Improving the superhydrophobicity of polydimethylsiloxane (PDMS) is a current interest in a wide range of applications from biomedical to aerospace. Although many fabrication techniques are available to improve the superhydrophobicity of PDMS, a significant problem occurs when the fabrication technique applies as a scalable but simple one. Here, we have described simple methods to achieve superhydrophobicity of PDMS using short-chained fluorinated polyhedral oligomeric silsesquioxanes (FPOSS). Two species of FPOSS were incorporated into PDMS using four different methods; non-solvent blending, solvent blending, spraying FPOSS/PDMS solution onto a partially cured PDMS matrix and spraying only FPOSS solution onto partially cured PDMS surfaces. Among two FPOSS species, spraying FPOSS onto partially cured PDMS produced a superhydrophobic surface with a static water contact angle of 167° ± 1°. Trifluoropropylisobutyl POSS (TFP) resulted in a higher hydrophobicity than trifluoropropyl POSS cages (CM). The multi-scale structured surface morphology, compatibility of functional groups attached to FPOSS and the fluorine content have shown a significant contribution on the superhydrophobicity in FPOSS/PDMS systems. Amorphous nature of the PDMS has improved upon incorporating FPOSS. Hence, this work presents a detailed study on the effect of the preparation method of FPOSS/PDMS composite on its superhydrophobicity.
We report on the design and performance of a time-resolved Coherent Raman spectroscopy system with time resolution of better than 120 fs. The coherent transients can be traced with more than 75 dB dynamic range while accessing and probing Raman active modes across a 250–2400 cm−1 frequency. The system delivers an equivalent spectral resolution of better than 0.1 cm−1 regarding line bandwidth parameters for probed Raman resonances.
Time-domain coherent Raman spectroscopy technique with excellent time (<120 fs) and equivalent spectral resolutions (up to ∼0.1 cm −1 ) has been applied to selectively measure ultrafast decay rates of optical phonons in technologically important wide-bandgap materials. The decays of intrinsic vibrations have been traced in time within multiple orders and phonon decay times varied broadly within 0.45−1.7 ps range. Primary decay routes via third-and fourth-order parametric phonon interactions have been analyzed to provide important estimates for zero-temperature decay rates and line widths for the main Raman active vibrations.
Decays of coherent phonons have been traced with 120 fs resolution in technologically important perovskites of BaSnO
3
and SrTiO
3
. The phonon decay rates of 1.23-1.82 ps
-1
are explained within the framework of anharmonic potential theory.
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