Preparation and Evaluation of the Bioinspired PS/PDMS Photochromic Films by the Self-Assembly Dip–Drawing Method

Abstract

Emulsifier-free emulsion polymerization was employed to synthesize polystyrene (PS) microspheres, which were then self-assembled into an ordered periodic structure. A photochromic film was formed by adding polydimethylsiloxane (PDMS) around the self-assembly of PS microspheres on a PDMS substrate. During polymerization, the PS microspheres shrunk depending on the amount of the hydrophilic comonomer, sodium 4-styrenesulfonate (NaSS). Variation in structural color was strongly affected by the size of the PS microspheres. Scanning electron microscopy was used to observe the surface and cross sections of the self-assembled microspheres. Results showed that the order and stacking thickness of microspheres were dependent on the drawing rate of the substrate and suspension concentration. High-transmittance photochromic films could be prepared when the drawing rate was lower than 1 μm/s and the suspension concentration was 20 wt %. PDMS surrounding the vacant space between regularly arranged PS microspheres could not only protect them but also increase the degree of matching between the refractive indices of PS and PDMS. The stability of the reflected structural color increased, and the optical transmittance of the photochromic film approached 95% after PDMS was poured between the PS microspheres. A special pattern could be designed and embedded inside the photochromic film. The PS/PDMS photochromic films can also be applied in decorative painting as well as in security devices, color-changing false nails, and privacy filters.

Photonic Crystal-Based Sensors for Detecting Alcohol Concentration

“…Sci. 2016, 6, 67 6 of 13 of the PS microspheres was due to van der Waals attraction and electrostatic repulsion between the microspheres, which were balanced at the air/suspension interface [24]. Figure 5a,b are the FE-SEM images of TiO2 structure after 2 h sintering at 500 and 600 °C, respectively.…”

“…The substrate surface became hydrophilic by using oxygen plasma (PCD-150, All Real Technology Co., Ltd., Kaohsiung, Taiwan) treatment was carried out at a pressure of 300 mTorr, with 20 sccm oxygen flow under 100 W electric power. Then, the PS suspension was diluted with deionized water to 30 wt %, and dip-drawing was conducted at rates of 1 µm/s [24], and a close packed opal photonic crystals array was formed.…”

“…The orderly arrangement arranged in a compact-ordered periodic structure. The orderly arrangement of the PS microspheres was due to van der Waals attraction and electrostatic repulsion between the microspheres, which were balanced at the air/suspension interface [24].…”

Strongly Iridescent Hybrid Photonic Sensors Based on Self-Assembled Nanoparticles for Hazardous Solvent Detection

“…Depositing uniform three dimensional nanoparticle structures on hyrdophobic substrates has been one of the challenges to produce strongly iridescent materials. This was successfully achieved by using techniques such as dip-coating [ 16 , 29 ] or Langmuir-Blodgett deposition [ 30 , 31 ]. However, the commonly employed thin film deposition technique—spin-coating—is usually avoided, as it has a tendency to create non-uniform films due to the fast drying kinetics resulting from the quick rotation of the substrate [ 24 ].…”

Scalable Fabrication of Quasi-Three-Dimensional Chiral Plasmonic Oligomers Based on Stepwise Colloid Sphere Lithography Technology

“…This measurable chiroptical effect paves a way to achieve the structural characterization and spectroscopy of chiral molecules and manipulate the polarization state of light. However, the magnetoelectric coupling in the natural chiral molecules, such as DNA, proteins, amino acids, and viruses, is very weak [2]. This limits the ability of practical applications for the polarization manipulation and high-sensitivity sensing.…”