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24 results on '"Donovan, Brian R."'

1. Catalytic Chain Transfer in Crosslinking Photopolymerizations.

Author

Bagnall, Nicholas R., Jones, Meredith H., Donovan, Brian R., and Worrell, Brady T.

Subjects
PHOTOPOLYMERIZATION, THREE-dimensional printing, PHOTOCHEMISTRY, COBALOXIMES, COBALT
Abstract

Presented here is a detailed account of the development and implementation of macrocyclic cobaloxime complexes as sulfur-free, catalytic chain transfer agents (CTAs) in crosslinking photopolymerizations. Although much of this review is dedicated to understanding the fundamentals of catalytic chain transfer (CCT) in photopolymerizations, its impact on network topology and resultant mechanical properties, future goals of applying this technology to multimaterial 3D printing are also discussed. It is our long-term ambition for catalytic, sulfur-free CTAs to supplant existing consumptive, sulfur-based agents to provide new, unexplored, and not currently possible to fabricate photopolymeric materials with a specific eye towards application in dentistry, additive manufacturing, and responsive materials. 1 Introduction 2 History of Catalytic Chain Transfer (CCT) 3 Understanding Catalyst Purity and Chain Transfer Activity 4 Evidencing CCT in a Crosslinking Photopolymerization 5 Comparing Cobalt(II)-Catalysts to Other Relevant CTAs 6 Performance of Cobalt(II)-Catalysts in Commercial Resins 7 Limitations of Approach and Looking Forward [ABSTRACT FROM AUTHOR]

Published
2024
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2. Eloquence as Virtue in Ancient Theory.

Author

Donovan, Brian R.

Abstract

Plato attacked the sophists' claim that they taught "virtue," and he believed that rhetoric, which they taught, was not an "art." If the notions of virtue and art are brought together and integrated to constitute an antithesis, the sophistic position becomes more intelligible and defensible. The Greek term "arete," translated as "virtue," can be manifested either as excellence in a particular role or in the whole of living. The term "techne," which has been translated as "art," is better imagined as any distinctly specialized trade or craft. Thus the antithesis is between civic virtue and specialized technical skill. Long before Plato, and contrary to the Platonic view, Homer conceived of eloquence as both arete and techne. In both the "Iliad" and "Odyssey," Homer suggests that eloquence is not only a specialized skill, but also an integral part of overall human excellence. To Socrates and Plato, the technical knowledge of artisans was the only kind of ordinary human knowledge that was genuine. An examination of the first third of Plato's dialogue "Protagoras" shows how Plato obscures the issue by exploiting the flexibility of the two terms arete and techne, and by studied neglect of the intimate connection between teaching arete and techne rhetoric. Modern educators can admit both arete and techne on the basis of a larger view of eloquence as radically non-specialized and morally requisite for all in a democratic society. (Nineteen references are attached.) (SG)

Published
1992

4. Protagorean Epistemology and Dialectic.

Author

Donovan, Brian R.

Abstract

Contemporary dispute among teachers of rhetoric between those who prefer the classical tradition of rhetoric and those who champion an epistemic view of rhetoric has antecedents among the disputes of the ancient Greek scholars. Some of the vital themes of epistemology can be traced back to Protagoras of Abdera, one of the two great leaders of the Sophistic movement and a pioneer of epistemic rhetoric. Comparatively little contemporary attention has been paid to his work, and there are only four or five sentences that can with any confidence be attributed to his authorship. Other evidence of Protagoras' views must be sought in the works of Diogenes Laertius, Sextus Empiricus, and Plato. While Parmenides rejected all assertions of not-being, and Socrates and Plato objectified being in a world of "ideal forms," Protagoras and his fellow Sophist Gorgius of Leontini took an opposing view. Gorgius identified flaws in Parmenidean logic and went on to demonstrate that nothing absolutely "is." In Plato's dialogue "Theaetetus," Protagoras calls upon Socrates to look beyond the surface of Protagoras' assertion that man is the measure of all things to the logos of the statement. This call to anti-logic was a particularly Protagorean approach to dialectic. A coherent dialectical method emerges from Protagorean epistemology: (1) that there are at least two opposed "logoi" in everything; (2) that it is the function and excellence of discourse to bring both out; and (3) that it can be demonstrated that there is no contradiction between the two. (SG)

Published
1990

6. The Project of Protagoras.

Author

Donovan, Brian R.

Abstract

Argues that Protagoras, a leading sophist of the fifth century B.C.E., not only arrived at a theory of truth close to present-day antifoundationalism but also took the next step toward developing workable, socially constituted truths and knowledge for everyday practice. Sketches out Protagoras's project to employ the power of literacy for social uses. (TB)

Published
1993

12. Liquid Crystalline Elastomers: Microstructured Photopolymerization of Liquid Crystalline Elastomers in Oxygen‐Rich Environments (Adv. Funct. Mater. 40/2019)

Author

McCracken, Joselle M., primary, Tondiglia, Vincent P., additional, Auguste, Anesia D., additional, Godman, Nicholas P., additional, Donovan, Brian R., additional, Bagnall, Brody N., additional, Fowler, Hayden E., additional, Baxter, Chance M., additional, Matavulj, Valentina, additional, Berrigan, John D., additional, and White, Timothy J., additional

Published
2019
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13. Mechanotropic Elastomers

Author

Donovan, Brian R., primary, Fowler, Hayden E., additional, Matavulj, Valentina M., additional, and White, Timothy J., additional

Published
2019
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16. Microstructured Photopolymerization of Liquid Crystalline Elastomers in Oxygen‐Rich Environments

Author

McCracken, Joselle M., primary, Tondiglia, Vincent P., additional, Auguste, Anesia D., additional, Godman, Nicholas P., additional, Donovan, Brian R., additional, Bagnall, Brody N., additional, Fowler, Hayden E., additional, Baxter, Chance M., additional, Matavulj, Valentina, additional, Berrigan, John D., additional, and White, Timothy J., additional

Published
2019
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17. All‐Optical Control of Shape

Author

Donovan, Brian R., primary, Matavulj, Valentina M., additional, Ahn, Suk‐kyun, additional, Guin, Tyler, additional, and White, Timothy J., additional

Published
2018
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24. Mechanotropic Elastomers.

Author

Donovan BR, Fowler HE, Matavulj VM, and White TJ

Abstract

Liquid crystal elastomers (LCEs) are anisotropic polymeric materials. When subjected to an applied stress, liquid crystalline (LC) mesogens within the elastomeric polymer network (re)orient to the loading direction. The (re)orientation during deformation results in nonlinear stress-strain dependence (referred to as soft elasticity). Here, we uniquely explore mechanotropic phase transitions in elastomers with appreciable mesogenic content and compare these responses to LCEs in the polydomain orientation. The isotropic (amorphous) elastomers undergo significant directional orientation upon loading, evident in strong birefringence and x-ray diffraction. Functionally, the mechanotropic displacement of the elastomers to load is also nonlinear. However, unlike the analogous polydomain LCE compositions examined here, the isotropic elastomers rapidly recover after deformation. The mechanotropic orientation of the mesogens in these materials increase the toughness of these thiol-ene photopolymers by nearly 1300 % relative to a chemically similar elastomer prepared from wholly isotropic precursors., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Published
2019
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