Morphological heterogeneity

Fig. 67 Schematic of phase behaviour for blend of novolac epoxy resin with nearly symmetric poly(methyl acrylate-co-glycidylmelhacrylate)-0-polyisoprene. Ordered L can be swollen with up to about 30% of resin before macroscopic phase separation occurs, producing heterogeneous morphologies containing various amounts of L, C, worm-like micelles and pristine epoxy. At lower concentrations, disordered worm-like micelles transform into vesicles in dilute limit. According to [201]. Copyright 2003 Wiley...

Shao, Z., Hu, X. W., Frische, S., and Vollrath, F. (1999). Heterogeneous morphology of Nephila edulis spider silk and its significance for mechanical properties. Polymer 40, 4709-4711. 

The effective conductivity of the membrane depends on its random heterogeneous morphology—namely, the size distribution and connectivity of fhe proton-bearing aqueous pafhways. On fhe basis of the cluster network model, a random network model of microporous PEMs was developed in Eikerling ef al. If included effecfs of varying connectivity of the pore network and of swelling of pores upon water uptake. The model was applied to exploring the dependence of membrane conductivity on water content and... 

Calculations from SCF theory of the mixed layer structure, and of the interaction potential for a pair of mixed layers as a function of interlayer separation, suggest that the mixed layer has a heterogeneous morphology perpendicular to die interface (Parkinson et al., 2005). This localized segregation arises from the excluded volume interaction between spaced-out casein chains and the dense brush-like layer that was invoked in the simple SCF model to represent the p-lactoglobulin adsorbed monolayer. 

Dynamic Mechanical Spectroscopy. As pointed out above, the heterogeneous morphology, observed in the present study, implies network flaws (weak connections between the primary and secondary microgels). However, the low cyclic strains applied in dynamic mechanical tests detect only the effect of the basic network structure and not the network flaws. Therefore, as observed experimentally (, ) dynamic mechanical spectroscopy should not indicate heterogeneity in the samples. 

Perineuriomas are distinctive PNSTs that are uncommon in the skin. They are heterogeneous morphologically some demonstrate a constituency of bland spindle cells that form vaguely concentric profiles in partially myxoid stroma, whereas others may resemble... 

From the above work our data suggests that the PIR values calculated for different chemistries do correspond to the natural weatherability of the polymer systems. This would have to be confirmed with more extensive studies with chemistries that have UV durability performance closer together. However, in the case of polymeric blends the PIR values show poor correlation with the known outdoor performance and this is always likely to be the case where the blends produce complex heterogeneous morphologies. 

The dominant and most reported component of root plaques is various oxidized compounds of iron. Microscopic observations of root plaques show a highly heterogenous morphology composed mostly of an amorphous material dispersed throughout nodules (50-300 nm in diameter), needles (50-100 nm in length), and filaments with variable lengths. This iron plaque formation on roots results from diffusion of Fe + toward the root zone in response to concentration gradients at the interface (similar to those observed at the soil-floodwater interface). The oxidized rhizosphere functions as a sink for Fe + and other reduced substances. 

Whereas incompatible partners in polyblends usually result in heterogeneous morphologies (e.g., styrene-butadiene SB), and often in highly resilient plastics, compatible partners result in plastics with moderate property profiles in accordance with the mixing percentages (e.g., PC/PBT). 

Poly(3-methyl thlophene)/sawdust was fabricated by in situ chemical oxidation with FeClj to remove methylene blue. The adsorption capacity can reach 191 mg/g, which was seven times higher than sawdust [82]. The increased surface area may be ascribed to the high adsorption capacity, as indicated from the change of surface morphology in Figme 11.17. Sawdust had a smooth surface and layer structure, while poly(3-methyl thiophene)/saw-dust composite had heterogeneous morphology with porous surface area. 

FIGURE 1 Crystalline regions separated by disordered regions eonstitutes the heterogeneous morphology in eompositefibere. 

The heterogeneous morphology and microphase separation process of block PLCs are closely related to the processing history and the molecular structures. For PET/PHB PLCs, PET-rich and PHB-rich phases are detected by SEM observation of etched samples [41,42]. When the PHB content is lower than 50 mol%, the PET-rich phase is continuous, and vice versa when the PHB content is higher than 60 mol%. The size of the PET-rich phase was found to be 10-20 pm with 40mol% PHB and 3-6 pm with 80 mol% PHB. In addition, the phase dimension will be influenced by the thermal and mechanical history. Joseph et al. have reported [41,42] that in an injection molded plaque of PET/PHB PLCs, PHB was richer in the skin while PET was richer in the core. However, there is controversy concerning this observation [3]. 

Polymer alloys often exhibit microphase separation. The heterogeneous morphologies are determined not only by the composition of the system but by the processing conditions as well. The microstructure influences the properties of polymeric alloys [40]. For example, the addition of a second phase of dispersed rubbery particles into the polymer matrix results in a great enhancement of toughness [41]. 

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