14
views
0
recommends
+1 Recommend
0 collections
    0
    shares
      • Record: found
      • Abstract: not found
      • Article: not found

      Polymer crystals

      Reports on Progress in Physics
      IOP Publishing

      Read this article at

      ScienceOpenPublisher
      Bookmark
          There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.

          Related collections

          Most cited references159

          • Record: found
          • Abstract: not found
          • Article: not found

          I. Liquid crystals. On the theory of liquid crystals

          F. Frank (1958)
            Bookmark
            • Record: found
            • Abstract: found
            • Article: found
            Is Open Access

            Melting Process and the Equilibrium Melting Temperature of Polychlorotrifluoroethylene

            A new method of estimating the equilibrium melting temperature, T m , of a polymer is described, and applied to polychlorotrifluoroethylene (PCTFE). Experimentally determined values of the so-called observed melting point, T m ′ ( obs ) , are plotted as a function of the isothermal crystallization temperature, T x . When freed of secondary effects, such as recrystallization, the data fit a straight line of positive slope on a T m ′ ( obs ) versus T x plot, T x being the abscissa. This line is then extrapolated to its intersection with the line T m ′ ( obs ) = T x . The temperature at this intersection is T m . This intersection is at 224 °C for PCTFE, and T m is quoted as 224 ± 1 °C. (The highest melting point actually attained for a specimen was 218.2 °C.) The value of T m estimated using the extrapolation procedure is compared with that estimated using the customary method of slow stepwise warming. A theoretical justification is given for making the type of plot mentioned above. The most important assumption used in the theory is that one of the dimensions of the growing crystal retains a value rather close to that of the appropriate growth nucleus during an isothermal crystallization, the other two dimensions being large in comparison. Combination of this with the fact that the relevant dimension of the growth nucleus will vary as the reciprocal of the degree of supercooling leads to the prediction of melting points that increase linearly with crystallization temperature. The assumption that one of the dimensions of the crystal retains a value fairly close to that of a growth nucleus can readily be justified on the basis of polymer crystal growth with chain folds. Its justification in the case of the customary bundlelike mode of crystallization is less clear. It is demonstrated experimentally that even the largest detectible crystals in PCTFE are only about 70 percent thicker than a primary nucleus, when secondary effects are minimized. The application of the theory to systems other than PCTFE is discussed briefly, and some preliminary measurements on polyethylene mentioned. Some points relating to the shape of the melting curves of highly crystalline polymers are also brought out.
              Bookmark
              • Record: found
              • Abstract: not found
              • Article: not found

              A note on single crystals in polymers: Evidence for a folded chain configuration

              A. Keller (1957)
                Bookmark

                Author and article information

                Journal
                Reports on Progress in Physics
                Rep. Prog. Phys.
                IOP Publishing
                00344885
                July 1 1968
                August 5 2002
                : 31
                : 2
                : 623-704
                Article
                10.1088/0034-4885/31/2/304
                884cc009-a0f5-40f4-bc9b-80c46cdad3f8
                © 2002
                History

                Comments

                Comment on this article