Effect of polydispersity on the cloud‐point curves of polymer mixtures

Abstract

A method is presented for the calculation of cloud‐point curves of polymer–polymer mixtures when the polymers involved are polydisperse. The method is based on the Flory–Huggins free energy of mixing with a concentration‐independent χ parameter. Numerical results are given for cases in which the molecular weight distributions are represented by the Schulz–Flory type. When the two polymers have similar average molecular weights and polydispersities, the cloud‐point curves become flatter as the polydispersity increases. When the two polymers have similar average molecular weights but differ in polydispersity, the cloud‐point curves become more skewed as the difference in the polydispersity increases. The results point out that, if the polydispersity effect is not properly accounted for, the value of χ deduced from experimental cloud points is liable to be in error, especially with regard to its temperature coefficient and its concentration dependence.

Effect of Deuterium Substitution on the Physical Properties of Polymer Melts and Blends

“…This should affect at least the binodal. Calculations in ref 31 for example (which assumed a concentration independent χ-parameter), showed a general broadening of the binodal upon increase in polydispersity, and further, skewing of the boundary was observed toward higher mass fractions of the more polydisperse component (which in the present case, would be the PVME).…”

Prediction of Initial Miscibility for Ternary Polyurethane Reaction Mixtures on Basis of Solubility Parameters and Flory–Huggins Theory

“…Despite the deviation in the UCST these results demonstrate the applicability of the presented method to estimate phase diagrams of PEPs using the data provided by Fedors. To this day the deviation in the higher temperature range above 130 °C is not yet fully understood, but we assume that molecular weight distribution effects and composition‐dependency of the interaction parameter could play a crucial role.…”

“…Flory–Huggins (FH) theory and the concept of solubility parameters (SPs) were applied to predict phase equilibria. For the sake of simplicity and applicability, a straightforward approach excluding sophisticated mathematical models (e.g., composition‐dependent interaction parameters or polydispersity effects) was chosen. The critical factor in the estimation of phase diagrams via FH theory is the application of suitable binary interaction parameters (BIP).…”

Melt‐state miscibility of poly(ethylene‐co‐1‐octene) and linear polyethylene

“…The critical point of miscibility for a blend is defined by critical interaction parameter, χ c , and critical volume fraction, ϕ c , which are given by the following equations,13–15 which can be applied to blend systems of homopolymer/homopolymer, homopolymer/random copolymer, or random copolymer/random copolymer with different compositions.…”