Tuning chelating groups and comonomers in spiropyran-containing copolymer thin films for color-specific metal ion binding

Abstract

Photochromic molecules can be used to selectively bind divalent metal ions. In order to study the influence of increased chelation in spiropyran-containing copolymers, we synthesized two derivatives: spiropyran methacrylate (SPMA) and spiropyran methacrylate with a methoxy substituent in the 8 0 position of the benzopyran ring (MEO). Additionally, the comonomer with which spiropyran was polymerized is also varied between methyl methacrylate (MMA) and 2,2,2-trifluoroethyl methacrylate (TFEMA) to tune the colorimetric response. Fourier transform-infrared (FT-IR) spectroscopy was used to characterize the photoinduced conversion of spiropyran to merocyanine, as well as the merocyanine-metal ion (MC-M 2+ ) interaction. By means of UV-Vis absorption spectroscopy, we demonstrate that each metal ion gives rise to a unique colorimetric response for the various spiropyran-containing copolymers studied.

Photochromic sensors: a versatile approach for recognition and discrimination

“…96,97 As shown in Fig. Locklin and co-workers designed a copolymer poly(MMA 90 -co-SPMA 10 ) consisting of 10 mol% spiropyran methacrylate derivative (SPMA) and 90 mol% methyl methacrylate (MMA), to investigate its responses to divalent metal ions.…”

Micro-Capillary Coatings Based on Spiropyran Polymeric Brushes for Metal Ion Binding, Detection, and Release in Continuous Flow

“…In addition, this metal ion uptake and release behaviour is photo-controlled using external light sources. Although photo-controlled metal ion detection using spiropyran derivatives has been previously demonstrated by us [ 17 ] and others [ 33 , 34 , 35 , 36 , 37 ], this represents the first example in which photo-controlled uptake and release has been demonstrated within a micro-capillary system using polymeric brushes, in a continuous flow regime. Although, without doubt, there are many specific sensor molecules for quantitative metal ion detection, the ability to achieve a self-indicating flow-system, capable of photo-controlled binding and release, may prove to be of particular importance for the integration of advanced bioinspired functionalities in microfluidic systems.…”

“…In this context, there have been several research studies on SP-derivatives for metal ion binding, predominantly for divalent metal ions such as Zn 2+ [ 32 , 33 ], Co 2+ [ 10 , 33 , 34 ], Cu 2+ [ 33 , 34 ], Ni 2+ [ 30 , 33 ], and Cd 2+ [ 35 ], in which binding generally happens in a 2:1 ratio of merocyanine to M 2+ , due to the coordination of the divalent metal ion by two MC phenolate anions [ 35 ]. Several research groups have attempted to increase the number of binding sites and achieve a 1:1 binding ratio (merocyanine: M 2+ ) through variation of the R group in the eighth position of the benzopyran ring to include methoxy [ 34 ] or allyl substituents [ 34 ], or by functionalising the indolic nitrogen with carboxylic acid [ 36 ], ester [ 37 ], or hydroxyl-terminated moieties [ 34 ]. These groups can promote complex formation by offering additional sites to the merocyanine phenolate anion for stabilisation of the metal centre, resulting in a thermodynamically stable MC:M 2+ complex [ 32 ].…”

Light-responsive polymers for microfluidic applications

“…-integrated onto silica beads, 67,68 membranes or thin films. 69 -integrated in the surface of the microchannels and fibers. 70,71 For instance, metals such as Co 2+ , [72][73][74][75][76] Zn 2+ , 77,78 Mg 2+ , 79 Cu 2+ , 79,80 Fe 2+ and Ni 2+ , 80 were detected (Fig.…”