Reaction-induced segregation

Reaction induced phase separation (RIPS) from a homogeneous initial mixture. A third component which is initially soluble in the epoxy precursors but segregates during the chemical reaction (usually a thermoplastic or an elastomer) is incorporated in the system. Segregation generates the final two-phase morphology. 

Finally, the confined microenvironment of a NR might induce segregation or phase separation of solvents and reactants inside. For example, the displacement of a given solvent with the absorbed reactants can result in a different reaction mechanism or kinetics [9]. 

In a study of the application of Pd-Si amorphous alloys as selective hydrogenation catalysts [3] it was found that in situ activation provides a route to active and selective catalysts, whereas ex situ activation caused the crystallization of the system into the thermodynamically stable Pd + SiC>2 system, which is indistinguishable in its activity and poor selectivity from conventional catalysts of the same composition. In this study it was possible to show conclusively that all amorphous alloys are not amorphous on their surfaces as they undergo, in reaction gas atmospheres, chemically-induced phase segregation which starts the crystallization process according to Figure 2 (pathway 2). 

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