Amorphous polymer structure, generation

Amino-5-nitropyrimidine, cocrystallization, 455 Amorphous polymers, criteria for use in second harmonic generation, 250-251 Amphiphilic molecules polar Z-type Langmuir-Blodgett films, formation, 473-479 structures, transfer behavior, and contact angles, 474,476-477r Anharmonic oscillator models, nonlinear optical effect-microstructure relationship, 361... 

Here, we are concerned with amorphous polymers. Hence, amorphous structures have to be generated, by some means, that are low in energy, have an appropriate distribution of torsional angles, a physically acceptable distribution of unoccupied volume, and so on. In order to avoid surface effects, it is customary to employ periodic continuation conditions The primary simulation box is surrounded by periodic images of itself and when an atom exits the box through one face of the box it reenters it through the opposite face. In order to keep the effect of chain ends minimal, we usually employ a single polymer chain per simulation box. For the chain the periodic continuation conditions imply, that it is folded into the box (if it leaves the box on one face, it reenters it... 

For numerical results, it must be emphasized that the WLF equation is good for the range Tg to Tg + 100. In equations (8.48) and (8.49), T must be larger than Tg or Tq. Its power lies in its generality no particular chemical structure is assumed other than a linear amorphous polymer above Tg. For a generation of polymer scientists and rheologists, the WLF equation has provided a mainstay both in utility and theory. 

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