Stimuli-responsive polymer colloids: Switchable surfactants for polymers and coatings

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"Smart" materials undergo dramatic changes in their properties in response to some change in their environment, known as a "trigger". The sudden switch in physical or chemical properties is useful in the design of materials used in diverse markets including electronics, health care and industrial products. Recently, the authors demonstrated that finely divided dispersions of small polymer particles ("polymer nanospheres") in water could be rapidly aggregated to yield a mixture of clear water and polymer nanospheres. This change was triggered by simply exposing the mixture to air. The key material, known as a "switchable surfactant", is a special type of smart soap that ensures the polymer nanospheres remain uniformly dispersed when the surfactant is switched "on" (when carbon dioxide is present). However when the atmosphere of carbon dioxide is replaced by air for example, the polymer nanospheres aggregate and settle out of their suspended state. (Recycled carbon dioxide can be used, eliminating concerns of greenhouse gas emissions.) Dispersions of polymer nanospheres are widely used in many important industrial products, including latex paints, adhesives coatings and resin manufacture. In some products, it is necessary to add chemicals such as acids or salts to destabilize the dispersion. These chemicals must either be removed at a cost to the consumer, or are discharged into the environment. The use of switchable surfactants could eliminate these problems. Polymer nanospheres are also increasingly being used in specialty fields, including advanced electronics and in the biomedical area as diagnostic tools. The ability to radically alter the state of a polymer nanosphere dispersion from uniformly suspended to aggregated may provide significant economic opportunities in both emerging areas of advanced materials as well as in more traditional markets. This project would be the first application of "switchable surfactants" to the field of polymer nanospheres, and would create a new class of smart materials.