Polymeric soluble, insoluble

The first synthesis of (3-lactams bound to a soluble/insoluble polyethylene glycol monomethylether polymeric matrix has been realized by standard reactions carried out on immobilized imines. From the polymer, [3-lactams were removed under acidic and basic conditions [76, 77]. The reactivity of the immobilized reagent was tested by synthesizing p-lactam from imines and an enolate 8a and the... 

Scheme 7 (a) Synthesis of [3-lactam bound to a soluble/insoluble polyethylene glycol mono-methylether polymeric mallix. (b) Stereoselective and solid phase synthesis of [3-lactam... 

Most dispersion polymerizations in C02, including the monomers methyl methacrylate, styrene, and vinyl acetate, have been summarized elsewhere (Canelas and DeSimone, 1997b Kendall et al., 1999) and will not be covered in this chapter. In a dispersion polymerization, the insoluble polymer is sterically stabilized as colloidal polymer particles by the surfactant that is adsorbed or chemically grafted to the particles. Effective surfactants in the dispersion polymerizations include C02-soluble homopolymers, block and random copolymers, and reactive macromonomers. Polymeric surfactants for C02 have been designed by combining C02-soluble (C02-philic) polymers, such as polydimethylsiloxane (PDMS) or PFOA, with C02-insoluble (C02-phobic) polymers, such as hydrophilic or lipophilic polymers (Betts et al., 1996, 1998 Guan and DeSimone, 1994). Several advances in C02-based dispersion polymerizations will be reviewed in the following section. 

The fullerenes [8, 9, 16] are well-defined molecular solids for the smallest compounds mainly for Cao, C70, C72 and Cg4 which can be obtained in measurable quantities as purified materials. These molecules are soluble in solvents such as toluene or trichlorbenzenc. They form deeply colored solutions which can be purified by liquid phase chromatography. The respective molecular solid needs careful sublimation to remove solvent and gas adducts. Fullerenes are air sensitive [ 17] and light sensitive [11] and decompose slowly by polymerization (becoming insoluble after storage in air). 

In dispersion polymerization, by contrast to emulsion or suspension polymerization, a monomer which is soluble in the reaction medium is polymerized. In analogy to fhe aforementioned types of polymerization, an insoluble polymer is obtained. The reaction is carried out in the presence of non-ionic surfactants or soluble polymers, which can stabilize the polymer particles generated to form a stable latex. Wifh particle sizes of ca. 1 to 15 pm, dispersion polymerization can cover the particle size range between emulsion and suspension polymerization. 

Studies on the formation of polymer latex particles have provided an alternative mechanism whereby uniform particles can result from a homogeneous nucleation-precipitation reaction. In emulsion polymerization, an insoluble monomer is mixed with water and a water-soluble free radical initiator is added. Final particle size depends on... 

The observed high cyclization is attributed to an interaction between the double bonds in the transition state, since a strong bathochromic shift of the absorption due to the double bonds is observed in the uv spectrum. Six-membered rings as well as five-membered rings have been observed experimentally in the polymerization of 1,6 dienes. As expected, the extent of cyclization in this case depends strongly on the thermodynamic quality of the solvent (Table 16-10). In such polymerizations, soluble products are obtained, even at highest yields, because of the strong cyclization, whereas extensive reaction as for Equation (16-54a) would lead to cross-linked, insoluble polymers. 

While the alkali metal salts are water soluble, those of many other metals can be highly polymeric and insoluble in most solvents. These latter compounds are ionic coordination polymers of which a typical formula is [M (R2P02)2l , where M is a divalent metal such as Co, Zn, Be, Cu and R can be various combinations of alkyl and/or aryl groups. Their molecular weight can exceed 50,000 and they resist decomposition at temperatures up to SOO C. Some varieties form long flexible threads, while with suitable choice of R, the side group interactions can further modify the polymer properties. Some varieties which are soluble in organic solvents can produce transparent flexible Aims on evaporation. 

Chloral was known to give only insoluble, presumably isotactic polymer, fluoral could be polymerized to insoluble and soluble presumable atactic polymer. 

Depolymerization of phosphates is unidirectional in aqueous environments, with the exception of some biological systems that convert ADP and orthophosphates back to ATP, etc. Soluble silicates can be polymerized to silica gels or Si02 from aqueous solutions, while sparingly soluble (insoluble) silicates are usually highly refractory. These behaviors of silicates can complicate a study of these systems compared to similar phosphate systems. 

Other solubilization and partitioning phenomena are important, both within the context of microemulsions and in the absence of added immiscible solvent. In regular micellar solutions, micelles promote the solubility of many compounds otherwise insoluble in water. The amount of chemical component solubilized in a micellar solution will, typically, be much smaller than can be accommodated in microemulsion fonnation, such as when only a few molecules per micelle are solubilized. Such limited solubilization is nevertheless quite useful. The incoriDoration of minor quantities of pyrene and related optical probes into micelles are a key to the use of fluorescence depolarization in quantifying micellar aggregation numbers and micellar microviscosities [48]. Micellar solubilization makes it possible to measure acid-base or electrochemical properties of compounds otherwise insoluble in aqueous solution. Micellar solubilization facilitates micellar catalysis (see section C2.3.10) and emulsion polymerization (see section C2.3.12). On the other hand, there are untoward effects of micellar solubilization in practical applications of surfactants. Wlren one has a multiphase... 

Initiators of suspension polymerization are organic peroxides or azo compounds that are soluble in the monomer phase but insoluble in the water phase. The amount of initiator influences both the polymerization rate and the molecular weight of the product (95). 

Amidation. Heating of the diammonium salt or reaction of the dimethyl ester with concentrated ammonium hydroxide gives adipamide [628-94-4] mp 228°C, which is relatively insoluble in cold water. Substituted amides are readily formed when amines are used. The most industrially significant reaction of adipic acid is its reaction with diamines, specifically 1,6-hexanediamine. A water-soluble polymeric salt is formed initially upon mixing solutions of the two materials then hea ting with removal of water produces the polyamide, nylon-6,6. This reaction has been studied extensively, and the hterature contains hundreds of references to it and to polyamide product properties (31). 

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