Covalently
cross-linked rubbers are indispensable in many important
fields due to their unique entropic elasticity. For rubbers cross-linking,
the addition of toxic curing agents, release of toxic volatile organic
compounds (VOCs), and recycling of waste rubber are three important
issues. A combination of green curing chemistry and efficient recycling
into commercial polyolefin rubbers is of great importance. Herein,
we demonstrate a facile and promising way to incorporate dynamic covalent
bonds into ethylene-propylene-diene monomer (EPDM)/carbon black (CB)
composites. The epoxy-functionalized EPDM (e-EPDM) was prepared using
an in situ epoxidation reaction and then cured with
biobased decanedioicacid (DA) through the reactions between the epoxy
groups in e-EPDM and the carboxylic groups in DA. Because of the existence
of exchangeable β-hydroxyl ester, the covalently cross-linked
networks in e-EPDM/CB composites were able to rearrange their topological
structure at high temperature, endowing the composites with recycled
and reshaped abilities. More importantly, the recycled e-EPDM/CB composites
still exhibit outstanding mechanical properties which can meet the
needs of practical applications. This strategy may provide an efficient,
green, and sustainable way to address the problems brought from rubbers
cross-linking.
In this work, polydopamine-coated
gold nanoparticles (Au@PDAs) were synthesized
by the oxidative self-polymerization of dopamine (DA) on the surface
of AuNPs and applied for the first time as a signal-amplification
label in lateral flow immunoassays
(LFIAs)
for the sensitive detection of zearalenone (ZEN) in maize. The PDA
layer functioned as a linker between AuNPs and anti-ZEN monoclonal
antibody (mAb) to form a probe (Au@PDA-mAb). Compared with AuNPs,
Au@PDA had excellent color intensity, colloidal stability, and mAb
coupling efficiency. The limit of detection of the Au@PDA-based LFIA
(Au@PDA-LFIA) was 7.4 pg/mL, which was 10-fold lower than that of
the traditional AuNP-based LFIA (AuNP-LFIA) (76.1 pg/mL). The recoveries
of Au@PDA-LFIA were 93.80–111.82%, with the coefficient of
variation of 1.08–9.04%. In addition, the reliability of Au@PDA-LFIA
was further confirmed by the high-performance liquid chromatography
method. Overall, our study showed that PDA coating can chemically
modify the surface of AuNPs through a simple method and can thus significantly
improve the detection sensitivity of LFIA.
Immunochromatographic assay (ICA) is widely applied in various fields. However, severe matrix interference and weak signal output present major challenges in achieving accurate and ultrasensitive detection in ICA. Here, a polydopamine (PDA)-mediated magnetic bimetallic nanozyme (Fe 3 O 4 @PDA@Pd/Pt) with peroxidase-like activity was synthesized and used as a probe in ICA. The magnetic property of Fe 3 O 4 @PDA@Pd/Pt enabled effective magnetic enrichment of targets, thereby reducing the matrix interference in the sample. PDA coating on the magnetic bimetallic nanozyme was employed as a mediator and a stabilizer. It improved the catalytic ability and stability of the magnetic bimetallic nanozyme by providing more coordination sites for Pd/Pt growth and functional groups (−NH and −OH). In addition, the Pd/Pt bimetallic synergistic effect could further enhance the catalytic ability of the nanozyme. A method was developed by integrating Fe 3 O 4 , PDA, and Pd/Pt into Fe 3 O 4 @PDA@Pd/Pt as a probe in ICA. With the proposed method, human chorionic gonadotropin and Escherichia coli O157:H7 were successfully detected to be as low as 0.0094 mIU/mL in human blood serum and 9 × 10 1 CFU/mL in the milk sample, respectively. This method may be readily adapted for accurate and ultrasensitive detection of other biomolecules in various fields.
The
vulcanization of rubber is a chemical process to improve the
mechanical properties by cross-linking unsaturated polymer chains.
Zinc oxide (ZnO) acts as an activator, boosting the rubbers’
sulfur vulcanization. Maintaining the level of ZnO content in the
rubber compounds as low as possible is desirable, not only for economic
reasons but also to reduce the environmental footprint of the process.
In this contribution, octylamine (OA) capped ZnO nanoparticles (5
nm diameter), prepared through a thermal decomposition method, were
demonstrated to be efficient activators for the sulfur vulcanization
of natural rubber, enabling the reduction of the required amount of
ZnO as compared to commercial systems. The effect of different ZnO
activators (OA capped ZnO/commercial indirect process ZnO) on the
curing characteristics, cross-linking densities, and mechanical performance,
as well as the thermal behavior of rubber compounds, were investigated.
Compared to the commercial indirect process ZnO, OA capped ZnO nanoparticles
not only effectively enhanced the curing efficiency of natural rubber
but also improved the mechanical performance of the composites after
vulcanization. This was interpreted
as, by applying the OA capped ZnO nanoparticles, the ZnO levels in
rubber compounding were significantly reduced under the industrial
vulcanization condition (151 °C, 30 min).
The
introduction of dynamic covalent bonds into chemically cross-linked
networks is an effective strategy to solve intrinsic problems of inability
to be reprocessed or recycled for thermosetting polymers. Imine bonds
(also known as Schiff bases) are promising candidates for constructing
covalent adaptable networks (CANs) because of their easily triggered
exchange reactions. However, it remains a challenge for polyimine
vitrimers to improve the creep resistance and thermal stability due
to their unstable imine-based networks. In this work, we report a
green strategy to prepare a series of partially bio-based, malleable,
recyclable, and robust poly(amide–imine) vitrimers by bulk
polymerization for the first time. The amide bonds are introduced
into polyimine vitrimers for the improvement of mechanical property,
thermal stability, and creep resistance. A series of H2N-terminated prepolymers with tunable structures were first synthesized,
which combined the amide and imine groups together. Then, a bio-based
trimethyl citrate was selected as the curing agent to react with H2N-terminated prepolymers for the construction of CANs with
amide bonds as cross-linking points. The imine groups accompanied
by a dynamic exchange nature endowed the poly(amide–imine)
vitrimers with reprocessability, self-healing property, and degradability.
Meanwhile, the amide groups with inherent intermolecular hydrogen
bonding enhanced the mechanical properties, thermal stability, and
creep resistance of poly(amide–imine) thermosets.
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