## LSU Historical Dissertations and Theses

1996

Dissertation

#### Degree Name

Doctor of Philosophy (PhD)

Chemistry

William H. Daly

#### Abstract

The structures of a number of novel poly(aryl ether) sulfones (nitro, aminomethyl, methyl and ethyl derivatives), which have applications as separation membranes, were determined unequivocally for the first time by applying sophisticated two-dimensional nuclear magnetic resonance (NMR) methods. The degree of substitution (DS) was found to vary among the products from 0.1 percent to about 2 percent (DS: nitro, 2.0; amino, 0.11; aminomethyl, 0.76; methyl, 2.12; ethyl, 2.05). Poly($\gamma$-stearyl-$\alpha$,L-glutamate), PSLG, is a "fuzzy rod" polymer composed of a central backbone that can exist as an $\alpha$-helix. This backbone, a polypeptide, is hydrophilic. The stearyl side chains (the "fuzzy" part of the molecule) are hydrocarbon segments of length C$\sb{18}$. These are hydrophobic, so the rigid-rod is soluble in hydrocarbon solvents, an unusual behavior for such systems. The purpose of this thesis was to look for interactions between the rigid-rod and a random coil polymer, polyethylene (PE). Deuterium NMR data, on samples containing no more than 5 percent deuterated polyethylene (DPE), indicated a small interaction between the two polymers. Differential scanning calorimetry (DSC) identified a transition not found in either blend component, occurring at about 75$\sp\circ$C on cooling and at about 95$\sp\circ$C on heating. Its detection is dependent on the rate of temperature change and occurs near the point where a rapid change in crystallinity is seen in the deuterium NMR. The DSC and NMR work detect a small interaction between the rods and coils. Polarized light and epifluorescence microscopy showed that at low levels of PE (10 percent range), the blends components behave independently. At high PE levels (180 percent), the micrographs show the composites are more than a sum of the parts. There is formation of ordered domains of PSLG, possibly initiated by an interfacial interaction with the overwhelming PE component. The use of dye-labeled PSLG confirmed the identification of these ordered regions as PSLG. For the first time, diffusion of pure PSLG was studied using the fluorescence photobleaching recovery experiment. The results indicated diffusion began near the side-chain melting point of 50$\sp\circ$C.

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