title: The Orange Side of Disperse Red 1: Humidity-Driven Color Switching in Supramolecular Azo-Polymer Materials Based on Reversible Dye Aggregation.
abstract: Humidity detection, and the quest for low-cost facile humidity-sensitive indicator materials is of great interest for many fields, including semi-conductor processing, food transport and storage, and pharmaceuticals. Ideal humidity-detection materials for a these applications might be based on simple clear optical readout with no power supply, i.e.: a clear color change observed by the naked eye of any untrained observer, since it doesn't require any extra instrumentation or interpretation. Here, the introduction of a synthesis-free one-step procedure, based on physical mixing of easily available commercial materials, for producing a humidity memory material which can be easily painted onto a wide variety of surfaces and undergoes a remarkable color change (approximately 100 nm blue-shift of λMAX) upon exposure to various thresholds of levels of ambient humidity is reported. This strong color change, easily visible to as a red-to-orange color switch, is locked in until inspection, but can then be restored reversibly if desired, after moderate heating. By taking advantage of spontaneously-forming reversible 'soft' supramolecular bonds between a red-colored azo dye and a host polymer matrix, a reversible dye 'migration' aggregation appearing orange, and dis-aggregation back to red can be achieved, to function as the sensor.
authors.affiliation: Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, Quebec, H3A 0B8, Canada.|Institute for Macromolecular Chemistry, University of Freiburg, Stefan-Meier-Str. 31, 79104, Freiburg, Germany.
authors.forename: Simon
authors.initials: S
authors.lastname: Schoelch
authors.affiliation: Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, Quebec, H3A 0B8, Canada.|Department of Chemistry and Bioengineering, Tampere University of Technology, FI-33101, Tampere, Finland.
authors.forename: Jaana
authors.initials: J
authors.lastname: Vapaavuori
authors.affiliation: Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, Quebec, H3A 0B8, Canada.
authors.forename: Frédéric-Guillaume
authors.initials: FG
authors.lastname: Rollet
authors.affiliation: Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montreal, Quebec, H3A 0B8, Canada.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Barrett
mesh_terms: D001391:Azo Compounds / Q000737:chemistry*; D003116:Color; D004396:Coloring Agents / Q000138:chemical synthesis* / Q000737:chemistry; D006813:Humidity; D015394:Molecular Structure; D011108:Polymers / Q000737:chemistry*
chemical_list: D001391:Azo Compounds; D004396:Coloring Agents; D011108:Polymers; C069318:Disperse Red 1
keywords: azobenzenes; chromophore aggregation; humidity sensors; optical readout; stimuli-responsive materials; supramolecular materials