Oppositely charged polyelectrolytes tend to self-assemble in solution to form insoluble complexes (PECs). These complexes find use in many applications (e.g., controlled release, separation and sensor technologies), but are typically limited to planar, cylindrical or spherical geometries. With the intent of expanding this range of structural motifs, we have developed a simple strategy for directing PEC assembly using light. Commonly used polyelectrolytes, polyallylamine (PAH) and polystyrene sulphonate (PSS), were mixed in the presence of a photoacid generator. The solutions were prepared at pH 11.6 (significantly above the pKa of PAH) to ensure that almost all of the PAH amine groups were neutral. When exposed to longwave UV light (? = 365 nm) the photoacid generator lowered the local pH and protonated the PAH amine groups. This protonation lead to the self-assembly of PSS and PAH into PECs whose shape could be tuned by varying the photoirradiation pattern (in this case using a photomask). The assembly and properties of these PECs were probed using phase studies, isothermal titration calorimetry, elemental analysis and microscopy. The formation of these diverse and tunable structures suggests photodirected assembly as an attractive strategy for the fabrication of anisotropic PECs with custom-designed shapes.

Photodirected assembly of polyelectrolyte complexes

246th National Meeting (2013)

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