Crystallization of polymers

The proof that these expressions are equivalent to Eq. (1.35) under suitable conditions is found in statistics textbooks. We shall have occasion to use the Poisson approximation to the binomial in discussing crystallization of polymers in Chap. 4, and the distribution of molecular weights of certain polymers in Chap. 6. The normal distribution is the familiar bell-shaped distribution that is known in academic circles as the curve. We shall use it in discussing diffusion in Chap. 9. 

The electron micrographs of Fig. 4.11 are more than mere examples of electron microscopy technique. They are the first occasion we have had to actually look at single crystals of polymers. Although there is a great deal to be learned from studies of single crystals by electron microscopy, we shall limit ourselves to just a few observations ... 

Mandelkern, L., Crystallization of Polymers, McGraw-Hill, New York, 1964. 

The crystallization of polymer melts at high pressure (several thousand of atmospheres), just as the crystallization in flowing melts and stirred solutions, leads to the formation of ECC in which the molecules assume almost completely extended conformations. This suprising feet (the crystallization was carried out at hydrostatic compression) was first extablished experimentally by Wunderlich30 and then confirmed by other authors31 33. However, diverse opinions exist about the mechanism of ECC formation. 

Many papers deal with the crystallization of polymer melts and solutions under the conditions of molecular orientation achieved by the methods described above. Various physical methods have been used in these investigations electron microscopy, X-ray diffraction, birefringence, differential scanning calorimetry, etc. As a result, the properties of these systems have been described in detail and definite conclusions concerning their structure have been drawn (e.g.4 13 19,39,52)). 

Mandelkern, L. Crystallization of polymers, New York McGraw-Hill 1964... 

On the other hand, bulky crosslinks as developed during the crystallization of polymer melts (no solvent) lower the relaxation exponent. The lowest values of n which we have been able to generate so far occurred with physical gels in which the crosslinks consisted of large crystalline regions [68, 69]. 

L. Mandelkern, The structure of polymers crystallized in the bulk. In M. Dosiere (Ed.), Crystallization of Polymers, NATO ASI Series, Kluwer Academic Publishers, The Netherlands, 1995, p. 25. 

Mandelkern L (2002) Crystallization of polymers,vol 1, 2nd edn. Equilibrium concepts. Cambridge University Press, Cambridge, p 42... 

In the world of molecular simulation, it would be more conventional to consider that the present model is a coarse grained model of real polymers, where the real time-scale is much longer than that of the present MD simulation time-scale. However, we did not intend to make a coarse grained model. The crystallization of polymers was shown to be rather universal. Various kinds of polymers, either fast crystallizing or slow crystallizing, were known to follow the same scheme with respect to the molecular mechanism of crystallization. So we studied this simple model expecting that the present model would also follow the same crystallization scheme and show the general molecular mechanisms of polymer crystallization. 

Kaji K, Nishida K, Kanaya T, Matsuba G, Konishi T, Imai M (2005) Spinodal crystallization of polymers Crystallization from the unstable melt. Adv Polym Sci (in this volume)... 

Spinodal Crystallization of Polymers Crystallization from the Unstable Melt... 

Mandelkern, L. "Crystallization of Polymers," McGraw-Hill Book Co., New York, 1963, Ch. 4. 

Kaji, K., Nishida, K., Kanaya, T., Matsuba, G., Konishi, T. and Imai, M. Spinodal Crystallization of Polymers Crystallization from the Unstable Melt. Vol. 191, pp. 187-240. 

Chiral Crystallization of Polymers with Helical Chain Conformations References... 

Crystallization of polymers in chiral crystals, even in the case of achiral polymers, is quite frequent and strictly related to the occurrence of helical conformations of the chains. The crystallizable polymer consists of a regular sequence of a chemical repeating unit which can be chiral if it presents an asymmetric center or achiral. On the contrary, helical conformations assumed by the polymer chains in the crystalline state are intrinsically chiral, even though the chemical repeat is achiral. Three possible cases can be distinguished ... 

However, defects and distortions are present in crystals of polymers and they play an important role in the Crystal Structures of polymers, X-ray diffraction data provides a lot of information... 

Among the phenomena mentioned above important features of spherulitic crystallization of polymers are ... 

Magill, J. H Rates of crystallization of polymers In Polymer Handbook, 4th Edn, Wiley-Interscience, New York, 1999, VI373-VI375. 

To facilitate and accelerate folding and crystallization of polymer chains, internal plasticizers are often added to PET to serve as crystallation promoters. Such additives are usually based on poly(ether ester)s. These plasticizers are liquids that are typically added at levels of 2-4 wt%. They reduce cycle time in injection moulding operations by increasing the rate of crystalline formation. They also plasticize the resin and act as processing aids by virtue of their lubricating action in the melt. On a molecular level, these plasticizers reduce the intermolecular... 

In many cases it is possible to convert a single crystal of monomer completely to a single crystal of polymer in a homogeneous process, the perfection of the product crystal being comparable to that of the parent. The synthesis in this way of polymer crystals over IS cm long and 10 g in weight has been described (193). 

---