Porous elastomeric polymers have been used in a wide range of applications due to their unique characteristics such as biocompatibility, gas permeability, thermal stability, and hydrophobic and dielectric properties. Poly(dimethyl siloxane) (PDMS), a commercially available elastomer, has also been shown to exhibit specific acoustic properties. However, the materials properties were limited due to a lack of control over the chemistry used to prepare the crosslinked PDMS elastomer. Here, the synthesis of PDMS-based polymerized medium internal phase emulsions (polyMIPEs) with tunable storage shear moduli (G') have been prepared using macromolecular thiol-ene reactions. Storage shear moduli values from ~38 to ~330 kPa were achieved by changing the stoichiometric ratio of the thiol-to ene-functionalized PDMS whereas the porosity of the polyMIPEs was controlled by the volume of aqueous phase used in the emulsion formulation. Very low sound velocities (~40 m/s) through the porous materials were recorded using acoustic characterization. Therefore, this work provides an example of the synthesis of soft polyMIPEs with possible applications as acoustic materials.
Porous PDMS elastomers were synthesized using emulsion templated thiol–ene “click” reactions to obtain materials with tunable storage moduli at a single porosity value that achieve low sound speed values of ∼40 m s−1.
Implantable neural electrodes are generally used to record the electrical activity of neurons and to stimulate neurons in the nervous system. Biofouling triggered by inflammatory responses can dramatically affect the performance of neural electrodes, resulting in decreased signal sensitivity and consistency over time. Thus, long-term clinical applications require electrically conducting electrode materials with reduced dimensions, high flexibility, and antibiofouling properties that can reduce the degree of inflammatory reactions and increase the lifetime of neural electrodes. Carbon nanotubes (CNTs) are well known to form flexible assemblies such as CNT fibers. Herein, we report the covalent functionalization of predefined CNT fiber and film surfaces with hydrophilic, antibiofouling phosphorylcholine (PC) molecules. The electrochemical and spectroscopic characteristics, impedance properties, hydrophilicity, and in vitro antifouling nature of the functionalized CNT surfaces were evaluated. The hydrophilicity of the functionalized CNT films was demonstrated by a decrease in the static contact angle from 134.4°± 3.9°before to 15.7°± 1.5°after one and fully wetting after three functionalization cycles, respectively. In addition, the extent of protein absorption on the functionalized CNT films was significantly lower than that on the nonfunctionalized CNT film. Surprisingly, the faradic charge-transfer properties and impedance of the CNT assemblies were preserved after functionalization with PC molecules. These functionalized CNT assemblies are promising for the development of low-impedance neural electrodes with higher hydrophilicity and protein-fouling resistance to inhibit inflammatory responses.
Polymer foams (PFs) are among the most industrially produced
polymeric
materials, and they are found in applications including aerospace,
packaging, textiles, and biomaterials. PFs are predominantly prepared
using gas-blowing techniques, but PFs can also be prepared from templating
techniques such as polymerized high internal phase emulsions (polyHIPEs).
PolyHIPEs have many experimental design variables which control the
physical, mechanical, and chemical properties of the resulting PFs.
Both rigid and elastic polyHIPEs can be prepared, but while elastomeric
polyHIPEs are less commonly reported than hard polyHIPEs, elastomeric
polyHIPEs are instrumental in the realization of new materials in
applications including flexible separation membranes, energy storage
in soft robotics, and 3D-printed soft tissue engineering scaffolds.
Furthermore, there are few limitations to the types of polymers and
polymerization methods that have been used to prepare elastic polyHIPEs
due to the wide range of polymerization conditions that are compatible
with the polyHIPE method. In this review, an overview of the chemistry
used to prepare elastic polyHIPEs from early reports to modern polymerization
methods is provided, focusing on the applications that flexible polyHIPEs
are used in. The review consists of four sections organized around
polymer classes used in the preparation of polyHIPEs: (meth)acrylics
and (meth)acrylamides, silicones, polyesters and polyurethanes, and
naturally occurring polymers. Within each section, the common properties,
current challenges, and an outlook is suggested on where elastomeric
polyHIPEs can be expected to continue to make broad, positive impacts
on materials and technology for the future.
Hydrogels with the ability to repair damage or undergo controllable changes in stiffness and swelling are becoming increasingly important in multiple technologies. For example, hydrogels performing as dynamic matrices are...
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