Computer calculations of heterogeneous equilibria in the system C-O-H-N-Si-Ar

crystal height increased rapidly in the first 5 min of crystallization time, then proceeded more slowly. Approximately 40% of the height attained in 10rain was reached in l min; 75% of this height was reached in 5 min. The width of the lamellae did not vary with crystallization time. These results are in accordance with previous data obtained for epitaxial crystallization of polyethylene [1], and seem to be generally characteristic of solution epitaxial crystallization of polymers. Selected-area electron diffraction clearly shows the presence of two chain orientations 90 ~ apart (Figs. lb and 2b). All diffraction patterns obtained indexed as form I, as shown in Fig. 3. All reflections in Fig. 2b index as Okl, indicating that the bc plane and thus the chain axis are both parallel to the substrate surface. "Extra" reflections, which do not index as 0 k l were occasionally observed (e.g. in Fig. lb), and probably result from "toppled over" epitaxial crystals which are still more or less oriented with respect to the substrate directions. Patterns containing these "extra" reflections in addition to the usual Okl reflections were occasionally observed on KC1 also. Similar electron diffraction patterns from thinner films (1 and 5 rain crystallization times) showed that the same crystal structure (form I) persisted to within 30 A of the substrate surface. Acknowledgements The authors appreciate the Financial support of the National Science Foundation, grant number DMR 76-81768. We also appreciate helpful discussions with Scott Rickert concerning the initial experiments.