Griffin, L. Frank, F. Dawson and Vand, Nature , , Forty, A. Williams, R.
DoITPoMS - TLP Library Crystallinity in polymers
Download references. Reprints and Permissions. Physics Reports Progress in Polymer Science Polymer Crystallization Macromolecules By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate. Advanced search. Skip to main content. Subscribe Search My Account Login. Abstract THE role of dislocations in crystal growth has been discussed by N. Rent or Buy article Get time limited or full article access on ReadCube.
We carried out simulations of isothermal crystallization by instantaneous cooling systems to target quench temperatures, denoted by Tq. The system volume decreases with D DOI: Here the values are weight-averaged over the whole systems. E DOI: Under supercooling, entanglements are arrested by the high density of nucleation in accord with a growth rate that is faster than the ratio between gyration radius and the disentanglement time. If we consider entanglements like physical cross-links, the situation is similar to crystallization in a rubbery material as discussed by Flory.
In Figure 3d, we show normalized probabilities p ns for the number of folding stems per crystallized bundle, ns. We calculated ns by analyzing the crystalline structure via the algorithm described in previous work,50 which tracks the birth of a crystallized bundle. This result indicates that the chain folds are preferred in slower crystal growth, in agreement with results for the growth of a single crystal from melt by self-seeding.
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To be more quantitative, the former decreases by factor 1. These results show a decoupling of stem length and growth rate and indicate that the stem length lamellar thickness does not result exclusively from a competition between thermal dynamics and growth kinetics, as described by the classic LH theory. A direct relation between the entanglement length in the amorphous polymer melt at the onset of crystallization and the resulting stem length in the crystalline phase had been revealed earlier. Thus, it provides an ideal test of the previously found topological principle for thickness selection.
Interestingly, the folding factor f can be related with the one recently observed in NMR experiments by Miyoshi et al.
Figure 6. The color bar is shown at the right top corner. One can also see that the crystallization within the pure melt proceeds form a larger amount of nucleation sites and is thus apparently more homogeneous.
In the present condensed polymer solutions, the crystalline regions are temperature as the stem length. The initial entanglements are thus almost preserved. One can see that the growth rate decreases with G DOI: Thermodynamic driving force in nucleation and growth processes. Extension of the theory of growth of chain-folded polymer crystals to large undercoolings. Colloquium: Laws conrolling crystallization and melting in bulk polymers. Rate-theory model of polymer crystallization. New explanation for chain folding in polymers. Spinodal-assisted crystallization in polymer melts.
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Polymer Crystallization Research in China
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Molecular mechanisms of polymer crystallization from solution. Molecular dynamics modeling of polymer crystallization: from simple polymers to helical ones. Molecular dynamics simulations of steady-state crystal growth and homogeneous nucleation in polyethylene-like polymer. Such bridging chains could stabilize the network of crystalline regions, providing a direct analogy to the elastic LJ model. In particular, we have studied the entanglement properties of these systems using two variants PPA and Z1 to calculate the primitive path and the entanglement length.
The equilibrium weight-averaged entanglement length in the concentrated solution above the point of crystallization Tc is found to scale with a power of volume fraction. Upon crystallization, we show that there is a decoupling of stem length and growth rate. Both the values of folding numbers and the trend with respect to concentration are in agreement with recent experimental results.
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Folding of polymer chains in the early stage of crystallization.