Self-organization kinetics in polypeptide electrospun fibers

• The self-organization of matter is currently of great interest.
• We have electrospun polypeptide fibers and analyzed the kinetics of annealing.
• Two different model polymers were studied, and annealing was done in water.
• Materials analysis was carried out by energy-dispersive X-ray spectroscopy.
• The kinetics data support structural change along two parallel pathways.

Self-organization processes are a major focus of current scientific interest worldwide. Novel materials research and development increasingly seeks to exploit ways in which matter self-organizes. Here, self-organization kinetics have been measured for electrospun fiber annealing. A key feature of such materials is a large surface-to-volume ratio. Fibers were spun from aqueous solutions of poly(l-ornithine) Br− (PLO) or co-poly(l-glutamic acid4, l-tyrosine1) Na+ (PLEY), model synthetic polypeptides. After crosslinking in situ, fibers were annealed in water at 22 °C. Analysis by infrared (IR) spectroscopy has revealed that annealing involved polymer restructuring within fibers on a time scale of 29 min for PLO and 63 min for PLEY. The largest changes in the distribution of polymer conformations occurred in the first 13 min of annealing. There was a substantial decrease in the amount of Na+ bound to PLEY fibers during annealing, according to energy-dispersive X-ray spectroscopy (EDX) analysis. Two parallel pathways provided a better account of the annealing trajectory than a single pathway with multiple transition states. This study advances current understanding of polypeptide-based materials and suggests approaches for applications development.

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