Study of self-assembly and environmental response properties of block ionomer complexes.

摘要

A new class of self-assembling polymer-colloid materials, namely, surfactant-based block ionomer complexes (BIC), have recently been described. This thesis documents attempts to the comprehensive physicochemical characterization of BIC, to extend the knowledge of their basic properties of these materials, to facilitate future application-driven research. Several methods of preparation of BIC from different surfactants (single-, double- and triple-tail quaternary aliphatic amines) were optimized. Studies of the relationships between the surfactant structure and BIC self-assembly demonstrated surfactant packing preferences to play a major role in defining the morphologies of BIC. Methods for establishing control over BIC morphology by changing the composition of mixtures of different surfactants were explored and mixing behavior of surfactants in BIC was analyzed. Random distribution of single- and double-tail surfactants and segregation of single- and triple-tail surfactants in corresponding mixed BIC was demonstrated by electron microscopy and fluorescence energy transfer measurements.; Packing of the surfactants inside hydrophobic domains of BIC was studied by fluorescence anisotropy measurements, revealing changes relative to micellar packing of surfactant. The results suggested higher microviscosity of the hydrophobic regions, caused by cooperative electrostatic interactions of the surfactant head groups with the polyion chains. The order parameter for BIC was also higher, which is caused either by greater extent of alignment of the surfactant tails, or by slower rotational relaxation of BIC particles as a whole. Moderately low values of the order parameters indicated that the surfactant tails in BIC stay in a relatively disordered state. Effects of the addition of co-surfactants (aliphatic alcohols) on microviscosity and order of the hydrophobic domains of BIC were determined. In general, alcohols increased microviscosity and decreased the order parameter. The magnitudes of these effects were related to the chain lengths of alcohols.; The effects of alteration of the environmental parameters (pH, ionic strength and nature of counterions, temperature) on the structure of BIC were explored. Critical pH, ion concentration, temperature, and concentration of surfactant, characterizing the range of BIC stability, were determined.