6533b82cfe1ef96bd128fdcc
RESEARCH PRODUCT
Phase Transitions in Polymeric Systems
Kurt Bindersubject
PhysicsPersistence lengthSpinodalPhase transitionMean field theoryChemical physicsCritical point (thermodynamics)Spinodal decompositionGyrationPhase diagramdescription
The study of collective phenomena in polymeric systems is a particular challenge,because there occurs structure simultaneously on many length scales. Restricting attention to neutral flexible linear macromolecules, we disregard here interesting problems like polyelectrolytes, stiff chains or chains with stiff parts, branched chains and polymer networks, and all combinations thereof including e.g. liquid crystalline polymers, and treat only the simplest case. But already then there occurs structure from the scale of a covalent bond along the backbone of a chain (~ 1 A) over the scale of the persistence length (~ 10 A) to the coil gyration radius R g (~ 102 A), in the description of a single coil (Fig.l) [1]. Near phase transitions, much larger length scales characteristic of collective phenomena appear: e.g., in a polymer mixture near the critical point of unmixing, this length is the correlation length ξ of concentration fluctuations [2,3]. One expects that this length is of the order of R g far away from the critical point, but approaching the “spinodal curve” it is enhanced by a factor ∣l-T/T sp(o)∣−1/2, according to mean field theory [2–4]. Here T is the temperature of the binary (AB) mixture, ϕ the volume fraction of species A, and T sp(ϕ) locates the “spinodal curve” in the phase diagram (Fig.2) [4,5].
year | journal | country | edition | language |
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1995-01-01 |