Polymeric nonionic

The aggregation numbers Nagg is determined as 27 for C1-(EO)53-C4-VB and 38 for Cr(EO)53-C7-VB micelles by analysis of fluorescence curves. A micelle formation mechanism is proposed for nonionic polymeric surfactants with weakly hydrophobic groups. At low concentrations of PEO macromonomers, large loosely aggregated structures involving the PEO chains are formed. At higher concentrations normal micelles form. These are star-shaped, with a hydrophobic core surrounded by a corona of PEO chains. 

The rate of polymerization was found to be independent of emulsifier concentration around CMC (1.8x10 4mol dm 3) and up to ca. 10 3 mol dm 3 and then strongly increased with increasing emulsifier concentration (Fig. 5). It can be seen that, for this system, the break in the dependence of the rate on surfactant concentration does not coincide with the CMC of either the surfactant or the surfactant/PEO-MA macromonomer. In fact, these two values are identical at room temperature at 50 °C the CMC of the surfactant is lower than at 20 °C. The kinetics of particle nucleation for the present nonionic polymerization of BA may not follow a micellar mechanism. 

To remove the feedback regulation mechanism and to avoid product degradation various adsorbents have been used for the in situ separation of plant cell cultures as shown in Table 1. In situ removal with polymeric adsorbents stimulated anthraquinone production more than the adsorbent-free control in Cinchona ledgeriana cells [35]. It was found that nonionic polymeric resins such as Amberlite XAD-2 and XAD-4 without specific functional groups are suitable for the adsorption of plant metabolite [36]. The use of the natural polymeric resin XAD-4 for the recovery of indole alkaloids showed that this resin could concentrate the alkaloids ajmalicine by two orders of magnitude over solvent extraction [37] but the adsorption by this resin proved to be relatively nonspecific. A more specific selectivity would be beneficial because plant cells produce a large number of biosynthetically related products and the purification of a several chemically similar solutes mixture is difficult [16]. 

The surfactant selection determines the emulsion properties, such as stability, particle size, viscosity, and internal phase content. A correct balance between the hydrophobic and hydrophilic character of the emulsifier is necessary for minimizing the surfactant concentration at the resin-water interface. The surfactants used in resin emulsification can be ionic (in most cases anionic), nonionic, polymeric, or a combination of these. 

Based on Luo s simulations [128], it has been found that the super-swelHng state is rather sensitive to recipe variations. Simply increasing the costabilizer level and/or using a nonionic polymeric surfactant would probably eliminate super-swelling, and hence, the instabihty. More recently, Sanderson [310] reported that two strategies could successfully form stable latex from RAFT miniemulsion polymerization ... 

Self-assembly using nonionic polymeric surfactants... 

DaRocha SRP, Psathas PA, Klein E, Johnston KP. Concentrated C02-in-water emulsions with nonionic polymeric surfactants. J Colloid Interface Sci 2001 239 241-253. 

Examples of the Adsorption Isotherms of Nonionic Polymeric Surfactants... 

Three main mechanisms of stabilisation can be considered (i) electrostatic, as produced by ionic surfactants (ii) steric, as produced by nonionic polymeric surfactants of the A-B, B-A-B, A-B-A or AB graft copolymers (where A is the anchor chain and B is the stabilising chain and (iii) electrosteric, as produced by polyelectrolytes. 

A second adsorption method which is similar to activated carbon is shown schematically in Figure 3. This involves the use of a nonionic polymeric adsorbent (5-8), such as Amberlite XAD2 or Diaion HP20. 

Should solvent extraction be inapplicable as a primary purification stage, adsorption methods should be evaluated. Sequential use of ion exchangers and nonionic polymeric resins will often effect considerable purification. If the resins are to be used regularly such that >50 L will be used during a project, it will be more economical to obtain them directly from the manufacturers rather than from laboratory suppliers. Guidance in the use of ion exchangers is relatively sparse a useful introduction is provided by Harland (14) (see Chapter 5). 

Initially, Gandini and Plesch proposed that the perchloric acid-initiated low temperature polymerization of styrene is based on monomer insertion on the nonionic perchlorate chain ends, which was based on the observation that the polymerization mixture was not conductive [68, 69]. These nonionic polymerizations were referred to as pseudo-cationic polymerizations. However, more detailed investigations by stopped-flow UV-vis spectroscopy revealed the presence of short-lived carbocations indicating that these are the propagating species in the cationic polymerization of styrene [70, 71]. This was also confirmed for the polymerization of styrene with trifiic acid for which Matyjaszewski and Sigwalt showed that the covalent triflic ester adduct was unstable even at -78 °C leading to carbocationic propagating species [72]. 

Self-assembly of block copolymers that are made of poly(ethylene oxide), PEO, as the hydrophilic non-ionic block, has been extensively explored. The research interest in PEO-containing block copolymers was motivated, to a great extent, by potential biomedical applications, which rely on the finding that PEO moieties are biocompatible. Because amphiphilic block copolymers of PEO and poly(propylene oxide) PPO (pluronics) are produced on an industrial scale, research on these nonionic polymeric surfactants resulted in many technological applications. Both PPO and PEO are thermoresponsive, having a low solution critical temperature (LSCT),... 

Pt / poly(ethyleneglycol)-monomethylether 10-undecenoate nonionic polymerized micelle 306... 

These dispersants, with a molecular weight in the range of several hundred to several thousand, are also classified into nonionic and ionic types. Common nonionic polymeric dispersants are poly(ethylene oxide) (PEO), or poly(ethylene... 

Gd + complexes is synthetically one of the easiest ways to create nanosize systems. MiceUe-like structures can also be obtained from block copolymers which consist of a nonionic hydrophilic polar part (the Gd chelate) and a hydrophobic part (for instance, methylene groups) which behave as typical nonionic polymeric surfactants. ... 

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