Coalescence of upper and lower miscibility gaps in systems with concentration-dependent interactions
- Michigan Molecular Institute, Midland, MI (United States)
- Polymer Institute, Sittard (Netherlands)
The merging of upper and lower critical solution temperature miscibility gaps is investigated theoretically for binary systems whose interaction parameter g depends strongly on concentration. The process is called forth by increasing the chain lengths m{sub 1} and m{sub 2} of both components while keeping their ratio m{sub 2}/m{sub 1} constant. The principal mechanisms of merging, referred to as sideways coalescence, seem to be different for systems symmetric (m{sub 2} = m{sub 1}) and asymmetric (m{sub 2} = 2m{sub 1}) in molecular size. However, both displayed pattern sequences should be representative of small-molecule mixtures as well as polymer blends. Literature data on miscibility gaps and heats of mixing in the system chlorinated polyethylene/poly (methyl methacrylate) point to the relevance of the theoretical considerations. Furthermore, criteria for various landmark situations are derived in terms of concentration ({var_phi}{sub 2},T), the boundary between the LCST and UCST behavior in T vs {var_phi}{sub 2}, plane may be not only horizontal (as customary) but also vertical, or, in general, inclined. The binodal slope, dT/d{var_phi}{sub 2}, can be rigorously related to the spinodal function, and the result utilized for pinpointing the moment of sideways coalescence between the two gaps. Also, the condition is derived for the singular point marking the transition between two types of binodal patterns. 28 refs., 7 figs., 1 tab.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 411984
- Journal Information:
- Journal of Physical Chemistry, Vol. 96, Issue 10; Other Information: PBD: 14 May 1992
- Country of Publication:
- United States
- Language:
- English
Similar Records
Effect of crystallite size on solid state miscibility: Applications to the pyrite-cattierite system
Microstructure and Crystal-Amorphous Interphases in Melt-Miscible Semicrystalline Polymer Blends. Ph.D. Thesis