All ETDs from UAB

Advisory Committee Chair

Eugenia Kharlampieva

Advisory Committee Members

Wayne J Brouillette

Aaron S Catledge

Ashish K Pathak

Sadanandan E Velu

Document Type

Dissertation

Date of Award

2013

Degree Name by School

Doctor of Philosophy (PhD) College of Arts and Sciences

Abstract

The research presented in this thesis is focused at the design and fabrication of pH-responsive layer-by-layer (LbL) hydrogels and the synthesis of the ABA block copolymer poly(2-methyloxazoline)-block-poly(dimethylsiloxane)-block-poly(2-methyl-oxazoline) (PMOXA-b-PDMS-b-PMOXA). Ultrathin stimuli-responsive layer-by-layer hydrogels, as compared to bulk hydrogels, can respond to external stimuli in a short time range (usually within seconds) which renders them particularly useful in sensing. Moreover, layer-by-layer technique allows the hydrogel film to be deposited with controlled thickness growth. However, the fabrication of LbL hydrogels with controllable cross-linking density and swelling degree still remains challenging. In chapter two, novel pH-sensitive LbL hydrogels based on poly(4-vinyl pyridine) (P4VP) were fabricated. Amino-containing units with appropriate molar ratio were incor-porated into the P4VP during polymerization to provide the copolymers with certain amount of cross-linking sites; thus, it was possible to fabricate P4VP LbL hydrogels with controllable cross-linking density. In chapter three, the pH-triggered swelling behavior and surface wettability of P4VP hydrogels were examined. The (P4VP-NH2-4) multilayer hydrogel, containing 4% amino-bearing units, exhibited 10-fold swelling at pH=2 and a sharp transition from hydrophilic to hydrophobic state when pH changed from 2 to 6. In contrast, the (P4VP-NH2-7) hydrogel film displayed merely a 4-fold swelling at pH=2. In chapter four, novel polyacid LbL hydrogels were synthesized and their pH-triggered swelling was investigated. Poly(acrylic acid) (PAA) and poly(meth- acrylic acid) (PMAA) have been applied in biomedical research due to their biocompatibility. PAA or PMAA copolymer incorporated amino groups were able to cross-link either by the for-mation of amide bonds or by selectively reacting with amino groups with cross-linking reagent. PMAA LbL hydrogel cross-linked among amino groups presented higher swell-ing degree. Further, spin-assisted assembled multilayer hydrogels displayed higher swell-ing than dipped hydrogels. In chapter five, a synthetic protocol for ABA-type block copolymer PMOXA-b-PDMS-b-PMOXA was established. This copolymer could assemble into nano-sized pol-ymersomes for advanced applications in therapeutics and diagnostics. However, the syn-thesis of this copolymer has not been thoroughly discussed in the previous studies. The modified procedure allowed us to build up a library of this copolymer with variable hy-drophilic to hydrophobic ratios.

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