Poly(methyl methacrylate)-Supported Polydiacetylene Films: Unique Chromatic Transitions and Molecular Sensing Kaviya Parambath Kootery, † Hao Jiang, † Sofiya Kolusheva, ‡ T. P. Vinod, † Margarita Ritenberg, † Leila Zeiri, ‡ Roman Volinsky, § Danilo Malferrari, ∥ Paola Galletti, ∥,⊥ Emilio Tagliavini, ∥,⊥ and Raz Jelinek* ,†,‡ † Department of Chemistry and ‡ Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, Beer Sheva 84105, Israel § Department of Biomedical Engineering and Computational Science, Aalto University, Helsinki, Finland ∥ Interdipartimental Center for Industrial research (CIRI) Energy & Environment, University of Bologna, via S. Alberto 163, 48123 Ravenna, Italy ⊥ Department of Chemistry “G. Ciamician”, University of Bologna, via Selmi 2, 40126 Bologna, Italy ABSTRACT: Polydiacetylenes (PDAs) constitute a family of conjugated polymers exhibiting unique colorimetric and fluorescence transitions, and have attracted significant interest as chemo- and biosensing materials. We spin-coated PDA films upon poly(methyl methacrylate) (PMMA), and investigated the photophysical properties and sensing applications of the new PDA configuration. Specifically, the as-polymerized blue PDA layer underwent distinct transformations to purple, red, and yellow phases, which could be quantified through conventional color scanning combined with application of image analysis algorithms. Furthermore, we recorded a reversible red-purple PDA transition that was induced by ultraviolet irradiation, a phenomenon that had not been reported previously in PDA film systems. We show that distinct color and fluorescence transitions were induced in the PMMA-supported PDA films by amphiphilic substancessurfactants and ionic liquidsand that the chromatic transformations were correlated to the analyte structures and properties. Overall, this study presents a new chromatic PDA film system in which noncovalent interactions between the PMMA substrate and spin-coated PDA give rise to distinct chromatic properties and molecular sensing capabilities. KEYWORDS: polydiacetylene, colorimetric sensors, spin coating, PMMA, thin films ■ INTRODUCTION Polydiacetylenes (PDAs) are π-conjugated polymers displaying unique structural and chromatic properties. 1−8 These polymers, first synthesized in the late 1960s, have attracted considerable interest both scientifically and as promising sensing platforms, primarily because of their visible color transformations (generally from blue to red), induced by varied external stimuli, such as heat, 9 ionic strength, 10 mechanical pressures, and interactions with biological and chemical molecules. 11,12 Modulation of the fluorescence emission of PDA systems which usually accompany the color changes has also contributed to progress in this field as the fluorescence phenomena opened routes for high sensitivity sensing and microscopic imaging. 13,14 The intriguing chromatic properties of PDA assemblies are believed to arise from the ene-yne topotactic polymerization process, made possible through self-assembly of the diacetylene monomers stabilized through a hydrogen bond network. 15 This generic structural/chromatic feature of PDA systems has been attained in numerous morphologies, including vesicles, 16,17 thin films, 18 fibers, 19 stacked domains, 20 and others. Notably, recent studies have shown that color reversibility (generally from the red phase back to the initial blue phase) could be accomplished through modification of the PDA headgroup moieties. 21 Further expanding the technological and scientific scope of the field has been the demonstration of PDA assemblies exhibiting colors other than blue and red, including yellow and orange PDA. 22−24 Supported PDA films, in particular, exhibit distinct practical advantages and have attracted considerable interest and research activities. 25,26 Such assemblies are generally robust and stable, and their molecular and macroscopic properties can be better controlled than vesicular systems. Film properties can be also thoroughly analyzed through application of advanced surface characterization techniques. 26 Solid-supported PDA films have been constructed via diverse techniques, including Langmuir monolayers, 27 dip-coating, 28 and spin-coating. 29 Here, we present a study of new PDA films prepared through spin-coating of the diacetylene monomers onto poly(methyl Received: March 11, 2014 Accepted: May 9, 2014 Published: May 9, 2014 Research Article www.acsami.org © 2014 American Chemical Society 8613 dx.doi.org/10.1021/am501414z | ACS Appl. Mater. Interfaces 2014, 6, 8613−8620