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Design of polymeric substrates for controlled molecular crystallization

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dc.contributor.advisor Bernhardt L. Trout and T. Alan Hatton. en_US Diao, Ying, Ph.D. Massachusetts Institute of Technology en_US
dc.contributor.other Massachusetts Institute of Technology. Dept. of Chemical Engineering. en_US 2012-04-26T18:50:50Z 2012-04-26T18:50:50Z 2012 en_US 2012 en_US
dc.description Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2012. en_US
dc.description Cataloged from PDF version of thesis. en_US
dc.description Includes bibliographical references (p. 171-175). en_US
dc.description.abstract It is essential to control crystallization in many areas of science and technology, such as the production of pharmaceuticals, pigments, concrete, semiconductors, as well as the formation of biominerals. In most practical circumstances, crystallization starts with heterogeneous nucleation at a foreign surface. Despite its widespread occurrence, mechanistic understanding of the role of a surface in heterogeneous nucleation is limited, especially in a solution environment. My thesis aims at elucidating the roles of surface chemistry and nanostructure on nucleation to enable rational design of surfaces for controlling crystallization from solution. To this end, I systematically investigated the role of surface chemistry, morphology, in particular porous structures of various polymeric materials on heterogeneous nucleation using small organic molecules as model compounds. I have demonstrated quantitatively the significance of surface chemistry to nucleation kinetics using a variety of polymer surfaces. By tuning the surface composition of the polymers, aspirin nucleation was promoted by up to an order of magnitude compared to the bulk. Further mechanistic investigations revealed that, macroscopically, it is through interfacial free energies that the surfaces influence the surface nucleation activity. Equipped with nucleation induction time statistics as a powerful tool, I found that nanoscopic pores of 50-100 nm accelerated nucleation by up to two orders of magnitude compared with surfaces without pores. Moreover, I demonstrated for the first time that the shape of surface nanopores is essential in determining the nucleation behavior, using lithographic methods for nanopatterning the polymer films. A molecular mechanism was further proposed based on additional mechanistic investigations. Furthermore, the nanoconfinement effect on nucleation was studied using polymeric microgels with tunable nanostructures and chemistry, whose mesh sizes range from 0.7-2 nm. We presented the first experimental evidence for the existence of an optimum confinement size at which the rate of nucleation was dramatically enhanced by up to four orders of magnitude. The degree of nucleation enhancement depends on the extent of polymer-solute interactions, whose role was elucidated from the perspective of adsorptive partitioning and nucleation-templating effect. In addition, the microgel nanostructure was also shown to play an important role in determining the crystal polymorphism of pharmaceutical compounds. en_US
dc.description.statementofresponsibility by Ying Diao. en_US
dc.format.extent 175 p. en_US
dc.language.iso eng en_US
dc.publisher Massachusetts Institute of Technology en_US
dc.rights M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission. en_US
dc.rights.uri en_US
dc.subject Chemical Engineering. en_US
dc.title Design of polymeric substrates for controlled molecular crystallization en_US
dc.type Thesis en_US Ph.D. en_US
dc.contributor.department Massachusetts Institute of Technology. Dept. of Chemical Engineering. en_US
dc.identifier.oclc 784152235 en_US

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