Folded crystals

Note Fibrous crystals may comprise essentially extended chains parallel to the fibre axis however, macroscopic polymer fibres containing chain-folded crystals are also known. 

Assembly of a TV Swarm intelligence City growth Protein folding Crystallization... 

The molecular processes that take place during polymer crystallization can be investigated from different viewpoints. A global approach determines the shape and conformation of chains in the polymer melt, and infers processes that lead to the lamellar chain folded crystal. Alternatively, analysis of the final crystal structure may help us to work backwards and gain insights into processes that take place in the last stages of crystal build-up. It is clear, however, that the two approaches should lead to the same conclusions, since the crystallization processes that occur should not, and certainly do not, depend on the viewpoint adopted for their analysis. 

Fig. 14 Binary phase diagram for C246H494 in octacosane. The top curve shows the equilibrium liquidus for extended-chain crystals, and the bottom line the metastable liquidus for once-folded crystals. Experimental dissolution temperatures are fitted to the Flory-Huggins equation with / = 0.15 (solid lines). Vertical dotted lines (a) and (b) indicate the concentrations at which the growth rates were determined as a function of Tc in [29]. Horizontal dotted lines indicate the temperatures at which the rates were determined in [45] as a function of concentration. G(c) at Tc = 106.3 °C, measured along line (c), is shown in Fig. 12. The shading indicates schematically the crystal growth rate (black = fast), and the dashed line the position of the growth rate minimum...

There is experimental evidence in favour of two-dimensional secondary nucleation of chain-folded crystals. 

Fig. 11 The variation in the a(+) and b(D) cell parameters for C294H590 twice-folded crystals. The left-hand axis refers to the a cell parameter and the right hand axis to the b cell parameter...

Hexagonal Two values One principal direction aligned with three-fold crystal axis two principal values equal in magnitude... 

Monoclinic Three values plus one angle One principal direction aligned with two-fold crystal axis no restrictions on values... 

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