ISSN:
0449-2978
Keywords:
Physics
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
A new type of long-range interaction between chain segments and solvent molecules in a polymer molecule is introduced. It can be depicted as an “interfacial” free energy, due to the more or less diffuse interface between the interior of a polymer coil and the surrounding solvent. Flory's calculation of the coil expansion α is extended for this effect, by using theoretical approaches developed by van der Waals, Cahn and Hilliard, and Debye for inhomogeneous systems (interfaces). It is found that Flory's equation for α is replaced by: \documentclass{article}\pagestyle{empty}\begin{document}$ \alpha ^5 - \alpha ^3 = 2C_M \psi _1 M^{1/2} \left[ {1 - \left( {\theta /T} \right) + \left( {15/2\alpha ^2 } \right)\left( {\theta /T} \right)\left( {l^2 /\overline {r_0^2 } } \right)} \right] $\end{document} where the last term is due to the “interfacial” free-energy correction. The Debye molecular interaction length l is also found in theories on light scattering of binary mixtures near the critical solution temperature. An important result of this equation is that at T = θ, α is not equal to unity, as before, but somewhat larger, depending on the molar mass of the polymer and the solvent type. A calculation shows that the “interfacial” free energy correction may contribute substantially to the “solvent” effects on the expansion of a polymer molecule at the θ temperature, as has recently been reported in the literature.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pol.1969.160071001
