RESUMEN
Depending on their aspect ratio, rod-shaped particles exhibit a much richer 2D and 3D phase behavior than their spherical counterparts, with additional nematic and smectic phases accompanied by defined orientational ordering. While the phase diagram of colloidal hard rods is extensively explored, little is known about the influence of softness in such systems, partly due to the absence of appropriate model systems. Additionally, investigating higher volume fractions for long rods is usually complicated because non-equilibrium dynamical arrest is likely to precede the formation of more defined states. This has motivated us to develop micrometric rod-like microgels with limited sedimentation that can respond to temperature and reversibly reorganize into defined phases via annealing and seeding procedures. A detailed procedure is presented for synthesizing rod-shaped hollow poly(N-isopropylacrylamide) microgels using micrometric silica rods as sacrificial templates. Their morphological characterization is conducted through a combination of microscopy and light scattering techniques, evidencing the unconstrained swelling of rod-shaped hollow microgels compared to core-shell microgel rods. Different aspects of their assembly in dispersion and at interfaces are further tested to illustrate the opportunities and challenges offered by such systems that combine softness, anisotropy, and thermoresponsivity.
RESUMEN
In this work, we developed a synthetic strategy to synthesize dual-temperature-responsive low surface fouling zwitterionic microgels. Statistical poly(N-vinylcaprolactam-co-glycidyl methacrylate) copolymers were synthesized by RAFT polymerization and post-modified by thiol-epoxy click reaction with thiol end-group-modified poly(sulfobetaine) macro-RAFT (PSB-SH) to obtain poly(N-vinylcaprolactam-co-glycidyl methacrylate)-graft-poly(sulfobetaine) (PVCL-co-PGMA-g-PSB) graft copolymers. Synthesized graft copolymers were cross-linked by diamine cross-linker in water-in-oil (w/o) inverse mini-emulsion to obtain zwitterionic microgels. Using this approach, we synthesized microgels with unique microstructure, high loading and uniform distribution of poly(sulfobetaine) chains, which exhibits tunable dual-volume phase transition temperatures. The microgels also showed excellent antifouling property reflected in strongly reduced protein absorption on a microgel-coated surface observed in real time by a Quartz Crystal Microbalance with Dissipation (QCM-D) monitoring experiment with continuous flow of protein solution. Therefore, this kind of zwitterionic microgel can be potentially used for temperature-triggered drug delivery and anti-bioadhesion coating material as well.