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Dilution wave and negative-order crystallization kinetics of chain molecules
G Ungar1, P K Mandal, P G Higgs
1Department of Engineering Materials, University of Sheffield, Sheffield S1 3JD, United Kingdom. g.ungar@sheffield.ac.uk
Abstract:
We show that the crystal growth rate of a very long-chain n-alkane C C(198)H(398) from solution can decrease with increasing supersaturation and follow strongly negative order kinetics. The experimental behavior can be well represented by a theoretical model which allows the molecule to attach and detach as either extended or folded in two. The obstruction of extended-chain growth by unstable folded depositions increases disproportionately with increasing concentration. As a consequence of this abnormal kinetics, a "dilution wave" can propagate and trigger a folded-to-extended-chain transformation on its way.