Physical Review Letters -- May 4, 1998 -- Volume 80, Issue 18, pp. 4092-4094

Globule-to-Coil Transition of a Single Homopolymer Chain in Solution

Chi Wu1,2 and Xiaohui Wang1
1Department of Chemistry, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
2The Open Laboratory of Bond Selective Chemistry, Department of Chemical Physics, University of Science and Technology of China, Hefei, Anhui, China

(Received 2 December 1997; revised 5 March 1998)

Using a nearly monodisperse high molar mass poly(N -isopropylacrylamide) (PNIPAM) sample, we successfully made the conformation change of individual PNIPAM chains from a coil to a fully collapsed stable single chain globule in an extremely dilute aqueous solution, which enabled us to study for the first time the globule-to-coil transition of a single homopolymer chain in solution. A comparison to the coil-to-globule and the globule-to-coil transitions revealed a hysteresis in the globule-to-coil transition. Our results also confirmed the existence of two additional thermodynamically stable states between the coil and the globule states, namely, the crumpled coil and the molten globule. © 1998 The American Physical Society

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