Laponite® Nanoparticle Doped Polyelectrolyte Hydrogels

• Main Author: Wu, Jiyuan
• Format: Dissertation
• Language: English
• Published: ProQuest Dissertations & Theses 01-01-2022
• Subjects: Air pollution; Analytical chemistry; Atmospheric Chemistry; Atmospheric sciences; Biomedical engineering; Brain research; Chemistry; Drug delivery systems; Engineering; Environmental engineering; Gold; Hydrogels; Materials science; Mechanical properties; Mechanics; Medical imaging; Medicine; Nanocomposites; Nanomaterials; Nanoparticles; Nanotechnology; Neurosciences; Optics; Particle size; Pharmacology; Physics; Polymer chemistry; Polymerization; Polymers; Regenerative medicine; Rheology; Spectrum analysis; Time series; Tissue engineering; Ultrasonic imaging; Viscoelasticity; Water treatment
• ISBN: 9798377674474

Introducing nano-materials into polymeric hydrogels often enhances mechanical strength and toughness. With the advantages of hydrogels, such as biocompatibility, biodegradability and porosity, the resulting hydrogel nanocomposites are often termed `smart' drug carriers, in the case of this research, pH-responsive hydrogels, demonstrating efficient transport and targeted, controlled release. However, due to nano-composite opacity and high-nano-particle loading, the widely available light-scattering diagnostics for particle size and zeta-potential are not readily applied to nano-composite hydrogels. In the other hand, electroacoustic characterization, can provide micro-structural insights by registering the so-called electrokinetic sonic amplitude (ESA). ESA has recently been applied to uncharged nanoparticle-doped hydrogels, and charged hydrogels without nanoparticles. This thesis examines, for the first time, the electroacoustic response of a model polyelectrolyte hydrogel with charged nanoparticle inclusions: Laponite® XLG-doped acrylamide-co-acrylic acid hydrogels. The acrylic-acid monomer fraction and Laponite® concentration were systematically varied in the ranges 0-1 and 0-1 wt%, respectively, reporting the ESA, conductivity, and linear viscoelasticity. Comparing these data to benchmark literature on acrylamide-co-acrylic acid based hydrogels (without nanoparticles), Laponite® was found to increase the ESA and conductivity, but decrease the stiffness. Quantitative interpretations were undertaken using theoretical models for the ESA and conductivity. The decrease in stiffness with Laponite®-doping contrasts with many studies on Laponite®-doped poly(acrylamide)- and poly(acrylic acid)-based hydrogels. This seems to reflect a high degree of acrylic acid neutralization, which promotes electrostatic repulsion between Laponite® and the polymer network, thus transforming Laponite® to a much more passive nano-particulate filler at neutral pH. This observation may have beneficial technological implications, e.g., promoting NP release. Further insights were gained by comparing polymeric hydrogels with their monomer-solution counterparts, enabling the effects of polymerization and cross-linking to be examined in more detail.