Abstract
AbstractThis article describes the design and synthesis of a new series of hydrogel membranes composed of trialkyne derivatives of glycerol ethoxylate and bisphenol A diazide (BA‐diazide) or diazide‐terminated PEG600 monomer via a Cu(I)‐catalyzed photoclick reaction. The water‐swollen hydrogel membranes display thermoresponsive actuation and their lower critical solution temperature (LCST) values are determined by differential scanning calorimetry. Glycerol ethoxylate moiety serves as the thermoresponsive component and hydrophilic part, while the azide‐based component acts as the hydrophobic comonomer and most likely provides a critical hydrophobic/hydrophilic balance contributing also to the significant mechanical strength of the membranes. These hydrogels exhibit a reversible shape‐memory effect in response to temperature through a defined phase transition. The swelling and deswelling behavior of the membranes are systematically examined. Due to the click nature of the reaction, easy availability of azide and alkyne functional‐monomers, and the polymer architecture, the glass transition temperature (Tg) is easily controlled through monomer design and crosslink density by varying the feed ratio of different monomers. The mechanical properties of the membranes are studied by universal tensile testing measurements. Moreover, the hydrogels show the ability to absorb a dye and release it in a controlled manner by applying heat below and above the LCST.
Highlights
This article describes the design and synthesis of a new series of hydrogel of potential applications in different fields, such as drug delivery[1,2,3] tissue engimembranes composed of trialkyne derivatives of glycerol ethoxylate and neering,[4] biosensing,[5] smart coatings,[6]
We have successfully synthesized a series of thermoresponsive, rigid and strong Shape-memory hydrogels (SMHs) containing a trialkyne derivative of glycerol ethoxylate via Cu(I)-catalyzed photoclick reaction
To the best of our knowledge, this is the first report describing the use of glycerol ethoxylate moiety to induce a controlled thermoresponsive behavior depending on the feed ratio of other hydrophobic comonomers during the click photopolymerization
Summary
We employed a photoinitiator, 2,2-dimethoxy2-phenylacetophenone (DMPA), and a PMDETA copperchelating click ligand. The transmittance at 2101 cm−1 of BA-diazide monomer can be ascribed to the stretching frequency of azide group, whereas the peak at 3245 cm−1 and 2114 cm−1 corresponds to C H and C C bond stretching frequencies of the alkyne groups of the glycerol ethoxylate moiety. Successful incorporation of BA-diazide monomer into the copolymers was confirmed from the presence of proton resonances around 6.47, 5.20 ppm, corresponding to the aromatic proton along with the additional triazole signal at 7.8 ppm in the 1H NMR spectra of the polymer. To establish the versatility of the membrane preparation method, we synthesized some other polymers comprising different types of azide and alkynes (Scheme 1)
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