skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Toward Molecular Engineering of Polymer Glasses

Abstract

Glass formation has been central to fabrication technologies since the dawn of civilization. Glasses not only encompass window panes, the insulation in our homes, the optical fibers supplying our cable TV, and vessels for eating and drinking, but they also include a vast array of ‘‘plastic’’ polymeric materials. Glasses find applications in high technology (e.g., producing microelectronic materials, etc., amorphous semiconductors), and recent advances have created ‘‘plastic metallic glasses’’ that are promising for fabricating everyday structural materials. Many commercially relevant systems, such as microemulsions and colloidal suspensions, have complex molecular structures and thus solidify by glass formation. Despite the importance of understanding the fundamental nature of glass formation for the synthesis of new materials, a predictive molecular theory has been lacking. Much of our understanding of glass formation derives from the analysis of experimental data, a process that has uncovered a number of interesting universal behaviors, namely, relations between properties that are independent of molecular details. However, these empirically derived relations and their limitations remain to be understood on the basis of theories, and, more importantly, there is strong need for theories of the explicit variation with molecular system to enable the rational design and tailoring of new materials. Wemore » have recently developed the generalized entropy theory, the only analytic, theory that enables describing the dependence of the properties of glass-formation on monomer molecular structures. These properties include the two central quantities of glass formation, the glass transition temperature and the glass fragility parameter, material dependent properties that govern how a material may be processed (e.g., by extrusion, ink jet, molding, etc.) Our recent works, which are further described below, extend the studies of glass formation in polymer systems to test the theory by directly comparing between the predictions of our generalized entropy theory with experiment and with simulations and to expand the vistas of the theory to describe a wider range of important systems (e.g. glass formation in binary blends and systems with specific interactions) and phenomena that are describable by the generalized entropy theory. In addition, we have addressed longstanding fundamental problems associated with the validity of the Adam-Gibbs theory, one of the underpinnings of the general entropy theory. Theoretical advances to enable describing the properties of glass-formation over a wider class of important polymeric systems, included semi-flexible systems, the more general situation of specific interactions, and more. Our recent work removes the simplest approximation uses the simplest model in which the interaction is approximated by a single, monomer average. Thus, the theory has been extended to allow some variations of the energy parameters between the atoms within the monomers. The theory has also been extended to include all the contributions from chain semi-flexibility. Both projects are extremely difficult, but the payback is that the process of solving the problems developed strong theoretical skills in Dr. Xu, who has recently begun a postdoc position at ORNL. The theory has also been extended to describe glass formation in partially miscible blends, with good general agreement with experiment. Again, the development of the theory presented an extremely difficult problem, but the payback is the development of a theory for a very important class of systems. Another project provides an extremely simple approximation for certain properties of glass formation in polymer melts and should make the theory more accessible to everyone.« less

Authors:
 [1];  [1];  [1];  [2]
  1. Univ. of Chicago, IL (United States)
  2. National Inst. of Standards and Technology (NIST), Boulder, CO (United States)
Publication Date:
Research Org.:
Univ. of Chicago, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1349873
Report Number(s):
DOE-UCHICAGO-0008631
DOE Contract Number:
SC0008631
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; glass formation; free volume; entropic barriers; enthalpic barriers; thermodynamic scaling; polymer blends; miscibility; concentration fluctuations; glassy dynamics; phase transitions; electrostatic polarization; aggregation; multiple scattering theory; surface charges; specific interactions; polymer melts; cohesive energy; chain stiffness; glass transition temperature; fragility parameter; Adam-Gibbs theory; generalized entropy theory; transition state theory; grand canonical ensemble; structural relaxation; structural relaxation time; mechanical response; dynamic moduli; time-temperature superposition; dielectric response; monomer molecular structure; polymer packing; comparison with experiments for granular materials; image method for spheres; thermodynamical properties; glasses; molecular dynamics simulations; image method; electrostatics; induced charge; Poisson’s equation

Citation Formats

Freed, Karl F., Xu, Wen-Sheng, Dudowicz, Jacek B., and Douglas, Jack F. Toward Molecular Engineering of Polymer Glasses. United States: N. p., 2017. Web. doi:10.2172/1349873.
Freed, Karl F., Xu, Wen-Sheng, Dudowicz, Jacek B., & Douglas, Jack F. Toward Molecular Engineering of Polymer Glasses. United States. doi:10.2172/1349873.
Freed, Karl F., Xu, Wen-Sheng, Dudowicz, Jacek B., and Douglas, Jack F. Wed . "Toward Molecular Engineering of Polymer Glasses". United States. doi:10.2172/1349873. https://www.osti.gov/servlets/purl/1349873.
@article{osti_1349873,
title = {Toward Molecular Engineering of Polymer Glasses},
author = {Freed, Karl F. and Xu, Wen-Sheng and Dudowicz, Jacek B. and Douglas, Jack F.},
abstractNote = {Glass formation has been central to fabrication technologies since the dawn of civilization. Glasses not only encompass window panes, the insulation in our homes, the optical fibers supplying our cable TV, and vessels for eating and drinking, but they also include a vast array of ‘‘plastic’’ polymeric materials. Glasses find applications in high technology (e.g., producing microelectronic materials, etc., amorphous semiconductors), and recent advances have created ‘‘plastic metallic glasses’’ that are promising for fabricating everyday structural materials. Many commercially relevant systems, such as microemulsions and colloidal suspensions, have complex molecular structures and thus solidify by glass formation. Despite the importance of understanding the fundamental nature of glass formation for the synthesis of new materials, a predictive molecular theory has been lacking. Much of our understanding of glass formation derives from the analysis of experimental data, a process that has uncovered a number of interesting universal behaviors, namely, relations between properties that are independent of molecular details. However, these empirically derived relations and their limitations remain to be understood on the basis of theories, and, more importantly, there is strong need for theories of the explicit variation with molecular system to enable the rational design and tailoring of new materials. We have recently developed the generalized entropy theory, the only analytic, theory that enables describing the dependence of the properties of glass-formation on monomer molecular structures. These properties include the two central quantities of glass formation, the glass transition temperature and the glass fragility parameter, material dependent properties that govern how a material may be processed (e.g., by extrusion, ink jet, molding, etc.) Our recent works, which are further described below, extend the studies of glass formation in polymer systems to test the theory by directly comparing between the predictions of our generalized entropy theory with experiment and with simulations and to expand the vistas of the theory to describe a wider range of important systems (e.g. glass formation in binary blends and systems with specific interactions) and phenomena that are describable by the generalized entropy theory. In addition, we have addressed longstanding fundamental problems associated with the validity of the Adam-Gibbs theory, one of the underpinnings of the general entropy theory. Theoretical advances to enable describing the properties of glass-formation over a wider class of important polymeric systems, included semi-flexible systems, the more general situation of specific interactions, and more. Our recent work removes the simplest approximation uses the simplest model in which the interaction is approximated by a single, monomer average. Thus, the theory has been extended to allow some variations of the energy parameters between the atoms within the monomers. The theory has also been extended to include all the contributions from chain semi-flexibility. Both projects are extremely difficult, but the payback is that the process of solving the problems developed strong theoretical skills in Dr. Xu, who has recently begun a postdoc position at ORNL. The theory has also been extended to describe glass formation in partially miscible blends, with good general agreement with experiment. Again, the development of the theory presented an extremely difficult problem, but the payback is the development of a theory for a very important class of systems. Another project provides an extremely simple approximation for certain properties of glass formation in polymer melts and should make the theory more accessible to everyone.},
doi = {10.2172/1349873},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Wed Apr 05 00:00:00 EDT 2017},
month = {Wed Apr 05 00:00:00 EDT 2017}
}

Technical Report:

Save / Share:
  • This report summarizes the technical progress made in the past three years on CRADA No. 1078, Molecular Engineering of Polymer Alloys. The thrust of this CRADA was to start with the basic ideas of PRISM theory and develop it to the point where it could be applied to modeling of polymer alloys. In this program, BIOSYM, Sandia and the University of Illinois worked jointly to develop the theoretical techniques and numerical formalisms necessary to implement the theoretical ideas into commercial software aimed at molecular engineering of polymer alloys. This CRADA focused on developing the techniques required to make the transitionmore » from theory to practice. These techniques were then used by BIOSYM to incorporate PRISM theory and other new developments into their commercial software.« less
  • The DOE has provided, by means of the American Recovery and Reinvestment Act (ARRA), $146,400 in funding for the purchase of scientific equipment. Specifically, these funds have enabled the purchase of two scientific cameras that have already been applied to the research in microcavity plasmas at the University of Illinois (Urbana). The first camera system that was purchased with these funds is a gated ICCD system that allows events as short as 5 ns in time to be captured. It is difficult to express the impact that this equipment has already had on our research. Despite having arrived just 6more » - 7 months ago, this camera system has already been used by five graduate students and several undergraduates to capture phenomena that we simply could not see in the past. As an example, the low temperature plasma confined to a spiral structure we fabricate in the Al/Al₂O₃ materials system appears, on long time scales such as those we see with our eyes, to be spatially uniform. However, when captured with the new camera system, the plasma actually is formed initially at the center of the spiral and then moves radially (literally, "jumping" over channels as it goes) at a velocity of a few km/sec. This is an exciting result and I should add that the camera shows that plasma standing waves are produced in some of the structures as well. We do not currently understand all of the phenomena we are witnessing but it is obvious that this new system has quite literally opened new areas of plasma research and application. The second system purchased under this ARRA grant is an infrared system that is far more sensitive than anything our laboratory (or the University of Illinois, for that matter) has had previously. Although fewer experiments have been completed to date with this second camera, it is already clear that it is, indeed, extremely sensitive and it is slated for several experiments in the near future in which we will be measuring the infrared spectra of several arrays of microcavity plasmas. In summary, let me express my thanks to the DOE for granting these funds. We are most grateful for the extraordinary scientific capability that thee funds provide our students. We expect that the scientific data already acquired by this equipment will result in several publications in the next 2 - 3 months (two are being written now). Furthermore, the ability we now have to watch plasmas evolve on the nanosecond time scale has given us several ideas that are likely to result in patent applications. On behalf of our students and myself, I thank the DOE for this exceptional equipment.« less
  • The feasibility of producing radiation-resistant silicon solar cells by the use of a graded base structure is being studied. Methods of fabrication of both n on p and p on n graded base cells are discussed and the results of efficiency measurements at sea level and on Table Mountain are presented. The results of bombarding the cells with 1-Mev electrons are shown and compared with the results obtained by bombarding n on p cells having a uniform base region of 25 ohm cm resistivity. The results of experiments designed to measure the presence Of an electric field in the basemore » region of the graded base cells by carrier transient time measurements are given. The results indicated that the graded base structure affects the transport properties of minority carriers injected into the base region of the cells. The electron irradiation experiments also indicated that the performance of the cells when subjected to l-Mev electron bombardment is at least as good and may be superior to that reported on other silicon cells. (M.C.G.)« less
  • Activities in a program for development of radioresistant solar cells are reported. The program is devoted to development of cells showing a factor of 10 improvement in radiation resistance compared with cells currently available. Radiation resistance was achieved by the use of a graded base structure in which an impurity gradient is introduced inio the base region of the cell. The effect of this impurity gradient is to form an electric field in the base region of the cell which accelerates the light produced minority carriers toward the junction. Techniques were established for fabricating n on p cells with gradientsmore » of impurities in the base regions. Cells made by these techniques showed conversion efficiencies in excess of 10% when measured in sunlight. These cells, when subject to high energy electron and proton irradiation, showed a factor of 3 to 5 improvement in radiation resistance over conventional n on p cells. Irradiation results are included along with discussion of device theory and fabrication techniques. (J.R.D.)« less