Phase-separated systems, morphology

Non-Random Systems. As pointed out by Cahn and Hilliard(10,11), phase separation in the thermodynamically unstable region may lead to a non-random morphology via spinodal decomposition. This model is especially convenient for discussing the development of phase separating systems. In the linearized Cahn-Hilliard approach, the free energy of an inhomogeneous binary mixture is taken as ... 

Miscible blends of poly(vinyl methyl ether) and polystyrene exhibit phase separation at temperatures above 100 C as a result of a lower critical solution temperature and have a well defined phase diagram ( ). This system has become a model blend for studying thermodynamics of mixing, and phase separation kinetics and resultant morphologies obtained by nucleation and growth and spinodal decomposition mechanisms. As a result of its accessible lower critical solution temperature, the PVME/PS system was selected to examine the effects of phase separation and morphology on the damping behavior of the blends and IPNs. 

Branched polymers have attracted increasing interest due to their numerous and various applications originating from a large variety of available polymer topologies, compositions, or morphologies for phase separating systems, as emulsifier and interfacial compatibilizers, or for surface modification properties. Graft copolymers are one of the important... 

The formation of phase-separated domains is identical to the development of interfaces between the conjugate phase domains. That is, the local morphology of phase-separating system may be affected by the presence of additional interfaces such as substrate surfaces and container walls. 

The solvent in the blends can increase the mobility of the polymer molecules and decrease the interaction force between the macromolecules. From Figure 15.18, it can be seen that the solvent in an immiscible polymer pair can decrease the free energy level of the system and increase the miscibility of the two polymers. Therefore, the solvent concentration can influence the resultant pattern in the spinodal decomposition indeed, the solvent concentration can be changed to investigate the influence of solvent composition on the morphology of phase separation. The morphology evolution of ternary systems with different solvent composition is shown in Figure 15.22 in this case the initial condition is the same. 

Semi-IPNs include the early polymer blend of phenolic resin combined with natural rubber to yield improved toughness for phenolic based compositions. With the addition of sulfur, simultaneous IPNs have also been reported. The addition of engineering polymers (PSF, PES, PPO, PEI) to epoxy illustrates a more recent area of research, involving systems classified as semi-IPNs. The phase separation and morphology of PEI/epoxy semi-IPNs was reported by... 

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