Groupe du prof: Julian Zhu et Xavier Banquy
Titre: “crystalline colloidal arrays formed by core-shell particles with UCST properties”
Résumé:
Photonic crystal with structural color is widely existent in nature. Photonic crystals formed by colloidal particles are also called crystalline colloidal arrays (CCAs). The artificial CCAs with stimuli-responsiveness are usually designed for the application of sensor. The responsiveness can come from hydrogel matrix, in which CCAs are embedded. The responsive hydrogel matrix is not necessary if the colloidal particle is stimuli-responsive. Our group has studied polymeric core-shell colloidal particle with a non-responsive core and a responsive shell over 15 years. The CCAs formed by core-shell colloidal particles were designed to be responsive to glucose, pH, ethanol, and temperature. However, the thermos-responsive property of core-shell particles that our group reported was just lower critical solution temperature (LCST). The core-shell particle with upper critical solution temperature (UCST) was not studied yet. My PhD project is to design and prepare CCAs formed by core-shell colloidal particles with UCST properties. The mechanism of UCST property is based on the polymer-polymer interaction including hydrogen bonding and ionic interactions. Three UCST polymers, Poly(N-acryloyl glycinamide) (PNAGA), Polymethacrylamide (PMAM), Poly(2-(Methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide) (PDMAPS) were used as the shell in my project. The good progress is that monodispersed core-shell particles can be synthesized, and CCAs with iridescence formed by the core-shell particles were successfully prepared. However, the UCST behavior is not expressed, or very weak. The reason might be that the molecular weight of the UCST polymer is not high enough to have strong polymer-polymer interactions, which is the mechanism of UCST property. Therefore, my future work is to synthesize high enough molecular weight of shell polymer using surface-initiated ATRP polymerization. Another direction is to embed CCAs into UCST hydrogel matrix, in which case the UCST property is from the hydrogel matrix instead of colloidal particles.
