Layered structure, polymer blends

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. 

Barrier polymers, 3 375-405 applications, 3 405 barrier structures, 3 394-399 carbon dioxide transport, 3 403 flavor and aroma transport, 3 403-405 health and safety factors, 3 405 immiscible blends, 3 396-398 large molecule permeation, 3 388-390 layered structures, 3 394-396 miscible blends, 3 398-399 oxygen transport, 3 402 permanent gas permeation, 3 380-383 permeability prediction, 3 399-401 permeation process, 3 376-380 physical factors affecting permeability, 3 390-393... 

It is a common phenomenon that the intercalated-exfoliated clay coexists in the bulk and in the interface of a blend. Previous studies of polymer blend-clay systems usually show that the clay resides either at the interface [81] or in the bulk [82]. The simultaneous existence of clay layers in the interface and bulk allows two functions to be attributed to the nanoclay particles one as a compatibilizer because the clays are being accumulated at the interface, and the other as a nanofiller that can reinforce the rubber polymer and subsequently improve the mechanical properties of the compound. The firm existence of the exfoliated clay layers and an interconnected chain-like structure at the interface of CR and EPDM (as evident from Fig. 42a, b) surely affects the interfacial energy between CR and EPDM, and these arrangements seem to enhance the compatibility between the two rubbers. 

Barrier polymers are often used in combination with other polymers or substances. The combinations may result in a layered structure either by coexfrnsion, lamination, or coating. The combinations may be blends that are either miscible or immiscible. In each case, die blend seeks to combine the best properties of two or more materials to enhance die value of a final structure. 

Immiscibility of polymers in the melt is a common phenomenon, typically leading to a two-phase random morphology. If the phase separation occurs by a spinodal decomposition process, it is possible to control the kinetics in a manner that leads to multiphase polymeric materials with a variety of co-continuous structures. Common morphologies of polymer blends include droplet, fiber, lamellar (layered) and co-continuous microstructures. The distinguishing feature of co-continuous morphologies is the mutual interpenetration of the two phases and an image analysis technique using TEM has been described for co-continuous evaluation.25... 

The structure of the low bandgap polymeric semiconductor and the dopant dye is plotted in Fig. 5.19. The average thickness of the active layers, determined by AFM measurements, is between 80 and 110 nm. In order to obtain a better understanding of the transport behavior of polymer blends, low temperature studies of cells with pristine MDMO-PPV and MDMO-PPV/PTPTB 1 1 (wt. %) with Au electrodes were carried out. Au has a high work function and should therefore be a good hole injection contact and provide a high barrier for electron injection. The device will therefore be a hole-only device, as described earlier in this chapter [14]. 

The variation of the chemical composition of the substrate (not realized in a continuous tunable fashion) leads to drastic modifications of surface fields exerted by the polymer/substrate (i.e.,II) interface [94,97, 111, 114,119]. The substrate may, for instance, change contact angles with the blend phase from zero to a finite value. As a result the final morphology changes from a layered structure of Fig. 5b into a column structure of Fig. 5c [94,114]. On the other hand our very recent experiment [16] has shown that the surface fields are temperature dependent. Therefore, although it has been shown that surface-induced spinodal decomposition yields coexisting bilayer structure (Fig. 5b) at a singular temperature [114,115], that in principle may not be necessary true for other temperatures. This motivated our comparative studies [107] on coexistence compositions determined with two techniques described above interfacial relaxation and spinodal decomposition. 

Figure 7.10 Tandem solar cell structure for polymer blend solar cells, based on the design demonstrated by Hadipour et al. (2006). In this all-solution-processed device, the top cell consists of a polymer PCBM bulk heterojunction with an absorption maximum of 550 nm and preferentially absorbs short-wavelength light, while the bottom cell is made from a bulk heterojunction of PCBM with a red-absortring polymer and absorbs longer-wavelength light. The composite gold-PEDOT PSS internal layer connects the two cells in...

Chasteen SV, Harter JO, Rumbles G, Scott JC, Nakazawa Y, Jones M, Horhold H-H, Tillman H, Carter SA (2006) Comparison of blended versus layered structures for poly(p-phenylene vinylene)-based polymer photovoltaics. J Appl Phys 99 033709... 

Both in compatible and in incompatible polymer blends, the dynamics of chains at interfaces and the static interfacial structure are of very great theoretical and practical interest [354-356] adhesion of polymer layers to walls, mechanical properties of inhomogeneous blends etc. may affect the application of polymeric materials, and at the same time fundamental questions are involved. This field of research is very active, and a complete coverage of the ongoing research in this area is not at all intended rather we indicate only a few topics that are closely related to problems treated in previous sections of the present review. 

Figures la and Ic show the structure of the phase-separated polymer blend films obtained by dip coating from a PS-COOH/PMMA (30 70 weight ratio) solution. The morphology of the as-deposited films of two different (15 and 30 nm) thicknesses agreed well with their PS content of 30%. Indeed, the minor PS phase was dispersed in the major PMMA phase. However, after the anneahng and extraction of PMMA, the grafted PS layer demonstrated a rather different type of surface structures for the PS-COOH /PMMA films of different...

Photovoltaic performance has been tested for the two polymers with a layered structure of glass/ITO/PEDOT PSS/polymer PCBM blend/LiF/Al. The PCE for POT-co-DOT is quite low, due to high dark current or low shunt resistance and low Vqc- Raising HOMO closer to LUMO of PCBM diminishes the values of Vqc- However, solar cells made from PF-co-DTB exhibits higher PCE with a high value of Vqc up to 0.76 V. The best obtained performance is from the blend with the wt. ratio of PE-co-DTB to PCBM being 1 4. The /sc is 4.31 mA/cm, V oc is 0.76 V, FF is 48.6%, and PCE is 1.6%. Annealing at 110°C increased the Vqc from 0.76 to 0.79 V. However, the /sc was decreased with no enhancement on the overall PCE. 

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