Stability of the sectored morphology of polymer crystallites

Alageshan, Jaya Kumar; Hatwalne, Yashodhan; Muthukumar, Murugappan

doi:10.1103/physreve.94.032506

Cited by 2 publications

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References 33 publications

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“…Nucleation and crystal growth, first intensively investigated in metals and for small crystallizable molecules, have attracted considerable interest in polymer science. − Polymer crystallization is a first-order transition, which requires to transform a material consisting of random coiled polymeric chains into a nearly perfectly ordered state. − In contrast to the melting behavior of crystals of small molecules, long chain polymer crystals may possess a strong melt memory of the previously molten crystalline structures, having for example a dramatic influence on the dynamics of subsequent crystallization processes and the resulting crystal morphology. − For most semicrystalline polymers, crystallization usually initiated either by homogeneous nucleation or via heterogeneous nucleation. − All memory of previous crystalline structures is expected to relax and disappear if these crystals are melted above the equilibrium melting point for a sufficiently long time. , Melting or annealing a polymer crystal below the equilibrium melting point will allow for a number of surviving “small crystals” or “bundles of partially ordered chain segments”. This number depends drastically on the temperature used for melting and annealing.…”

Section: Introductionmentioning

confidence: 99%

Systematic Control of Self-Seeding Crystallization Patterns of Poly(ethylene oxide) in Thin Films

et al. 2018

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Using optical microscopy and atomic force microscopy, we studied systematically crystallization patterns in thin films of a low molecular weight poly(ethylene oxide) (PEO) resulting from a kinetically controlled self-seeding approach. In particular, the influence of seeding temperature (T s) and heating rate (V h) on the various resulting crystallization patterns was investigated. Crystallization at 49 °C resulted in dendritic PEO crystals consisting of almost exclusively twice-folded chains. Upon heating these crystals, we observed crystal thickening due to a reduction in the average number of chain folds. On the basis of the detected morphology, we deduced that the density of seeded PEO crystals decreased when increasing T s from 54 to 57 °C. At the highest V h (i.e., 100 °C/min), only a few well-separated faceted single crystals of PEO were grown from individual seeds. In contrast to such random distribution of crystals, because of a faster reduction of chain folds at the edges of PEO lamellae, an almost continuous sequence of seeded crystals was formed at the periphery of the original crystals at significantly lower V h (i.e., 10 °C/min). Interestingly, reflecting the different metastable states within the initial crystal resulting from seeding at T s = 54 °C, the seeding probability for crystals at the diagonals was higher than for the major side branches. In addition, we estimated activation energies (213–376 kJ/mol) for thickening of PEO lamellar crystal from an Arrhenius-type behavior of the lateral spreading rates as a function of V h. Our findings suggest that the interplay between thickening and melting of metastable states within the initial crystals is considered as responsible for the resulting nucleation density and crystal morphology induced by self-seeding.

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