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Polymer functionalized nanoparticles in liquid crystals: combining PDLCs with LC nanocomposites
摘要： Liquid crystal (LC)–polymer blends are important stimuli responsive materials already employed in a wide range of applications whereas nanoparticle (NP)–LC blends are an emerging class of nanocomposites. Polymer ligands offer the advantages of synthetic simplicity along with chemical and molecular weight tunability. Here we 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 by DSC, POM and 13C NMR spectroscopy. Both PEO and the AuNP–PEO form uniform dispersions in isotropic 5CB and phase separate below the I–N phase transition temperature. Above the PEO crystallization temperature, the PEO/5CB blends show the expected biphasic state of PEO rich-isotropic liquid co-existing with PEO-poor nematic droplets. At PEO concentrations above 10 wt%, nematic 5CB nucleates with PEO crystallization. Both PEO and AuNP–PEO induce homeotropic alignment of the 5CB matrix immediately below TNI. The AuNP–PEO/5CB blends form thermally reversible cellular networks similar to AuNPs functionalized with low molecular weight mesogenic ligands. A thermodynamic model to account for the observed phase behavior is presented.
关键词： Polymer blends,Nanoparticles,Liquid crystal,Phase behavior,Thermodynamic model
更新于2025-09-23 15:21:01
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Terahertz Nonlinear Optics of Graphene: From Saturable Absorption to High‐Harmonics Generation
摘要： Graphene has long been predicted to show exceptional nonlinear optical properties, especially in the technologically important terahertz (THz) frequency range. Recent experiments have shown that this atomically thin material indeed exhibits possibly the largest nonlinear coefficients of any material known to date, paving the way for practical graphene-based applications in ultrafast (opto-)electronics operating at THz rates. Here the advances in the booming field of nonlinear THz optics of graphene are reported, and the state-of-the-art understanding of the nature of the nonlinear interaction of graphene with the THz fields based on the thermodynamic model of electron transport in graphene is described. A comparison between different mechanisms of nonlinear interaction of graphene with light fields in THz, infrared, and visible frequency ranges is also provided. Finally, the perspectives for the expected technological applications of graphene based on its extraordinary THz nonlinear properties are summarized. This report covers the evolution of the field of THz nonlinear optics of graphene from the very pioneering to the state-of-the-art works. It also serves as a concise overview of the current understanding of THz nonlinear optics of graphene and as a compact reference for researchers entering the field, as well as for the technology developers.
关键词： terahertz,high-harmonics generation,nonlinear optics,thermodynamic model,graphene
更新于2025-09-11 14:15:04