Salt‐Induced Depression of Lower Critical Solution Temperature in a Surface‐Grafted Neutral Thermoresponsive Polymer

Abstract

Summary: Quartz crystal microbalance with dissipation monitoring (QCM‐D) is employed to determine the effect of salt on the volume phase transition of thermoresponsive polymer brushes. Changes in mass and viscoelasticity of poly(N‐isopropylacrylamide) (PNIPAM) layers grafted from a QCM‐D crystal are measured as a function of temperature, upon contact with aqueous solutions of varying salt concentrations. The phase‐transition temperature of PNIPAM brushes, TC,graft, quantified from the QCM‐D measurements is found to decrease as the concentration of salt is increased. This phenomenon is explained by the tendency of salt ions to affect the structure of water molecules (Hofmeister effect). However, in contrast to the linear decrease in phase‐transition temperature upon increasing salt concentration observed for free PNIPAM, the trend in TC,graft for PNIPAM brushes is distinctively non‐linear.

Recent developments in superhydrophobic surfaces and their relevance to marine fouling: a review

“…The temperature-induced wettability variation has been confirmed by several groups on systems involving surface-grafted PNIPAAm. In a recent paper from the authors' laboratory, some studies are summarised that demonstrate the coil-to-globule transition in surface-grafted PNIPAAm is affected by the presence of salt (Jhon et al 2006). The latter effect may be particularly important when considering application of PNIPAAm-based smart coatings in salty waters (e.g.…”

Thermoresponsive Polymers for Biomedical Applications

“…Another important consideration when studying these gels is the effect of salt on the LCST of the polymers. Jhon et al studied this effect with PNIPAAm brushes and found salt to lower the LCST due to the Hofmeister effect of salt on the structure of water molecules [74].…”

Quartz Crystal Microbalance Studies on Conformational Change of Polymer Chains at Interface

“…[6] In principle, such a technique can detect the adsorption, conformation and interactions of macromolecules at interface. [7][8][9][10][11][12][13][14] This short review deals with the QCM-D studies on conformational change of polymer chains. Due to the limited space, we intend to mainly review what has been done in this laboratory though other research groups have done excellent work in this field.…”