Lower critical solution temperature behavior

Further heating led to liquid-liquid phase separation observed as a cloud point. This is an example of LCST (lower critical solution temperature) behavior. 

As binary PPE/SAN blends form the reference systems and the starting point for the foaming analysis, their miscibility will be considered first. As demonstrated in the literature [41, 42], both miscibility and phase adhesion of PPE/SAN blends are critically dependent on the composition of SAN, more precisely on the ratio between styrene and acrylonitrile (AN). Miscibility at all temperatures occurs up to 9.8 wt% of AN in SAN, whereas higher contents above 12.4 wt% lead to phase separation, independent of the temperature. Intermediate compositions exhibit a lower critical solution temperature behavior (LCST). Taking into account the technically relevant AN content SAN copolymers between 19 and 35 wt%, blends of SAN and PPE are not miscible. As the AN content of the SAN copolymer, selected in this work, is 19 wt%, the observed PPE/SAN blends show a distinct two-phase structure and an interfacial width of only 5 nm [42],... 

Irani, C. A. Cozewith, "Lower Critical Solution Temperature Behavior of Ethylene Propylene Copolymers in Multicomponent Solvents," J. Appl. Polym. Sci., 31, 1879 (1986). 

WEN Weng, Y., Ding, Y., Zhang, G., Microcalorimetric investigation on the lower critical solution temperature behavior of A-isopropylacrylamide-co-acrylic acid copolymer in aqueous solution, J. Phys. Chem. B, 110, 11813, 2006. 

MA3 Maeda, Y., Sakamoto, J., Wang, S.-Y., and Mizmio, Y., Lower critical solution temperature behavior of poly(A -(2-ethoxyethyl)aciylainide) as compared with poly(Y-isopropylacrylamide), J. Phys. Chem. B, 113, 12456, 2009. 

WEB Weber,C., Becer, C.R., Hoogenboom, R., and Schubert, U.S., Lower critical solution temperature behavior of comb and graft shaped poly[ohgo(2-ethyl-2-oxazoline) methacrylate]s,M7crorwo/ecM/e5, 42, 2965, 2009. 

In contrast to organosoluble polymers, for most known water-based nonionic polymers, the quaUty of water as a solvent decreases upon an increase in temperature. This is known as LCST (lower critical solution temperature) behavior [144], Experimental observations of LCST behavior (thermoinduced collapse) of neutral stars or spherical polymer brushes in water are rare [145, 146], and do not yet provide systematic relationships between the LCST and the degree of branching. 

Ougizawa, T., Inoue, T. Kammer, H.W. 1985, Upper and lower critical solution temperature behavior in polymer blends . Macromolecules, vol. 18, pp. 2092-2094. 

Smith, G. D. Bedrov, D. Roles of enthalpy, entropy, and hydrogen bonding in the lower critical solution temperature behavior of poly (ethylene oxide)/water solutions. J. Phys. Chem. B 2003,107, 3095-3097. 

Fig. 6. Schematic representation of possible phase diagrams for binary mixtures the shaded areas indicate two phase regions (a) upper critical solution temperature behavior (UCST) (b) lower critical solution temperature behavior (LOST) (c) combination of LOST and UCST, mostly observed in nonpolar polymer solutions (d) phase diagram showing upper, lower, and quasilower critical phase boundaries (e) immiscibility loop and (f) hourglass-shaped phase boundary obtained by convergence of upper and lower critical boundaries.

This is a simple model and cannot account for all the issues of mixture thermodynamics. Interaction parameters deduced from various phase behavior information are often believed to include other effects than purely enthalpic ones. This way, the LCST (lower critical solution temperature) behavior observed in polymer blends can be explained and accounted for quantitatively. These theories refine the binary interaction parameter by removing extraneous effects. EOS effects do not favor phase... 

FIGURE 3.15 Liquid-liquid equilibrium in the system HDPE-butyl acetate. The system displays both upper and lower critical solution temperature behaviors. The experimental data for molecular weights 13,600 and 64,000. Lines are simplified PC-SAFT correlations with kjj = 0.0156 for both molecular weights. (From Fluid Phase Equilib., 222-223, von Solms, N., Kouskoumvekaki, I.A.. Lindvig, T., Michelsen, M.L., and Kontogeorgis, G.M., A novel approach to liquid-liquid equilibrium in polymer systems with application to simplified PC-SAFT, 87-93, Copyright 2004, with permission from Elsevier.)... 

Rabeony et al 1998, Effect of pressure on polymer blend miscibility A temperature-pressure superposition. Macromolecules, Vol. 31, No. 19, PP. 6511-6514 Rodgers, 1991, Procedure for predicting lower critical solution temperature behavior in binary blends of polymers. Macromolecules, Vol. 24, No. 14, PP. 4101-4109 Rudolf Cantow, 1995, Description of phase-behavior of polymer blends by different equation-of-state theories. 2. excess volumes and influence of pressure on miscibility. Macromolecules, Vol. 28, No. 19, PP. 6595-6599... 

PVME was shown to exhibit marginal miscibihty with poly(benzyl methacrylate) with lest behavior [805]. This blend appears to offer distinct similarities to PS/PVME blends. Immisci-bility of PVME with a host of other poly(meth)acrylates was observed. Misdbihty of PVME was reported with PEA, PnPA and PnBA but not PMAc [806]. Lower critical solution temperature behavior was noted for PVME/PEA and PVME/PnBA. PMMA misdbihty with an alternating copolymer of propylene-carbon monoxide was estabhshed by DSC, DMA, FTIR and NMR studies [807]. Poly(4-vinyl pyridine) and poly(2-vinyl pyridine) were found to be miscible with poly(2-hydroxyethyl methacrylate) and poly(3-hydroxypropyl methacrylate), attributed to hydrogen bonding [808]. Poly(2-vinyl pyridine) blends showed lest behavior. 

IRA Irani, C.A. and Cozewith, C., Lower critical solution temperature behavior of ethylene-propylene copolymers in multicomponent solvents, J. Appl. Polym. Sci., 31,1879, 1986. 86KUE Kuecuekyavruz, Z. and Kuecuekyavruz, S., Theta-hehaviour of poly(p-tert-butylstyrene)-b-poly(dimethylsiloxane)-h-poly(p-tert-hutylstyrene), M A rowo/. Chem., 187, 2469, 1986. 86RAE Raetzsch, M.T., Kehlen, H., Browarzik, D., and Schirutschke, M., Cloud-point curve for the system copoly(ethylene-vinyl acetate) + methyl acetate. Measurement and prediction by continuous thermodynamics, J. Macromol. Sci.-Chem. A, 23, 1349, 1986. 

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