Photoswitchable Layer-by-Layer Coatings Based on Photochromic Polynorbornenes Bearing Spiropyran Side Groups

Abstract

Herein, we present the synthesis of linear photochromic norbornene polymers bearing spiropyran side groups (poly(SP-R)) and their assembly into layer-by-layer (LbL) films on glass substrates when converted to poly(MC-R) under UV irradiation. The LbL films were composed of bilayers of poly(allylamine hydrochloride) (PAH) and poly(MC-R), forming (PAH/poly(MC-R)) coatings. The merocyanine (MC) form presents a significant absorption band in the visible spectral region, which allowed tracking of the LbL deposition process by UV-vis spectroscopy, which showed a linear increase of the characteristic MC absorbance band with increasing number of bilayers. The thickness and morphology of the (PAH/poly(MC-R)) films were characterized by ellipsometry and scanning electron microscopy, respectively, with a height of ∼27.5 nm for the first bilayer and an overall height of ∼165 nm for the (PAH/poly(MC-R)) multilayer film. Prolonged white light irradiation (22 h) resulted in a gradual decrease of the MC band by 90.4 ± 2.9% relative to the baseline, indicating the potential application of these films as coatings for photocontrolled delivery systems.

Nanoparticles in Polyelectrolyte Multilayer Layer-by-Layer (LbL) Films and Capsules—Key Enabling Components of Hybrid Coatings

“…Polysaccharides and nanogels were employed in polyelectrolyte multilayers proving that the presence of nanogel particles is beneficial for construction of a drug depot system [127]. Linear photochromic norbornene polymers assembled in LbL films exhibited a drastic decrease of the merocyanine band under a prolonged white light irradiation that potentially could be employed as photo-controlled drug depot system [128]. Bioactive thin films were prepared via encapsulation of biomacromolecules such as an enzyme (beta-lactamase, BlaP) into aluminosilicate halloysite nanotubes and their subsequent use for the fabrication of enzymatic coatings by LbL that potentially could act for effluent decontamination [129].…”

Light‐Responsive Polymer Membranes

“…Under white light irradiation in water, the photoconversion of negatively charged MC to the neutral SP form in the thinner LbL film caused the disassembly of the first layers and detachment of the second film. Following this idea, Campos et al investigated the photoinduced disassembly using Vis light of a LbL film made with bilayers of poly(allylamine hydrochloride) and photochromic norbornene polymer bearing merocyanine side groups . Such films were able to disassemble under photoirradiation with white light, due to the photoconversion of the MC molecules from their zwitterionic opened form to the neutral SP closed form.…”

Photochromic Polyamide 6 Based on Spiropyran Synthesized via Hydrolyzed Ring-Opening Polymerization

“…Chemical modification and covalent bonding of SP to the polymer matrix via polymerization will enhance the photostability and photofatigue and the spiropyran moiety can be used in most polymerization conditions. Polymer materials with SP could be found in films [ 19 , 20 , 21 ], gels [ 22 , 23 , 24 ] and electrospun nanofibers [ 25 , 26 , 27 ]. For instance, Mahdavian and coworkers [ 26 ] synthesized photoresponsive polymethyl methacrylate and poly(methyl methacrylate- co -butyl acrylate) chemically modified with spiropyran through emulsion polymerization and the corresponding nanofibers had excellent responsivity of acid-base vapors.…”