Stimuli-Responsive Zwitterionic Core–Shell Microgels for Antifouling Surface Coatings

Abstract

Fouling on filtration membranes is induced by the nonspecific interactions between the membrane surface and the foulants, and effectively hinders their efficient use in various applications. Here, we established a facile method for the coating of membrane surface with a dual stimuli-responsive antifouling microgel system enriched with a high polyzwitterion content. Different poly(sulfobetaine) (PSB) zwitterionic polymers with defined molecular weights and narrow dispersities were synthesized by reversible addition−fragmentation chain transfer (RAFT) polymerization and integrated onto poly(N-vinylcaprolactam) (PVCL) microgels via a controlled dosage of a cross-linker, adapting a precipitation polymerization technique to obtain a core−shell microstructure. Increasing the PSB macro-RAFT concentration resulted in a shift of both upper critical solution temperature and lower critical solution temperature toward higher temperatures. Cryogenic transmission electron microscopy at different temperatures suggested the formation of a core−shell morphology with a PVCL-rich core and a PSB-rich shell. On the other hand, the significant variations of different characteristic proton signals and reversible phase transitions of the microgel constituents were confirmed by temperature-dependent 1 H NMR studies. Utilizing a quartz crystal microbalance with dissipation monitoring, we have been able to observe and quantitatively describe the antipolyelectrolyte behavior of the zwitterionic microgels. The oscillation frequency of the sensor proved to change reversibly according to the variations of the NaCl concentration, showing, in fact, the effect of the interaction between the salt and the opposite charges present in the microgel deposited on the sensor. Poly(ethersulfone) membranes, chosen as the model surface, when functionalized with zwitterionic microgel coatings, displayed protein-repelling property, stimulated by different transition temperatures, and showed even better performances at increasing NaCl concentration. These kinds of stimuli-responsive zwitterionic microgel can act as temperature-triggered drug delivery systems and as potential coating materials to prevent bioadhesion and biofouling as well.

Unraveling the Mechanism and Kinetics of Binding of an LCI‐eGFP‐Polymer for Antifouling Coatings

“…The values of fouling are almost on par to those of best polymer brushes [ 40,58,100,101 ] and much lower than for other hydrophilic coatings based on grafted linear [ 39,102 ] or star‐shaped [ 103 ] polymers, hydrogels [ 104 ] and even four orders of magnitude lower than microgels. [ 105 ]…”

DNase I functional microgels for neutrophil extracellular trap disruption

“…In a typical adsorption experiment by QCM-D, with an increase of adsorbed mass on the surface, the Δf decreases. 64 With the injection of 0.1% BSA (in PBS pH 5.0) used as a model foulant onto the DNase I MG coated QCM-D chip, the frequency of the crystal sensor slightly decreased (Fig. S8-1 †) due to the mass adsorption on the coated surface.…”

Zwitterionic Nanogels and Microgels: An Overview on Their Synthesis and Applications

“…In a recent study in our group, we synthesized poly( N ‐vinylcaprolactam‐ co ‐sulfobetaine) (PSB‐PVCL)‐based core‐shell microgels and they have shown that the presence of poly(sulfobetaine) (PSB) shell inhibits protein adsorption on the microgel surfaces in an efficient manner compared to pure Poly( N ‐vinylcaprolactam) microgels when coated on commercially available poly(ether sulfone) (PES) membranes. [ 167 ] Interestingly, it was observed that at temperatures below the phase transition range of the PSB block, anti‐fouling was relatively poorer, owing to the inability of the PSB chains to form a hydration layer due to their dipole–dipole induced collapsed conformation. This anti‐fouling property was improved with increasing temperature as the PSB chains stretch out and can form hydrogen bonding with water, evident by the lack of fluorescence intensity from the FITC‐BSA proteins ( Figure a).…”