The fabrication of freestanding, sub-100 nm-thick, pH-responsive hydrogel membranes with controlled nano-morphology, based on modified poly(hydroxyethyl methacrylate) (PHEMA) is presented. Polymer hydrogel-brush films were first synthesized by surface-initiated atom transfer radical polymerization (SI-ATRP) and subsequently detached from silicon substrates by UV-induced photo-cleavage of a specially designed linker within the initiator groups. The detachment was also assisted by pH-induced osmotic forces generated within the films in the swollen state. The mechanical properties and morphology of the freestanding films were studied by atomic force microscopy (AFM). Inclusion of nanopores of controlled diameter was accomplished by performing SI-ATRP from initiator-coated surfaces that had previously been patterned with polystyrene nanoparticles. Assembly parameters and particle sizes could be varied, in order to fabricate nanoporous hydrogel-brush membranes with tunable pore coverage and characteristics. Additionally, due to the presence of weak polyacid functions within the hydrogel, the membranes exhibited pH-dependent thickness in water and reversible opening/closing of the pores.

Surfactant‐driven interfacial instability of emulsion droplets has recently emerged as a means for shaping polymeric particles with controllable surface texture. This paper presents a suspension polymerization‐based method to produce surface‐textured polystyrene particles by inducing an instability at the interface of prepolymerized emulsion droplets followed by rapid cooling. The interaction of two surface‐active components, i.e., arachidic acid and cetyltrimethylammonium bromide (CTAB) at the phase boundary triggers the interfacial deformation at a specific point in time. Rapid cooling freezes the deformed emulsion droplets in a nonequilibrium state. Viscosity is proposed as the key parameter influencing the particle morphology, which can be controlled by easily adjustable factors such as initiator concentration, temperature, time, and cooling rate. Contact angle hysteresis measurements of particle thin layers spread on a flat substrate reveal a strong influence of the particle surface texture on the wetting behavior. The presented particle synthesis method requires no specialized equipment and has a high potential for upscaling, making it promising for various applications including hydrophobic coatings, catalyst supports, separation technology, tissue engineering, or drug delivery.

No abstract