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You searched for subject:(compelxation). Showing records 1 – 2 of 2 total matches.

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Michigan Technological University

1. Narkar, Ameya Ravindra. PH RESPONSIVE, ADHESIVE HYDROGELS BASED ON REVERSIBLE CATECHOL - BORONIC ACID COMPLEXATION.

Degree: PhD, Department of Biomedical Engineering, 2015, Michigan Technological University

Smart hydrogel adhesives with tunable properties consist of adhesive moieties in the polymer network that respond to external stimuli like pH, temperature, etc. Responsiveness of smart adhesives to pH, in particular, is important because of the simple actuation mechanism and the ability to achieve facile bonding and debonding upon command. Covalently crosslinked hydrogel adhesives were prepared by employing an N-HEAA (hydroxyethyl acrylamide) backbone embedded with dopamine methacrylamide (DMA), a marine mussel inspired adhesive protein and 3-acrylamido phenylboronic acid (AAPBA), to determine the effect of pH on the interfacial binding properties of the hydrogel adhesive with a borosilicate glass substrate. Swelling tests were performed to determine the response of the synthesized hydrogels to changes in pH values. These tests revealed that in a pH 3 buffered solution, hydrogels containing DMA and AAPBA showed a shrinking trend, while at pH 9, a swelling phenomenon was observed. The evidence from oscillatory rheometry tests exhibited elevated loss moduli (Gʹ) for hydrogels with DMA and AAPBA at pH 9, when compared to the relevant controls. In conjunction, the data from swelling tests and rheometry explained the unusual swelling of the hydrogels and formation of the catechol-boronate complex at pH 9, which caused more than an order of magnitude of increase in the Gʺ owing to the viscous dissipation of energy at that pH as compared to the control gels. The interfacial binding properties were tested by performing contact mechanics tests, in the presence of an acidic/basic medium. The maximum work of adhesion values of 0.59<em>mJ/m2</em> were obtained for hydrogels with 2.5mol% DMA and 10mol%AAPBA in the polymer network, when tested against a borosilicate glass surface wetted with 250μL of the pH 3 solution. At pH 9, this value reduced to as much as 1/5th of its value at pH 3. Earlier works have proposed that the oxidation of the catecholic groups that are chiefly responsible for adhesion with an inorganic substrate, is a deterrent to the adhesive properties of a hydrogel. We have accomplished the development of a model adhesive system in which we utilized the pH responsiveness of the hydrogels to demonstrate the elevated and reduced works of adhesion at acidic and basic pHs respectively. We believe that the catechol- boronic acid complex at pH 9 will allow for the reversible DOPA- facilitated adhesion. Reversibility studies performed in this direction revealed that while the hydrogels could recover their shape in terms of the measured diameters, further testing and analysis is required for understanding the ideal composition of the hydrogel and environmental trigger to actuate reversibility. Advisors/Committee Members: Bruce P. Lee.

Subjects/Keywords: adhesive; catechol; compelxation; pH; reversible; Biomedical Engineering and Bioengineering

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Narkar, A. R. (2015). PH RESPONSIVE, ADHESIVE HYDROGELS BASED ON REVERSIBLE CATECHOL - BORONIC ACID COMPLEXATION. (Doctoral Dissertation). Michigan Technological University. Retrieved from https://digitalcommons.mtu.edu/etds/1002

Chicago Manual of Style (16th Edition):

Narkar, Ameya Ravindra. “PH RESPONSIVE, ADHESIVE HYDROGELS BASED ON REVERSIBLE CATECHOL - BORONIC ACID COMPLEXATION.” 2015. Doctoral Dissertation, Michigan Technological University. Accessed January 25, 2021. https://digitalcommons.mtu.edu/etds/1002.

MLA Handbook (7th Edition):

Narkar, Ameya Ravindra. “PH RESPONSIVE, ADHESIVE HYDROGELS BASED ON REVERSIBLE CATECHOL - BORONIC ACID COMPLEXATION.” 2015. Web. 25 Jan 2021.

Vancouver:

Narkar AR. PH RESPONSIVE, ADHESIVE HYDROGELS BASED ON REVERSIBLE CATECHOL - BORONIC ACID COMPLEXATION. [Internet] [Doctoral dissertation]. Michigan Technological University; 2015. [cited 2021 Jan 25]. Available from: https://digitalcommons.mtu.edu/etds/1002.

Council of Science Editors:

Narkar AR. PH RESPONSIVE, ADHESIVE HYDROGELS BASED ON REVERSIBLE CATECHOL - BORONIC ACID COMPLEXATION. [Doctoral Dissertation]. Michigan Technological University; 2015. Available from: https://digitalcommons.mtu.edu/etds/1002


University of Michigan

2. Salehi, Ali. Equilibrium Phase Behavior and Mass Transport in Neutral and Oppositely Charged Polymer Assemblies.

Degree: PhD, Chemical Engineering, 2018, University of Michigan

Polyelectrolyte (PE) complexation (PEC) occurs upon mixing solutions of oppositely charged ‎polyelectrolytes. This electrostatic self-assembly paradigm is also extended to layer-by-layer ‎‎(LbL) assembled polyelectrolyte multilayers (PEM). Despite the broad applications of both PEC ‎and PEM, bulk phase behavior of PEC and mass transport controlling the structure and film ‎growth rate of PEMs and their connection is poorly understood. In this doctoral work, we ‎present a combined experimental and theoretical investigation of PEC and PEM LbL assembly. ‎We first observe that polymer-specific interactions have a profound effect on both PEC and LbL ‎growth rate while salinity has a non-monotonic and a rather universal effect on LbL growth rate ‎of fully ionized polyelectrolytes when normalized by the critical salinity required to suppress ‎PEC. We next develop a free energy model of PEC by incorporating counterion association-‎dissociation, cross-chain ion pairing (IP) and protonation, treating each as a reversible reaction ‎using laws of mass action. The importance of each reaction is controlled by a corresponding ‎chemistry-dependent standard free energy input parameter that could be measured via ‎experimentation or molecular simulations. In monophasic systems, the thermodynamic model can ‎qualitatively explain the shifts in acidity and basicity observed in potentiometric titration of weak ‎PEs in the presence of salt and oppositely charged PEs in accordance with Le Châtelier’s ‎principle. We demonstrate how a competition between counterion condensation and IP can ‎explain the complex coacervation of strongly charged PEs. Binodal diagrams predicted in our ‎model are most sensitive to IP strength both for weak and strong PEs. We compare binodal ‎diagrams predicted by our model against experimental data, and find a plausible parameter set ‎that leads to agreement between them. Finally, we develop a transport modeling framework for ‎LbL assembly by variational minimization of the Rayleighian of a mixture of oppositely charged ‎PEs, simple salt and water with respect to species velocities yielding species flux laws that equate ‎the net mutual friction between components with the diffusional driving force on each species. ‎The latter includes gradients in the conventional mixing chemical potential, electrostatic potential ‎and mechanical stress (only for PEs). We also develop a constitutive equation for mixtures of PEs ‎that accounts for solvent imbibition and IP. The result is a modification of the upper-convected ‎Maxwell model. Our LbL transport model captures PE adsorption and film swelling in the ‎equilibrium limit. A dynamic coupling of elastic stress and diffusion is applied in a different ‎context to an electroneutral system involving drug release from polymer tablets, capturing ‎Fickian, anomalous and case II modes of drug transport that arise naturally from the model. In ‎addition to LbL, the transport framework proposed in this work can be applied to any system of ‎charged and neutral components.‎ Advisors/Committee Members: Larson, Ronald G (committee member), Thornton, Katsuyo S (committee member), Glotzer, Sharon C (committee member), Kotov, Nicholas (committee member).

Subjects/Keywords: Polyelectrolyte Compelxation; Mass Transport; Thermodynamics; Modeling; Layer-by-Layer Assembly; Chemical Engineering; Engineering

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Salehi, A. (2018). Equilibrium Phase Behavior and Mass Transport in Neutral and Oppositely Charged Polymer Assemblies. (Doctoral Dissertation). University of Michigan. Retrieved from http://hdl.handle.net/2027.42/143922

Chicago Manual of Style (16th Edition):

Salehi, Ali. “Equilibrium Phase Behavior and Mass Transport in Neutral and Oppositely Charged Polymer Assemblies.” 2018. Doctoral Dissertation, University of Michigan. Accessed January 25, 2021. http://hdl.handle.net/2027.42/143922.

MLA Handbook (7th Edition):

Salehi, Ali. “Equilibrium Phase Behavior and Mass Transport in Neutral and Oppositely Charged Polymer Assemblies.” 2018. Web. 25 Jan 2021.

Vancouver:

Salehi A. Equilibrium Phase Behavior and Mass Transport in Neutral and Oppositely Charged Polymer Assemblies. [Internet] [Doctoral dissertation]. University of Michigan; 2018. [cited 2021 Jan 25]. Available from: http://hdl.handle.net/2027.42/143922.

Council of Science Editors:

Salehi A. Equilibrium Phase Behavior and Mass Transport in Neutral and Oppositely Charged Polymer Assemblies. [Doctoral Dissertation]. University of Michigan; 2018. Available from: http://hdl.handle.net/2027.42/143922

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