All ETDs from UAB

Advisory Committee Chair

Eugenia Kharlampieva

Advisory Committee Members

Shane A Catledge

Aaron L Lucius

Peter E Prevelige Jr

Sergey Vyazovkin

Document Type

Dissertation

Date of Award

2015

Degree Name by School

Doctor of Philosophy (PhD) College of Arts and Sciences

Abstract

Ultrathin temperature-responsive hydrogels offer fast (in a matter of seconds) response to external stimuli and precise control over the hydrogel composition that has proven to be extremely important for bio-related applications and sensing. These hydrogels can typically uptake ~ 90% of water by volume and are capable of drastic and reversible volume change in response to applied stimuli which makes them ideal candidates to host and deliver small molecules and proteins. The multilayer hydrogels are fabricated by first covalently cross-linking hydrogen-bonded layer-by-layer (LBL) films that serve as templates for hydrogel assembly. This is followed by release of the uncross-linked polymers to yield the free hydrogel network. The advantage of this assembly is precise control over the hydrogel thickness, cross-link density and composition while preserving highly reversible volume change in response to stimuli. In addition to cross-link density and composition, the degree of stimuli response (swelling/shrinking) of multilayer hydrogels prepared by LBL deposition is strongly dependent on the chain conformation and degree of layer intermixing of the deposited polymers. The research described in this thesis is focused on the assembly and stimuli-responsive properties of pH- and temperature-responsive nanothin multilayer hydrogels of regulated architecture with special emphasis on the effect of ions on the hydrogel structure and stimuli-responsive properties. The potential applications of these hydrogels in sensing and drug delivery are also presented. In chapter two, the temperature-responsive properties of nanothin poly(N-vinylcaprolactam) (PVCL) multilayer hydrogels in the presence of Hofmeister anions is investigated. The work described in chapter three addresses the effect of anions on the internal architecture of hydrogen-bonded films of PVCL/poly(methacrylic acid) (PMAA) and poly(N-vinylcaprolactam-co-aminopropylmethacrylamide) (PVCL-co-NH2)/PMAA. The hydrogen-bonded films were assembled in the presence of different salts and the architecture of the hydrogen-bonded films was investigated by neutron reflectivity. The complexation of pH-responsive PMAA hydrogels with copper (II) ions and the stability of these (PMAA)-Cu2+ complexes in amino acid solutions is described in chapter four. Chapter five discusses temperature-responsive poly(N-vinylcaprolactam-co-acrylic acid) core-shell nanogels that were assembled into single component temperature-responsive multilayer hydrogels. Temperature-triggered drug delivery through artificial skin and entrapment of multiple drugs is also presented.

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