Superabsorbent hydrogels are significant
not only in materials
science but also in industries and daily life, being used in diapers
or soil conditioners as typical examples. The main feature of these
materials is their capacity to hold considerable amount of water,
which is strongly dependent on the cross-linking density. This study
focuses on the preparation of hydrogels by reweighing the effect of
cross-linking density on physical properties, which provides green
fabrication of bilayered hydrogels that consist of homogeneous structural
motifs but show programmed responses via sequential radical polymerization.
In particular, when two hydrogel layers containing different cross-linking
densities are joined together, an integrated linear bilayer shows
heterogeneous deformation triggered by water. We monitor the linear
hydrogel bilayer bending into a circle and engineer it by incorporating
disperse dyes, changing colors as well as physical properties. In
addition, we demonstrate an electric circuit switch using a patterned
hydrogel. Anisotropic shape change of the polyelectrolyte switch closes
an open circuit and lights a light-emitting diode in red. This proposed
fabrication and engineering can be expanded to other superabsorbent
systems and create smart responses in cross-linked systems for biomedical
or environmental applications.
A sustainable
biobased thermoset exhibiting shape-memory behavior
and modular recycling capabilities has been developed herein. The
prepared thermoset consists of naringenin and biocompatible polymer
components. Naringenin, which has three phenolic moieties, has been
converted to a multifunctional monomer containing glycidyl groups
and readily formed a thermosetting network via epoxide ring opening
reaction with a poly(ethylene glycol) diacid under solvent-free conditions.
The resulting material is malleable yet as strong as articular cartilage
and selectively absorbs water when compared with n-dodecane oil. Moreover, the thermoset can be physically reused.
After being crumpled, stretched, or coiled, the initial shape of the
material is restored in response to heat or water. Furthermore, the
material is amenable to chemical recycling in a bulk state via transesterification,
and its components can be recovered on a molecular level after degradation
under benign conditions, as was confirmed using a model compound.
Compressible, microporous polymers have been prepared as a monolithic sponge and further regulated macroscopic conductivity when combined with carbon materials.
This paper describes the design of poly(benzyl ether)-based amphiphiles that are capable of selective and molecular demicellization via headto-tail depolymerization, triggered by a specific stimulus. The amphiphiles were synthesized by living anionic polymerization with sequential additions of two quinone methide monomers, followed by postpolymerization reaction. The amphiphiles also effectively formed polymeric micelles under aqueous conditions. The cooperative depolymerization behavior and assembly propensity of the copolymers enabled depolymerization-induced demicellization, which proceeded completely or partially under the control of an applied molecular signal. As a proof of concept, a hydrophobic model drug, doxorubicin, was loaded inside the micelles, which were then degraded on the molecular level, leading to controlled yet complete release of the cargo molecules. It is envisioned that the design concept for the micelles can be further expanded to targeted delivery systems or removable micellar encapsulants.
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