Template effects of micro-pores created by the self-assembly of surfactant molecules in polystyrene thin film

Abstract

The objective of this thesis is to develop an emulsion-driven technique for patterning polymer films and to explore possible micro-environmental effects of the patterns created. Polystyrene (PS) is selected as the host matrix of the thin film on which a particular pattern can be created through spin-coating of a water-in-oil (W/O) emulsion. The nature and the amount of surfactant used for emulsification are crucial to the formation of the pattern on the PS film. It has been identified that Span-80 and AOT among the three types of surfactants (cationic, anionic, and nonionic) used in this study are most effective for creating distinct patterns on PS film. Of these two sole patterns achieved, Span-80 gave rise to an ordered collection of semi-spherical pores with a diameter of about 1 m on the PS film. Besides the study on pattern-generation capability of surfactant molecules, an extensive investigation has also been carried out to utilize micro-pores on Span-80-PS membrane as a chemical "reactor" for testing the combinatorial effect. Two types of chemical processes have been employed to examine the concept; they are recrystallization of acrylamide (a unit operation), the growth of nickel needles, and copper nanoparticles (chemical reactions), respectively. The results suggest the existence of a micro-environment effect in such micro-reactor, which guides the above process and reactions to follow well defined pathways.