Reversible disulphide formation in polymer networks: A versatile functional group from synthesis to applications

A substantial effort has been made in the last few decades to develop responsive materials that produce a selective answer to well-defined environmental stimuli. In our present review, we focus on the chemistry of thiol-disulphide equilibrium and its incorporation into polymer-based soft materials. Because several papers and extensive reviews have focused on reduction-sensitive drug delivery and gene transfer, we would like to especially emphasise the importance of disulphide formation and the exploitation of reversible thiol-disulphide interconversion in synthesis and its applications. We report the most important synthetic strategies that utilise disulphide formation. However, a major portion of our overview will concentrate on taking advantage of the thiol-disulphide exchange and the reversibility of this reaction in a wide range of applications, such as advanced drug delivery vehicles, bioartificial implants and self-healing and shape-imprinting polymers. In certain cases, the reversibility is only proven and used in one cycle, but in some cases, the process is practically reversible, at least in the time range of the dedicated application. The reversibility of the reaction is an important requirement for the long-term use of these polymers as implant materials; therefore, aside from better understanding the redox processes in living cells, the future direction of this research can lead to the improvement of reversible responses. (C) 2013 Elsevier Ltd. All rights reserved.