Poly(acrylic acid)–poly(ethoxylated
trimethylolpropane triacrylate)
(PAA–PETPTA) Janus microspheres with “respiratory”
function for controlled release were prepared by polymerization of
acrylic acid–ethoxylated trimethylolpropane triacrylate (AA–ETPTA)
Janus microdroplets in a continuous oil phase in a simple capillary-based
microfluidic device with the assistance of UV radiation. The flow
rate ratios of AA and ETPTA phases and surfactant content in the continuous
oil phase have a significant effect on the structure of the Janus
microspheres. PAA part in the Janus microspheres has respiratory function
for loading and release due to the different stimuli responses to
different pHs. The hollow structure of PETPTA part with different
sizes of opening serves as the host materials for PAA and could control
release rate further due to the different opening sizes. The obtained
PAA–PETPTA Janus microspheres showed high rhodamine B (RhB)
loading of 860 mg g–1 and different controlled-release
behavior in water with different pHs. The release rate increases with
the increase of pH and the contact area of PAA part with water. The
maximum controlled-release time for RhB was about 3 h in water with
pH of 5. In addition, the Janus microspheres also showed controlled-release
behavior for larger size guests, e.g., 150 nm polystyrene beads, which
indicated a wide range of application. The loading and release behaviors
for guests, for instance, for RhB, have almost no change even after
six times of reuse, which indicated a high stability.