ELECTRO- AND PHOTOACTIVE FUNCTIONAL POLYMER MATERIALS BASED ON MOLECULAR SWITCHES

ELECTRO- AND PHOTORESPONSIVE SMART MATERIALS ARE ESSENTIAL TOOLS FOR THE DEVELOPMENT OF ADVANCED AND COMPETITIVE INDUSTRIAL TECHNOLOGIES, AS IDENTIFIED BY THE "PLAN ESTATAL DE INVESTIGACION CIENTIFICA" AND THE HORIZON EUROPE PROGRAMS THROUGH THEIR THEMATIC PRIORITY "DIGITAL, INDUSTRY, SPACE AND DEFENSE". A VERY PROMISING STRATEGY TOWARD THESE MATERIALS IS THE INTEGRATION OF MOLECULAR ELECTRO- AND PHOTOSWITCHES INTO APPROPRIATE PLATFORMS, WHICH GRANTS ACCESS TO VOLTAGE- AND LIGHT-SENSITIVE FUNCTIONAL MATERIALS FOR DIVERSE APPLICATIONS. BASED ON OUR EXPERIENCE IN THE FIELD OF MOLECULAR SWITCHES, IN THIS PROJECT WE WILL EXPLORE THE COMBINED USE OF THESE COMPOUNDS WITH POLYMER MATRICES FOR THE FABRICATION OF NOVEL ELECTRO- AND PHOTOACTIVE SMART MATERIALS AND DEVICES TARGETING THREE DIFFERENT AREAS OF TECHNOLOGICAL RELEVANCE: ELECTRO(FLUORO)CHROMIC DISPLAYS, (BIO)SENSORS AND POLYMER SELF-HEALING. ELECTRO(FLUORO)CHROMIC DISPLAYS ARE ATTRACTING ENORMOUS INTEREST AS ENERGY-SAVING ALTERNATIVES TO CURRENT DEVICES BASED ON LIQUID CRYSTALS AND LIGHT-EMITTING DIODES FOR THE STORAGE AND READOUT OF INFORMATION. HOWEVER, THEIR PRACTICAL APPLICATION IS STILL HAMPERED BY SEVERAL LIMITATIONS, WHICH WE WILL TACKLE HEREIN BY INCORPORATING SPIROCYCLIC MEISENHEIMER COMPOUNDS, A NEW FAMILY OF REDOX-RESPONSIVE MOLECULAR SWITCHES, INTO TRANSPARENT AND CONDUCTIVE IONOGELS. THIS SHOULD ALLOW US THE PREPARATION OF ELECTRO(FLUORO)CHROMIC DISPLAYS FEATURING SIMPLE ARCHITECTURE, FACILE FABRICATION AND LOW COST, AMPLE COLOR VARIABILITY AND PERMANENT COLORATION IN THE ABSENCE OF APPLIED VOLTAGES. (BIO)SENSING IS ANOTHER AREA OF APPLICATION OF ELECTRO(FLUORO)CHROMIC AND OTHER STIMULI-RESPONSIVE CHROMIC SYSTEMS, WHERE THEY ARE USED AS TRANSDUCERS TO CONVERT ANALYTE RECOGNITION INTO READABLE OPTICAL SIGNALS. HOWEVER, THE (FLUORO)CHROMIC SIGNALS NORMALLY GENERATED IN THESE DEVICES ARE IRREVERSIBLE, WHICH IMPEDES SENSOR REUSABILITY. TO SOLVE THIS DRAWBACK, IN THIS PROJECT WE PROPOSE THE USE OF DITHIENYLETHENE PHOTOSWITCHES AS STIMULI-RESPONSIVE CHROMIC MATERIALS THAT CAN BE RECYCLED VIA LIGHT IRRADIATION. BY INTEGRATING THESE MOLECULAR SYSTEMS INTO IONOGELS AND SILK FIBROIN MATRICES, THE GENERALITY OF THIS CONCEPT WILL BE EXPLORED THROUGH THE FABRICATION OF TWO DISTINCTIVE TYPES OF BIOCOMPATIBLE, REUSABLE AND SENSITIVE WEARABLE SENSORS: IN SITU ENZYMATIC BIOSENSORS OF GLUCOSE METABOLISM AND GAMMA-RAY SENSORS FOR REAL-TIME DOSIMETRY IN RADIOTHERAPY. AS FOR POLYMER SELF-HEALING, IT IS A MUCH-DESIRED STRATEGY FOR EXTENDING THE SERVICE LIFE OF PLASTICS, INCREASING THEIR SAFETY AND RELIABILITY, AND REDUCING WASTE PRODUCTION. HEREIN WE WILL EXPLORE A NOVEL INTEGRAL APPROACH TOWARD POLYMER SELF-HEALING, WHICH CONSISTS IN IDENTIFYING MECHANICAL DAMAGE VIA OPTICAL SELF-REPORTING AND THEN LOCALLY REPAIRING IT AT AMBIENT CONDITIONS. FOR OPTICAL SELF-REPORTING, WE WILL DEVELOP NEW HIGH-SENSITIVITY MECHANICAL PROBES BASED ON SPIROPYRANS AND SPIROCYCLIC MEISENHEIMER COMPOUNDS, WHILE BOTH PHOTO- AND ELECTROINDUCED SELF-HEALING WILL BE ATTEMPTED USING DITHIENYLETHENE AND SPIROPYRAN SWITCHES, RESPECTIVELY. THESE STUDIES WILL BE APPLIED TO TWO CONTRASTING TYPES OF POLYMER MATERIALS OF TECHNOLOGICAL RELEVANCE: SOFT IONOGELS AND GLASSY POLYBENZOXAZINES, WHICH ARE PHENOLIC RESINS UTILIZED AS HIGH-PERFORMANCE THERMOSETS.