研究目的
To compare the phase behavior of 5CB blended with poly(ethylene oxide) (PEO) and with gold NPs functionalized with thiolated PEO (AuNP–PEO) as a function of PEO concentration, and to understand the effect of PEO alone and PEO tethered to NPs on the LC phase behavior, the extent to which the spatial distribution of the NPs can be controlled, and the effect of crystallization of PEO.
研究成果
The study shows that polymer functionalized NPs may offer a useful alternative to using custom-synthesized mesogenic ligands to prepare liquid crystal nanocomposites. The properties of gold NPs with polymer ligands blended with a simple nematic were characterized and compared to the analogous polymer/LC blends and dispersions of the same gold NPs with mesogenic ligands. A thermodynamic model was able to explain the experimentally observed phase behavior of low molecular weight PEO in 5CB.
研究不足
The study focuses on high particle concentrations for spectroscopic characterization purposes. The effect of lower particle concentrations, tuning the ligand shell by molecular weight, chain density by adding short spacer ligands, and/or chain stiffness by using rigid-rod type polymers, are areas for future research.
1：Experimental Design and Method Selection
The phase behavior of 5CB blended with PEO and AuNP–PEO was characterized by differential scanning calorimetry (DSC), polarized optical microscopy (POM), and 13C NMR spectroscopy.
2：Sample Selection and Data Sources
Gold nanoparticles (AuNPs) functionalized with thiolated polyethylene oxide (PEO-SH, MW 2000 g mol?1) ligands (AuNP–PEO) were synthesized and dispersed in the nematic liquid crystal 4-n-pentyl-40-cyanobiphenyl (5CB). Concentrations of 1, 10, 20 and 50 wt% AuNP–PEO in 5CB were prepared.
3：List of Experimental Equipment and Materials
Nikon Eclipse LV100POL optical microscope, Mettler FP52 heating plate, 500 MHz Varian VNMRS spectrometer, DSC Q2000 (TA Instruments), TGA Q500 (TA Instruments).
4：Experimental Procedures and Operational Workflow
POM images were acquired with a cooling rate of 1 deg min?1. 13C NMR spectra were collected at intervals of 0.3 or 0.5 degrees after equilibrating. DSC experiments were done by heating at 1 °C min?1 from ?40 °C to 100 °C and cooling at the same rate.
5：Data Analysis Methods
The order parameter was calculated from the 13C chemical shifts using a semi-empirical equation. The nematic fractions were calculated from the intensities of the isotropic and nematic 13C peaks.
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