Minority phase volume fraction, polymer

Figure 41. The percolation threshold determination for polymer blends undergoing the phase separation. Minority phase volume fraction, fm, is plotted versus the Euler characteristic density for several simulation runs at different quench conditions, /meq- = 0.225,..., 0.5. The bicontinuous morphology (%Euier < 0) has not been observed for fm < 0.29, nor has the droplet morphology (/(Euler > 0) been observed for/m > 0.31. This observation suggests that the percolation occurs at fm = 0.3 0.01.

Figure 6.3 shows crystal-shaped platinum deposits juxtaposed to the computer simulations. Note that the computer simulation were calculated for a minority phase volume fraction of 12%, while depending on the assumed polymer densities, the copolymer PLA volume fraction lies between 36 and 39 %. As discussed previously, for these high volume fractions the computer model predicts that the < 110> directions form vertices and tlius, increase the number of faces surrounding the < 100 > vertices by a factor of two to a total of 8 facets. 

Fig. 51 Phase diagram for PS-PI diblock copolymer (Mn = 33 kg/mol, 31vol% PS) as function of temperature, T, and polymer volume fraction, cp, for solutions in dioctyl ph-thalate (DOP), di-n-butyl phthalate (DBP), diethyl phthalate (DEP) and M-tetradecane (C14). ( ) ODT (o) OOT ( ) dilute solution critical micelle temperature, cmt. Subscript 1 identifies phase as normal (PS chains reside in minor domains) subscript 2 indicates inverted phases (PS chains located in major domains). Phase boundaries are drawn as guide to eye, except for DOP in which OOT and ODT phase boundaries (solid lines) show previously determined scaling of PS-PI interaction parameter (xodt

In block copolymers, the different monomers are arranged in blocks, which are usually incompatible and show a nanophase separation. Depending on the amount (volume fraction) of the different components, typical morphological types will appear spheres, cylinders of the minor component in the matrix of the major component, lamellae, and gyroids see Fig. 1.10 and also Fig. 3.2. The polymer chains are well phase-separated by a narrow interphase a few nanometers thick. The appearance of phase separation in the block copolymers is also visible in the existence of two separate glass transition temperatures corresponding to two homopolymers. 

Microphase structure and growth mechanism of polymer blends in the late stage of phase separation are dominantly controlled by the volume fraction v of minority phase. At the critical condition v = 0.5 the co-continuous structure is formed, while at the off-critical condition v 0.5 the droplet structure has to appear. Here, more explicit relation of the morphological structure to the fractional phase volume will be investigated using System B. In particular, our attention has been focused on morphological structure in crossover region from the critical to the off-critical. 

More dramatically, the less viscous polymer tends to form the continuous matrix phase and the more viscous, undeformable dispersed domains remain large and discrete. Such effects have been observed even when the fluid polymer was only a minor fraction of the total volume, such as 25% EVA -I- 75% polyvinyl chloride [24]. 

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