Since being developed over 50 years ago, aromatic polyamides have been used industrially for numerous highperformance applications due to their heat resistance, chemical stability, and high strength. Despite this extensive time span, limited applications as surface coatings have been explored due to most aromatic polyamides being insoluble in organic solvents and their extremely high melting temperatures. However, new polymerization techniques have been developed to overcome this insolubility, allowing applications such as reverse osmosis membranes and gas separation membranes to be developed. With the recent advancement of substituent effect chain-growth condensation polymerization, controlled growth aromatic polyamides have been shown to grow from flat and curved surfaces. In this study, aromatic polyamides with a protecting side chain were grown from flat and curved surfaces to allow for post polymerization deprotection and the introduction of hydrogen bonding along the backbone of the polyamide. The aromatic polyamide brushes formed were then characterized using transmission electron microscope and atomic force microscopy to explore important physical properties of the polymer brushes, including grafting density and Young's modulus. The introduction of hydrogen bonding dramatically increased the Young's modulus of the aromatic polyamide brushes from 5−6 to 22−32 GPa. Our results demonstrate the tunability of the aromatic polyamide brushes to achieve high mechanical strength and pave the way for their application in areas such as high-performance coatings.
Transparent microelectrodes have recently emerged as a promising approach to combine electrophysiology with optophysiology for multifunctional biointerfacing. High-performance flexible platforms that allow seamless integration with soft tissue systems for such applications are urgently needed. Here, silver nanowires (Ag NWs)-based transparent microelectrodes and interconnects are designed to meet this demand. The Ag NWs percolating networks are patterned on flexible polymer substrates using an innovative photolithography-based solution-processing technique. The resulting nanowire networks exhibit a high average optical transparency of 76.1-90.0% over the visible spectrum, low normalized electrochemical impedance of 3.4-15 Ω cm2 at 1 kHz which is even better than those of opaque solid Ag films, superior sheet resistance of 11-25 Ω sq−1, excellent mechanical stability up to 10,000 bending cycles, good biocompatibility and chemical stability. Studies on Langendorff-perfused mouse and rat hearts demonstrate that the Ag NWs microelectrodes enable high-fidelity real-time monitoring of heart rhythm during co-localized optogenetic pacing and optical mapping with negligible light-induced electrical artifacts. This proof-of-concept work illustrates that the solution-processed, transparent, and flexible Ag NWs networks are a promising candidate for the next-generation of large-area multifunctional biointerfaces for interrogating complex biological systems in basic and translational research.
the presence of organic macromolecules (or foulants) can
exacerbate silica scaling of membranes, the effects of the types and
physicochemical properties of macromolecules on silica scale formation
remain poorly understood. We herein use a quartz crystal microbalance
with dissipation monitoring to investigate the kinetics of silica
mass deposition on sensors coated by lysozyme, bovine serum albumin
(BSA), humic acid, or alginate. Our results show that deposited silica
mass resulting from heterogeneous nucleation of monosilicic acid cannot
be explained by the free energy barrier to nucleation but instead
linearly correlated to the hydration energy of the macromolecule-covered
surfaces. The most silica heterogeneous nucleation occurs on the most
hydrophilic alginate-coated surface, which is likely due to the favorable
interaction between silicic acid and alginate via hydrogen bonding
and chemical reactions. For the deposition of silica aggregates formed
from bulk nucleation, the deposited silica mass is the highest on
the BSA-coated surface, consistent with the greatest adhesion force
between BSA and silica measured using force spectroscopy. Finally,
silica scaling on macromolecule-coated surfaces is promoted by calcium
ions, and the deposition of silica is mostly irreversible upon rinsing
In this study, biosilica of high purity was successfully prepared from marine diatom ( Nitzschia closterium and Thalassiosira ) biomass using an optimized novel method with acid washing treatment followed by thermal treatment of the biomass. The optimal condition of the method was 2% diluted HCl washing and baking at 600°C. The SiO 2 contents of N . closterium biosilica and Thalassiosira biosilica were 92.23% and 91.52%, respectively, which were both higher than that of diatomite biosilica. The SiO 2 morphologies of both biosilica are typical amorphous silica. Besides, N . closterium biosilica possessed micropores and fi bers with a surface area of 59.81 m 2 /g. And Thalassiosira biosilica possessed a mesoporous hierarchical skeleton with a surface area of 9.91 m 2 /g. The results suggest that the biosilica samples obtained in this study present highly porous structures. The prepared porous biosilica material possesses great potential to be used as drug delivery carrier, biosensor, biocatalyst as well as adsorbent in the future.
With growing freshwater scarcity in many areas of the world, purifying alternative sources of water such as seawater, brackish water, and wastewater has become increasingly important. One of the main ways this is done is using reverse osmosis (RO) membranes composed of aromatic polyamide films synthesized using interfacial polymerization. These membranes have become the industry standard due to their excellent salt rejection. However, issues with fouling, degradation, and delamination plague current technology, which has led to renewed interest in finding innovative solutions. Polyethylene glycol (PEG) has been used extensively for its antifouling properties and has been incorporated into RO membranes with some success. In this study, oligoethylene glycol (OEG)-functionalized aromatic polyamides were covalently grown using surface initiation from silicon wafers, quartz crystal microbalance (QCM) sensors, and silica particles to form high grafting density polymer brushes. Initially, solution-based kinetic studies were used to optimize the polymerization conditions of the OEG-functionalized monomers. The optimized conditions were then used for surface-initiated substituent effect chain-growth condensation polymerization of the monomers. The use of these conditions produced uniform OEGfunctionalized aromatic polyamide brushes with well-defined molecular weight and narrow molecular weight distribution. QCM and atomic force microscopy were used to demonstrate the drastically improved antifouling characteristics of the brushes as compared to PEG monolayers and aromatic polyamides brushes without the OEG functionalization.
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