(255bc) Metal Nanocrystals Embedded in Polymer Thin Films for the Reporting of Material State

Stimuli-responsive materials able to detect thermal, mechanical, optical and chemical solicitation have been used to effectively develop sensors, probes and information displays by taking advantage of organic or inorganic chromophores such as metal derivatives, that is metal nanoparticles and nanocrystalline semiconductors, since they confer to their embedding material a variation in the opto-electronic properties as a response to the stimulus. Surface-initiated polymerization (SIP) is able to provide improved adhesion of the polymer film via chemisorption, superior control of the film thickness and composition, easy separation of the film from the monomer, tunability to multiple substrate compositions, and the ability to prepare uniform films on planar and nonplanar geometries. Among the various types of SIP, SI-ROMP has emerged over the past decade as a rapid and tunable SIP technique. Here we report the incorporation of CdSe nanocrystals and Au nanoparticles into a surface-tethered polymer film. The incorporation of the CdSe nanocrystals and Au nanoparticles into the polymer matrix enables the sensing of changes to the material state due to external mechanical and chemical stresses. In the case of the CdSe nanocrystals, external mechanical and chemical stresses elicit local damage to the polymer matrix, such as micro cracks or delamination, and causes the detachment of CdSe surface ligands and the aggregation of the CdSe nanocrystals leading to a change in the emission properties of the nanocrystals. The emission properties of the nanocrystals were determined by utilizing an integrating sphere. In the case of the Au nanoparticles, external mechanical and chemical stresses elicit local damage to the polymer matrix and causes the detachement of Au surface ligands and the aggregation of the Au nanoparticles leading to a change in the absorption properties of the nanoparticles. The absorption properties of the nanoparticles were determined by UV-VIS spectroscopy and polarization modulation-infrared reflectance-absorption spectroscopy (PM-IRRAS).