Tunable Thermoresponsive Polymeric Platforms on Gold by Photoiniferter-Based Surface Grafting

摘要

The surface tethering of "smart" polymers has so far been explored with a variety of methods, including the "graftingto" approach,[1] physical adsorption,[2,3] and the "graftingfrom" technique.[4-8] The last of these methods is recognized as being very versatile, and enables the formation of patterned polymeric brushes. It exploits such techniques as microcontact printing (lCP)[9] and tip-assisted nanolithography[ 7] in order to deposit the initiators from which the polymer chains may eventually be grown. There has been great interest in using poly(N-isopropylacrylamide) (PNIPAM) as a prototype "smart" polymer in biological applications, as it exhibits a lower critical solution temperature (LCST) in aqueous environments. Upon passing the LCST by heating, PNIPAM precipitates at physiologically relevant temperatures, which form the basis for responsive applications. PNIPAM is also a prime target polymer for surface- and interface- related use, as many biological, biomedical, and sensing applications, such as protein adsorption, cell adhesion, and biosensors, benefit from thermal control of the conformation of surface-grafted chains.[10-14] The possibility of controlling the chemistry and, at the same time, the topography of a surface- bound polymeric platform represents a fundamental issue in materials science and biotechnology.