Drag force of polyethyleneglycol in flows of polymer solutions measured using a scanning probe microscope

Abstract

The drag force of polyethyleneglycol thiol (mPEG–SH) attached to a cantilever probe in the flows of glycerol and polyethyleneglycol (PEG) solutions was measured. The effects of the molecular weights of mPEG–SH, solute, and molecular weights of PEGs in the flows on the drag force were investigated. The drag force of mPEG–SH with any molecular weight in the flows of glycerol solutions was described well by the stem and ellipsoidal-flower model proposed in a previous study. However, the drag force further increased in the flow of the PEG solutions. To describe the increment, an assumption of polymer entanglement with mPEG–SH attached to the probe in the flow was employed. The modified stem and ellipsoidal-flower model that employed polymer entanglements fit well to the drag force of mPEG–SH with any molecular weight in the flow of the polymer solution.