Temperature controlled surface hydrophobicity and interaction forces induced by poly (N-isopropylacrylamide)

Abstract

Poly (N-isopropylacrylamide) (PNIPAM) is a temperature responsive polymer. At temperature below its lower critical solution temperature (LCST 32 °C) PNIPAM is soluble in water and hydrophilic. At temperature above the LCST, the polymer becomes hydrophobic and insoluble in water. At temperatures above the LCST, PNIPAM has been shown to induce flotation of previously hydrophilic minerals. The mechanism is believed to be an increase in particle hydrophobicity when PNIPAM adsorbs to the particle surfaces at high temperature. This paper investigates the interaction forces between bare silica surfaces in PNIPAM solutions. The influence of three phase contact angles on these interactions, in the pr..