Amphiphilic water-soluble polymers

In 2004, Weberskirch and co-workers tried a new approach by synthesising [RhBr(COD)(NHC)] 23 (NHC = l-(2 -hydroxyethyl)-3-methylimidazolidine-2-ylidene) [28]. Subsequently, attaching the unsymmetrical, monohydroxy-functionalised NHC by ester groups to an amphiphilic, water-soluble polymer support (ps)... 

Fig. 4 Two-dimensional diagram for monomers of amphiphilic water-soluble polymers. The numbers next to the points are the measurement temperatures in degrees Celsius. (Adapted from Ref. [25])...

Amphiphilic water-soluble polymers and their faydrophobically driven self-associations have been studied extensively because of their potentials in industrial and biological applications (1-10). 

Various types of amphiphilic water-soluble polymers have been a focus of considerable interest over the past decade from both scientific and practical perspectives. The scientific interests are derived from their molecular selforganization phenomena, which are relevant to biological polymer systems and to their nanoscopic molecular frameworks as a basis of materials science. Practical interests stem from their usefulness in a variety of applications, such as polymeric surfactants, emulsifiers, solubilizers, associative thickeners, rheology modifiers, flocculants, and colloid stabilizers. These applications are particularly important in such industries as paint, coating, printing, paper, ceramic, drug, and cosmetic or personal care goods [1-3]. In addition, these water-based polymers have become more important than ever as environmentally friendly materials. 

This subject can be considered in terms of five different types of molecules or materials (a) biologically inert, water-insoluble polymers (b) water-insoluble polymers that bear biologically active surface groups (c) water-swellable polymeric gels, or amphiphilic polymers that function as membranes (d) water-insoluble but bioerodable polymers that erode in aqueous media with concurrent release of a linked or entrapped bioactive molecule and (e) water-soluble polymers that bear bioactive agents as side groups. 

A concept of amphiphilicity, as applied to single monomer units of designed water-soluble polymers, is presented in the third chapter by Okhapkin, Makhaeva, and Khokhlov. The concept is relevant to biomolecular structures and assemblies in aqueous solution. The authors consider the substantial body of information obtained experimentally and theoretically on surface molecular chemical structures, including those that are prospective for surface catalysis. Unusual conformational behaviors of single amphiphilic polymers recently observed in simulations are also discussed in detail. 

In aqueous solutions of Cm-(EO)n amphiphilic molecules, two interesting features are observed. First, isotropic micellar solutions undergo phase separation on heating. Such behavior is typical of hydrophobic interaction and is also observed for several water-soluble polymers. Hydrophobic interaction results from a change of order in the water structure [54]. Second, at high concentration, liquid crystalline phase behavior is observed with several structures [55]. 

Polymeric micelles. When water-soluble polymers are conjugated with lipophilic, poorly water-soluble polymers, the resulting copolymers are amphiphilic and can be used to constitute spherical micelles.54 The sizes of the polymeric micelles range between 10 and 100 nm, which is ideal for preferential extravasation at the fenestrated capillary blood vessels. The polymeric micelles have a hydrophobic core consisting of the... 

Abstract A concept of amphiphilicity in application to monomer units of water-soluble polymers is presented. Molecular simulation and experimental studies of polymers consisting of amphiphilic monomers units are reviewed. Those polymers reveal unusual conformational behavior in aqueous solutions forming nanostructures of nonspherical shape. Self-association of amphiphilic thermosensitive polymers in water solutions is discussed. Possibilities for the use of thermosensitive copolymers as catalysts are described. The sharp water-organic boundaries formed by polymer associates in water solutions are shown to be a prospective medium for catalysis owing to adsorption of interfacially active substrates at the interface. 

However, normally, the groups of both types are present in synthetic and natural monomer units of water-soluble polymers (Scheme 2), which suggests that the units are amphiphilic rather than hydrophobic or hydrophilic. Vasilevskaya et al. [22,23] reported a dumbbell model of the monomer unit in a chain in which a new representation of monomer units was proposed. In this representation, the amphiphilic character of the monomer units was... 

The present review has the following structure. In Sect. 2, the properties of amphiphilic monomers are discussed and a special classification of monomer units according to interfacial and partition properties is described. Also, the possibility of nanostructure formation in polymers composed of amphiphilic monomers is touched upon. This topic is more broadly treated in Sect. 3, where conformational properties of a key class of water-soluble polymers are... 

Thus, it was shown that many building blocks of natural and synthetic polymers are amphiphilic and interfacially active. For the monomers of several important water-soluble polymers, interfacial activity prevails over affinity to either bulk phase. Accordingly, it appears relevant to try to predict... 

The properties associated with the amphiphilic monomer units are strongly exemplified in thermosensitive water-soluble polymers, typical examples of which are shown in Scheme 5. Thermosensitive polymers possess a lower critical solution temperature (LCST) in water solutions. Due to their sharp response to temperature variation, they are widely used in various scientific and technological applications. Drug and gene delivery [1-3], chromatographic [9,10], membrane technology [11,12], and catalyst immobiliza-... 

Usually, the fabrication of a close - packed assembly of amphiphilic molecules at an air - water interface by the Langmuir method requires suitable subphase conditions related to the ionic species and its concentration, pH, temperature and addition of another complementary solutes. In the last case, to explore the feasibility of enhancing the interactions of some amphiphilic polymers with water soluble polymers at the air - water interface, it was studied the system of poly(monomethyl itaconate) (PMMel) as subphase stabilizer of maleic anhydride - alt - stearyl methacrylate(MA-alt-StM) monolayers at the air - water interface. 

Heinz BS et al (2001) Grafting of functionalized water soluble polymers on gold surfaces. In McCormick CL (ed) Stimuli-responsive water soluble and amphiphilic polymers. ACS symposium series, vol 780. ACS, Washington DC, p 162... 

Instead of conventional surfactant molecules, amphiphilic water soluble macromonomers, especially PEO macromonomers, have been used extensively as a reactive emulsifier and as steric stabilizer polymer, as summarized in Table 5. Generally speaking, however, the mechanism for the particle nucleation in the emulsion polymerization systems using macromonomers has been poorly established when compared to the dispersion copolymerizations with macromonomers as mentioned earlier. 

Water-soluble polymers conjugated with lipids can form micelles in aqueous media, and they can be used for the solubilization and enhanced delivery of a variety of sparingly soluble drugs. The basic structures of these polymer-lipid conjugates are similar to amphiphilic block copolymers except for the fact that hydrophobic parts are composed of lipids instead of hydro-phobic polymers. For example, a hydrophilic PEG block is conjugated with phosphatidylethanolamine. ... 

Fullerenes and their derivatives are of broad interest in various fields ranging from ferromagnetism [87] over their application as possible HIV inhibitors [88] to tumor-therapeutic active substance in biological systems [89]. Although C6o is insoluble in water, dissolution may be accomplished by using water-soluble polymers [90] or surfactant solutions containing amphiphilic block-copolymers [91], micelles or liposomes [92, 93]. The immobilization of... 

PVP is a nonionic water-soluble polymer that interacts with water-soluble dyes to form water-soluble complexes with less fabric substantivity than the free dye. Additionally, PVP inhibits soil redeposition and is particularly effective with synthetic fibers and synthetic cotton blends. The polymer comprises hydrophilic, dipolar imido groups in conjunction with hydrophobic, apolar methylene and methine groups. The combination of dipolar and amphiphilic character make PVP soluble in water and organic solvents such as alcohols and partially halogenated alkanes, and will complex a variety of polarizable and acidic compounds. PVP is particularly effective with blue dyes and not as effective with acid red dyes. 

The non-amphiphilic polymers can be widely considered as homopolymers or random copolymers. Most of the studies focussed on water-soluble polymers, but some studies on oil-soluble polymers exist as well. The water-soluble polymers can be uncharged or... 

The vast majority of synthesized amphiphilic and water-soluble polymers belongs to the class of polyelectrolytes, presumably because of the insolubility of most of the neutral macromolecules of that sort [42,56-58,61]. Thus... 

Last but not least, the success of aqueous-phase catalysis has drawn the interest of the homogeneous-catalysis community to other biphasic possibilities such as or-ganic/organic separations, fluorous phases, nonaqueous ionic liquids, supercritical solvents, amphiphilic compounds, or water-soluble, polymer-bound catalysts. As in the field of aqueous-phase catalysis, the first textbooks on these developments have been published, not to mention Job s book on Aqueous Organometallic Catalysis which followed three years after our own publication and which put the spotlight on Job s special merits as one of the pioneers in aqueous biphasic catalysis. Up to now, most of the alternatives mentioned are only in a state of intensive development (except for one industrial realization that of Swan/Chematur for hydrogenations in scC02 [2]) but other pilot plant adaptations and even technical operations may be expected in the near future. 

Another pyrrolidone-based phosphine has been incorporated into amphiphilic, water-soluble diblock co-polymers based on 2-oxazalone derivatives (Scheme 61). The synthesis involved the initial preparation of a diblock co-polymer precursor with ester functionalities in the side chain. This was achieved by sequential polymerization of 2-methyl-2-oxazoline to form the hydrophilic block that provides water solubility, and subsequently a mixture of ester-functionalized oxazoline 147 and 2-nonyl-2-oxazoline, the latter increasing the hydrophobicity of the second polymer block. Having made the backbone, the ester functionalities were converted into carboxylic acids giving polymer 148, which was then reacted with the phosphine ligand to give the desired supported material, 149. This was used in asymmetric hydrogenation reactions with success. 

Water-soluble polymers prepared from a hydrophilic polyester have been shown to be highly effective water-soluble polymer-supported catalysts for aqueous biphasic hydrogenations [169]. The necessary amphiphilic polyester 134 with a BINAP ligand in the main polymer chain was prepared according to Eq. 74 using terephthaloyl chloride, dihydroxy-PEG4000) a diaminated BI-... 

Water-soluble polymer-bound Pd(0)-phosphine catalyst has also been efficiently used in aqueous or mixed aqueous/organic media, the catalyst being recycled by solvent or thermal preparation methods [17]. Amphiphilic resin-supported palladium-phosphine complexes show high catalytic activity in allylic substitution reactions of various allylic acetates with different nucleophiles in aqueous media [18, 19]. Enantiomeric excess up to 98% is obtained using amphiphilic resin-supported MOP ligand or resin-supported P,N-chelating palladium complexes, the catalyst being recyclable [20,21]. The catalyst could be recovered by simple filtration and re-used without any loss of activity and enantioselectivity. 

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