Title

Carbon-13 NMR Characterization and Solution Behavior Studies of Model Polysaccharide and Synthetic Acrylamide-Based Copolymers (Cellulose)

Date of Award

1985

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Polymers and High Performance Materials

First Advisor

Charles L. McCormick

Advisor Department

Polymers and High Performance Materials

Abstract

The monomer compositions of copolymers of acrylamide (AM) with diacetone acrylamide (DAAM), sodium acrylate (HPAM), sodium-2-acrylamido-2-methylpropane sulfonate (AMPS), sodium-2-sulfoethyl methacrylate (SEMNa), and sodium-3-acrylamido-3-methylbutanoate (NaAMB) have been determined by carbon-13 nuclear magnetic resonance. The technique has also been applied to a terpolymer containing AM, DAAM, and AMPS and to graft copolymers of AM, AM-co-DAAM, and AM-co-AMPS on a dextran backbone. The determination of the degree of substitution of three 2,4-dichlorophenoxyacetic acid esters of poly(vinyl alcohol), starch, and cellulose was attempted. By utilizing pulse repetitions greater than 5T(,1)'s and gated decoupling, polymer compositions comparable to elemental analysis were calculated. While the elemental analysis technique is superior in precision, the accuracy of the carbon-13 NMR method is potentially better considering polymer contamination with carbon containing solvents. Copolymers of AM and DAAM have been shown to increase their intrinsic viscosities in aqueous salt solutions. A mechanism of increase has been proposed in which the salt solutions result in a maximum conformational change in copolymers containing 20% DAAM monomer thereby stabilizing the hydrophobic interactions by which polymer-polymer aggregates are formed. Infrared and NMR studies have shown that a previously proposed intramonomer H-bonded ring mechanism cannot be substantiated. A mechanism for the dissolution of cellulose by LiCl/DMAc has been investigated. Through chemical shift studies of model compounds in various salt-amide combinations, it has been shown that the LiCl/DMAc and the LiCl/NMP solvents serve to interact at the hydroxyls of cellulose therefore disrupting crystallinity and allowing dissolution. Carbon-13 NMR characterization confirms that LiCl/DMAc is a "true" solvent for cellulose and that it exists as a slowly reorienting chain even at 90(DEGREES)C.