Resolving tension on the surface of polymer mixes (Vol. 49, No. 1)

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A new study finds a simple formula to explain what happens on the surface of melted mixes of short- and long-strand polymers.

Better than playing with Legos, throwing polymer chains of different lengths into a mix can yield surprising results. In a new study published recently, physicists focus on how a mixture of chemically identical chains into a melt produces unique effects on their surface. That’s because of the way short and long polymer chains interact with each other. In these kinds of melts, polymer chain ends have, over time, a preference for the surface. Now, the authors have studied the effects of enriching long-chain polymer melts with short-chain polymers. They performed numerical simulations to explain the decreased tension on the surface of the melt, due to short chains segregating at the surface over time as disorder grows in the melt. They found an elegant formula to calculate the surface tension of such melts, connected to the relative weight of their components.

P. Mahmoudi and M.W. Matsen, Entropic segregation of short polymers to the surface of a polydisperse melt, Eur. Phys. J. E 40, 85 (2017)