Ray Baughman became the Robert A. Welch Professor of Chemistry and Director of the NanoTech Institute at the University of Texas in Dallas in August 2001, after 31 years in industry. He is a member of the National Academy of Engineering, the Academy of Medicine, Engineering and Science of Texas, Academia Europaea, and the European Academy of Sciences and Arts
Formation thermodynamics is examined for two different types of point defects which interrupt con... more Formation thermodynamics is examined for two different types of point defects which interrupt conjugation in polydiacetylene crystals: bond-alternation and orbital-flip defects. While bond-alternation defects in these polymers are analogous to previously investigated radical pair defects in the polyenes, much lower equilibrium concentrations are expected in the polydiacetylenes than in the polyenes. For polydiacetylenes with small substituent groups or high-energy side-group packing, orbital-flip defects provide a more plausible rationale for explaining observed thermochromism and carrier trapping effects in photoconductivity. During the formation of this type of defect, a π orbital at each of the two neighboring sp2 carbon atoms is rotated by 90°, so that the rotated π orbitals become conjugated with the out-of-plane orbitals neighboring sp carbon atoms. Thereby the system of overlapping π orbitals is interrupted without substantially decreasing the electronic stabilization energy. With an intramolecular strain energy increase of only about 2.6 kcal/mole, the polymer chain can return to lattice register within one monomer unit of the defect center. Since the electronic stabilization energy change is even smaller (about 0.2 kcal/mole), the major contribution to defect formation energy arises from the side-group rotations.
The energetic degeneracy of the phase-shifted trans polyacetylene chain segments on opposite side... more The energetic degeneracy of the phase-shifted trans polyacetylene chain segments on opposite sides of a soliton center is removed by interchain interactions, which are shown to have important consequences for soliton physics. This energy difference (ESL), the solition-lattice energy, has been calculated from available structural data as a sum of atom-centered, bond-centered, and electrostatic contributions. While ESL is small per C2H2 length of phase-shifted chain (roughly 4 cal/mol for P21/n and 14 cal/mol for P21/a), the resultant total energy cannot generally be ignored since it diverges with increasing separation between soliton and antisoliton or between soliton and chain segment end. Consequences of the interchain interactions are major changes in the equilibrium concentration of soliton pairs, localization of solitons in the proximity of a stationary defect which shifts bond alternation (for chains much longer than the soliton width), and a predicted temperature dependence of phase coherence in bond alternation. Analysis of experimental data provides upper limit estimates for the average chain conjugation length and a lower limit estimate for ESL (greater than 3 cal/mol), which is consistent with the energy calculations based on intermolecular potentials.
Page 1. [18] a) JL Kim, JK Kim, HN Cho, DY Kim, CY Kim, SI Hong, Macromolecules 2000, 33, 5880. b... more Page 1. [18] a) JL Kim, JK Kim, HN Cho, DY Kim, CY Kim, SI Hong, Macromolecules 2000, 33, 5880. b) XW Zhan, YQ Liu, X. Wu, SA Wang, DB Zhu, Macromolecules 2002, 35, 2529. c) CJ Ton-zola, MM Alam, BA Bean, SA Jenekhe, Macromolecules 2004, 37, 3554. ...
The high cost of powerful, large-stroke, high-stress artificial muscle fibers and wires has combi... more The high cost of powerful, large-stroke, high-stress artificial muscle fibers and wires has combined with typical performance problems, like low-cycle-life under high load, hysteretic behavior, and low efficiencies, to restrict applications. We here demonstrate that inexpensive, high-strength polymer fibers used for fishing line and sewing thread can be easily transformed by non-conventional, extreme twist-insertion processes to provide fast, long-life tensile and torsional muscles that contract by over 49% and lift 100 times heavier loads than the same length and weight natural muscle. These muscles, which are normally thermally actuated, can be powered electrically using sub-volt voltages, photonically, chemically, or by harvesting chemical or thermal energy to provide over 2 times higher specific work than competing nickel-titanium actuator wires. A single muscle fiber weighing 600 mg, made by coiling an 860 μm diameter nylon fishing line, can reversibly lift a kilogram weight 3 cm, and accomplish this once per second when powered by a 75°C temperature change. By weaving or braiding these fibers, we demonstrate textiles that open and close in response to temperature, which might lead to clothing that changes porosity to provide protection and comfort. Use of these muscles for harvesting thermal energy and for window shutters that help conserve energy is demonstrated
In the past decade, anisotropic molecular conductors have been found which possess unusual electr... more In the past decade, anisotropic molecular conductors have been found which possess unusual electrical, optical, magnetic, and, in some cases, mechanical properties. Exploitation of these properties for specific devices is inevitable, and a number of diverse applications of molecular metals have been reported over the past few years. Specifically, these materials have found use as components in batteries, electrolytic capacitors, thermistors, electrochromic displays, optical printing techniques, electrophotography, as electrodes, antistatic coatings, etc. A mora critical and detailed review of the state of the art in this area is given in a paper by Dr. Yoshimura at this NATO-ARI. The scope of this study group is to evaluate the status of applications, to indicate problem areas, and to identify some fruitful directions for future work. But, it must be kept in mind that this is a young field where potential applications are still in a very early stage of development. Consequently, a certain amount of speculation and generalization is unavoidable.
This overview focuses on our teams work on using twisted yarns and highly elastic coiled yarns fo... more This overview focuses on our teams work on using twisted yarns and highly elastic coiled yarns for artificial muscles, energy harvesting, energy storage, sensing, and refrigeration. Despite the diversity of these applications for coiled carbon nanotube and polymer yarns, similar fabrication methods are applicable and conversion of coiling twist to yarn twist results in yarn elasticity, actuation, twistocaloric cooling, and the capacitance changes used for energy harvesting and sensing. Likewise, the same biscrolling method yields coiled yarns containing up to 95 weight percent of guest powders that provide various new properties. The obtained performance of the coiled polymer and carbon nanotube yarns are remarkable, such as artificial muscles that generate up to 98 times the output mechanical power than the maximum for the same weight human muscle and mechanical energy harvesters providing a higher peak electrical power per weight than prior art material-based mechanical energy harvesters for stretch frequencies between a few Hz and 600 Hz.
Formation thermodynamics is examined for two different types of point defects which interrupt con... more Formation thermodynamics is examined for two different types of point defects which interrupt conjugation in polydiacetylene crystals: bond-alternation and orbital-flip defects. While bond-alternation defects in these polymers are analogous to previously investigated radical pair defects in the polyenes, much lower equilibrium concentrations are expected in the polydiacetylenes than in the polyenes. For polydiacetylenes with small substituent groups or high-energy side-group packing, orbital-flip defects provide a more plausible rationale for explaining observed thermochromism and carrier trapping effects in photoconductivity. During the formation of this type of defect, a π orbital at each of the two neighboring sp2 carbon atoms is rotated by 90°, so that the rotated π orbitals become conjugated with the out-of-plane orbitals neighboring sp carbon atoms. Thereby the system of overlapping π orbitals is interrupted without substantially decreasing the electronic stabilization energy. With an intramolecular strain energy increase of only about 2.6 kcal/mole, the polymer chain can return to lattice register within one monomer unit of the defect center. Since the electronic stabilization energy change is even smaller (about 0.2 kcal/mole), the major contribution to defect formation energy arises from the side-group rotations.
The energetic degeneracy of the phase-shifted trans polyacetylene chain segments on opposite side... more The energetic degeneracy of the phase-shifted trans polyacetylene chain segments on opposite sides of a soliton center is removed by interchain interactions, which are shown to have important consequences for soliton physics. This energy difference (ESL), the solition-lattice energy, has been calculated from available structural data as a sum of atom-centered, bond-centered, and electrostatic contributions. While ESL is small per C2H2 length of phase-shifted chain (roughly 4 cal/mol for P21/n and 14 cal/mol for P21/a), the resultant total energy cannot generally be ignored since it diverges with increasing separation between soliton and antisoliton or between soliton and chain segment end. Consequences of the interchain interactions are major changes in the equilibrium concentration of soliton pairs, localization of solitons in the proximity of a stationary defect which shifts bond alternation (for chains much longer than the soliton width), and a predicted temperature dependence of phase coherence in bond alternation. Analysis of experimental data provides upper limit estimates for the average chain conjugation length and a lower limit estimate for ESL (greater than 3 cal/mol), which is consistent with the energy calculations based on intermolecular potentials.
Page 1. [18] a) JL Kim, JK Kim, HN Cho, DY Kim, CY Kim, SI Hong, Macromolecules 2000, 33, 5880. b... more Page 1. [18] a) JL Kim, JK Kim, HN Cho, DY Kim, CY Kim, SI Hong, Macromolecules 2000, 33, 5880. b) XW Zhan, YQ Liu, X. Wu, SA Wang, DB Zhu, Macromolecules 2002, 35, 2529. c) CJ Ton-zola, MM Alam, BA Bean, SA Jenekhe, Macromolecules 2004, 37, 3554. ...
The high cost of powerful, large-stroke, high-stress artificial muscle fibers and wires has combi... more The high cost of powerful, large-stroke, high-stress artificial muscle fibers and wires has combined with typical performance problems, like low-cycle-life under high load, hysteretic behavior, and low efficiencies, to restrict applications. We here demonstrate that inexpensive, high-strength polymer fibers used for fishing line and sewing thread can be easily transformed by non-conventional, extreme twist-insertion processes to provide fast, long-life tensile and torsional muscles that contract by over 49% and lift 100 times heavier loads than the same length and weight natural muscle. These muscles, which are normally thermally actuated, can be powered electrically using sub-volt voltages, photonically, chemically, or by harvesting chemical or thermal energy to provide over 2 times higher specific work than competing nickel-titanium actuator wires. A single muscle fiber weighing 600 mg, made by coiling an 860 μm diameter nylon fishing line, can reversibly lift a kilogram weight 3 cm, and accomplish this once per second when powered by a 75°C temperature change. By weaving or braiding these fibers, we demonstrate textiles that open and close in response to temperature, which might lead to clothing that changes porosity to provide protection and comfort. Use of these muscles for harvesting thermal energy and for window shutters that help conserve energy is demonstrated
In the past decade, anisotropic molecular conductors have been found which possess unusual electr... more In the past decade, anisotropic molecular conductors have been found which possess unusual electrical, optical, magnetic, and, in some cases, mechanical properties. Exploitation of these properties for specific devices is inevitable, and a number of diverse applications of molecular metals have been reported over the past few years. Specifically, these materials have found use as components in batteries, electrolytic capacitors, thermistors, electrochromic displays, optical printing techniques, electrophotography, as electrodes, antistatic coatings, etc. A mora critical and detailed review of the state of the art in this area is given in a paper by Dr. Yoshimura at this NATO-ARI. The scope of this study group is to evaluate the status of applications, to indicate problem areas, and to identify some fruitful directions for future work. But, it must be kept in mind that this is a young field where potential applications are still in a very early stage of development. Consequently, a certain amount of speculation and generalization is unavoidable.
This overview focuses on our teams work on using twisted yarns and highly elastic coiled yarns fo... more This overview focuses on our teams work on using twisted yarns and highly elastic coiled yarns for artificial muscles, energy harvesting, energy storage, sensing, and refrigeration. Despite the diversity of these applications for coiled carbon nanotube and polymer yarns, similar fabrication methods are applicable and conversion of coiling twist to yarn twist results in yarn elasticity, actuation, twistocaloric cooling, and the capacitance changes used for energy harvesting and sensing. Likewise, the same biscrolling method yields coiled yarns containing up to 95 weight percent of guest powders that provide various new properties. The obtained performance of the coiled polymer and carbon nanotube yarns are remarkable, such as artificial muscles that generate up to 98 times the output mechanical power than the maximum for the same weight human muscle and mechanical energy harvesters providing a higher peak electrical power per weight than prior art material-based mechanical energy harvesters for stretch frequencies between a few Hz and 600 Hz.
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