Material Properties and Particle Dynamics

We examined two bulk-immiscible polymers (polystyrene and polyvinyl chloride) that are soluble in THF [29]. We have not characterized evaporation rates of pure THF droplets, but estimate on the basis of vapor pressure differences relative to water, that evaporation is roughly a factor of five times more rapid (for a given droplet size). To provide some kind of relative time scale, a water droplet with an initial diameter of 10 pm will evaporate to =1 pm diameter in about 5 ms in a dry Argon atmosphere [160]. 

The data shown in Fig. 13 also illustrates the tunable nature of a material property in PVC/PS composite particles - namely the dielectric constant manifested in the refractive index. Both Re(n) and Im(n) for the polymer-blend microparticles are intermediate between the values determined for pure singlecomponent particles (PVC Re(n) =1.4780, Im(n) =10 PS Re(n) =1.5908, Im(n) =2x10 ) and can be controlled by adjusting the weight fractions of polymers. Interestingly, the measured refractive index for composite particles is very close to estimates obtained from a simple mass-weighted average of the two spe- 

In order to develop some insight into the structure, and properties of polymer blend particles, we have also investigated this problem using molecular dynamics simulation tools. Using classical molecular dynamics techniques (discussed in detail in the following chapter), we have examined polymer nanoparticles of 

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