Advanced materials that are capable of undergoing physical or chemical changes in response to external stimuli have great potential in the fields of medicine, biotechnology, electronics and personal care.1–3 Commonly referred to as “smart polymers,” these materials can respond to temperature, pH, light, sound and mechanical forces, among others.
A variety of smart polymers exist for applications including self-healing materials, tissue engineering, medical imaging and data storage. Liquid crystalline displays are a prime example of an optically responsive material that has led to an immensely profitable industry; however, self-assembling micelles and gels are the most relevant to personal care, having potential for molecular encapsulation and triggered release.
Smart polymers can be engineered to contain reactive molecules, commonly dubbed “molecular switches,” that respond to external stimuli and cause systemic changes to the polymer structure. For example, chemical or electronic changes disrupt the polymeric macromolecular structure and trigger the subsequent release of entrapped compounds (see Figure 1).
Such changes can be engineered to be reversible or irreversible, depending on the end use. The specificity of a molecular switch to a single stimulus is critical for controlled release, although multi-triggered systems capable of responding to systematic stimuli are being developed for advanced applications. Herein the authors describe several stimuli-responsive materials that have potential applications for personal care and related biomedical fields.