Critical phenomena and polymer coil-to-globule transition

Abstract

Small-angle scattering techniques including laser light scattering (LLS), small-angle X-ray scattering (SAXS) and small-angle neutron scattering (SANS) have been useful tools to measure the static and dynamic properties (in terms of critical fluctuations) of fluids, fluid mixtures, polymer and micellar solutions, polymer blends and metallic alloys. A brief review is given of recent results in critical-phenomena experiments using small-angle scattering techniques. Topics of current interest are pointed out, and a guide to the vast literature on critical opalescence is provided. Coil-toglobule transition in polymer solutions has been a classic experimental challenge over the past decade. In order to succeed in reaching the collapsed regime, it becomes important to realize that single coil contraction of a linear polymer molecule in solution takes place in the neighborhood of phase separations. By using the recent development of a small-angle lightscattering spectrometer and by taking advantage of a successful polymer fractionation experiment, the transition behavior of linear polystyrene in cyclohexane from the 69 state to the collapsed regime can be characterized based on both the radius of gyration and the hydrodynamic radius.

Phase Behavior of Polystyrene-Brush-Coated Nanoparticles in Cyclohexane

“…The spatial constitution and the solution behavior of polymers in different solvents have been the focus of interest for many theoretical − as well as for experimental studies − involving investigations on synthetic polymers and on biopolymers such as DNA. − Beside single polymeric chains, polymer brushes and surface-bound polymers are of interest. − Reliable experimental studies became possible after 1970 due to the enhancement of spectroscopical scattering methods (SAXS, SANS, SLS, DLS). Different approaches have been applied in order to explain the phase behavior of polymers in solution, including the volume transition behavior of certain polymers at ϑ-conditions and the phase separation due to critical solution behavior.…”

“…The spatial constitution and the solution behavior of polymers in different solvents have been the focus of interest for many theoretical [7][8][9][10] as well as for experimental studies [11][12][13][14][15][16][17] involving investigations on synthetic polymers and on biopolymers such as DNA. [18][19][20] Beside single polymeric chains, polymer brushes and surface-bound polymers are of interest.…”

N-Isopropylacrylamide andN-Isopropylmethacryl-amide: Cloud Points of Mixtures and Copolymers

“…[7] For these purposes, the polymers have been applied as single chains, [3] macroscopic gels, [8] microgels, [9] or lattices. [10] An excellent review covering all these aspects was published by Schild. [11] The molecular reason of the phenomenon of phase separation in these polymers is believed to be the hydrophilic/hydrophobic interaction between various groups on the polymer chain.…”

Cooperativity of the Coil-Globule Transition in a Homopolymer: Microcalorimetric Study of Poly(N-isopropylacrylamide)

“…(3) Qtr (Note that the quantity Qti/Cp(Tm) = AT can be regarded as the effective temperature interval of the transition. The larger the cooperative unit, the sharper is the peak in Cp- (7), i.e. the narrower is AT.…”