Thermoresponsive Polymers and Inverse Opal Hydrogels for the Detection of Diols

Abstract

Responsive inverse opal hydrogels functionalized by boroxole moieties were synthesized and explored as sensor platforms for various low molar mass as well as polymeric diols and polyols, including saccharides, glycopolymers and catechols, by exploiting the diol induced modulation of their structural color. The underlying thermoresponsive water-soluble copolymers and hydrogels exhibit a coil-to-globule or volume phase transition, respectively, of the LCST-type. They were prepared from oligoethylene oxide methacrylate (macro)monomers and functionalized via copolymerization to bear benzoboroxole moieties. The resulting copolymers represent weak polyacids, which can bind specifically to diols within an appropriate pH window. Due to the resulting modulation of the overall hydrophilicity of the systems and the consequent shift of their phase transition temperature, the usefulness of such systems for indicating the presence of catechols, saccharides, and glycopolymers was studied, exploiting the diol/polyol induced shifts of the soluble polymers' cloud point, or the induced changes of the hydrogels' swelling. In particular, the increased acidity of benzoboroxoles compared to standard phenylboronic acids allowed performing the studies in PBS buffer (phosphate buffered saline) at the physiologically relevant pH of 7.4. The inverse opals constructed of these thermo- and analyte-responsive hydrogels enabled following the binding of specific diols by the induced shift of the optical stop band. Their highly porous structure enabled the facile and specific optical detection of not only low molar mass but also of high molar mass diol/polyol analytes such as glycopolymers. Accordingly, such thermoresponsive inverse opal systems functionalized with recognition units represent attractive and promising platforms for the facile sensing of even rather big analytes by simple optical means, or even by the bare eye.

The challenges of glycan recognition with natural and artificial receptors

“…catechols, saccharides and glycopolymers) at physiologically relevant pH values. 139 Moreover, benzoboroxole-containing nanoparticles have turned out to be promising options for immunological applications such as internalisation of dendritic cells and controlled antigen release. 140 These nanoparticles, stable under physiological conditions, were obtained by mixing glycopolymers and a benzoboroxole-containing polymer.…”

Order–Disorder Transition in Doped Microgel Colloidal Crystals and Its Application for Optical Sensing

“…The periodic spatial modulation of refractive index in PCs allows Bragg reflection effects to occur, inhibits the propagation of light of certain wavelengths through the medium, and thus creates a so-called partial or full band gap or stop band . Up to now, many stimuli-responsive PCs, for example polymerized crystalline colloidal arrays, − inverse opal hydrogels, − and polymerized microgel colloidal crystals, have been designed for this purpose. These materials are usually fabricated from hydrogels, which respond to an external stimulus or an analyte and change its degree of swelling.…”

Emergent Soft Lithographic Tools for the Fabrication of Functional Polymeric Microstructures

“…[109,122] The tunable structural color of these PMs is applicable to optical prostheses, [123] passive humidity [120,121] and strain sensing, [124,125] and chemical detection. [126,127] [104]. C) Natural products can be replicated in various polymers (e. g., polystyrene (PS) or polyvinyl alcohol (PVA), and D) their properties are improved via replication (demonstrated by superhydrophobicity) by using a different material than that of the natural structure.…”