Gated Photoreactivity of Pyrene Copolymers in Multiresponsive Cross-Linked starPEG-Hydrogels

Abstract

The synthesis and manufacturing of multiresponsive polymer hydrogels using simple components is a notable challenge. Pyrene is an excimer-forming fluorophore mostly used as microenvironmental probe and for the localization of molecules in close proximity in artificial and biomaterials. Here we make use of the solvophobic preaggregation and photolysis properties of pyrene to construct multiresponsive hydrogels. We synthesize poly­(ethylene glycol) (PEG) hydrogels from well-defined pyrene-substituted macro-cross-linkers and elucidate their intricate intra- and intermolecular excimer formation pathways. We find that controlling the water content of the hydrogels through the degree of swelling acts as a gating stimulus governing the photoinduced solvolysis of pyrenylmethyl esters from their poly­(methacrylate) backbone. This allows the implementation of a simple transient photolithography process. We thus demonstrate that multiresponsive soft materials with complex optical and mechanical responses can be obtained with comparatively little synthetic effort.

Microgels react to force: mechanical properties, syntheses, and force-activated functions

“…82 While the mechanical properties of such regular microgels have not been explored in detail, the outstanding elastic extendibility rooted in the even distribution of mechanical load to all polymer segments of the regular architecture is described for their bulk hydrogel counterparts. 83 Core-shell microgels. When typical gradient polymerizations of, e.g., the NIPAAm-BIS system, are additionally biased by employing a monomer that reacts slower in a copolymerization than the employed crosslinker, 84 core-shell microgels may be obtained.…”

“…82 While the mechanical properties of such regular microgels have not been explored in detail, the outstanding elastic extendibility rooted in the even distribution of mechanical load to all polymer segments of the regular architecture is described for their bulk hydrogel counterparts. 83…”

Star polymer networks: a toolbox for cross-linked polymers with controlled structure

“…The advantages of the thiol-MI reaction made it useful to construct model SPNs for the fundamental physics of hydrogels, including mechanical properties, [113][114][115][116] microscopic structure, 117 water and polymer dynamics in hydrogels, [118][119][120][121][122] and thermodynamics and swelling behavior. [123][124][125] The reaction has also been employed for various functional materials such as stimuli-responsive polymer networks [126][127][128][129][130] and ion gels. [131][132][133] Most studies have used a standard combination of 4f-PEG-SH and 4f-PEG-MI.…”

Programming Soft Shape-Morphing Systems by Harnessing Strain Mismatch and Snap-Through Bistability: A Review

“…Photolithography is one of the most common fabrication methods to tessellate hydrogels with different swelling ratios in a single-layer structure [ 65 , 66 , 67 , 68 ]. Local photo-polymerization guided by photomasks can generate heterogeneous hydrogel structures with different degrees of crosslinking.…”