Coupling of gelation and glass transition in a biphasic colloidal mixture—from gel-to-defective gel-to-glass
作者：賈迪，Javoris Hollingsworth，周治，程賀，韓志超
關(guān)鍵字：gelation, glass transition, defective gel
論文來源：期刊
具體來源：soft matter DOI: 10.1039/c5sm01531f
發(fā)表時間：2015年
The
state transition from gel to glass is studied in a biphasic mixture of
polystyrene core/poly (N-isopropylacrylamide)
shell (CS) microgels and sulfonated polystyrene (PSS) particles. At 35 °C, the
interaction between CS is due to short-range Van der Waals attraction, while
that between PSS is from long-range electrostatic repulsion. During variation
of the relative ratio of the two species at a fixed apparent total volume
fraction, the mixture exhibits a
gel-to-defective gel-to-glass transition. When small amounts of PSS are
introduced into the CS gel network, some of them are kinetically trapped,
causing a change in its fractal structure, and act as defects to weaken the macroscopic gel strength. An increase of PSS content in the
mixture promotes the switch from gel to defective gel, e.g., the typical two-step yielding gel merges into one-step
yielding. This phenomenon is an indication that inter-cluster bond breakage
coincides with intra-cluster bond fracture. As the relative volume fraction of PSS exceeds a critical threshold, the
gel network can no longer be formed; hence, the mixture exhibits
characteristics of glass. A state diagram of the biphasic mixture is
constructed, and the landscape of the different transitions will be described
in future studies.