Multiresponsive Spiropyran-Based Copolymers Synthesized by Atom Transfer Radical Polymerization

Abstract

Multiresponsive spiropyran-based random copolymers were synthesized by atom transfer radical polymerization. The polymers were prepared by the copolymerization of 2-(dimethylamino)ethyl methacrylate (DMAEMA) with the photochromic monomer 1′,3′,3′-trimethyl-6-methacryloyloxyspiro(2H-1-benzopyran-2,2′-indoline) (SP). The solvatochromic, pH, temperature, and light responsive behavior of the PDMAEMA-co-PSP polymers in solution was monitored by UV/vis spectroscopy. The copolymers exhibited “reverse photochromism” and stabilized the planar zwitterionic form of the chromophore, leading to “negative solvatochromism” upon increasing the polarity of the solvent, in contrast to a poly(methyl methacrylate)-co-PSP analogue which stabilized a nonpolar photoisomer and exhibited negligible sensitivity to the polarity of the surrounding medium, before irradiation. Moreover, the PDMAEMA-co-PSP copolymers exhibited a reversible pH-responsive character in aqueous media; the addition of a strong acid induced the SP-to-merocyanine (MC) isomerization, the formation of [MC−OH]+ and [SP−NH]+ species, and the disappearance of the H-type aggregates, whereas the initial SP moieties were recovered in alkaline media. The chromophore content and the photoinduced MC-to-SP isomerization affected the transition temperature of the PDMAEMA-co-PSP polymers. The lower critical solution temperature (LCST) of the copolymers increased with their content in hydrophilic MC moieties, while the MC-to-SP photoinduced isomerization decreased significantly the LCST due to the hydrophobic character of the SP units. Finally, the copolymers exhibited a first-order photoinduced bleaching of the chromophore units in water and acetonitrile, with a slower decoloration rate in the aqueous medium due to the effective stabilization of the bipolar MC form in the polar environment.

Synthesis of spiropyran-containing random copolymer by atom transfer radical polymerization and its complexation with metal ions

“…[45] This will give rise to a greater energy gap between the two MC states and a hypsochromic shift of the absorption band. [46] In addition, an obvious color change is also observed because of the 'negative' solvatochromism of the photochromic species at different solvents as presented in Figure 5 inset. …”

Multi‐stimuli‐responsive Polymers Based on Calix[4]arenes and Dibenzo‐18‐crown‐6‐ethers

“…When PNIPAM is functionalized with spirobenzopyran, the thermal response is provided by the polymer chain and the spirobenzopyran acts as the photo and pHsensitive unit 83 . In the case of using spiropyran and PDMAEMA 84 , both the polymer and the photo-switch contribute to the pH stimulus. Plamper et al 85 used hexacyanocobaltate(III) as a trivalent counterion, which induces a UCST transition for aqueous solutions of PDMAEMA (apart from the LCST, which is controllable by pH).…”

Fluorescent Dyes Used in Polymer Carriers as Imaging Agents in Anticancer Therapy

“…These optically switchable dualcolor NPs binding with HMGA1 proteins undergo endocytosis and they can be identified from autofluorescence of live cells, thus improve a tool for imaging. Furthermore, the SP molecules were grafted onto a diblock copolymer polystyrene-co-polyacrylic acid chain (PSPAA-SP) obtained from atom-transfer radical polymerization (ATRP) by using monomers of styrene and tert-butylacrylate [268]. Thus, copolymers of PSPAA-SP containing both the hydrophilic and hydrophobic segments self-assembled into nanomicelles in nonpolar solvent (toluene).…”