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Our research, at present, has three main thrusts, all related to characterization of polymer morphology and structure. These include characterization of 1) the morphology, crystal structure and transitions in both main chain thermotropic liquid crystal polymers (LCPs) and several flexible backbone polyesters. 2) the morphology of nascent polytetrafluoroethylene dispersion particles and the effect of deformation and annealing and 3) the structure and properties of zein (corn protein) packaging films.

Two types of LCPs are under investigation, several series of polyesters containing flexible (aliphatic) segments of varying length and a number of semi-rigid homo- and co-polymer polyesters. Electron microscopy (EM) and diffraction (ED) are the primary characterization techniques, accompanied by a broad range of other techniques as appropriate.

The flexible backbone LCP polyesters have been shown to crystallize from the LC state by chain folding, similar to that observed for normal flexible polymers such as polyethylene, for flexible segment lengths as small as 4 CH2s; this occurs even though one of the polyester series is a random terpolymer. Many of the observations suggest chain folding in the LC state in thin films and on surfaces. Quenching studies are in progress to both characterize the morphology of the LC states and to permit characterization of crystallization by heating from the "glassy" LC and isotropic states.

An apparently general technique has been developed, in cooperation with Prof. F. Rybnikar, Tomas Bata University, Zlin, Czech Republic, for the simultaneous polymerization-crystallization in thin films, from the monomer melt or solution, of condensation polymers as lamellar single disclination domains and single crystals. With an extended chain thickness of ca. 100 Å, regardless of the polymerization temperature and time, the lamellar crystals are ideal for electron diffraction characterization of the crystal structure. Homopolymer and co-polymer LCP samples have extended from "rigid" rod polyesters based on "simple" monomers such as o-, m- or p-acetoxybenzoic acid (ABA) and 2,6 acetoxynaphthoic acid (ANA) to complex ones containing various side groups such as phenyl anthracene units. and poly(p-phenylene terephthalamide), as well as intractable polymers such as polyterephthalic anhydride.

The thin film studies have been complemented by bulk melt and dilute solution polymerization-crystallization of some of the polymers; for PpABA the resulting solution polymerized structures vary from thick (extended chain, 1-5 m) hexagonal shaped lamellae to long, single crystal whiskers depending on the solution concentration and temperature. The whiskers have permitted ready determination of ED zone patterns not available by tilting the single crystals. The use of a hot stage in the EM has permitted characterization of the transition behavior of several of the LCPs.

The confined thin film polymerization technique has also been applied to such flexible backbone polymers as polyethylene terephthalate (PET), polybutylene terephthalate and polytrimethylene terephthalate. For PET, for instance, the resulting crystal structure is suggested to be "more perfect" than that obtainable by any processing of previously polymerized material; we obtain a crystal density of 1.55 g/cm3 with crystal densities as compared to values in the literature varying from a low of 1.31 to 1.53 g/cm3 as a function of processing history.

Annealing of isolated PTFE dispersion particles near 350 °C results in large scale molecular motion of individual molecules on the substrate and the growth of folded chain, lamellar single crystals despite molecular weights > 10 6. Deformation of the particles results in 10 nm diameter fibrils; if annealed on the substrate the result is shish-kebabs due to nucleation and growth of lamellae on the fibrils from the mobile molecules. Characterization of the structure of the nascent particles and correlation of the morphology of bulk PTFE and the single crystal lamellae is underway.

The protein zein is a potential film forming byproduct of the production of ethanol from corn; it is hydrophobic; its molecular weight of ca. 25,000 is greater than that of many commercial polyamides. In collaboration with Profs. M. Cheryan and G. Padua in the College of Agriculture, we are involved in a project to economically purify the zein during ethanol production and develop a commercially feasible process to produce biodegradable (edible) packaging films. Of concern in our research is characterization of the morphology and properties of the film as a function of processing history, with the goal of improving the properties of the films currently being produced. In current films, which approach those of low density polyethylene in properties, the zein has remained folded (in the biological sense); desired is a method to unfold and orient the molecules.