Linear polymer blends

Exclusively mechanically interlocked linear polymer blends, typically, are not thermodynamically phase stable. Given sufficient thermal energy (Tuse>Tg), molecular motion will cause disentanglement of the chains and demixing to occur. To avoid phase separation, crosslinking of one or both components results in the formation of a semi-IPN or full-IPN, respectively. Crosslinking effectively slows or stops polymer molecular diffusion and halts the phase decomposition process. 

Massa, Voit, and coworkers1231 conducted a survey of the phase behavior of blends of these polyester hyperbranched polymers with linear polymers. Blend miscibility of a hydroxyl terminated polyester was comparable to that of poly(vinylphenol) indicating strong H-bonding interactions, whereas miscibility of an acetoxy terminated analog decreased relative to the hydroxy derivative. 

Conformation and Topology of Cyclic-Linear Polymer Blends... 

Self-diffusivity of cyclic polymers (CPs) (triangles) and linear polymers (LPs) (circles) for N = 150 (open symbols) and N = 300 (fUled symbols) at different cydic linear polymer blend (CLB) compositions. 

Subramanian, G., and Shanbhag, S., 2009. Conformational free energy of melts of ring-linear polymer blends, Phys. Rev. E., 80(4) 041806+. 

Reports on the conformation and topology of cyclic linear polymer blends (CLBs)... 

The properties of polymer mixtures depend on the method by which they are obtained and are determined by many factors by sizes of particles of the dispersed phase, by their shape and number in bulk, and by the thermodynamic affinity of the components for one another [19]. Linear polymers blend either in the course of their mutual dissolution or, in two-phase systems, under conditions of thermodynamic incompatibility of the components, when the dispersion is forced. The mixtures formed can be compatible (forming true solutions of one polymer in another), incompatible (representing a typical colloid system), quasicompatible (characterized by microscopic homogeneity at a level above heterogeneity on the molecular level), or pseudocompatible (with a strong adhesion interaction on the boundary) [106]. 

I. Mitra, X. Li, S.L. Pesek, B. Makerenko, B.S. Lokitz, D. Uhrig, J.R Anker, R. Verduzco, G.E. Stein, Thin film phase behavior of bottlebrush/linear polymer blends. Macromolecules 47 (15) (2014) 5269-5276. 

In general, the microphase structure of IPNs may be described as a nonequilibrium one. Indeed, if the phase separation were realized under equilibrium, then, in accordance with the most general thermodynamic rules, the composition and the ratio of phases would be determined only by the phase diagram of the system, and not by the conditions of the separation or chemical kinetics. The situation typical of IPNs and of linear polymer blends may never be realized in polymer solutions or in alloys of low molecular mass substances. Thus, the first reason for the nonequiHbrium consists in the specific conditions of IPN formation. 

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