## Dissertation Archive

#### Title

Synthesis, Characterization and Solution Behavior of Hydrophobically Modified Polyelectrolytes

1993

Dissertation

#### Degree Name

Doctor of Philosophy (PhD)

#### Department

Polymers and High Performance Materials

Charles L. McCormick

The objective of this research is to study associating behavior of amphipathic polymers in aqueous media. The naphthalene-containing, hydrophobically associating model terpolymers were prepared by copolymerization of maleic anhydride and ethyl vinyl ether followed by post-modification with octyl and dodecyl amines and then hydrolysis. Viscosity studies indicate that these amphipathic systems form intramolecular association in dilute and semi-dilute solutions at various pH values and ionic strength. The dodecyl terpolymers show more pronounced hydrophobic associations than do the octyl analogs. Change in solution pH or addition of NaCl significantly lowers the viscosity of the polymer solution indicating a more collapsed conformation. Fluorescence lifetimes increase with increasing hydrophobe content. The lifetime of the monomer emission decreases with increasing pH, demonstrating a more hydrated environment experienced by the probe within the polymer coil. I$\sb{\rm E}$/I$\sb{\rm M}$ values of the terpolymers with low hydrophobe content decrease with increasing pH from 3 to 10 while the terpolymers with moderate hydrophobe content exhibit a maximum I$\sb{\rm E}$/I$\sb{\rm M}$ in the same pH range. The second system involves a series of acrylamide based, cationic copolymers. A novel cation monomer, N,N-dimethyl-N-dodecyl-N-(2-acrylamidoethyl)ammonium bromide (DAMAB), was first synthesized. This monomer possesses a CMC of 4.9 $\times$ 10$\sp{-3}$M and is readily copolymerizable with acrylamide (AM) via micellar and solution techniques. The rheological properties of the copolymers are strongly affected by their microstructures. A random copolymer with 5 mole% of DAMAB obtained by solution polymerization in t-butanol exhibits a tendency for intramolecular association, while microheterogeneous copolymerization of AM with 5 and 10 mole% of DAMAB in water yields microblocky structures which promote intermolecular association. The interactions of surfactants sodium dodecyl sulfate (SDS), trimethyltetradecylammonium bromide (TTAB), and Triton X-100 with AM/DAMAB copolymers are affected greatly by both the microstructures of the copolymers and the nature of the surfactants. Addition of Triton X-100 results in a large increase in the viscosity for the microblock copolymers at concentrations well below the critical overlap concentration while a random copolymer with 5 mole% DAMAB exhibits a collapsed conformation in the presence of TTAB. A strong viscosity enhancement is observed when SDS was added to the solution of a random copolymer containing 0.32 mole% DAMAB. A series of copolymers with rigid backbones was obtained by cyclocopolymerization of N,N-diallyl-N,N-dimethylammonium chloride and N,N-diallyl-N-alkoxybenzyl-N-methylammonium chloride in aqueous solution. The copolymer compositions were determined by $\sp1$H NMR and UV techniques. The copolymers in dilute solutions exhibit primarily intramolecular association in both water and electrolyte solutions. Shear thickening behavior of the copolymers is interpreted by intra- and intermolecular associations. Addition of SDS results in a large increase in the viscosity. (Abstract shortened by UMI.)