| Homopolymer Self-assembly into Stable Nanoparticles: Concerted Action of Hydrophobic Association and Hydrogen Bonding in Thermoresponsive Poly(alkylacrylic acid)s. | |
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MedLine Citation:
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PMID: 22280359 Owner: NLM Status: Publisher |
Abstract/OtherAbstract:
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A new approach to polymer self-assembly was presented recently [M. Sedlák, Č. Koňák, J. Dybal, Macromolecules 42 (2009), 7430-7438 and 7439-7446.] where stable polymeric nanoparticles were formed from poly(ethylacrylic acid) homopolymers without any assembly-triggering additives, simply by heating polymer solution under conditions of thermosensitivity to certain temperature. In the current paper, we present successful results on poly(propylacrylic acid), which is a more hydrophobic polymer. On the other hand we also present results on a less hydrophobic polymer from this series, poly(methacrylic acid), from which nanoparticles cannot be formed. Comparison of results on all three polymers gives a solid physico-chemical insight and supports the molecular mechanism of the self-assembly suggested previously: The solvent quality gradually worsens upon heating of a thermosensitive polymer solution and polymer-polymer contacts are preferred over polymer-solvent contacts, which leads to the formation of polymer assemblies. The presence of a significant amount of charge on chains prevents macroscopic phase separation. Upon subsequent cooling to laboratory temperature, the assemblies (nanoparticles) should eventually dissolve, however, this is not the case due to the fact that polymer chains brought to a close proximity at elevated temperatures become hydrogen-bonded. In addition, hydrogen bonds strengthen upon cooling. Mainly carboxylic-carboxylate hydrogen bonds (COOH….COO-) are responsible for the irreversibility of the process and the stability of nanoparticles. Conclusions are supported by results from static and dynamic light scattering, and FTIR spectroscopy. Size of nanoparticles can be monitored during the growth and custom-tailored by tuning critical parameters, especially the degree of ionization, temperature, and time of heating. Nanoparticles are stable over long periods of time. They are stable in a broad range of salt concentrations, including physiological conditions, and posses a mild acceptable degree of polydispersity. |
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Authors:
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Marian Sedlak |
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Publication Detail:
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Type: JOURNAL ARTICLE Date: 2012-1-26 |
Journal Detail:
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Title: The journal of physical chemistry. B Volume: - ISSN: 1520-5207 ISO Abbreviation: - Publication Date: 2012 Jan |
Date Detail:
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Created Date: 2012-1-27 Completed Date: - Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 101157530 Medline TA: J Phys Chem B Country: - |
Other Details:
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Languages: ENG Pagination: - Citation Subset: - |
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From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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