Interplay between caging and bonding in binary concentrated colloidal suspensions
作者：Di Jia; He Cheng;* Charles C. Han*
關鍵字：biphasic colloid, repulsive galss, attractive glass, gel
論文來源：期刊
具體來源：langmuir
發表時間：2018年
When a liquid becomes dynamically arrested, a gel, repulsive glass or an attractive glass state will form. Bonding and caging mechanisms decide their static structures and dynamic properties. In order to better understand their interplay, the competition between bonding and caging in a binary mixture of polystyrene core/poly(N-isopropylacrylamide) shell (CS) microgels and sulfonated polystyrene (PSS) particles is studied. CS microgels have short-range attraction above the volume phase transition temperature, while PSS species experiences relatively long-range electrostatic repulsion. Adding more PSS into the binary mixture will, of course, increase the total effective volume fraction, but lead to different properties in gel or glass states, respectively. For instance, in gels, it increases the localization length and weakens the gel; while in glass, it decreases the localization length and strengthens the glass. It thus implies that the static and dynamic properties of gels are mainly controlled by bonding, and those of both repulsive and attractive glass are governed by caging. On the other hand, increasing the temperature will decrease the effective volume fraction because of the volume phase transition of the CS microgels. A discontinuous repulsive glass-to-liquid-to-gel transition can be observed when PSS concentration is low, but a continuous repulsive glass-to-gel transition can also be observed with the increase of PSS concentration. It may hint that glass transition and physical gelation share a similar mechanism, while the former has longer relaxation time.