Effective Path Length in Attenuated Total Reflection Spectroscopy

Averett, Lacey A.; Griffiths, Peter R.; Nishikida, Koichi

doi:10.1021/ac7025892

Cited by 108 publications

(79 citation statements)

References 7 publications

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“…Both the real part and the imaginary part of the refractive index change as a function of λ in proximity of the sample absorption peaks 24. This is particularly relevant for the strong absorption peaks characteristic of PMMA for which the influence of the extinction coefficient on d p cannot be neglected 24, 26. It should be noted that, contrary to the first PTIR reports,14 where light was transmitted through the sample and totally reflected at the sample‐air interface, the experimental conditions used here ( θ = 45°, n 1 = 2.438, n2 ( λ ) = 1.2 to 1.65, k 2 ( λ ) = 0 to 0.4)24 ensure that total internal reflection is achieved at all wavelengths (from 1800 cm −1 to 1200 cm −1 ) at the prism‐sample interface.…”

Section: Resultsmentioning

confidence: 99%

Chemical Imaging Beyond the Diffraction Limit: Experimental Validation of the PTIR Technique

Lahiri

Holland

Centrone

2012

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Photothermal induced resonance (PTIR) has recently attracted great interest for enabling chemical identification and imaging with nanoscale resolution. In this work, electron beam nanopatterned polymer samples are fabricated directly on 3D zinc selenide prisms and used to experimentally evaluate the PTIR lateral resolution, sensitivity and linearity. It is shown that PTIR lateral resolution for chemical imaging is comparable to the lateral resolution obtained in the atomic force microscopy height images, up to the smallest feature measured (100 nm). Spectra and chemical maps are produced from the thinnest sample analyzed (40 nm). More importantly, experiments show for the first time that the PTIR signal increases linearly with thickness for samples up to ≈ 1 μm (linearity limit); a necessary requirement towards the use of the PTIR technique for quantitative chemical analysis at the nanoscale. Finally, the analysis of thicker samples provides the first evidence that the previously developed PTIR signal generation theory is correct. It is believed that the findings of this work will foster nanotechnology development in disparate applications by proving the basis for quantitative chemical analysis with nanoscale resolution.

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Section: Resultsmentioning

confidence: 99%

Chemical Imaging Beyond the Diffraction Limit: Experimental Validation of the PTIR Technique

Lahiri

Holland

Centrone

2012

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157

256

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“…) is nearly a linear function of the wavenumber. 69 Using this approximation and assuming molar absorption coefficients determined from solution are valid in the bulk, the PE-g and PE-v compositions were quantified using Equations 1-3:…”

Section: Samplementioning

confidence: 99%

Phase Separation and Self-Assembly in Vitrimers: Hierarchical Morphology of Molten and Semicrystalline Polyethylene/Dioxaborolane Maleimide Systems

2018

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Vitrimers -a class of polymer networks which are covalently crosslinked and insoluble like thermosets, but flow when heated like thermoplastics -contain dynamic links and/or crosslinks that undergo an associative exchange reaction. These dynamic crosslinks enable vitrimers to have interesting mechanical/rheological behavior, self-healing, adhesive, and shape memory properties.We demonstrate that vitrimers can self-assemble into complex meso-and nanostructures when crosslinks and backbone monomers strongly interact. Vitrimers featuring polyethylene (PE) as the backbone and dioxaborolane maleimide as the crosslinkable moiety were studied in both the molten and semi-crystalline states. We observed that PE vitrimers macroscopically phase separated into dioxaborolane maleimide rich and poor regions, and characterized the extent of phase separation by optical transmission measurements. This phase separation can explain the relatively low insoluble fractions and overall crystallinities of PE vitrimers. Using synchrotronsourced small-angle X-ray scattering (SAXS), we discovered that PE vitrimers and their linear precursors micro-phase separated into hierarchical nanostructures. Fitting of the SAXS patterns to a scattering model strongly suggests that the nanostructures -which persist in both the melt and amorphous fraction of the semi-crystalline state -may be described as dioxaborolane maleimide rich aggregates packed in a mass fractal arrangement. These findings of hierarchical meso-and nanostructures point out that incompatibility effects between network components and resulting self-assembly must be considered for understanding behavior and the rational design of vitrimer materials.Thermoplastics and thermoplastic elastomers are soluble in good solvents and flow when heated above the glass or melting temperature. Thermosets and rubbers do not flow and are not soluble.Vitrimers, a class of polymers introduced by Leibler and collaborators in 2011, flow when heated, but remain insoluble. 1 Vitrimers are made of polymer networks which contain covalent crosslinks that undergo dynamic associative exchange reactions. The covalent crosslinks in a vitrimer maintain network connectivity at all times and temperatures. Unlike materials employing dissociative crosslinking mechanisms, 2 vitrimers cannot be completely dissolved -even in good solvents. 1,3 Associative exchange reactions permit the network topology to fluctuate and the system to flow when stress is applied, and exchange reaction kinetics control the vitrimer relaxation dynamics and viscosity. 2,4,5,6 The initial reports of vitrimer systems focused on epoxy networks that reorganized via metal-catalyzed transesterification. 1,4,6 Today, the library of dynamic exchange reactions has expanded to include chemistries that are catalytically-controlled (olefin metathesis and transcarbonation) 7,8 or catalyst-free (transamination, 9,10,11 trans-N-alkylation, 12,13 reversible addition of thiols, 14 imine exchange, 15,16 addition-fragmentation chain transfer, 17,18 boronic est...

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“…Averett and Griffiths [27] showed that for a ZnSe IRE with q ¼ 45 and n 2 ¼ 1.5, the average value of d e,s and d e,p is approximately equal to 2d p . Thus, in this work the path length (b) was assumed to be equal to 2d p .…”

Section: Infrared Spectroscopy Analysismentioning

confidence: 99%