Poly metastable state

The effect of dissolved CO2 on the miscibility of polymer blends and on phase transitions of block copolymers has been measured with spectroscopy and scattering (40). The shifts in phase diagrams with CO2 pressure can be pronounced. Polymer blends may be trapped kinetically in metastable states before they have time to phase separate. Metastable polymer blends of polycarbonate (PC) and poly(styrene-cn-acrylonitiile) were formed with liquid and supercritical fluid CO2 in the PCA process, without the need for a surfactant. Because of the rapid mass transfer between the CO2 phase and the solution phase, the blends were trapped in a metastable state before they... 

Another similar bistable side-chain poly[2]catenane 64 was rejxjrted by Stoddart and coworkers (Scheme 17.19), using a method similar to that employed when preparing 59 [122]. The [2]catenane monomer 60 bearing an alkyne group was first prepared, as described above. As shown in Scheme 17.19, monomer 60 was bistable and composed of two switchable isomers a ground-state co-conformation (GSCC) and the metastable-state co-conformation (MSCC), which corresponded to the locations of the tetrathiafulvalene (TTF) and dioxynaphthalene (DNP) units of... 

In the 1930 s it was shown by E. Vorlander [Trans. Faraday Soc., 29, 907 (1933)] that some liquid crystals could be quick frozen to a metastable brittle glassy state. By working with a polymeric molecule, a synthetic polypeptide called poly-y-benzyl-L-glutamate, we have been able to obtain stable solid films with a liquid crystalline local structure. These films can be obtained in conditions describable as rubbery, leathery, or glassy, as is common for polymer films. The unusual local structure of the molecules in the liquid crystalline phase gives rise to magnetic and optical properties heretofore not obtainable with polymeric systems. 

Fig. Phase diagram of the mixture polystyrene and polyvinyl methyl ether, molecular weights being = 62700 (PVME) and Mw = 60(W0 (PS), as obtained from light scattering. The lower curve describes the miscibility gap binodaF, coexistence curve ), the upper curve describes the spinodal curve, which touches the coexistence curve in the critical point. The shaded region in between binodal and spinodal is believed to describe homogeneously mixed metastable one-phase states. From Snyder et al. [27]. b Phase diagram for polyisoprene-poly(ethylene-propylene) with molecular weights of 2000 and 5000, respectively. From Cumming et al [70]...

Solid state NMR was used to study the dynamics found in isotactic-poly(l-butene). " In particular the dynamics found in a metastable crystal was studied and compared to previous work in the area. 

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