posted on 2024-01-11, 15:11authored byShuang Liu, Li Peng, Siying Xiang, Hongbo Chen, Yajiang Huang, Xianbo Huang, Qian Huang
Entangled polymer solutions show different rheological
behavior
from melts in fast extensional flow. This discrepancy is not expected
according to the classic tube model and is an urgent issue to be solved
in polymer physics. While in the tube model the polymer concentration
is considered to be homogeneous, we show that extensional flow-induced
concentration gradient may happen in polymer solutions even with chemically
identical solutes and solvents. Through labeling an aggregation-induced
emission (AIE) probe on oligomeric solvents, the flow-induced concentration
gradient is visualized by combining extensional rheology and ex situ fluorescence microscopy. Microdomains of oligomeric
solvents with a length scale of tens of micrometers are observed,
and their influence on rheological behavior cannot be ignored.