Raymond J. Thibault

University of Massachusetts Amherst, Amherst Center, MA, United States

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Publications (10)52.69 Total impact

  • Raymond J. Thibault, Vincent M. Rotello
    02/2008: pages 1 - 7; , ISBN: 9780470384053
  • R. J. Thibault, O. Uzun, R. Hong, V. M. Rotello
    Advanced Materials 07/2006; 18(16):2179 - 2183. · 14.83 Impact Factor
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    ABSTRACT: Random polystyrene copolymers grafted with complementary recognition elements were combined in chloroform producing vesicular aggregates, that is, recognition-induced polymersomes (RIPs). Reflection interference contrast microscopy (RICM) in solution, coupled with optical microscopy (OM) and atomic force microscopy (AFM) on solid substrates, were used to determine the wall thickness of the RIPs. Rather than a conventional mono- or bilayer structure (approximately 10 or approximately 20 nm, respectively) the RIP membrane was 43+/-7 nm thick. Structural arrangement of the polymer chains on the RIP wall were characterized by using angle-resolved X-ray photoelectron spectroscopy (AR-XPS). The interior portion of the vesicle membrane was found to be more polar, containing more recognition units, than the exterior part. This gradient suggests that a rapid self-sorting of polymers takes place during the formation of RIPs, providing the likely mechanism for vesicle self-assembly.
    Chemistry 12/2005; 11(23):6916-20. · 5.83 Impact Factor
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    ABSTRACT: Polystyrene functionalized with diamidopyridine (DAP) recognition units self-assembles in nonpolar media to form thermally reversible micrometer-scale spherical aggregates. The size and the thermal stability of these microspheres can be controlled by the molecular weight of the polymer. The addition of thymine-functionalized polymer to these self-assembled microspheres converted them into vesicular aggregates with a controlled size. The morphology change was reversible: the addition of DAP-functionalized polymer converted the vesicles back to microspheres.
    Journal of the American Chemical Society 11/2004; 126(45):14773-7. · 10.68 Impact Factor
  • Raymond Thibault, Vincent Rotello
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    ABSTRACT: The concepts of molecular recognition present powerful tools for the control of polymer assemblies. In recent years, numerous researchers have coupled supramolecular chemistry with polymer synthesis and engineering, creating a discipline located squarely at the interface of chemistry and polymer science. This review will present an overview of the field of supramolecular polymer science, establishing fundamental differences between main- and sidechain supramolecular polymers and demonstrating the utility of these methodologies in polymer structure control, guest sensing, surface deposition, and in the formation of microscale aggregates.
    Polymer News 01/2004; 29(2):40-49.
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    ABSTRACT: Bis-thymine units were used to noncovalently cross-link a complementary diamidopyridine-functionalized copolymer. Upon combination in noncompetitive solvents, discrete micron-scale spherical aggregates were formed arising from specific three-point polymer-cross-linker hydrogen bonding interactions. The diameter of these microspheres could be controlled through spacer structure. The cross-linking process was fully thermally reversible, with complete dissolution observed at 50 degrees C and reformation of the aggregates upon return to ambient temperature. This process could be repeated multiply, with lower particle dispersity observed arising from the annealing process.
    Journal of the American Chemical Society 10/2003; 125(37):11249-52. · 10.68 Impact Factor
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    ABSTRACT: Specific hydrogen-bonding interactions between polymers and surface-tethered recognition elements were used to selectively modify self-assembled monolayers (SAMs) on gold. The interfacial recognition processes were followed by observing frequency changes of thymine-SAM modified quartz crystal microbalance (QCM) chips during adsorption of diamidopyridine-functionalized (DAP) polystyrene from a nonpolar solvent. QCM studies combined with X-ray photoelectron spectroscopy (XPS), water contact angle, and ellipsometry measurements of the polymer-modified surfaces demonstrate the selectivity of the polymer−surface hydrogen-bonding interactions. These studies also indicate that the degree of recognition element functionalization of both the polymer and the surface is crucial in determining the rate, selectivity, and coverage of polymer on the surface.
    Langmuir. 07/2003; 19(17).
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    ABSTRACT: We have explored the interactions of mono- and multivalent guests with Recognition-Induced Polymersomes (RIPs) formed from complementary random copolymers featuring diamidopyridine and thymine functionality. Addition of monovalent guests featuring imide functionality to these RIPs induced a temporary swelling of the vesicles, followed by dissociation of the vesicles due to competitive binding of the guest. Conversely, multivalent thymine-functionalized nanoparticle guests were rapidly incorporated into the RIPs, inducing a contraction of RIP diameter over time. These mono- and multivalent interactions were extremely specific: highly analogous control systems showed no interaction with the RIP structures. Taken together, these studies demonstrate highly selective molecular "lock and key" control over higher-order assembly and recognition processes.
    Journal of the American Chemical Society 01/2003; 124(51):15249-54. · 10.68 Impact Factor
  • Ulf Drechsler, Raymond J. Thibault, Vincent M. Rotello
    Macromolecules. 11/2002;
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    ABSTRACT: Flavin mononucleotide (FMN, 1) provides a dynamic conformational probe for studying the covalent cross-linking of dopants into silica. Excitation of FMN 1 leads to photodecomposition only when the side chain is in an appropriate geometry to allow a six-membered ring transition state. Our investigations indicate that the rate of photodecomposition dramatically changes in the sol−gel through the course of the gelation and aging process. Rapid changes in the decomposition rate were observed in the sol very early in the gelation process, indicating that the hydroxyl groups of 1 become covalently fixed within the silicate matrix and that silicate structure is formed around this site very early in the sol−gel process.
    Langmuir. 10/2002; 18(24).