Crystal chain-folding principle

A path with a lower positive free-enthalpy barrier to crystallization than to the extended-chain crystals involves ufolded-chain macroconformation and leads to the chain-folding principle. Crystallization occurs first with shorter, chain-folded segments of the molecules, as shown schematically at B of Fig. 5.42 (A B). From... 

Fig. 3.1. Illustration to the chain-folding principle of pol5mier crystallization. The metastable chain-folding is a favorite pathway in the kinetic selections of polymer crystal nucleation...

Chain Folding Principle and Single Crystal Sectorization. How can... 

Figure 3. Schematic representation of a polymer single crystal, illustrating the principle of chain folding (13)...

A core assumption when discussing the crystallization kinetics of polymers is that the theories must consider the effects of chain folding. In Chapter 2 the principles of crystallization were outlined and the importance of the differences... 

A key problem is to theoretically establish the appropriate primary and secondary nucleation processes that are operative. This includes defining the geometry of the rate controlling nucleus, i.e. whether it is two-dimensional or three-dimensional. It should be recalled that the experimental results can fit either model. Of crucial importance is the chain conformation within the nucleus. Conventional type data are not discriminatory. They can be fitted by either a bundle type nucleus, or one in which the chains are regularly folded with adjacent re-entry. At present, either type of nucleus is consistent with the experimental results. It is important that it be recognized that it is not necessary for there to be a one-to-one relation between the nucleus structure and the mature crystallite that evolves. It is not necessary to assume a regularly folded chain nucleus in order for a mature lamellar crystallite to evolve. It is important that the crucial role of nucleation in polymer crystallization be taken from the realm of assumption and placed on a first principled theoretical base. Similar concerns can be expressed with respect to the transport term. 

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