Bibliographic Citation
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| Title | Unsolved problems of crystallization and melting of flexible macromolecules. Attempts at the understanding of the molecular process by experiments and computer simulation |
| Creator/Author | Wunderlich, B. [Tennessee Univ., Knoxville, TN (United States). Dept. of Chemistry]|[Oak Ridge National Lab., TN (United States)] |
| Publication Date | 1992 Oct 01 |
| OSTI Identifier | OSTI ID: 10182063; Legacy ID: DE92040876 |
| Report Number(s) | CONF-9209207--1 |
| DOE Contract Number | AC05-84OR21400 |
| Other Number(s) | Other: ON: DE92040876; CNN: Grant DMR 92-00520 |
| Resource Type | Conference |
| Specific Type | Technical Report |
| Resource Relation | Conference: NATO workshop on crystallization of polymers,Mons (Belgium),6-12 Sep 1992; Other Information: PBD: [1992] |
| Research Org | Oak Ridge National Lab., TN (United States) |
| Sponsoring Org | USDOE, Washington, DC (United States);National Science Foundation, Washington, DC (United States) |
| Subject | 36 MATERIALS SCIENCE; POLYMERS; CRYSTALLIZATION; POLYETHYLENES; POLYETHYLENE GLYCOLS; MOLECULAR CRYSTALS; NUCLEATION; MELTING; KINETICS; THERMODYNAMICS; COMPUTERIZED SIMULATION |
| Description/Abstract | The thermodynamics, kinetics, and computer simulations of crystallization and melting is discussed. The thermodynamics is shown to be well understood, although for many specific crystals not enough details for full description are available. Experiments on the crystallization kinetics of poly(ethylene) and poly(oxyethylene) in the presence of crystal nuclei as a function of molecular mass revealed that with increasing mass, the crystallization behavior deviates increasingly from that of small, rigid molecules. Instead of showing a continuously changing, linear crystallization rate with temperature through the equilibrium melting temperature, T{sub m}{sup 0}, these flexible macromolecules show a region of practically zero crystallization rate between T{sub m}{sup 0} and about (T{sub m}{sup 0} - 15) K, creating a temperature region of metastability in the melt that cannot be broken by nucleation with pregrown crystals. Molecular Nucleation was proposed as a cooperative process to be of overriding importance for the description of polymer crystallization, and to be at the center of segregation of molecules of lower molecular mass by growing crystal fronts. Initial efforts to model sufficiently large crystals using Monte Carlo and molecular dynamics methods are presented. Some of the short-time intermediates in the melting, crystallization, and annealing processes seem to have little similarity to commonly assumed models of crystallization and melting and are presented as discussion topics. |
| Country of Publication | United States |
| Language | English |
| Format | Medium: X; Size: 12 p. |
| Availability | OSTI; NTIS; INIS; GPO Dep. |
| System Entry Date | 2008 Feb 12 |
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