Abstract
HypothesisMixtures of colloids and supramolecular polymers may exhibit stimuli-responsive phase behaviour. However, in theoretical descriptions of such systems, the polymers are commonly described either as flexible chains or as rigid rods, while in experimental systems supramolecular polymers usually fall in between these two limits. We expect the flexibility of the polymers to have a profound effect on the stimuli-responsive phase behaviour. TheoryWe propose a general approach to predict the phase behaviour of colloidal hard spheres mixed with covalent or supramolecular polymers of arbitrary persistence length using free volume theory and an interpolation between flexible and rigid chains. FindingsThe binodals are predicted to shift to lower monomer concentrations as the persistence length is increased, making the polymers more efficient depletants. The persistence length is therefore an additional degree of freedom for manipulating the phase behaviour of colloid–polymer mixtures. We show that by manipulating the persistence length of temperature responsive supramolecular polymers, a wide range of phase diagrams with various topologies can be obtained. For example, we find phase diagrams with a critical point but no triple point or displaying two triple points for temperature-sensitive supramolecular polymers mixed with hard spheres.
Highlights
IntroductionIt turned out that the phase behaviour differed strongly in a quantitative sense; for rigid depletants phase transitions occur at relatively low concentrations
Theory: We propose a general approach to predict the phase behaviour of colloidal hard spheres mixed with covalent or supramolecular polymers of arbitrary persistence length using free volume theory and an interpolation between flexible and rigid chains
The theory is an improvement on a previous theory on semiflexibility by Tuinier [18] in covalent colloid–polymer mixtures as this was only correct near the flexible limit
Summary
It turned out that the phase behaviour differed strongly in a quantitative sense; for rigid depletants phase transitions occur at relatively low concentrations These descriptions are only valid in the two extreme limits of (non) flexibility, while in reality supramolecular polymers are often in between these limits [12,13,14], denoted as semiflexible. We derive a new framework to calculate the phase behaviour of covalent polymers mixed with colloidal spheres based on similar methodology using FVT for the full range of polymer chain stiffness We apply this to supramolecular polymers to compute the phase behaviour as a function of polymer persistence length
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