Molecular Entanglement and Electrospinnability of Biopolymers

The overall goal of this procedure is to use radiological studies to evaluate the electros spin ability of biopolymers. This is accomplished by first preparing biopolymer dispersions in solvent. The second step is to run sheer radiology tests on the dispersions.

Next, the dispersions are subject to electro spinning and their electro spin ability is observed. The final step is to correlate the sheer viscosity data with electro spin ability. Ultimately, an electro spin ability map can be constructed as a function of biopolymer concentration and solvent composition.

Though the method can provide insight into the effect of molecular interaction on the electro spin ability of starch and pollutant, it can also be applied to the electro spinning of other polymer systems. Begin the protocol by preparing a range of biopolymer mass concentrations. Produce samples with mass concentrations of 0.1 to 30%by first weighing the biopolymer powder into a 50 milliliter test tube.

For this video, starch shown here or polan is used, take account of the moisture content of the powder before adding aqueous dimethyl sulfoxide solution. Once this is done, put a stir bar in the biopolymer solution. Place the test tube in a beaker containing enough water to immerse the sample.

Place this on a magnetic stir or hot plate and start constant stirring while bringing the water to a boil. Maintain this for about an hour. When the hour has ended, turn off the heat and allow the dispersion to cool to room temperature.

Once at room temperature, the dispersion is ready for radiological testing and electro spinning. Before radiological testing, warm up the TER and set the stage temperature to 20 degrees Celsius. Set up a 25 millimeter cone probe and calibrate the gap between it and the stage.

When ready. Load 0.41 milliliters of the biopolymer dispersion onto the center of the stage. Be certain the dispersion is at the center of the stage.

Lower the probe to set the position. Make sure the dispersion spreads evenly within the gap. Perform the radiological test in logarithmic mode, starting at a shear rate of 100 per second and ending at 0.1 per second.

Make both clockwise and counterclockwise measurements after testing different polymer concentrations. Plot the apparent sheer viscosity against shear rate for each concentration on the same graph as in this plot for jellos 80 starch in pure DMSO at 20 degrees Celsius. This is the analogous plot for Polan.

Use the data to approximate the zero shear viscosities from that, determine and plot the specific viscosity of the solvent as a function of concentration using the JELLOS 80 starch plot. As an example, the region with the smaller slope is the semi dilute unentangled regime. The region with the larger slope is the semi dilute entangled regime.

The intersection of the two fitted lines is the entanglement concentration for starch in pure DMSO is found to be 6.88%The entanglement concentration in Polan in pure DMSO is 4.3%The next step is to assemble the electro spinning setup, which is done in a fume hood for safety. This consists of a syringe pump on a support that can be adjusted vertically. The pump accommodates a syringe with a blunt needle oriented vertically.

These are placed above a coagulation bath containing pure ethanol. Employ a high voltage DC power supply and attach a wire to its ground terminal and extend it to the coagulation bath. To ground the coagulation bath.

Immerse the other end of the wire in the ethanol and secure it. Next, remove the syringe for the pump and fill it with a dispersion composition above the entanglement concentration identified. In the radiological experiments, mount the syringe onto the pump.

Then extend a wire from the positive terminal of the high voltage power supply and clip it to the syringe needle before electro spinning. Insert a metal mesh in the bath to collect the fiber mat. Also set the distance between the needle tip and the surface of the coagulation bath.

The spinning distance begin with a spinning distance of seven centimeters. Set the syringe pump feed rate to 0.1 milliliters per hour. Then starting at zero volts, slowly ramp the voltage up to a maximum of 15 kilovolts.

Pay attention to the shape of the dispersion extruded at the needle tip note, when the dripping dispersion is accelerated and then elongated. Continue the experiment by exploring the range of voltage feed rates from 0.1 to 0.4 milliliters per hour and spinning distances from five to 10 centimeters. If a continuous jet is initiated from the tip, electro spinning has been achieved, allow the fibers to collect in the bath.

Be certain to record the parameters and collect the fibers. Rinse the collected fiber mat with pure ethanol. Then place it into a desiccate containing desiccant under vacuum.

Once electros spin ability has been demonstrated, move to another dispersion and repeat the steps until each biopolymer concentration has been tested. This is a scanning electron microscope image of well-formed fibers produced from electro spinning of Poland dispersion. The dispersion formed a stable and continuous jet and resulted in smooth fibers without droplets.

In contrast, these are poorly formed spon fibers. Note the tiny droplets that result from the dispersion being unable to form a stable jet. Similar results were obtained with jellos 80 starch.

Note that the thick fibers with rough surface result from a dispersion that is too viscous to develop whipping instability. Electro spinning was attempted for a range of polan and starch dispersions. These plots summarize the evaluation of electros spin ability as a function of DMSO, concentration in solvent and biopolymer concentration in dispersion.

Good electros spin ability is denoted with circles. Poor electros spin ability is marked by diamonds. The X is marked dispersions for which electro spinning could not be achieved.

The entanglement concentrations are approximately labeled. The shaded areas roughly represent electro spinn regions. Don't forget that working with high voltage of electro spinning can be extremely hazardous.

So while performing the procedure take precautions, such as making sure the app practice properly grounded, working the film hood and avoiding short spinning stances.