Computer modeling of polymer crystallization

Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 

4 Kinetic Monte Carlo, 201 Single-Chain Behavior in Crystallization, 202 

2 Molecular Dynamics Using Coarse-Grained Models, 206 

Polymer crystallization poses special challenges for investigation by molecular simulation. First, it must be recognized that crystallization is, by it nature, a dynamic process that takes place when a system is driven out of equilibrium. Consider the determination by computer 

Handbook of Polymer Crystallization, First Edition. Edited by Ewa Piorkowska and Gregory C. Rutledge. 2013 John Wiley Sons, Inc. Published 2013 by John Wiley Sons, Inc. 

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Rutledge G (2013) Chapter 6 computer modeling of polymer crystallization. In Piorkowska E, Rutledge GC (eds) Handbook of polymer crystallization. Wiley, Hoboken Sadler DM (1984) Chapter 4 structure of crystalline polymers. In Hall IH (ed) Elsevier Applied Science Publishers, London, p 125... 

The modern availability of sensitive experimental techniques using synchrotron radiation and atomic force microscopy, and fast computers for molecular modeling, has spurred recent intense interest in following the mechanism of polymer crystallization. In spite of the heroic efforts by the... 

Readers interested in learning more about predicting Tm are also referred to a review article by Dearden [177]. Finally, direct simulations of polymer crystallization are of increasing interest as computers become more powerful, and were reviewed in 1994 by Goldbeck-Wood [178], The later work of Madkour and Mark [179-182], which employs Monte Carlo simulations to model the crystallization of polypropylene, is also of interest. 

Faso M, Muneta LM, Muller M, Alcazar V, Chinesta F, Ammar A. Hierarchical approach to flow calculations for polymeric liquid crystals. In Faso M, Perpete FA, editors. Multiscale Modelling of Polymer Properties, Computer-Aided Chemical Engineering. Volume 22. Amsterdam Elsevier 2006. 

Cheng SZD, Noid DW, Wunderlich B (1989) Molecular Segregation and Nucleation of Poly(elhylaie oxide) Crystallized from the Melt. IV. Computer Modeling. J Polymer Sd Part B Polymer Phys 27 1149-1160. 

Although secondary nucleation theory was, for a period, widely accepted, it is now coming under increasing pressure, from experimental data, from computer simulation, and from new approaches to the fundamental process of crystalhzation. It is not clear at this stage whether all that is required is a few adjustments to the theory, or whether the idea of a nucleation barrier is flawed, or even if the idea that the crystal thickness seen is the fastest growing is correct. With the development of new theoretical tools, and the increased integration of theory with computer simulation, it is hoped that a more complete model for polymer crystallization can be developed. 

The continuous advances in experimental techniques have allowed detailed studies, for instance, in the early stages of crystallization, the results of which carmot be fully explained by the polymer crystallization theory proposed by Lauritzen and Hoffman in the 1960s. Also, the improvements in simulation packages have allowed very detailed computer simulations of the crystallization process, and those results are also not completely described by the LH model. This has generated the proposal of new polymer crystallization theories (i.e., the multistage model proposed by Strobl) and the corresponding debate in the pol)uner crystallization community. 

Crystallization in polymers has long been one of the most difficult problems in polymer science. It was to our great surprise that the computer simulations proved very useful in studying this historical problem, if we properly devised the molecular models and the crystallization conditions. But I am aware that there are many problems in the present simulation. Major criticisms will be why the crystallization is so fast, what kind of relevance the present model has to real polymer systems, and how we can bridge the space and time gaps between the present model and real polymers. 

However, It has been found that in many cases, simple models of the properties of atomic aggregates (monocrystals, poly crystals, and glasses) can account quantitatively for hardnesses. These models need not contain disposable parameters, but they must be tailored to take into account particular types of chemical bonding. That is, metals differ from covalent crystals which differ from ionic crystals which differ from molecular crystals, including polymers. Elaborate numerical computations are not necessary. 

P.-G. de Gennes later also considered the multisegment attraction regime. He suggested the so-called p-cluster model [11] in order to explain certain anomalies in behavior observed in many polymer species such as polyethyle-neoxide (PEO) see also [12]. The scenario of coil-globule transition with dominating multisegment interaction first considered by I.M. Lifshitz has been recently studied in [13]. The authors used a computer simulation of chains in a cubic spatial lattice to show that collapse of the polymer can be due to crystallization within the random coil. 

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