In situ Diffusion Studies Using Spatially Resolved Infrared Microspectroscopy

1996 ◽  
Vol 50 (11) ◽  
pp. 1339-1344 ◽  
Author(s):  
Sudarsana R. Challa ◽  
Shi-Qing Wang ◽  
Jack L. Koenig
Keyword(s):  
Polymer Fibers ◽  
Contact Method ◽  
Measured Concentration ◽  
Infrared Microspectroscopy ◽  
Spatially Resolved ◽  
Polymer Dispersed Liquid Crystals ◽  
Diffusion Studies ◽  
Polymer Dispersed ◽  
In Situ Diffusion

Spatially resolved infrared microspectroscopy is used in conjunction with the contact method to conduct in situ diffusion experiments of photocured polymer-dispersed liquid crystals (LCs). The system analyzed consists of a low-molecular-weight liquid crystal (E7) diffusing into a photopolymerizable monomer (NOA65). The measured concentration profiles were generated by monitoring the hydroxyl band of the monomer as a function of time and spatial position. The diffusion coefficients were calculated from least-squares fitting of the data. The system followed Fick's second law of diffusion. The diffusion coefficient for this system is (1.97 ± 0.2)(10−8) cm2/s. The morphology of the system after polymerization exhibited three distinct regions: nematic LC molecularly mixed in the cross-linked network of the polymer, nematic LC droplet gradient in the polymer matrix, and polymer fibers scattered in the continuous nematic LC.

In Situ Diffusion and Miscibility Studies of Thermoplastic PDLC Systems by FT-IR Microspectroscopy

1997 ◽  
Vol 51 (3) ◽  
pp. 297-303 ◽  
Author(s):  
Sudarsana R. Challa ◽  
Shi-Qing Wang ◽  
Jack L. Koenig
Keyword(s):  
Liquid Crystal ◽  
Phase Diagrams ◽  
Butyl Methacrylate ◽  
Contact Method ◽  
Polymer Dispersed Liquid Crystal ◽  
Polymer Dispersed ◽  
Ir Microspectroscopy ◽  
In Situ Diffusion ◽  
Miscibility Studies

Infrared microspectroscopy was used to study the interaction of liquid crystal (E7) with poly( n-butyl methacrylate) (PBMA). A novel experimental technique is introduced to conduct in situ diffusion and miscibility studies of polymer-dispersed liquid crystal (PDLC) systems. The amount of liquid crystal dissolved in the polymer matrix is determined by using the IR microspectroscope, which is a powerful tool for characterizing domains on the order of tens of micrometers. Quantitative phase diagrams are constructed for the PBMA and E7 mixture. It is observed that the diffusion of E7 into PBMA follows Fick's second law of diffusion with a diffusion coefficient of (1.3 ± 0.2) × 10−7 cm2/s at 61 °C. The intensities of the peaks in the IR spectrum were used as a measure of the concentration of the components. The combination of IR microspectroscopy with the contact method is proven to be a powerful technique for the quantitative elucidation of phase diagrams.

Characterization of Polymer-Dispersed Liquid Crystal Systems by FT-IR Microspectroscopy

1995 ◽  
Vol 49 (3) ◽  
pp. 267-272 ◽  
Author(s):  
Sudarsana R. Challa ◽  
Shi-Qing Wang ◽  
Jack L. Koenig
Keyword(s):  
Liquid Crystal ◽  
Power Laws ◽  
Butyl Methacrylate ◽  
Valuable Insight ◽  
Infrared Microspectroscopy ◽  
Polymer Dispersed Liquid Crystal ◽  
Spatially Resolved ◽  
The Matrix ◽  
Polymer Dispersed ◽  
Ft Ir

Infrared microspectroscopy was used to generate functional group images of liquid crystal (E7) droplets dispersed in poly( n-butyl methacrylate) (PBMA). The spatial concentration fluctuations that occur within the system were studied as a function of time. This approach is possible because spectral information can be obtained by focusing on regions on the order of tens of micrometers. The peak intensities were used as a measure of concentration of the components. The amount of liquid crystal dissolved in the polymer matrix determines the extent to which the polymer is plasticized, which in turn affects the shape and size of the droplets. The growth of the domains at any temperature is also determined by whether the system is maintained above or below the glass transition temperature of the matrix. It is observed that the growth of the droplets follows temporal power laws. The spatially resolved spectroscopic images provide valuable insight into the phase separation process and the formation of microdroplets of E7 in PBMA.

Determination of Solubility Limits of Photocured PDLC Systems Using Infrared Microspectroscopy

1997 ◽  
Vol 51 (1) ◽  
pp. 10-16 ◽  
Author(s):  
Sudarsana R. Challa ◽  
Shi-Qing Wang ◽  
Jack L. Koenig
Keyword(s):  
Liquid Crystal ◽  
Low Molecular Weight ◽  
Contact Method ◽  
Concentration Gradients ◽  
Uv Curable ◽  
Infrared Microspectroscopy ◽  
Polymer Dispersed Liquid Crystal ◽  
The Matrix ◽  
Polymer Dispersed

Infrared microspectroscopy is used to determine the solubility limits of a UV-curable polymer-dispersed liquid crystal (PDLC) system comprised of a low-molecular-weight liquid crystal (E7) and a photocurable monomer (NOA65). The LC is allowed to diffuse into the monomer by the contact method, and then the sample is subjected to curing. The morphology of the system after polymerizaton exhibits several distinct spatial regions, and the associated concentration gradients are measured. At an irradiation temperature of 30 °C, the concentration of LC in the matrix is found to be 27 ± 3%, and at a temperature of 100 °C, it is 65 ± 3%.

Morphology of reflection holograms formed in situ using polymer-dispersed liquid crystals

Polymer ◽  
1996 ◽  
Vol 37 (14) ◽  
pp. 3147-3150 ◽  
Author(s):  
T.J. Bunning ◽  
L.V. Natarajan ◽  
V.P. Tondiglia ◽  
R.L. Sutherland ◽  
D.L. Vezie ◽  
...  
Keyword(s):  
Liquid Crystals ◽  
Polymer Dispersed Liquid Crystals ◽  
Polymer Dispersed

FT-IR microspectroscopic analysis of diseased white matter brain tissues

1995 ◽  
Vol 53 ◽  
pp. 968-969
Author(s):  
Steven M. Le Vine ◽  
David L. Wetzel
Keyword(s):  
White Matter ◽  
Gray Matter ◽  
Twitcher Mouse ◽  
Grid Pattern ◽  
Marked Contrast ◽  
Spatially Resolved ◽  
Ft Ir ◽  
Ir Microspectroscopy ◽  
Chemical Evidence

In situ FT-IR microspectroscopy has allowed spatially resolved interrogation of different parts of brain tissue. In previous work the spectrrscopic features of normal barin tissue were characterized. The white matter, gray matter and basal ganglia were mapped from appropriate peak area measurements from spectra obtained in a grid pattern. Bands prevalent in white matter were mostly associated with the lipid. These included 2927 and 1469 cm-1 due to CH2 as well as carbonyl at 1740 cm-1. Also 1235 and 1085 cm-1 due to phospholipid and galactocerebroside, respectively (Figs 1and2). Localized chemical changes in the white matter as a result of white matter diseases have been studied. This involved the documentation of localized chemical evidence of demyelination in shiverer mice in which the spectra of white matter lacked the marked contrast between it and gray matter exhibited in the white matter of normal mice (Fig. 3).The twitcher mouse, a model of Krabbe’s desease, was also studied. The purpose in this case was to look for a localized build-up of psychosine in the white matter caused by deficiencies in the enzyme responsible for its breakdown under normal conditions.

scholarly journals Spatially Resolved Experimental Modal Analysis on High-Speed Composite Rotors Using a Non-Contact, Non-Rotating Sensor

Sensors ◽  
2021 ◽  
Vol 21 (14) ◽  
pp. 4705
Author(s):  
Julian Lich ◽  
Tino Wollmann ◽  
Angelos Filippatos ◽  
Maik Gude ◽  
Juergen Czarske ◽  
...  
Keyword(s):  
High Speed ◽  
Natural Frequencies ◽  
Mode Shapes ◽  
Fiber Reinforced ◽  
Structural Dynamic ◽  
Spatially Resolved ◽  
Glass Fiber Reinforced ◽  
Vibration Responses ◽  
And Performance

Due to their lightweight properties, fiber-reinforced composites are well suited for large and fast rotating structures, such as fan blades in turbomachines. To investigate rotor safety and performance, in situ measurements of the structural dynamic behaviour must be performed during rotating conditions. An approach to measuring spatially resolved vibration responses of a rotating structure with a non-contact, non-rotating sensor is investigated here. The resulting spectra can be assigned to specific locations on the structure and have similar properties to the spectra measured with co-rotating sensors, such as strain gauges. The sampling frequency is increased by performing consecutive measurements with a constant excitation function and varying time delays. The method allows for a paradigm shift to unambiguous identification of natural frequencies and mode shapes with arbitrary rotor shapes and excitation functions without the need for co-rotating sensors. Deflection measurements on a glass fiber-reinforced polymer disk were performed with a diffraction grating-based sensor system at 40 measurement points with an uncertainty below 15 μrad and a commercial triangulation sensor at 200 measurement points at surface speeds up to 300 m/s. A rotation-induced increase of two natural frequencies was measured, and their mode shapes were derived at the corresponding rotational speeds. A strain gauge was used for validation.

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