Fiber Alignment and Liquid Crystal Orientation of Cellulose Nanocrystals in the Electrospun Nanofibrous Mats

Sulfate cellulose nanocrystal (CNC) dispersions always present specific self-assembled cholesteric mesophases which is easily affected by the inherent properties of particle size, surface charge, and repulsion or affinity interaction, and external field force generated from ionic potential of added electrolytes, magnetic or electric field, and mechanical shearing or stretching. Aiming at understanding the liquid crystal orientation and fiber alignment under high-voltage electric field, randomly distributed, uniform-aligned, or core–sheath nanofibrous mats involving charged CNCs and PVA were electrospun; and among them, specific straight arrayed fine nanofibers with average diameter of 270 nm were manufactured by using a simple and versatile gap collector. Moreover, arrayed composite nanofibers regularly aligned along the vertical direction of gap plates and selectively reflected frequent and continuous birefringence which was regarded as nematic phases of CNCs induced by the uniaxial stretching under high-voltage electric field. As a synergic effect of rigidness of nanocrystals and stretching orientation of nematic phases, the aligned nanofibrous arrays exhibited a higher tensile strength and strain than the randomly oriented or core–sheath nanofibrous mats at the same loading of CNCs. By contrast, mesophase transition of CNCs from cholesteric to nematic occurred in the coaxially spun core–sheath nanofibers at a loss of long-ranged chiral twist. Hence, the structure-effect relationship between liquid crystal orientation of charged nanorods in polymer-based fine nanofibers and the flexibility or mechanical integrity of the aligned fiber array will be favorable for strategic development of functional liquid crystal fabrics

Energy-Transfer-Powered Sultine Synthesis

Molecules with precise sultine structures are particularly sought after since the function of a molecule depends on this interesting structure. Despite the positive pivotal significance of the sultines in synthesis, medicine, and materials science, the sultines’ chemistry long remains unexplored due to their inaccessibility; only very limited protocols have been developed. Here, we report an energy-transfer-powered intramolecular radical–radical cross-coupling cyclization for the practical and atom-economical assembly of otherwise challenging-to-access sultines under mild and operationally simple conditions using an inexpensive organic photocatalyst. Importantly, this work presents a practical method of trifluoromethyl radical generation from alkyl trifluoromethanesulfinate, and the obtained sultines were confirmed as promising electrolyte additives for high-voltage lithium batteries employing LiNi0.5Mn1.5O4 cathodes and carbonate electrolytes. Sultines were applied to build highly valuable sultones, mercaptoalkanols, and disulfides. Mechanistic studies and density functional theory calculations supported that the reaction likely proceeds through an energy-transfer-powered radical–radical cross-coupling cyclization process

Examples for the determination of radial magnification errors.

<p>(A) Radial intensity profile measured in scans of the precision mask. Blue lines are experimental scans, and shaded areas indicate the regions expected to be illuminated on the basis of the known mask geometry. In this example, the increasing difference between the edges corresponds to a calculated radial magnification error of -3.1%. (B—D) Examples for differences between the experimentally measured positions of the light/dark transitions (blue circles, arbitrarily aligned for absolute mask position) and the known edge distances of the mask. The solid lines indicate the linear or polynomial fit. (B) Approximately linear magnification error with a slope corresponding to an error of -0.04%. Also indicated as thin lines are the confidence intervals of the linear regression. (C) A bimodal shift pattern of left and right edges, likely resulting from out-of-focus location of the mask, with radial magnification error of -1.7%. (D) A non-linear distortion leading to a radial magnification error of -0.53% in the <i>s</i>-values from the analysis of back-transformed data. The thin grey lines in C and D indicate the best linear fit through all data points.</p

Analysis of the rotor temperature.

<p>(A) Temperature values obtained in different instruments of the spinning rotor, as measured in the iButton at 1,000 rpm after temperature equilibration, while the set point for the console temperature is 20°C (indicated as dotted vertical line). The box-and-whisker plot indicates the central 50% of the data as solid line, with the median displayed as vertical line, and individual circles for data in the upper and lower 25% percentiles. The mean and standard deviation is 19.62°C ± 0.41°C. (B) Correlation between iButton temperature and measured BSA monomer <i>s</i>-values corrected for radial magnification, scan time, scan velocity, but not viscosity (symbols). In addition to the data from the present study as shown in (A) (circles), also shown are measurements from the pilot study [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0126420#pone.0126420.ref027" target="_blank">27</a>] where the same experiments were carried out on instruments not included in the present study (stars). The dotted line describes the theoretically expected temperature-dependence considering solvent viscosity.</p

Absence of a long-term trend in <i>s</i>_{<i>20T</i>,<i>t</i>,<i>r</i>,<i>v</i>}-values of the BSA monomer with time of experiment for the three kits (blue, green, and magenta).

<p>Highlighted as bold solid line is the overall average, and the grey area indicates one standard deviation.</p

Corrected best-fit apparent monomer molecular mass from integration of the <i>c</i>(<i>s</i>) peak when scanned with the absorbance system (green) and the interference system (magenta).

<p>Only data with rmsd less than 0.01 OD or 0.01 fringes were included. The box-and-whisker plot indicates the central 50% of the data as solid line and draws the smaller and larger 25% percentiles as individual circles. The median is displayed as a vertical line.</p

Examples of transient changes in the console temperature reading during the SV experiment, as saved in the scan file data.

<p>For comparison, the maximum adiabatic cooling of -0.3°C would be expected after approximately 300 sec, recovering to the equilibrium temperature after approximately 1,200 s (see Fig 3 in [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0126420#pone.0126420.ref033" target="_blank">33</a>]).</p

Histogram and box-and-whisker plot of <i>s</i>-values of the BSA monomer after different corrections: Raw experimental <i>s</i>-values (black, with grey histogram), scan time corrected <i>s</i>_<i>t</i>-values (blue), rotor temperature corrected <i>s</i>_<i>20T</i>-values (green), or radial magnification corrected <i>s</i>_<i>r</i>-values (cyan), and fully corrected <i>s</i>_{<i>20T</i>,<i>t</i>,<i>r</i>,<i>v</i>}-values (red with red histogram).

<p>The box-and-whisker plots indicate the central 50% of the data as solid line and draw the smaller and larger 25% percentiles as individual circles. The median for each group is displayed as a vertical line.</p

Magnitude of the radial magnification correction obtained with the absorbance system (green) and the interference system (magenta).

<p>The box-and-whisker plot above the histogram indicates the central 50% of the data as solid horizontal line and draws data in the smallest and highest 25% percentiles as individual circles. The median is displayed as vertical line. The mean and standard deviations are -0.43% ±1.36% for the absorbance system, and -0.75% ± 0.82% for the interference system (once the three outliers are excluded).</p

Correlation between the ratio of uncorrected <i>s</i>-values for the BSA monomer peak from the simultaneously acquired interference and the absorbance data (<i>s</i>_IF/<i>s</i>_ABS) and the ratio of corresponding radial magnification correction factors measured independently with the steel mask (r_IF/r_ABS).

<p>Squares are a histogram with frequency as indicated in the sidebar. The dotted line indicates the ideally expected relationship assuming perfect measurements of <i>s</i>-values and radial magnification correction factors.</p