Chang-Jian Weng

UV-curable nanocasting technique to prepare bio-mimetic super-hydrophobic non-fluorinated polymeric surfaces for advanced anticorrosive coatings

In this study, a UV-curing nanocasting technique was first used to develop advanced anticorrosive coatings with bio-mimetic Xanthosoma sagittifolium leaf-like, non-fluorinated, super-hydrophobic polymeric surfaces. First of all, a transparent soft template with negative patterns of Xanthosoma sagittifolium leaf was fabricated by thermally curing the PDMS pre-polymer in molds at 60 °C for 4 h, followed by detaching the PDMS template from the surface of the natural leaf. Epoxy-acrylate coatings with biomimetic structures were prepared by performing the UV-radiation process after casting UV-curable precursor with photo-initiator onto a cold-rolled steel (CRS) electrode using the PDMS template. Subsequently, the UV-radiation process was carried out by using a light source with an intensity of 100 mW cm2 with an exposing wavelength of 365 nm. The surface morphology of as-synthesized epoxy-acrylate coatings obtained from this UV-curing nanocasting technique was found to have lots of micro-scaled mastoids, each decorated with many nano-scaled wrinkles and was investigated systematically by scanning electron microscopy (SEM) and atomic force microscopy (AFM). It should be noted that the water contact angle (CA) of coating with bio-mimetic natural leaf surface was 153°, which was found to significantly higher than that of the corresponding polymer with a smooth surface (i.e., CA = 81°). The significant increase of the contact angle indicated that this bio-mimetic morphology exhibited effectively water-repelling properties, implying that it may be a potential candidate as advanced anticorrosive coating materials, which can be identified by series of electrochemical corrosion measurements. For example, it should be noted that the corrosion potential (Ecorr) and corrosion current (Icorr), respectively, was found to shift from Ecorr = −730 mV and Icorr = 5.44 μA cm−2 of coating with smooth surface (SS) to Ecorr = −394 mV and Icorr = 2.30 μA cm−2 of coating with biomimetic super-hydrophobic surface (SPS).

Synergistic effect of electroactivity and hydrophobicity on the anticorrosion property of room-temperature-cured epoxy coatings with multi-scale structures mimicking the surface of Xanthosoma sagittifolium leaf†

A novel method is introduced to fabricate an electroactive epoxy (EE) coating with structured hydrophobic surfaces using an environmentally friendly process for anticorrosion application. First of all, the electroactive amine-capped aniline trimer (ACAT) was used as a curing agent to cure the epoxy resin and additionally provided electroactivity to the cured epoxy resin. The EE coating was cured at room temperature without using any solvent. The increased amount of the ACAT component in the EE coating not only accelerated the curing process but also promoted the thermal stability and anticorrosion performance. Subsequently, the multi-scale papilla-like structures on the surface of the Xanthosoma sagittifolium leaf were successfully replicated on the surface of the EE coating using PDMS as a negative template, as evidenced by the SEM investigation. The resulting hydrophobic electroactive epoxy (HEE) coating with the replicated nanostructured surface showed a hydrophobic characteristic with a water contact angle close to 120°. The developed HEE coating exhibited superior anticorrosion performance in electrochemical corrosion tests as its corrosion rate is better than that of the bare steel substrate by a factor of 450. The significantly improved corrosion protection is attributed to, besides the steel substrate isolated by the coating, the synergistic effect of electroactivity and hydrophobicity from the HEE coatings with the multi-scale structures mimicking the surface of the Xanthosoma sagittifolium leaf.

Polyaniline/carbon nanotube nanocomposite electrodes with biomimetic hierarchical structure for supercapacitors

Polyaniline (PANI)/multi-walled carbon nanotube (MWNT) nanocomposite films with three-dimensional architectures on the surface were prepared using fresh plant leaves as a template through the nanocasting technique. The biomimetic surface morphology of the PANI nanocomposite electrodes, including multiscale papilla-like and nanoscale texture, were successfully replicated from Xanthosoma sagittifolium leaves. The morphology, roughness and dispersed MWNTs of the PANI/MWNT nanocomposites were characterized using X-ray diffraction, scanning electron microscopy, transmission electron microscopy and atomic force microscopy. It was found that the well-dispersed MWNTs and the multiscale morphology formed a uniform nanocomposite, with an observed larger surface area, high specific capacitance and good cycling stability during the charge–discharge process. A specific capacitance as high as 535 F g−1 at a current density of 1 A g−1 was achieved for a 5 wt% MWNT loading coupled with the high roughness of the PANI nanocomposite, and the capacitance was maintained with the increment of the current density to 3 A g−1. These easily fabricated PANI nanocomposite electrodes show great potential for energy storage applications.

3D-bioprinting approach to fabricate superhydrophobic epoxy/organophilic clay as an advanced anticorrosive coating with the synergistic effect of superhydrophobicity and gas barrier properties†

Correction for ‘3D-bioprinting approach to fabricate superhydrophobic epoxy/organophilic clay as an advanced anticorrosive coating with the synergistic effect of superhydrophobicity and gas barrier properties’ by Chi-Hao Chang et al., J. Mater. Chem. A, 2013, 1, 13869–13877.

Synthesis of electroactive mesoporous gold–organosilica nanocomposite materials via a sol–gel process with non-surfactant templates and the electroanalysis of ascorbic acid

Electroactive mesoporous organosilica nanocomposites (EMONs) and electroactive mesoporous gold-organosilica nanocomposites (EMGONs) were successfully prepared in this work and were applied in ascorbic acid (AA) sensing. EMONs were synthesized by using an aniline pentamer (AP) as an electroactive segment which controlled the redox ability and influenced the degree of sensitivity of the nanocomposites towards AA. EMGONs were successfully prepared by a one-pot synthesis in HAuCl4 aqueous solution with different concentrations. Gold nanoparticles (AuNPs) were selectively reduced on an AP segment in an EMON matrix, which acted as a reductant as well as providing a large surface area to absorb and react with chloroaurate anions (AuCl4 -). The gold particle size can be controlled by varying the concentration of HAuCl4 (aq.), and distributed AuNPs with controllable size were fabricated for the EMGONs. A sensor constructed from an EMGON-modified carbon-paste electrode (CPE) demonstrated 21-fold and 6.3-fold higher electrocatalytic activity towards the oxidation of AA compared to those constructed using a bare CPE and EMON-modified CPE, respectively. The high surface area of the EMGON-modified CPE exhibited a good electrochemical response towards AA at a low oxidative potential with good stability and sensitivity and a wide linear analytical detection range.

Intrinsically electroactive polyimide microspheres fabricated by electrospraying technology for ascorbic acid detection

In this paper, we present the first fabrication of intrinsically electroactive polyimide microspheres (EPS) based on conjugated segments of an electroactive amino-capped aniline trimer (ACAT) of a diamine, 4,4′-(4,4′-isopropylidenediphenoxy)-bis(phthalic anhydride) (BSAA) and a dianhydride. EPS was successfully prepared using electrospraying technology and applied in the detection of ascorbic acid (AA). The particle size of EPS can be controlled by varying the concentration of spraying solution, while the electrocatalysis oxidation properties can be influenced by the different particle sizes of EPS. A sensor constructed using an EPSS (EPS with a small particle size)-modified carbon paste electrode (CPE) was found to show 4.38-fold and 1.81-fold higher electrocatalytic activities towards the oxidation of AA than those constructed using an EPI (electroactive polyimide) thin film and EPSL (EPS with large particles size), respectively.

A smart surface prepared using the switchable superhydrophobicity of neat electrospun intrinsically electroactive polyimide fiber mats

An electroactive polyimide fiber (EPF) mat based on conjugated segments of electroactive amino-capped aniline trimer (ACAT) as a diamine and 4,4′-(4,4′-sopropylidenediphenoxy)-bis(phthalic anhydride) (BSAA) as a dianhydride was successfully prepared by electro-spin technology with electrochemical activity and dopable properties, which were similar to polyaniline. The degree of electrochemical activity and dopable properties can be tuned by varying the content of ACAT existing in the as-prepared electro-spun EPF mats. After doping with perfluorooctanesulfonic acid (PFOS), the water contact angle of EPF surface is increased from hydrophobicity at 133° to superhydrophobicity at 155°. It is interesting that the EPF mat undergoes a switchable process from superhydrophobicity to superhydrophilicity via doping with PFOS and de-doping with ammonium gas.

Polymer nanocomposites in corrosion control

Abstract: Polymer/clay nanocomposites (PCN) are now of great interest to polymer scientists, physicists and material scientists because of the unique properties produced by combining these components at the nanoscale level. Measuring the corrosion protection effects of PCNs as coatings is crucial to gaining a fundamental understanding of the anticorrosion mechanism of these materials. Measurement of the anticorrosive properties of PCN is also helpful in establishing the gas barrier properties of polymer/clay interactions and their structure–property relationship in nanocomposites. This is because anticorrosive performance is strongly influenced by the nanoscale structure and interfacial characteristics. In this chapter, recent advances in PCN anticorrosive coatings are discussed.