Jinbo's Rainbow

image credit: Jinbo He, Polymer Science and Engineering
© 2007 University of Massachusetts Amherst

Some polymers, like poly(ethylene oxide) or poly(ethylene glycol), can crystallize. Like snowflakes, the crystals begin to grow from one point (the nucleus), and continue to grow outward from this point. With polymers, the crystals form very thin ribbons or lamellae, which are about ten nanometers thick (20,000 times thinner than a human hair). These ribbons grow outward in bundles that give rise to the texture seen in this reflection optical micrograph. The colors arise from the differences in the film thickness. The growth patterns of the polymers or plastics are critical in understanding and tailoring the properties of molded and extruded parts that we use in our everyday life.