Chih-Wei Peng

Nanocasting Technique to Prepare Lotus-leaf-like Superhydrophobic Electroactive Polyimide as Advanced Anticorrosive Coatings

Nanocasting technique was used to obtain a biomimetic superhydrophobic electroactive polyimide (SEPI) surface structure from a natural Xanthosoma sagittifolium leaf. An electroactive polyimide (EPI) was first synthesized through thermal imidization. An impression of the superhydrophobic Xanthosoma sagittifolium leaf was then nanocasted onto the surface of the EPI so that the resulting EPI was superhydrophobic and would prevent corrosion. Polydimethylsiloxane (PDMS) was then used as a negative template to transfer the impression of the superhydrophobic surface of the biomimetic EPI onto a cold-rolled steel (CRS) electrode. The superhydrophobic electroactive material could be used as advanced coatings that protect metals against corrosion. The morphology of the surface of the as-synthesized SEPI coating was investigated using scanning electron microscopy (SEM). The surface showed numerous micromastoids, each decorated with many nanowrinkles. The water contact angle (CA) for the SEPI coating was 155°, which was significantly larger than that for the EPI coating (i.e., CA = 87°). The significant increase in the contact angle indicated that the biomimetic morphology effectively repelled water. Potentiodynamic and electrochemical impedance spectroscopic measurements indicated that the SEPI coating offered better protection against corrosion than the EPI coating did.

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.

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.

Preparation and thermal properties of UV-curable polyacrylate–gold nanocomposite foams

In this study, we prepare UV-curable polyacrylate–gold nanocomposites (PGNs) for the first time and analyze their thermal properties. The microemulsion architectures of these PGNs contain gold nanoparticles (GNPs) whose surface is modified with carboxyl groups; furthermore, 2-hydroxyethyl methacrylate (HEMA) and methyl methacrylate (MMA) monomers are first chemisorbed onto the surface of the GNPs and then photopolymerized to form a shell. The effects of the dispersion characteristics of GNPs in a PGN matrix were analyzed by transmission electron microscopy (TEM). PGN foams (FPGNs) can be obtained by subjecting the as-prepared bulk PGN materials to physical batch foaming processes, where nitrogen is used as a blowing agent. The cellular structures of the prepared FPGNs were investigated by scanning electron microscopy (SEM). FPGNs containing 15 nm GNPs (herein, denoted by FPGN-15) were found to exhibit a smaller cell size and a higher cell density than FPGNs containing 25 nm GNPs (herein, denoted by FPGN-25). FPGN materials exhibit an apparent increase in thermal stability (including decomposition temperature (Td)) as well as a decrease in the thermal transport properties (including thermal conductivity (k) and thermal diffusivity (α)) as compared to their corresponding bulk PGN materials. Moreover, results of the measurements of the compression modulus showed that the mechanical strength of FPGN-15 and FPGN-25 increased by 72% and 57%, respectively, as compared to that of neat polyacrylate foam.