Poly different reaction media

Lipshutz and colleagues presented recently palladium-catalyzed direct coupling reactions of alkyl iodides and vinyl bromides or iodides catalyzed by 1 mol% Pd(amphos)Cl2 in the presence of zinc and TMEDA in a biphasic aqueous/poly-(ethylene glycol tocopheryl sebacate) reaction medium [198], Internal olefins were obtained in 51-95% yield. For aryl-substituted (Aj-vinyl bromides, retention of double bond geometry was observed, while different degrees of isomerization occurred for (Z)-isomers, which may indicate the intervention of a radical addition process in the course of the coupling process. Alkyl-substituted (Z)-vinyl halides were transformed in contrast with retention of alkene geometry. Aryl halides also reacted [199],... 

In a reactional medium (such as water, for several materials), the competition between dissolution and reprecipitation renders this interpretation more complex. Even though the main ideas remain valid, the first stages of the formation of a crystal may be the coalescence of two fairly large clusters, eliminating water, protons, and OH groups from the surface [2,94]. This step - often referred to as poly condensation [43,100] - has no clear activation energy and may differ significantly from classical nucleation. Hence, a conclusion dictated by conunon sense may hold true in some cases the metastable structure of the nanoparticle comes from a memory of the precursor or, in the case of amorphous nanoparticles, the precursor nanostructure constrains the atoms in positions such that crystallization is impossible. 

Choi JY, Tan LS, Baek JB (2006) Self-controlled synthesis of hyperbranched poly(ether ketone)s from A3-tB2 approach via different solubilities of monomers in the reaction medium. Macromolecules 39 9057-9063... 

We have reported the first example of a ring-opening metathesis polymerization in C02 [144,145]. In this work, bicyclo[2.2.1]hept-2-ene (norbornene) was polymerized in C02 and C02/methanol mixtures using a Ru(H20)6(tos)2 initiator (see Scheme 6). These reactions were carried out at 65 °C and pressure was varied from 60 to 345 bar they resulted in poly(norbornene) with similar conversions and molecular weights as those obtained in other solvent systems. JH NMR spectroscopy of the poly(norbornene) showed that the product from a polymerization in pure methanol had the same structure as the product from the polymerization in pure C02. More interestingly, it was shown that the cis/trans ratio of the polymer microstructure can be controlled by the addition of a methanol cosolvent to the polymerization medium (see Fig. 12). The poly(norbornene) prepared in pure methanol or in methanol/C02 mixtures had a very high trans-vinylene content, while the polymer prepared in pure C02 had very high ds-vinylene content. These results can be explained by the solvent effects on relative populations of the two different possible metal... 

Figure 10. Absorption spectra of a PPA film after different periods of irradiation at room temperature, using light of wavelengths between 220 and 340 tun from an AEI medium-pressure mercury lamp. Reprinted with permission fiom S. K. L. Li and J. E. Guillet, Studies of the photo-Fries reaction in solid poly(phenylacrylate), Macromolecules, 10, 840 (1977). Ccpyright 1977, American Chemical Society.

Bissessur and coworkers explored the inclusion of poly(2-ethylaniline) (PEA) and poly(2-propylaniline) (PPA) into GO, in addition to polyaniline [90]. The technique of intercalation differed from previously reported methods. They showed that polyaniUnes can be directly inserted into GO without the preparation of precursor phases. The polymers were first prepared from the monomers by oxidation with ammonium peroxydisulfate in acidic medium. GO, synthesized by using the Hummers method, was dispersed in deionized water with the aid of sonication. Colloidal suspensions of the polymers in NMF were then added to the aqueous GO suspensions. The reaction mixtures were then acidified and heated at 60 °C for 90 min. The intercalated phases were isolated via freezedrying. A similar process was used to intercalate polypyrrole into GO [91]. 

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