Phase poly blend

Blends with good mechanical properties can be made from DMPPO and polymers with which DMPPO is incompatible if an appropriate additive, compatibilizing agent, or treatment is used to increase the dispersion of the two phases. Such blends include mixtures of DMPPO with nylon, polycarbonate, polyester, ABS, and poly(phenylene sulfide). 

Phase-separated blends consisting of poly(4-phenylene sulfide) and poly(ethylene-co-propylene) or poly(cthylene-co-l-butylene) were prepared by Matsuoka et al. (3) and are discussed. 

Conducting polymer blends based upon polyaniline (PANI) are a new class of materials in which the percolation threshold for the onset of electrical conductivity can be reduced to volume fractions well below that required for classical percolation (16% by volume for globular conducting objects dispersed in an insulating matrix in three dimensions) [277,278], The origin of this remarkably low threshold for the onset of electrical conductivity is the self-assembled network morphology of the PANI poly blends, which forms during the course of liquid-liquid phase separation [61],... 

The effect of dissolved CO2 on the miscibility of polymer blends and on phase transitions of block copolymers has been measured with spectroscopy and scattering (40). The shifts in phase diagrams with CO2 pressure can be pronounced. Polymer blends may be trapped kinetically in metastable states before they have time to phase separate. Metastable polymer blends of polycarbonate (PC) and poly(styrene-cn-acrylonitiile) were formed with liquid and supercritical fluid CO2 in the PCA process, without the need for a surfactant. Because of the rapid mass transfer between the CO2 phase and the solution phase, the blends were trapped in a metastable state before they... 

Poly thiophene, PTP, and polypyrrole, PPR, blends with PS and PC were prepared by Wang et al. [1990] by thiophene or pyrrole electrochemical polymerization using electrodes coated with PS or PC hlms. The thiophene or pyrrole diffuses into the fihn and polymerizes in-situ in the film. Threshold conductivity occurs at 18 wt% for both conducting polymers in PS. Lower levels exist for PTP (12 wt%) and PPR (7 wt%) in PC. Miscibility of PPR/PC is attributed to the lower threshold limit as phase separated blends would be expected to have higher values. Previous studies with polyacetylene/PS blends reported threshold conductivity at 16 wt% polyacetylene [Aldissi and Bishop, 1985]. 

At the early development of polymer solar cells, a planar p-n junction structure represented the mainstream in mimicking conventional silicon-based solar cells. However, the obtained devices demonstrated poor photovoltaic performances due to the long distance between the exciton and junction interface and insufficient light absorption due to the thin light absorber. It was not until 1995 that the dilemma was overcome with the discovery of a novel bulk heterojunction in which donor and acceptor form interpenetrated phases. Poly[2-methoxy-5-(2 -ethylhexyloxy)-p-phenylene vinylene] was blended with Ceo or its derivatives to form the bulk heterojunction. A much improved power conversion efficiency of 2.9% was thus achieved under the illumination of 20 mW/cm. (Yu et al., 1995). The emergence of the donor/acceptor bulk-heterojunction structure had boosted the photovoltaic performances of polymer solar cells. Currently, a maximal power conversion efficiency of 10.6% had been reported on the basis of synthesizing appropriate polymer materials and designing a tandem structure (You et al., 2013). The detailed discussions are provided in Chapter 5. 

Proton spin-temperature equilibration between the hard- and soft-segment-rich domains of the polyurethane elastomer on the order of 10-100 ms might be considered fast relative to a macroscopically phase-separated blend [26] or copolymer, but slow relative to a strongly interacting mixture [25]. This is reasonable for a microphase-separated material whose solid state morphology has been the subject of considerable theoretical and experimental research. Under fortuitous circumstances, intimate (near-neighbor) contact between dissimilar molecules in a mixture can be studied via direct measurement of proton spin diffusion in a two-dimensional application of the 1H-CRAM PS experiment (Combined Rotation And Multiple Pulse Spectroscopy). Belfiore et al. [17,25,31] have detected intermolecular dipolar communication in a hydrogen-bonded cocrystallized solid solution of poly(ethylene oxide) and resorcinol on the f00-/xs time scale, whereas Ernst and coworkers [26] report the absence of proton spin diffusion on the 100-ms time scale for an immiscible blend of polystyrene and poly(vinyl methyl ether), cast from chloroform. 

Takayanagi and co-workers transformed the spring and dashpot relaxation models (Section 1.5.6) to plastic and rubber elements in an effort to better explain the mechanical behavior of poly blends (Takayanagi et ai, 1963). Some simple combinations of the Takayanagi models are shown in Figure 2.11. The plastic phase is denoted by P and the rubber phase by R, while the quantities X and (p are functions of the volume fractions of parallel and series elements, respectively. 

The polymer/solvent blend is extruded or cast at elevated temperatures. As the temperature approaches an ambient temperature, a polymer-rich phase separates from the solvent. The solvent is subsequently removed from the phase separated blend by leaching. Also, polymers, such as poly(sulfone), are suitable for leaching [57]. 

The binary blends of polycarbonate with poly(butylene terephthalate) (PBT/PC) or poly(ethylene terephthalate) (PET/PC) are now known to be essentially phase-separated blend systems exhibiting two glass transition temperatures in each case, one for the polycarbonate-rich phase and another for the polyester-rich phase (Murff et al. 1984 Huang and Wang 1986 Wahrmund et al. 1978). The evaluation of the amorphous phase miscibility in these blends was often complicated by the potential of a transesterification reaction between the two polymers during the melt blending, which may in principle lead to a block copolymer and eventually to... 

Phase separated blends of poly(vinyl alcohol) [PVA] and poly(vinyl acetate) [PVAc] were studied and evidence of intra-molecular and inter-molecular specific interactions was reported to depend on blend composition [ 59 ]. Blends with high PVA content were reported to have large intra-molecular specific interactions while blends with a high PVAc content showed inter-molecular interactions. The... 

Poly(e-caprolactone), with chemical structure 1, is unusual in that it has been reported to be miscible with several other polymers and is also considered to produce compatible, although phase-separated, blends with another group of polymers. In this context, miscible implies mutual solubility of polymers on a scale approaching molecular, and compatible implies the existence of useful combinations of properties for possible practical uses. 

Fig. 1. A molecular model of a condensed phase polymer blend. The example shown is used to study a mixture containing atactic polystyrene 40-mer (2 chains) and atactic poly(methyl methacrylate) 40-mer (2 chains). Figure la shows the cell with the molecules configured as they are in space the parts of the molecules lying outside the cell occupy adjacent cells in the periodic structure. To convey the space filling nature of the construction, Figure lb shows the same molecules packed in the cell. The model system was constructed using the Amorphous Cell module in the Materials Studio software package distributed by Accelrys (103). The amorphous cell system was constructed at a density of 1.12 g/cm at 300 K and the subsequent 80 ps of NPT dynamics at the same temperature and zero pressure equilibrated the system to a density of 1.057 g/cm .

Eaton and co-workers reported on force-mapping a phase-separated blend (218,243) of PMMA and poly(dodecyl methacrylate) (PDDMA). Using immodified silicon nitride probes, the PDDMA-rich domains, which exhibited higher adhesion, could be differentiated from the PMMA-rich domains. 

A similarly clear and predictable contrast has been reported by Feldman et al. for a phase separated blend of polystyrene (PS) and poly(methyl methacrylate) (PMMA) imaged with gold-coated and silicon oxide coated tips in perfluorodecahn (Fig. 18) [125]. Here the contrast is dominated by the dispersive van der Waals interactions, which have been selectively amplified by... 

Eaton et al. used FV mapping for imaging of a phase-separated blend of PMMA and poly(dodecyl methacrylate) (PDDMA) [190,191). Unmodified silicon nitride cantilevers were used in ambient conditions in air or in water using a liquid cell. Differences in pull-off forces correlated with features in topography, making it possible to distinguish between the PDDMA-rich... 

Double percolation phenomenon has been reported previously for two phase polymer blends loaded with carbon black (P-77). Very low percolation thresholds were reported when conductive carbon black was preferentially localized at the phase boundary (P). Figure 9 shows the volume resistivity of phase-separated nylon/poly-... 

Fig. 7.33. Debye-Bueche plots for two phase-separated blends of polystyrene and poly butadiene. (Reproduced with permission from [66]. Copyright 1993 American Chemical Society.)...

Sales, (.A Patricio, P.S.O., Machado, J.C., Silva, G.G., and Windmdller, D. (2008) Systematic investigation of the effects of temperature and pressure on gas transport through polyurethane/poly (methylmethacrylate) phase-separated blends. J. Membr. Sci., 310, 129-140. 

Figure 19.8 Fluorescence SNOM images of a phase-separated blend of polystyrene and poly (9,9-dioctylfluorene). (a-c) Surface topography, transmittance, and fluorescence images, respectively (d and e) Mapping of the amplitude and lifetime of the fluorescence decay...

The compatibility of the individual components of polymeric blends can lead to significant effects on the degradation of the polyhydroxyalkanoate component. This has been illustrated in a study on blends of PHB homopolymer with polycaprolactone, poly( 1,4-butylene adipate) and polyvinyl acetate [57]. Blends over wide composition ranges were incubated as thin films in aqueous solutions of an extracellular PHB depolymerase at 37 °C. The relative degradation rates were related to the miscibility and microstructure of the polymeric phases. For blends where PHB formed the continuous phase, degradation was relatively fast. 

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