The authors would like to acknowledge Dr. Will Osborn for helpful discussions and assistance with preparation of the cardstock template.

1. Dissolution of Coating on Copolymer Fibers to Aid in Fiber Separation
<ol>
	<li>Wearing appropriately selected chemically resistant gloves to prevent contamination of the fiber, cut 160 mm to 170 mm from each yarn bundle extracted using ceramic scissors or a fresh steel razor blade. Reserve the remainder of the yarn if needed for further analysis in a labeled container.</li>
	<li>Knot or clamp the ends of the yarn to keep the yarn from tangling when immersed in the solvent. 
	NOTE: For this study, solvents of wide ranging polarity (from the polarity series) were initially explored. Based on qualitative results, a more in-depth examination was conducted using acetone, water, and methanol. Finally, acetone was selected as the best solvent for fiber separation based on the ease of detangling and the scanning electron microscopy (SEM) results (described later).</li>
	<li>Immerse the fiber in 2 mL to 3 mL of the solvent in a labeled Petri dish and cover with the Petri dish lid.</li>
	<li>Allow the yarns to soak in acetone for 30 min, then discard the solvent.</li>
	<li>Repeat steps 1.3 to 1.4 at least two additional times and then allow the solvent to evaporate.</li>
	<li>To remove any acetone residue and to aid in drying, immerse the sample in 2 mL to 3 mL of methanol.</li>
	<li>Allow the yarns to soak in methanol at least 30 min.</li>
	<li>Remove the yarn from the solvent and allow to dry for at least 24 h.</li>
</ol>
2. Analysis of Coating Dissolution Step by Scanning Electron Microscopy
<ol>
	<li>Separate the individual fibers with tweezers, which are previously washed using different solvents from the yarn bundle, for analysis under a stereo microscope if necessary.</li>
	<li>Mount the fibers on a stainless-steel stub (1 cm diameter) by adhering them with tweezers onto double-sided carbon tape.</li>
	<li>Coat the fibers with a conductive material such as Au/Pd to mitigate the surface charging effects under the SEM.</li>
	<li>Load the fiber samples into a scanning electron microscope and image them at 2 kV accelerating voltage and 50 pA &#8211; 100 pA electron current. Apply charge neutralization settings to counter charging effects where necessary.</li>
</ol>
3. Analysis of Coating Dissolution Step by Fourier Transform Infrared Spectroscopy
<ol>
	<li>Cut approximately 30 mm to 40 mm of the washed yarn bundle.</li>
	<li>Obtain an adhesive IR sample card and remove the protective backing.</li>
	<li>While wearing gloves to protect the sample from contamination, slightly twist the fiber bundle to coalesce the sample for analysis and place the sample over the window in the card.</li>
	<li>Prepare the FTIR for analysis according to the manufacturer&#39;s specifications. Turn on the purge gas, fill the detector with liquid nitrogen, and install the ATR accessory using the magnetic alignment plate in the sample compartment.</li>
	<li>Program the parameters for number of scans and instrument resolution in the advanced measurement tab of the instrument software, in this case, 128 scans are averaged at a resolution of 4 cm-1.</li>
	<li>Clean the window of the ATR accessory with a low lint wipe and methanol.</li>
	<li>Collect a background by pressing the collect background button in the basic measurement window of the software with the parameters selected in step 3.5.</li>
	<li>Align the fiber sample over the window in the ATR accessory, using the microscope and video monitor to help position the fiber.</li>
	<li>Collect a sample spectrum by pressing the collect sample button in the basic measurement window of the software using the parameters selected in step 3.5.</li>
	<li>Repeat steps 3.6-3.9, collecting at least 3 spectra per sample until all samples have been analyzed.</li>
</ol>
4. Analysis of Fibers by Wide Angle X-Ray Scattering
<ol>
	<li>While wearing nitrile gloves, cut approximately 25 mm of the yarn from the yarn spool using a razor blade.</li>
	<li>Center each bundle of the yarn over the 6.25 mm inner hole of a 25 mm stainless steel washer.</li>
	<li>Tape the yarn bundle to the washer to hold it in place using cellophane tape.</li>
	<li>Repeat steps 4.1 to 4.3 for the other two types of yarn.</li>
	<li>Tape the washers containing the yarn bundles to a stainless-steel sample holder block (which contains metallic rods for positioning) as shown in Figure 1. The fibers should be in the vertical configuration for analysis.</li>
	<li>Mount a silver behenate control sample to the sample holder block in the same position as the washers.</li>
	<li>Open the door to the instrument and mount the sample holder block to the analysis stage using the magnetic alignment system.</li>
	<li>Close the door to the sample holder chamber and activate the vacuum pump to evacuate the sample analysis chamber. Monitor the vacuum gauge mounted next to the instrument until the vacuum reaches approximately 1600 Pa.</li>
	<li>Open the instrument software, activate the beam, and perform a horizontal scan to determine the x-location of each sample on the sample holder.</li>
	<li>After identifying x-location of each sample, perform a vertical scan to optimize the y-location to obtain the maximum signal intensity for each sample.</li>
	<li>Once the x and y-locations are determined, begin the measurement by analyzing the silver behenate control sample to determine the distance between the sample and each detector.</li>
	<li>Analyze the first fiber sample using a 10 min exposure time.</li>
	<li>Repeat step 4.13 two additional times for a total scan time of 30 min. 
	NOTE: This protocol is used instead of one long 30 min scan case because there are issues with the sample exposure to minimize wasted instrument time.</li>
	<li>Average the 3 scans to obtain the final result using the average function in Fit 2D software.</li>
	<li>Repeat steps 4.13-4.15 for each additional sample.</li>
</ol>
5. Yarn Disentanglement and Preparation for Tensile Testing
<ol>
	<li>Obtain a 30 cm x 30 cm or larger transparent plastic board (polycarbonate sheets are used in these experiments) that can be placed on a dark background, or a dark plastic board of the same dimensions.</li>
	<li>Cut pieces of low tack masking tape (approximately 10 mm 5 mm) and have them available for the following steps. Perform this step on a glass surface and cut the tape with a razor blade.</li>
	<li>Tape both ends of a 20 mm gauge rectangular paper template to the plastic board so that it lies completely flat. 
	NOTE: 20 mm is selected as the optimal gauge length for these tests based on previous work and the available jaw separation of the instrument.</li>
	<li>Wearing nitrile gloves to prevent contamination, cut approximately 70 mm to 80 mm of rinsed yarn and place it on a glass slide or other clean surface (Figure 2a-b).</li>
	<li>Using a stereo microscope to assist disentanglement, carefully remove a single fiber from the yarn using tweezers. Take care to avoid snagging or damaging the fiber during this process. Discard any fibers that are damaged (Figure 2c).</li>
	<li>Place a single fiber on top of the paper template, making sure that the fiber is aligned with the markers on the template (Figure 2d-f).</li>
	<li>Tape both ends of the fiber to the board. In order to improve the visibility of the fiber, put a dark background underneath the transparent plastic board or use a black plastic board. The fiber should lay straight and slightly taught across the template (Figure 2f).</li>
	<li>Repeat steps 5.3 to 5.7 until approximately 35 to 45 fibers are mounted on separate paper templates for each type of fiber. In this case, there are three types of fibers: PBIA-co-PPTA1, PBIA, and PBIA-co-PPTA3.</li>
	<li>Once all fibers are taped to the plastic board, add one small drop of cyanoacrylate adhesive to each end of the fiber aligned to the paper template. Leave 1 cm free of glue at the ends of the paper templates for gripping during tensile testing. 
	NOTE: Cyanoacrylate was found to be the best adhesive for this material, an unsuccessful attempt with a 24 h cure epoxy is shown in the Representative Results.</li>
	<li>Allow the adhesive to cure for at least 24 h before testing.</li>
</ol>
6. Single Fiber Tensile Testing
<ol>
	<li>Determine the gage length and the rate of extension that provides the most consistent results for the specimen of interest. These parameters may be dictated by the amount of available sample and by the limitations of the experimental setup.</li>
	<li>Prepare the instrument for testing by installing tensile grips and calibrating the gap.</li>
	<li>Program the instrument to move the grips to provide a gap of 30 mm, which is the gage length selected based on the size of the paper template and the 10 mm space left at each end for the jaw.</li>
	<li>Loosen the grip faces to create a gap for loading the paper template that contains the single fiber.</li>
	<li>Move one of the samples prepared in step 5 to the instrument. Using gloved hands, a small spatula, and tweezers, feed the template through both grips, using the marks on the template to assist the placement. Make sure that the glue is outside of the grip area.</li>
	<li>Gently align and close the top grip face, while still supporting the fiber so that it does not slide down.</li>
	<li>Tighten the top and bottom screws with a torque wrench until the screws are just tight.</li>
	<li>Repeat step 6.7 for the bottom screws.</li>
	<li>Tighten the screws on the upper and lower grips using a torque wrench. Take care to tighten the screws in a cross pattern to balance the load on the fiber. 
	NOTE: The appropriate torque to use may vary and must be experimentally determined. 30 cN&#183;m was used in these experiments.</li>
	<li>Trim both sides of the paper template with scissors.</li>
	<li>Program the instrument to perform the tensile test at a constant rate of extension of 0.0125 mm/s, monitor the display and stop the test when the fiber has broken.</li>
	<li>At the end of the test, remove the fiber from the grips by loosening the grip faces. Observe the break location and preserve the broken fiber in a labeled container for further analysis. 
	NOTE: Fibers that break at the grip face are discarded from analysis as &#34;jaw breaks&#34; as described in ASTM D3822.</li>
	<li>Return the gap to 30 mm and repeat steps 6.4-6.12 until all samples are tested.</li>
	<li>Save the broken fiber fragments in the template for further microscopic analysis.</li>
</ol>

<ol>
	<li>Joseph, A., Wiley, A., Orr, R., Schram, B., Dawes, J. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+impact+of+load+carriage+on+measures+of+power+and+agility+in+tactical+occupations:+A+critical+review.">The impact of load carriage on measures of power and agility in tactical occupations: A critical review.</a> International Journal of Environmental Research and Public Health. 15 (1), (2018).</li><li>. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> High-performance fibres. , (2001).</li><li>Messin, G. H. R., Rice, K. D., Riley, M. A., Watson, S. S., Sieber, J. R., Forster, A. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+moisture+on+copolymer+fibers+based+on+5-amino-2-(p-aminophenyl)-+benzimidazole.">Effect of moisture on copolymer fibers based on 5-amino-2-(p-aminophenyl)- benzimidazole.</a> Polymer Degradation and Stability. 96 (10), 1847-1857 (2011).</li><li>McDonough, W. G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Testing+and+analyses+of+copolymer+fibers+based+on+5-amino-2-(p-aminophenyl)-benzimidazole.">Testing and analyses of copolymer fibers based on 5-amino-2-(p-aminophenyl)-benzimidazole.</a> Fibers and Polymers. 16 (9), 1836-1852 (2015).</li><li>De Vos, R. E. T. P., Surquin, J. E., Marlieke, E. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> US patent. , (2013).</li><li>Lee, K. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> US patent. , (2014).</li><li>Mallon, F. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> US patent. , (2014).</li><li>Cunniff, P. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dimensionless+Parameters+for+Optimization+of+Textile-Based+Armor+Systems.">Dimensionless Parameters for Optimization of Textile-Based Armor Systems.</a> 18th Int Symp Ballist. , 1302-1310 (1999).</li><li>Cuniff, P. M., Song, J. W., Ward, J. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Investigation+of+High+Performance+Fibers+for+Ballistic+Impact+Resistance+Potential.">Investigation of High Performance Fibers for Ballistic Impact Resistance Potential.</a> Int SAMPE Tech Conf Ser. 21, 840-851 (1989).</li><li>Cheng, M., Chen, W., Weerasooriya, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanical+Properties+of+Kevlar&#174;+KM2+Single+Fiber.">Mechanical Properties of Kevlar&#174; KM2 Single Fiber.</a> Journal of Engineering Materials and Technolog. 127 (2), 197 (2005).</li><li>Forster, A. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hydrolytic+stability+of+polybenzobisoxazole+and+polyterephthalamide+body+armor.">Hydrolytic stability of polybenzobisoxazole and polyterephthalamide body armor.</a> Polymer Degradation and Stability. 96 (2), 247-254 (2011).</li><li>Forster, A. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Long-term+stability+of+UHMWPE+fibers.">Long-term stability of UHMWPE fibers.</a> Polymer Degradation and Stability. , 45-51 (2015).</li><li>Holmes, G. A., Kim, J. -. H., Ho, D. L., McDonough, W. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Role+of+Folding+in+the+Degradation+of+Ballistic+Fibers.">The Role of Folding in the Degradation of Ballistic Fibers.</a> Polymer Composites. 31, 879-886 (2010).</li><li>ASTM International. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> ASTM D3822/D3822M-14 Standard Test Method for Tensile Properties of Single Textile Fibers. , 1-10 (2015).</li><li>Levchenko, A. A., Antipov, E. M., Plate, N. 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The full description of the procedures used in this paper requires the identification of certain commercial products and their suppliers. The inclusion of such information should in no way be construed as indicating that such products or suppliers are endorsed by NIST or are recommended by NIST or that they are necessarily the best materials, instruments, software or suppliers for the purposes described.

The method described herein provides an alternate solvent-based protocol for removing coatings from aramid copolymer fibers without using water. Two previous studies3,4 showed the evidence of hydrolysis in the fibers of this chemical composition, with exposure to water vapor or liquid water. Avoiding hydrolysis during the sample preparation is critical for the next phase of experiments where these sets of fibers will be examined for their susceptibility to ageing...

Currently, significant focus in the field of personal protection is on reducing the mass of the body armor needed for personal protection for law enforcement and military applications1. Traditional armor designs have relied on materials like poly(p-phenylene terephthalamide) (PPTA), also known as aramid, and polyethylene to provide protection against ballistic threats2. However, there is an interest in exploring different high strength fiber materials for their potential to reduce the weight of armor required to stop a specific ballistic threat. This has led to the exploration of alternative materials such as aramid copolymer fibers. These fibers are made by the reaction of [5-amino-2-(p-aminophenyl)benzimidazole] (amidobenzimidazole, ABI) and p-phenylenediamine (p-PDA) with terephthaloyl chloride to form poly(p-phenylene-benzimidazole-terephthalamide-co-p-phenylene terephthalamide). In this study, we examine three different fibers, all of which are commercially produced materials obtained from an industry contact. One is a homopolymer fiber that is made by reacting ABI with p-phenylenediamine to form poly 5-amino-2-(p-aminophenyl)benzimidazole, or PBIA. The other two copolymer fibers examined in this study are expected to be random copolymers with different ratios of PBIA and PPTA linkages3. The relative ratios of these linkages could not be determined experimentally using solid-state nuclear magnetic resonance. These fibers are designated as PBIA-co-PPTA1, PBIA-co-PPTA3 to extend the designations used in a previous publication4. PBIA-co-PPTA3 was not previously studied, but has a similar structure. These fiber systems have also been the focus of several recently granted patents5,6,7.
Superior ballistic resistance of body armor is predicated on the mechanical properties of the materials that comprise it, such as ultimate tensile strength and strain to failure8,9,10. Significant efforts11,12,13 have been focused on examining the long-term stability of polymeric fibers used in body armor by investigating detrimental changes in these mechanical properties after exposure to environmental conditions. The effect of environmental conditions on aramid copolymer fibers has not been the subject of a lot of research3,4. One challenge to studying these materials is the difficulty in disentangling yarns for testing. Prior work by McDonough4 investigated a technique by which water was used to disentangle yarns prior to performing single fiber tensile testing. However, there was no complete understanding on whether the mechanical strength of the fibers was altered by this water exposure. An alternative to disentangling the fibers is to test the mechanical strength of the yarn bundle, however, this requires a large amount of material, and is considered to average the strength of the fibers in the yarn bundle, providing less specific information. The goal of this project is to examine the effect of elevated humidity and temperature on the mechanical properties of aramid copolymer fibers. Thus, it is essential to find an alternative solvent for coating removal and fiber disentanglement that will enable us to distinguish hydrolysis in the fibers due to the environmental exposure from that induced by sample preparation. The preparation of single fibers for testing is further complicated by their small size. In this work, we investigate several common solvents (water, methanol, and acetone) and select acetone as the best choice for the preparation of single fibers for testing. All fibers were rinsed with methanol before further testing. Fourier transform infrared (FTIR) spectroscopy is performed to determine if the coating dissolution and disentanglement step caused any chemical degradation in the material. The detailed video protocol showing the sample preparation steps of disentanglement, chemical analysis, and mechanical testing of copolymer aramid fibers is intended to assist other researchers in developing methodologies for performing similar studies of single fibers in their laboratories.

<table border="0" cellpadding="0" cellspacing="0" width="757">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Stereo microscope&#160;</td>
			<td style="width:83px;">National</td>
			<td style="width:119px;">DC4-456H</td>
			<td style="width:339px;">Digital microscope</td>
		</tr>
		<tr height="66">
			<td height="66" style="height:66px;width:216px;">RSA-G2 Solids Analyzer&#160;</td>
			<td style="width:83px;">TA Instruments</td>
			<td style="width:119px;"></td>
			<td style="width:339px;">Dynamic mechanical thermal analyzer used in transient tensile mode with Film Tension Clamp Accesory&#160;</td>
		</tr>
		<tr height="47">
			<td height="47" style="height:47px;width:216px;">Vertex 80</td>
			<td style="width:83px;">Bruker Optics</td>
			<td></td>
			<td style="width:339px;">Fourier Transform Infrared spectrometer used to analyze results of washing protocol, equipped with mercury cadmium telluride (MCT) detector.</td>
		</tr>
		<tr height="44">
			<td height="44" style="height:44px;width:216px;">Durascope</td>
			<td style="width:83px;">Smiths Detection</td>
			<td></td>
			<td style="width:339px;">Attenuated total reflectance accessory used to perform FTIR</td>
		</tr>
		<tr height="63">
			<td height="63" style="height:63px;width:216px;">Torque hex-end wrench</td>
			<td style="width:83px;">M.H.H. Engineering</td>
			<td style="width:119px;">Quickset Minor</td>
			<td>Torque wrench</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Methanol</td>
			<td style="width:83px;">J.T. Baker</td>
			<td style="width:119px;">9093-02</td>
			<td>methanol solvent</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Acetone</td>
			<td style="width:83px;">Fisher</td>
			<td style="width:119px;">A185-4</td>
			<td>acetone solvent</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Cyanoacrylate</td>
			<td style="width:83px;">Loctite</td>
			<td style="width:119px;"></td>
			<td>Super glue&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">FEI Helios 660 Dual Beam FIB/SEM</td>
			<td style="width:83px;">FEI Helios</td>
			<td style="width:119px;"></td>
			<td>Scanning electron microscope</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Denton Desktop sputter coater&#160;</td>
			<td style="width:83px;"></td>
			<td style="width:119px;"></td>
			<td>sputter coater</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:216px;">25 mm O.D. stainless steel washers with a 6.25 mm hole</td>
			<td style="width:83px;"></td>
			<td style="width:119px;"></td>
			<td style="width:339px;">25 mm O.D. stainless steel washers with a 6.25 mm hole</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Silver behenate&#160;</td>
			<td style="width:83px;"></td>
			<td style="width:119px;"></td>
			<td>Wide angle X-ray scattering (WAXS) standard</td>
		</tr>
		<tr height="126">
			<td height="126" style="height:126px;width:216px;">Xenocs Xeuss SAXS/WAXS small angle X-ray scattering system</td>
			<td style="width:83px;">Xenocs Xeuss</td>
			<td style="width:119px;"></td>
			<td style="width:339px;">SAXS/WAXS small angle X-ray scattering system equipped with an X-ray video-rate imager for SAXS analysis with a minimum Q = 0.0045 &#197;-1, detector separate X-ray video-rate imager for WAXS analysis (up to about 45&#176; 2&#952;) sample holder chamber.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:216px;">Fit 2D software</td>
			<td style="width:83px;"></td>
			<td style="width:119px;"></td>
			<td>Software to analyze WAXS data</td>
		</tr>
	</tbody>
</table>

disentangling high strength copolymer aramid fibers to enable the determination of their mechanical properties

Traditionally, soft body armor has been made from poly(p-phenylene terephthalamide) (PPTA) and ultra-high molecular weight polyethylene. However, to diversify the fiber choices in the United States body armor market, copolymer fibers based on the combination of 5-amino-2-(p-aminophenyl) benzimidazole (PBIA) and the more conventional PPTA were introduced. Little is known regarding the long-term stability of these fibers, but as condensation polymers, they are expected to have potential sensitivity to moisture and humidity. Therefore, characterizing the strength of the materials and understanding their vulnerability to environmental conditions is important for evaluating their use lifetime in safety applications. Ballistic resistance and other critical structural properties of these fibers are predicated on their strength. To accurately determine the strength of the individual fibers, it is necessary to disentangle them from the yarn without introducing any damage. Three aramid-based copolymer fibers were selected for the study. The fibers were washed with acetone followed by methanol to remove an organic coating that held the individual fibers in each yarn bundle together. This coating makes it difficult to separate single fibers from the yarn bundle for mechanical testing without damaging the fibers and affecting their strength. After washing, fourier transform infrared (FTIR) spectroscopy was performed on both washed and unwashed samples and the results were compared. This experiment has shown that there are no significant variations in the spectra of poly(p-phenylene-benzimidazole-terephthalamide-co-p-phenylene terephthalamide) (PBIA-co-PPTA1) and PBIA-co-PPTA3 after washing, and only a small variation in intensity for PBIA. This indicates that the acetone and methanol rinses are not adversely affecting the fibers and causing chemical degradation. Additionally, single fiber tensile testing was performed on the washed fibers to characterize their initial tensile strength and strain to failure, and compare those to other reported values. Iterative procedural development was necessary to find a successful method for performing tensile testing on these fibers.

The copolymer aramid fibers studied here are difficult to separate from yarn bundles into individual fibers for testing. The fibers are entangled and coated with processing chemicals that make them very difficult to separate without damaging the fibers. Figure 3 shows the structural morphology of fibers within a yarn. Even as part of a larger bundle, the fiber surfaces show extensive roughness and tears that are likely caused by strong adhesion to adjacent fi...

Watch this Scientific Journal Video about Disentangling High Strength Copolymer Aramid Fibers to Enable the Determination of Their Mechanical Properties at JoVE.com

Disentangling High Strength Copolymer Aramid Fibers to Enable the Determination of Their Mechanical Properties

The primary goal of the study is to develop a protocol to prepare consistent specimens for accurate mechanical testing of high strength copolymer aramid fibers, by removing a coating and disentangling the individual fiber strands without introducing significant chemical or physical degradation.

Traditionally, soft body armor has been made from poly(p-phenylene terephthalamide) (PPTA) and ultra-high molecular weight polyethylene. However, to ...

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7.1K Views.  National Institute of Standards and Technology. The primary goal of the study is to develop a protocol to prepare consistent specimens for accurate mechanical testing of high strength copolymer aramid fibers, by removing a coating and disentangling the individual fiber strands without introducing significant chemical or physical degradation.

Video: Disentangling High Strength Copolymer Aramid Fibers to Enable the Determination of Their Mechanical Properties

Determination of the Gas-phase Acidities of Oligopeptides

Amino acid residues located at different positions in folded proteins often exhibit different degrees of acidities. For example, a cysteine residue located at or near the N-terminus of a helix is often more acidic than that at or near the C-terminus 1-6. Although extensive experimental studies on the acid-base properties of peptides have been carried out in the condensed phase, in particular in aqueous solutions 6-8, the results are often complicated by solvent effects 7. In fact, most of the active sites in proteins are located near the interior region where solvent effects have been minimized 9,10. In order to understand intrinsic acid-base properties of peptides and proteins, it is important to perform the studies in a solvent-free environment.
We present a method to measure the acidities of oligopeptides in the gas-phase. We use a cysteine-containing oligopeptide, Ala3CysNH2 (A3CH), as the model compound. The measurements are based on the well-established extended Cooks kinetic method (Figure 1) 11-16. The experiments are carried out using a triple-quadrupole mass spectrometer interfaced with an electrospray ionization (ESI) ion source (Figure 2). For each peptide sample, several reference acids are selected. The reference acids are structurally similar organic compounds with known gas-phase acidities. A solution of the mixture of the peptide and a reference acid is introduced into the mass spectrometer, and a gas-phase proton-bound anionic cluster of peptide-reference acid is formed. The proton-bound cluster is mass isolated and subsequently fragmented via collision-induced dissociation (CID) experiments. The resulting fragment ion abundances are analyzed using a relationship between the acidities and the cluster ion dissociation kinetics. The gas-phase acidity of the peptide is then obtained by linear regression of the thermo-kinetic plots 17,18.
The method can be applied to a variety of molecular systems, including organic compounds, amino acids and their derivatives, oligonucleotides, and oligopeptides. By comparing the gas-phase acidities measured experimentally with those values calculated for different conformers, conformational effects on the acidities can be evaluated.

The determination of the gas-phase acidities of cysteine-containing oligopeptides is described. The experiments are performed using a triple quadrupole mass spectrometer. The relative acidities of the peptides are measured using collision-induced dissociation experiments, and the quantitative acidities are determined using the extended Cooks kinetic method.

Amino acid residues located at different positions in folded proteins often exhibit different degrees of acidities. For example, a cysteine residue ...

Rapid High Throughput Amylose Determination in Freeze Dried Potato Tuber Samples

This protocol describes a high through put colorimetric method that relies on the formation of a complex between iodine and chains of glucose molecules in starch. Iodine forms complexes with both amylose and long chains within amylopectin. After the addition of iodine to a starch sample, the maximum absorption of amylose and amylopectin occurs at 620 and 550 nm, respectively. The amylose/amylopectin ratio can be estimated from the ratio of the 620 and 550 nm absorbance values and comparing them to a standard curve in which specific known concentrations are plotted against absorption values. This high throughput, inexpensive method is reliable and reproducible, allowing the evaluation of large populations of potato clones.&#160;

This protocol describes a high through put colorimetric method that relies on the formation of a complex between iodine and chains of glucose molecules in ...

Gyroid Nickel Nanostructures from Diblock Copolymer Supramolecules

Nanoporous metal foams possess a unique combination of properties - they are catalytically active, thermally and electrically conductive, and furthermore, have high porosity, high surface-to-volume and strength-to-weight ratio. Unfortunately, common approaches for preparation of metallic nanostructures render materials with highly disordered architecture, which might have an adverse effect on their mechanical properties. Block copolymers have the ability to self-assemble into ordered nanostructures and can be applied as templates for the preparation of well-ordered metal nanofoams. Here we describe the application of a block copolymer-based supramolecular complex - polystyrene-block-poly(4-vinylpyridine)(pentadecylphenol) PS-b-P4VP(PDP) - as a precursor for well-ordered nickel nanofoam. The supramolecular complexes exhibit a phase behavior similar to conventional block copolymers and can self-assemble into the bicontinuous gyroid morphology with two PS networks placed in a P4VP(PDP) matrix. PDP can be dissolved in ethanol leading to the formation of a porous structure that can be backfilled with metal. Using electroless plating technique, nickel can be inserted into the template&#39;s channels. Finally, the remaining polymer can be removed via pyrolysis from the polymer/inorganic nanohybrid resulting in nanoporous nickel foam with inverse gyroid morphology.

This article describes the preparation of well-ordered nickel nanofoams via electroless metal deposition onto nanoporous templates obtained from self-assembled diblock copolymer based supramolecules.

Nanoporous metal foams possess a unique combination of properties - they are catalytically active, thermally and electrically conductive, and furthermore, ...

Structure and Coordination Determination of Peptide-metal Complexes Using 1D and 2D 1H NMR

Copper (I) binding by metallochaperone transport proteins prevents copper oxidation and release of the toxic ions that may participate in harmful redox reactions. The Cu (I) complex of the peptide model of a Cu (I) binding metallochaperone protein, which includes the sequence MTCSGCSRPG (underlined is conserved), was determined in solution under inert conditions by NMR spectroscopy.
NMR is a widely accepted technique for the determination of solution structures of proteins and peptides. Due to difficulty in crystallization to provide single crystals suitable for X-ray crystallography, the NMR technique is extremely valuable, especially as it provides information on the solution state rather than the solid state. Herein we describe all steps that are required for full three-dimensional structure determinations by NMR. The protocol includes sample preparation in an NMR tube, 1D and 2D data collection and processing, peak assignment and integration, molecular mechanics calculations, and structure analysis. Importantly, the analysis was first conducted without any preset metal-ligand bonds, to assure a reliable structure determination in an unbiased manner.

Structure and Coordination Determination of Peptide-metal Complexes Using 1D and 2D 1H NMR

The NMR-solution structure of a metallochaperone model peptide with Cu (I) was determined, and a detailed protocol from sample preparation and 1D and 2D data collection to a three-dimensional structure is described.

Copper (I) binding by metallochaperone transport proteins prevents copper oxidation and release of the toxic ions that may participate in harmful redox ...

Amide Coupling Reaction for the Synthesis of Bispyridine-based Ligands and Their Complexation to Platinum as Dinuclear Anticancer Agents

Amide coupling reactions can be used to synthesize bispyridine-based ligands for use as bridging linkers in multinuclear platinum anticancer drugs. Isonicotinic acid, or its derivatives, are coupled to variable length diaminoalkane chains under an inert atmosphere in anhydrous DMF or DMSO with the use of a weak base, triethylamine, and a coupling agent, 1-propylphosphonic anhydride. The products precipitate from solution upon formation or can be precipitated by the addition of water. If desired, the ligands can be further purified by recrystallization from hot water. Dinuclear platinum complex synthesis using the bispyridine ligands is done in hot water using transplatin. The most informative of the chemical characterization techniques to determine the structure and gross purity of both the bispyridine ligands and the final platinum complexes is 1H NMR with particular analysis of the aromatic region of the spectra (7-9 ppm). The platinum complexes have potential application as anticancer agents and the synthesis method can be modified to produce trinuclear and other multinuclear complexes with different hydrogen bonding functionality in the bridging ligand.

This protocol describes the use of amide coupling reactions of isonicotinic acid and diaminoalkanes to form bridging ligands suitable for use in the synthesis of multinuclear platinum complexes, which combine aspects of the anticancer drugs BBR3464 and picoplatin.

Amide coupling reactions can be used to synthesize bispyridine-based ligands for use as bridging linkers in multinuclear platinum anticancer drugs. ...

Synthesis of Non-uniformly Pr-doped SrTiO3 Ceramics and Their Thermoelectric Properties

We demonstrate a novel synthesis strategy for the preparation of Pr-doped SrTiO3 ceramics via a combination of solid state reaction and spark plasma sintering techniques. Polycrystalline ceramics possessing a unique morphology can be achieved by optimizing the process parameters, particularly spark plasma sintering heating rate. The phase and morphology of the synthesized ceramics were investigated in detail using X-ray diffraction, scanning electron microcopy and energy-dispersive X-ray spectroscopy. It was observed that the grains of these bulk Pr-doped SrTiO3 ceramics were enhanced with Pr-rich grain boundaries. Electronic and thermal transport properties were also investigated as a function of temperature and doping concentration. Such a microstructure was found to give rise to improved thermoelectric properties. Specifically, it resulted in a significant improvement in carrier mobility and the thermoelectric power factor. Simultaneously, it also led to a marked reduction in the thermal conductivity. As a result, a significant improvement (> 30%) in the thermoelectric figure of merit was achieved for the whole temperature range over all previously reported maximum values for SrTiO3-based ceramics. This synthesis demonstrates the steps for the preparation of bulk polycrystalline ceramics of non-uniformly Pr-doped SrTiO3.

Synthesis of Non-uniformly Pr-doped SrTiO3 Ceramics and Their Thermoelectric Properties

A protocol for the synthesis and processing of polycrystalline SrTiO3 ceramics doped non-uniformly with Pr is presented along with the investigation of their thermoelectric properties.

We demonstrate a novel synthesis strategy for the preparation of Pr-doped SrTiO3 ceramics via a combination of solid state reaction and spark plasma ...

Synthesis of Ligand-free CdS Nanoparticles within a Sulfur Copolymer Matrix

Aliphatic ligands are typically used during the synthesis of nanoparticles to help mediate their growth in addition to operating as high-temperature solvents. These coordinating ligands help solubilize and stabilize the nanoparticles while in solution, and can influence the resulting size and reactivity of the nanoparticles during their formation. Despite the ubiquity of using ligands during synthesis, the presence of aliphatic ligands on the nanoparticle surface can result in a number of problems during the end use of the nanoparticles, necessitating further ligand stripping or ligand exchange procedures. We have developed a way to synthesize cadmium sulfide (CdS) nanoparticles using a unique sulfur copolymer. This sulfur copolymer is primarily composed of elemental sulfur, which is a cheap and abundant material. The sulfur copolymer has the advantages of operating both as a high temperature solvent and as a sulfur source, which can react with a cadmium precursor during nanoparticle synthesis, resulting in the generation of ligand free CdS. During the reaction, only some of the copolymer is consumed to produce CdS, while the rest remains in the polymeric state, thereby producing a nanocomposite material. Once the reaction is finished, the copolymer stabilizes the nanoparticles within a solid polymeric matrix. The copolymer can then be removed before the nanoparticles are used, which produces nanoparticles that do not have organic coordinating ligands. This nascent synthesis technique presents a method to produce metal-sulfide nanoparticles for a wide variety of applications where the presence of organic ligands is not desired.

Herein we present a method to synthesize ligand-free cadmium sulfide (CdS) nanoparticles based on a unique sulfur copolymer. The sulfur copolymer operates as a high temperature solvent and a sulfur source during the nanoparticle synthesis and stabilizes the nanoparticles after the reaction.

Aliphatic ligands are typically used during the synthesis of nanoparticles to help mediate their growth in addition to operating as high-temperature ...

Anionic Polymerization of an Amphiphilic Copolymer for Preparation of Block Copolymer Micelles Stabilized by &#960;-&#960; Stacking Interactions

In this study, an amphiphilic copolymer that includes a core-forming block with phenyl groups was synthesized by living anionic polymerization of phenyl glycidyl ether (PheGE) on methoxy-polyethylene glycol (mPEG-b-PPheGE). Characterization of the copolymer revealed a narrow molecular distribution (PDI &#60; 1.03) and confirmed the degree of polymerization of mPEG122-b-(PheGE)15. The critical micelle concentration of the copolymer was evaluated using an established fluorescence method with the aggregation behavior evaluated by dynamic light scattering and transmission electronic microscopy. The potential of the copolymer for use in drug delivery applications was evaluated in a preliminary manner including in vitro biocompatibility, loading and release of the hydrophobic anti-cancer drug doxorubicin (DOX). A stable micelle formulation of DOX was prepared with drug loading levels up to 14% (wt%), drug loading efficiencies &#62; 60% (w/w) and sustained release of drug over 4 days under physiologically relevant conditions (acidic and neutral pH, presence of albumin). The high drug loading level and sustained release is attributed to stabilizing &#960;-&#960; interactions between DOX and the core-forming block of the micelles.

The key steps of living anionic polymerization of phenyl glycidyl ether (PheGE) on methoxy-polyethylene glycol (mPEG-b-PPheGE) are described. The resulting block copolymer micelles (BCMs) were loaded with doxorubicin 14% (wt%) and sustained release of drug over 4 days under physiologically relevant conditions was obtained.

In this study, an amphiphilic copolymer that includes a core-forming block with phenyl groups was synthesized by living anionic polymerization of phenyl ...

Synthesis and Characterization of Fe-doped Aluminosilicate Nanotubes with Enhanced Electron Conductive Properties

The goal of the protocol is to synthesize Fe-doped aluminosilicate nanotubes of the imogolite type with the formula (OH)3Al2-xFexO3SiOH. Doping with Fe aims at lowering the band gap of imogolite, an insulator with the chemical formula (OH)3Al2O3SiOH, and at modifying its adsorption properties towards azo-dyes, an important class of organic pollutants of both wastewater and groundwater.
Fe-doped nanotubes are obtained in two ways: by direct synthesis, where FeCl3 is added to an aqueous mixture of the Si and Al precursors, and by post-synthesis loading, where preformed nanotubes are put in contact with a FeCl3&#8226;6H2O aqueous solution. In both synthesis methods, isomorphic substitution of Al3+ by Fe3+ occurs, preserving the nanotube structure. Isomorphic substitution is indeed limited to a mass fraction of ~1.0% Fe, since at a higher Fe content (i.e., a mass fraction of 1.4% Fe), Fe2O3 clusters form, especially when the loading procedure is adopted. The physicochemical properties of the materials are studied by means of X-ray powder diffraction (XRD), N2 sorption isotherms at -196 &#176;C, high resolution transmission electron microscopy (HRTEM), diffuse reflectance (DR) UV-Vis spectroscopy, and &#950;-potential measurements. The most relevant result is the possibility to replace Al3+ ions (located on the outer surface of the nanotubes) by post-synthesis loading on preformed imogolite without perturbing the delicate hydrolysis equilibria occurring during nanotube formation. During the loading procedure, an anionic exchange occurs, where Al3+ ions on the outer surface of the nanotubes are replaced by Fe3+ ions. In Fe-doped aluminosilicate nanotubes, isomorphic substitution of Al3+ by Fe3+ is found to affect the band gap of doped imogolite. Nonetheless, Fe3+ sites on the outer surface of nanotubes are able to coordinate organic moieties, like the azo-dye Acid Orange 7, through a ligand-displacement mechanism occurring in an aqueous solution.

Here, we present a protocol to synthesize and characterize Fe-doped aluminosilicate nanotubes. The materials are obtained by either sol-gel synthesis upon addition of FeCl3&#8226;6H2O to the mixture containing the Si and Al precursors or by post-synthesis ionic exchange of preformed aluminosilicate nanotubes.

The goal of the protocol is to synthesize Fe-doped aluminosilicate nanotubes of the imogolite type with the formula (OH)3Al2-xFexO3SiOH. Doping with Fe ...

Grafting Multiwalled Carbon Nanotubes with Polystyrene to Enable Self-Assembly and Anisotropic Patchiness

We demonstrate a straightforward protocol to graft pristine multiwalled carbon nanotubes (MWCNTs) with polystyrene (PS) chains at the sidewalls through a free-radical polymerization strategy to enable the modulation of the nanotube surface properties and produce supramolecular self-assembly of the nanostructures. First, a selective hydroxylation of the pristine nanotubes through a biphasic catalytically mediated oxidation reaction creates superficially distributed reactive sites at the sidewalls. The latter reactive sites are subsequently modified with methacrylic moieties using a silylated methacrylic precursor to create polymerizable sites. Those polymerizable groups can address further polymerization of styrene to produce a hybrid nanomaterial containing PS chains grafted to the nanotube sidewalls. The polymer-graft content, amount of silylated methacrylic moieties introduced and hydroxylation modification of the nanotubes are identified and quantified by Thermogravimetric Analysis (TGA). The presence of reactive functional groups hydroxyl and silylated methacrylate are confirmed by Fourier Transform Infrared Spectroscopy (FT-IR). Polystyrene-grafted carbon nanotube solutions in tetrahydrofuran (THF) provide wall-to-wall collinearly self-assembled nanotubes when cast samples are analyzed by transmission electron microscopy (TEM). Those self-assemblies are not obtained when suitable blanks are similarly cast from analogous solutions containing non-grafted counterparts. Therefore, this method enables the modification of the nanotube anisotropic patchiness at the sidewalls which results into spontaneous auto-organization at the nanoscale.

A procedure for the synthesis of polystyrene-grafted multiwalled carbon nanotubes using successive chemical modification steps to selectively introduce the polymer chains to the sidewalls and their self-assembly via anisotropic patchiness is presented.

We demonstrate a straightforward protocol to graft pristine multiwalled carbon nanotubes (MWCNTs) with polystyrene (PS) chains at the sidewalls through a ...