Graduation Year

2007

Document Type

Thesis

Degree

M.S.B.E.

Degree Granting Department

Chemical Engineering

Major Professor

Vinay K. Gupta, Ph.D.

Co-Major Professor

John T. Wolan, Ph.D.

Committee Member

Norma Alcantar, Ph.D.

Keywords

pnipam, microgels, gold nanoparticles, molecular imprinting, interpenetrated networks

Abstract

Detection of trace elements such as organic contaminants, explosive residues, and

metal ions is an intellectually challenging task in science and engineering. It is also a

topic of increasing importance due to its impact on society and the environment.

Designing molecularly imprinted materials is one of the most promising approaches to

explore sensing and detection applications. “Stimuli-sensitive” polymer materials are

ideal candidates for these imprinted sensors as they are able to respond to changes in their

environment and can be tailored by cross-linking the polymer chains. The responses can

be amplified and transduced into measurable signals due to macromolecular properties

provided by the use of a polymer. The purpose of the research in this project is to

combine organic polymers with inorganic constituents to tailor the binding properties and

the responses of the composite material for detection of metals ions in aqueous solutions.

The research, here, is based on a thermally responsive polymer such as poly(Nisopropylacrylamide)

(PNIPAM), which exhibits a well-known reversible volume phase

transition in aqueous media around approximately 32°C. Combining cross-linked

microgels formed from PNIPAM and its copolymers with gold nanoparticles (GNP)

imparts the composite material with optical properties such as intense visible absorption

due to the unique surface plasmon absorption of these small nanoparticles. The use of

copolymers allows incorporation of functional groups, such as carboxylic acid, that are

potential sites for binding metal ions. Cross-linking of the metal ion binding polymer

imprints the metal ion in the PNIPAM microgel network.

In

this research, design of the composite material was investigated using

copolymers of NIPAM and acrylic acid (AA), copolymers of NIPAM and glycidyl

methacrylate (GMA), and interpenetrating networks of PNIPAM and PAA. A broad

spectrum of polymerization conditions were studied such as changes in cross-linking

density as well as changes in the synthetic procedure. Techniques such as turbidometry,

ultraviolet visible spectroscopy (UV-VIS), transmission electron microscopy (TEM), and

dynamic light scattering (DLS) were employed to characterize the microgels as well as

their composites with GNP. Preliminary investigation of imprinting the microgels with

heavy metal ions such as copper was also performed. The novel polymer-metal

nanocomposites explored here will serve as an important contribution for the current

ongoing research efforts in designing materials in the nano-scale capable of sensing and

detecting metal ions in solution with high selectivity.

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