Polymer brush films, comprising of polymer chains tethered to a surface, are intrinsically constrained systems. Low magnitude mechanical forces (10-100 pN) are believed to operate in polymer brushes and cause degradation or deformation. Examples from literature suggest that solvent-induced swelling of polymer brushes can amplify the existing tension at the interface leading to detachment of polymer chain from the surface, also known as degrafting. Degrafting is believed to be a result of swelling-induced acceleration of ester/amide/siloxane bond hydrolysis at the polymer brush interface. This often leads to failure of polymer coatings as sensors and anti-biofouling materials. Few strategies to overcome this is either by shielding the hydrolysis-sensitive linkages at the interface or using alternative anchor chemistries to minimize initiator hydrolysis. However, a systematic investigation of the interfacial properties of a polymer brush is missing, partly due to limited chemistries available for interfacial modifications.<br/>We designed a library of probes that can be inserted at the polymer brush interface and allow for systematic modulation of interfacial properties. These probes impart hydrophilic or hydrophobic characteristic to the interface depending on the functional groups involved. This hydrophobic/hydrophilic layer at the interface can fine tune the interfacial swelling and thereby, control the rate of degrafting. These probes have a broad scope of application in both hydrophobic and hydrophilic polymer brush systems and present us with an opportunity to better understand the degrafting phenomenon.

Polymer brush swelling and importance of the interfacial phenomena

ACS Spring 2022

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