Lattice Model of Living Polymerization. II: Interplay Between Polymerization and Phase Stability
J Dudowicz, Karl Freed, Jack F. Douglas
Representative spinodal curves and polymerization lines for the equilibrium polymerization of linear polymers in a solvent have been calculated using aFlory-Huggins type mean-field theory. The calculations are primarily restricted to systems that polymerize upon cooling, but examples are also given forsystems that polymerize upon heating. In the former case, we find that an increase in the magnitude of enthalpy of propagation |δh| (**stickingenergy**) leads to an elevation of the critical temperature Tc and to a decrease of the critical composition φc when |delta h| is larger than a critical value| δhc|. The shifts in the critical temperature and composition, δTc identical with} Tc(δh) - Tc (δh = 0) and δφcidentical with} φc(δh) - φc(δh = 0),vary linearly with δh for |δh| >|δhc|, so that δTc is proportional toδφc for a sufficiently large sticking energy. Variations in the phase boundaries with δh are also evaluated for systems that polymerizeupon heating, but the presence of multiple critical points in this case makes a general description of these changes difficult. The polymerization line isfound to be independent of solvent quality (χ interaction parameter) within the simple Flory-Huggins model, but the phase stability is stronglyinfluenced by the magnitude of both χ and δh. Similarities between living polymers and other types of associating polymers (thermally reversiblegels, micelles) suggest that some of the thermodynamic consequences of particle association in these self-assembling systems are insensitive to the detailednature of the clustering process. Thus, our results may have a much broader range of applicability than living polymer solutions (e.g., gelation in clay andother colloidal suspensions, cell aggregation, and self-organization of biologically significant structures that exist at equilibrium).
blends phase separation, lattice model, particle association
, Freed, K.
and Douglas, J.
Lattice Model of Living Polymerization. II: Interplay Between Polymerization and Phase Stability, Journal of Chemical Physics, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=851625
(Accessed February 26, 2024)