Competitive stickiness.Competitive stickiness Polymers generally have a strong tendency to adhere to adhere to verb 1. follow, keep, maintain, respect, observe, be true, fulfil, obey, heed, keep to, abide by, be loyal, mind, be constant, be faithful 2. surfaces -- changing flow patterns in pipes during chemical processing, interfering with water purification  It has been suggested that , , and be merged into this article or section. and altering the properties of biological implants. However, the details of what actually happens as polymer molecules shuttle back and forth between solution and surface have long remained elusive. Steve Granick and his co-workers at the University of Illinois at Urbana-Champaign Early years: 1867-1880 The Morrill Act of 1862 granted each state in the United States a portion of land on which to establish a major public state university, one which could teach agriculture, mechanic arts, and military training, "without excluding other scientific have embarked on a series of experiments to study this process. Their initial results suggest that certain polymer molecules not only readily stick to a given surface but also subsequently rearrange themselves to forge even tighter bonds. Moreover, a slight increase in a polymer molecule's length greatly enhances the polymer's stickness. To study the dynamics of polymer adsorption adsorption, adhesion of the molecules of liquids, gases, and dissolved substances to the surfaces of solids, as opposed to absorption, in which the molecules actually enter the absorbing medium (see adhesion and cohesion). , the team allowed polystyrene molecules dissolved in cyclohexane cyclohexane (sī'kləhĕk`sān), C6H12, colorless liquid hydrocarbon. It is a cyclic alkane that melts at 6°C; and boils at 81°C;. It is nearly insoluble in water. to coat a bare, specially prepared silicon surface. They then tracked the rate at which labeled polystyrene molecules--with deuterium deuterium (d  tēr`ēəm), isotope of hydrogen with mass no. 2. The deuterium nucleus, called a deuteron, contains one proton and one neutron. substituted for hydrogen -- displaced the original polystyrene molecules from the surface. They discovered that displacement occurred rapidly when the initial coating was new. In that case, the labeled polystyrene molecules easily shunted aside and replaced the original polystyrene molecules. But if the researchers allowed the original layer to age, displacement proved much more slow and difficult. This suggests that the extra time allows initially adsorbed molecules either to become more entangled en·tan·gle tr.v. en·tan·gled, en·tan·gling, en·tan·gles 1. To twist together or entwine into a confusing mass; snarl. 2. To complicate; confuse. 3. To involve in or as if in a tangle. or to anchor themselves more firmly to the surface. Granick and his colleagues also found that using longer polystyrene chains for the initial coating significantly slowed the displacement process. The displacement's extreme sensitivity to polymer chain length, combined with its dependence on the initial coating's age, helps account for conflicting reports in the past concerning polymer behavior, Granick says. "We're dealing with a complex phenomenon," he adds. "There are a million experiments left to do." |
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