Simulation of crystallization of entangled polymer chains

Abstract

The crystallization of entangled polymer chains is studied by three-dimensional Monte Carlo simulations using the bond fluctuation model. To simulate entanglement, a mobile chain is assumed to move in a frozen environment through fixed obstacles. Simulation indicates that the temperature scale can be divided into three regions. In region I, high supercooling, the crystallization rate is high while disentanglement rate is low. In region III, low supercooling, the crystallization rate is much lower compared with disentanglement. Both rates can match each other in region II. Simulation also shows different morphologies in different temperature regions. In the simulation, all chains are mobile, but entanglement may still exist due to a high concentration of monomers. A new layer of crystal is observed to form on the surface of the seed at higher temperature, while chains crystallize in situ without large-scale movement at lower temperature. In moderate temperature range, disentanglement could match crystallization, and the new layer of crystal could still form on the seed but with smaller thickness. By close observation, the new layer of crystal consists of more than one chain when crystallization forms at higher supercooling because the crystallization rate is high in this case; a new chain deposits on the seed and crystallizes before the completion of crystallization of the former attached chain.

Influence of Chain Topology on Polymer Dynamics and Crystallization. Investigation of Linear and Cyclic Poly(ε-caprolactone)s by 1H Solid-State NMR Methods

“…[5][6][7][8][9][10][11][12][13] Thus, the mechanisms involved in the crystallization of entangled polymers have recently attracted renewed attention. 2,[14][15][16][17][18] In this context, we investigate the influence of chain topology on polymer crystallization, addressing this issue by comparing crystallinity and chain mobility of cyclic polymer chains (free of loose chain ends) and linear chains with the same number of monomer units.…”

“…Although polymer crystals can exhibit numerous morphologies with hierarchies of molecular organization, still it remains unclear, what determines them to evolve. Furthermore, the influence of chain topology and molecular weight as well as the role of the entanglements prior to and during crystallization has not been entirely clarified yet and is the subject of ongoing discussion. − Thus, the mechanisms involved in the crystallization of entangled polymers have recently attracted renewed attention. ,− In this context, we investigate the influence of chain topology on polymer crystallization, addressing this issue by comparing crystallinity and chain mobility of cyclic polymer chains (free of loose chain ends) and linear chains with the same number of monomer units.…”

Translation and Rotation of Spherulites during the Crystallization of Isotactic Polypropylene with Reduced Chain Entanglements

“…They attributed the different characteristics, such as plateau modulus, crystallization rate, etc., to a melt state in which the chain dynamics was altered due to topological constraints, and they did not consider issues of flow associated with crystallization. Of course, the effects of entanglement on the crystallization kinetics of polymeric materials have been much studied because of its practical importance. − …”

Molecular Dynamics Study on the Crystallization of a Cluster of Polymer Chains Depending on the Initial Entanglement Structure

“…Computer simulation has gradually come to front to show capability of describing changes in microstructure at the atomistic level, which is difficult to observe directly in experiments. Many computer simulation studies − have been carried out to simulate polymer crystallization, but few are related to the entanglement. The difficulties in quantifying the entanglement density and in producing structures with different global or local entanglement densities give rise to a situation that only a few simulation works have been done on this aspect.…”