Charge-Dependent Microphase Separation in Thin Films from a Multiresponsive Pentablock Quaterpolymer: A GISAXS Investigation

Tunable
electrostatic interactions in thin films from (C-co-D)-b-B-b-A-b-B-b-(C-co-D)-type pentablock
quaterpolymers featuring hydrophobic end blocks as well as pH-responsive
and hydrophilic midblocks allow controlling their morphology both
by the choice of the pH value during film preparation and the solvent
polarity during solvent vapor swelling. The morphological changes
were characterized using grazing-incidence small-angle X-ray scattering,
and the data analysis was carried out on the basis of simulations
of two-dimensional scattering patterns. Dry films prepared at low
and at high pH values feature either weakly ordered spheres or totally
lack order, respectively. Swelling the former films in water vapor
triggers an order-to-disorder transition, which is reversed upon drying,
whereas films prepared at a high pH value remain disordered. Upon
swelling in toluene vapor, the morphology of films prepared at a low
pH value is stable, whereas the ones prepared at a high pH value microphase-separate
into a spherical morphology.