Shuaixia Tan

One step preparation of superhydrophobic polymeric surface with polystyrene under ambient atmosphere

Brassica oleracea-like polymer surface is facilely fabricated by one-step casting process using amorphous polystyrene (PS) under ambient atmosphere. The obtained coatings show excellent superhydrophobicity and only possess unitary micro-scale structure, similar to the natural brassica leaf. In addition, a simple topography analysis also roughly verifies superhydrophobic structure of branched and intermingled sticks and bumps. This process provides a fairly easy procedure for preparing superhydrophobic surface from common plastics. Moreover, it demonstrates that the micro/nano-binary structure is not necessary for superhydrophobicity, while unitary micro-scale structure for a polymer surface can exhibit outstanding water repellency as natural lotus.

Water uptake behavior of hydrogen-bonded PVPON–PAA LBL film

Hydrogen-bonded films of poly(vinylpyrrolidone) (PVPON) and poly(acrylic acid) (PAA) were built on a silicon and quartz surface using the layer-by-layer (LBL) assembly technique. Upon incubation, PVPON and PAA chains in the film can attain high-level miscibility and the film becomes homogeneous and transparent. TGA and elemental analysis indicate that the water content of the incubated PVPON-PAA film is only ∼4%. FT-IR proved that at high temperature these water molecules can be easily driven out of the film. When the incubated film was characterized with a spectrometer, it exhibited Fabry-Pérot fringes in the UV-visible-NIR spectrum. Such Fabry-Pérot fringes, sensitive to the change of water content in the film, were applied to study drying, drying-rewetting cycle, and humidity-responsive behavior of the film. The film exhibited reversible swelling-deswelling behavior during the incubation-heating cycles. The film thickness was found to decrease ∼10% upon drying. When the dry film was exposed to different humidity environments, it was found that the optical thickness of the film has a linear relationship with ambient humidity.

A Simple Approach for Fabricating a Superhydrophobic Surface Based on Poly(Methyl Methacrylate)

Superhydrophobic surfaces based on poly(methyl methacrylate) (PMMA) with flower-like structures were prepared by controlling the aminolysis reaction of surface ester groups and the surface morphology of PMMA. The effects of the aminolysis time and the processing temperature in stearic acid solution on the surface wettability and surface morphology were examined in detail. The combination of rough surface morphology and the presence of hydrophobic carbon chains on the top layer was responsible for the superhydrophobicity.

Fabrication of honeycomb-patterned polyalkylcyanoacrylate films from monomer solution by breath figures method.

Honeycomb-patterned polyalkylcyanoacrylate (PACA) films were prepared from the chloroform solutions of alkylcyanoacrylate (ACA) by breath figures (BFs) method. Condensed water droplets on the solution surface acted not only as templates to endow the ordered structure but also as initiators to trigger the polymerization of ACA. After the polymerization started, the in situ formed polymer chains self-assembled around the water droplets, structuring PACA film with a hexagonal arrangement of holes. This was the first time that polymerization was introduced to breath figures method. The formation mechanism and the influencing factors, including substrates, relative humidity, and solution concentrations were investigated. Hela cells were cultured on both flat and honeycomb-like PACA films to investigate their application as biomaterials.

Facile preparation of poly(ethyl α-cyanoacrylate) superhydrophobic and gradient wetting surfaces

Hollow microspheres of poly(ethyl alpha-cyanoacrylate) were prepared via vapor phase polymerization using micro-waterdroplets as template and initiator. Depending on the ratio of the shell thickness to the radius, the hollow microspheres would crimple to form either microballoons or microcups during drying. These two types of microparticles were used as building blocks to construct surfaces with diverse wettability. The microballoons linked up to form a porous-netlike surface which was rough enough to render the surface superhydrophobic, while the microcups-built surface showed less hydrophobicity. In addition, surfaces consisting of both microparticles with gradual decrease of roughness along the length direction were obtained, which presented gradient wetting property varied from superhydrophobic to hydrophobic. The as-formed superhydrophobic or gradient wetting surfaces may find potential applications in biomedical field because of the biocompatibility of poly(ethyl alpha-cyanoacrylate).

Field-driven gel actuator with versatile long-range locomotion in air

An approach to fabricate gel actuator using nonionic polymer gels and dielectric liquid pattern was developed. The actuator could be operated in air using a dc electric field and exhibited a rotation-slide complex motion on the horizontal and a snail-like or sliding motion on the slope with controlled path. The average rotational speed and the average climbing speed of the gel could reach 0.35rad∕s and 3.8mm∕s, respectively. The driving force of the gel originated from the electrohydrodynamic flow of the dielectric solvent inside and outside the gel induced by the ion-dragging mechanism under the electric field.

Optical investigation of diffusion of levofloxacin mesylate in agarose hydrogel

Real-time electronic speckle pattern interferometry method has been applied to study the diffusion behavior of levofloxacin mesylate (MSALVFX) in agarose hydrogel. The results show that the diffusivity of solute decreases with the increase of concentration of agarose and adapts to Kohlrauschs law. Furthermore, Amsdens model, based on the retardance effect associated with polymer chain flexibility, was employed to simulate the diffusion behavior. The consistent results suggest that the retardance effect dominates the diffusion process of MSALFVX in hydrogel; moreover, polymer chain flexibility greatly affects drug transport within the polymer matrix.

A developed full-field fem analysis combined with ESPI for the investigation of defect evolution in polymer films

A full-field finite element method (FEM) analysis combined with electronic speckle pattern interferometry (ESPI) measurement was developed to investigate defect evolution in polymer films. Different from the previous reports, which only compare the ESPI experimental and FEM simulated results at several points or lines, herein the full-field FEM results were exported, subtracted with a continuous distribution. By choosing proper parameters and number of substeps, the simulated and experimental results showed excellent correspondence. Furthermore, the displacement fields vertical to the tensional direction were also presented, and the strain field was preliminarily evaluated. The current method of combination of ESPI and FEM allows for capturing the experimental fringe maps to validate and optimize FEM results simulated, and would give a higher security to structural and mechanical analysis of polymeric materials.