximately 400 and 200 nm, respectively.