Future perspectives and recent advances in stimuli-responsive materials

Interest in stimuli-responsive polymers has persisted over many decades, and a great deal of work has been dedicated to developing environmentally sensitive macromolecules that can be crafted into new smart materials. However, the overwhelming majority of reports in the literature describe stimuli-responsive polymers that are sensitive to only a few common triggers, including changes in pH, temperature, and electrolyte concentration. Herein, we aim to highlight recent results and future trends that exploit stimuli that have not yet been as heavily considered, despite their unique potential. Many of the topics represent clear opportunities for making advances in biomedical fields due to their specificity and the ability to respond to stimuli that are inherently present in living systems. Recent results in the area of polymers that respond to specific antigen-antibody interactions, enzymes, and glucose are specifically discussed. Also considered are polymeric systems that respond to light, electric, magnetic, and sonic fields, all of which have potential in the area of controlled release as a result of their ability to be applied in a non-invasive and easily controlled manner. Thiol-responsive and redox-responsive polymers are also highlighted, with particular attention being devoted to their reversible dynamic covalent chemistry. It is our goal to emphasize these underutilized adaptive behaviors so that novel applications and new generations of smart materials can be realized.