Chi-Hao Chang

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.

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.

Self-Assembly Behavior of Amphiphilic Poly(amidoamine) Dendrimers with a Shell of Aniline Pentamer

A series of amphiphilic poly(amidoamine) dendrimers (PAMAM, G2-G5) composed of a hydrophilic core and a hydrophobic shell of aniline pentamer (AP) were synthesized and characterized. The modified dendrimers self-assembled to vesicular aggregates in water with the critical aggregation concentration (CAC) decreased in the order of G2 > G3 > G4 > G5. It was found that the modified dendrimers self-organized into spherical aggregates with a bilayer vesicular structures and that the dendrimers in higher generation have more order structure, which may be attributed to the crystallization induced by the compacted effect of AP segments. In addition, larger spherical vesicles were observed under acidic and alkaline conditions, as compared with sizes of aggregates in neutral medium. At low pH, the tertiary amine groups of PAMAM-AP were transformed to ammonium salts; the polarons were formed from AP units by doping with strong acids, thereby leading to the stability of vesicular aggregates being better than that in double distilled water. Nevertheless, in high pH environment, the deprotonation of PAMAM-AP caused the enhancement of π-π interactions, resulting in generation of twins or multilayered vesicles.

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.