The formation of specific phase-separated morphologies is central to achieving high performance polyurethanes. Polyurethanes are composed of various structural elements possessing a mixture of different functional groups, molecular weights, and sequence lengths. The chemistry, the phase behavior, and the kinetics of phase evolution will influence the type of phase-separated morphology formed. In fact, the phase behavior also depends upon the chemical structure and the molecular weight distribution of the components. Despite the importance of chemical structure, it is still not understood quantitatively. In addition, little is known about how the developing structure organizes into different phase-separated morphologies. The work herein addresses these issues. The molecular weight distributions, end groups, and linkages of polyurethane structural elements were quantitatively determined. The structural elements included polyether and polyester macrodiols, polyurethane prepolymers, and polyurea hard segments. Under homogeneous conditions, the molecular weight distribution formed obeys a Schultz-Flory distribution; although when toluene diisocyanates are used as the diisocyanate the effect of change in reactivity narrows the distribution. Under heterogeneous conditions, the phase separation of water causes a change in the local stoichiometry and narrows the distribution further. In the presence of typical polyurethane side reactions, the distribution is broadened. The formation of allophanate linkages was most prevalent in PPG prepolymers prepared at reaction temperatures of 145°C. Infrared spectroscopy was used to study the crystallization behavior of semicrystalline polyurethanes and the reaction and morphological evolution of polyurethane foams. Hydrogen bonding between urethane groups was shown to influence all aspects of the crystallization behavior, including the initial state, nucleation and growth rates, and the final morphology. Hydrogen bonding proves to be less crucial in the onset of phase separation in polyurethane foams. The most crucial parameter was shown to be hard segment anisotropy. Foams prepared from diisocyanates yielding highly anisotropic hard segments phase separate at lower reaction conversion, with a faster rate, and to a higher degree of phase separation and perfection.

The study of hydride generation as an analytical technique has occupied a section of analytical chemistry for a considerable period of time. Applications of the technique have built upon the existing background of chemistry with few forward steps. The progress of analytical chemistry requires that the fundamental chemistry be studied so that it may then be applied within the understood limitations. Hydride generation is a technique that is heavily influenced by a variety of factors including but not limited to pH and oxidation state. The required oxidation state for hydride generation of arsenic and antimony is +3 and depending upon sample preparation, adjustment of the oxidation state is required. Bromide has been identified as a reductant for pentavalent arsenic and antimony and can be applied to reduce selenium to the hydride forming state of Se IV. Experiments are then described that demonstrate the limitations and application of bromide as a reductant for the simultaneous reduction of arsenic, antimony and selenium to the optimum hydride forming state, prior to hydride generation. The post-column chemistry of arsenic is examined with the application of microwave-assisted chemistry to the digestion of organoarsenical species. A mixture of bromide and bromine is applied under conditions that are also successful for the post column digestion of organoselenium compounds. The significance of the post column digestion is that it will assist in the development of simultaneous determination of arsenic and selenium species. The post-column chemistry of antimony has thus far been limited to the addition of borohydride under conditions that compromise the sensitivity of the species studied and is limited to those species that are borohydride active. There are several reports in the literature of unidentified antimony species that were not identified by the technique of hydride generation. Therefore, the application of photo-oxidation to those species would enable their subsequent determination by hydride generation. Two small projects with graphite furnace atomic absorption spectrometry are also discussed. The first project describes the development of a method for the determination of gold in cell structures. The second describes the measurement of bismuth in transferrin protein.

Crucial parameters affecting protein-polyelectrolyte complexation include protein charge anisotropy, chain flexibility and polyelectrolyte (PE) charge sequence distribution. PE chain flexibility was found to affect the colloid-binding affinity: stiffer PE's binding more strongly than flexible PEs. However, the definition of chain stiffness should not be conflated with polyelectrolyte persistence length especially in the cases corresponding to the resistance of the chain to bending. A Monte Carlo study of the PE binding site coupled with protein electrostatic potential modeling has further clarified these issues by identifying the nonspecific polyelectrolyte binding site on serum albumin at conditions corresponding to experiments. Examination of the binding between serum albumin and decamers of acrylamidopropanesulfonate and acrylamide of different sequences has shown that the bound decamer retains much of its configurational entropy. Polyelectrolyte stiffness and charge sequences have profound effects on the formation of polyelectrolyte-protein coacervates, as shown by comparison of coacervates made with chitosan vs. those made with a more flexible and fully charged synthetic PE of the same structural charge density. The coacervates with chitosan differ markedly in rheology and dynamic light scattering, and SANS. These differences are explained in the context of a model in which coacervates contain protein-rich dense domains with sizes > than a few hundred nanometers. This model has been supported by fluorescence recovery after photobleaching, CryoTEM and pulsed field gradient NMR. In the context of this model, chain flexibility and the charges of ca, 50 nm polyelectrolyte-protein aggregates have been shown to affect the connectivity and size of the dense domains, which behave as transient obstacles to protein diffusion within the coacervates.