Polymer amphiphilic

It is commonplace to say that the properties of a copolymer depend not only on its chemical sequence but also on the chemical structure of its monomeric units. Therefore, the second important route in molecular design can be connected with designing monomeric units of the copolymer having a given sequence distribution. One of the promising ways in this direction is to adjust the amphiphilic properties of the copolymer chain. 

A large number of macromolecules possess a pronounced amphiphilicity in every repeat unit. Typical examples are synthetic polymers like poly(l-vinylimidazole), poly(JV-isopropylacrylamide), poly(2-ethyl acrylic acid), poly(styrene sulfonate), poly(4-vinylpyridine), methylcellulose, etc. Some of them are shown in Fig. 23. In each repeat unit of such polymers there are hydrophilic (polar) and hydrophobic (nonpolar) atomic groups, which have different affinity to water or other polar solvents. Also, many of the important biopolymers (proteins, polysaccharides, phospholipids) are typical amphiphiles. Moreover, among the synthetic polymers, polyamphiphiles are very close to biological macromolecules in nature and behavior. In principle, they may provide useful analogs of proteins and are important for modeling some fundamental properties and sophisticated functions of biopolymers such as protein folding and enzymatic activity. 

Since amphiphilic polymers contain monomeric units having hydropho-bic/hydrophilic character, they can exhibit conformational transitions induced by temperature, solvent composition, or pH variation [96]. Because of the presence of the two opposing interactions towards the solvent in which they are immersed, amphiphiles can self-assemble, forming a variety of supramolecular structures. Understanding the physics of self-association 

23 Examples of amphiphilic polymers a poly(l-vinylimidazole), b poly(iV-isopropyl acrylamide), and c poly(2-ethyl acrylic acid) 

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The pioneering work on amphiphilic polyelectrolytes goes back to 1951, when Strauss et al. [25] first synthesized amphiphilic polycations by quaternization of poly(2-vinylpyridine) with n-dodecyl bromide. They revealed that the long alkyl side chains attached to partially quaternized poly(vinylpyridine)s tended to aggregate in aqueous solution so that the polymers assumed a compact conformation when the mole fraction of the hydrophobic side chains exceeded a certain critical value. Thus, Strauss et al. became the first to show experimentally the intramolecular micellation of amphiphilic polymers and the existence of a critical content of hydrophobic residues which may be compared to the critical micelle concentration of ordinary surfactants. They called such amphiphilic polyelectrolytes polysoaps [25],... 

Fig. 3 a-c. Summary of data from different laboratories, obtained by surface force measurement, on the average layer thickness L as a function of tethered chain length for flat, tethered layers constructed by adsorption of amphiphilic polymers on mica. Adapted from Ref. 21. (a) Data of reference 20 on poly-tert-butylstyrene chains anchored by adsorbing blocks of poly-2-vinylpyridine. (b) Data of references 11 and 12 on polystyrene chains anchored by adsorbing blocks of poly-2-vinylpyridine. (c) Data of references 13 and 14 on polystyrene chains anchored by adsorbing zwitterionic groups [13] or by small adsorbing blocks of polyethyleneoxide [14]... 

Adsorption on solid matrices, which improves (at optimal protein/support ratios) enzyme dispersion, reduces diffusion limitations and favors substrate access to individual enzyme molecules. Immobilized lipases with excellent activity and stability were obtained by entrapping the enzymes in hydrophobic sol-gel materials [20]. Finally, in order to minimize substrate diffusion limitations and maximize enzyme dispersion, various approaches have been attempted to solubilize the biocatalysts in organic solvents. The most widespread method is the one based on the covalent linking of the amphiphilic polymer polyethylene glycol (PEG) to enzyme molecules [21]. 

Yin et al. [73,74] prepared new microgel star amphiphiles and stndied the compression behavior at the air-water interface. Particles were prepared in a two-step process. First, the gel core was synthesized by copolymerization of styrene and divinylbenzene in diox-ane using benzoylperoxide as initiator. Microgel particles 20 run in diameter were obtained. Second, the gel core was grafted with acrylic or methacryUc acid by free radical polymerization, resulting in amphiphilic polymer particles. These particles were spread from a dimethylformamide/chloroform (1 4) solution at the air-water interface. tt-A cnrves indicated low compressibility above lOmNm and collapse pressnres larger than 40 mNm With increase of the hydrophilic component, the molecnlar area of the polymer and the collapse pressure increased. 

N. Monfreux, P. Perrin, F. Lafuma, and C. Sawdon. Invertible emulsions stabilised by amphiphilic polymers and application to bore fluids (emulsions inversables stabilisees par des polymeres amphiphiles et application a des fluides de forage). Patent WO 0031154, 2000. 

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. 

K Ishihara, M Kobayashi, I Shinohara. Insulin permeation through amphiphilic polymer membranes having 2-hydroxyethyl methacrylate moiety. Polymer 16 647-651, 1984. 

Benjelloun A, Brembilla A, Lochon P, Adibnejad M, Viriot ML, Carre MC (1996) Detection of hydrophobic microdomains in aqueous solutions of amphiphilic polymers using fluorescent molecular rotors. Polymer (Guildford) 37(5) 879-883... 

Oheme and co-workers investigated335 in an aqueous micellar system the asymmetric hydrogenation of a-amino acid precursors using optically active rhodium-phosphine complexes. Surfactants of different types significantly enhance both activity and enantioselectivity provided that the concentration of the surfactants is above the critical micelle concentration. The application of amphiphilized polymers and polymerized micelles as surfactants facilitates the phase separation after the reaction. Table 2 shows selected hydrogenation results with and without amphiphiles and with amphiphilized polymers for the reaction in Scheme 61.335... 

Table 2 Selected hydrogenation results with and without amphiphiles and with amphiphilized polymers for...

Keywords Aliphatic polyesters Amphiphilic polymers Polymer micelles Self-assembly Smart materials... 

The addition of amphiphilic polymer in o/w or w/o/w emulsion systems is also useful to give surface functionality to MSs and NSs. Liang et al. reported preparation of NSs from poly(y-glutamic acid)-h-PLA, immobilizing galactose residues on the surface by an o/w emulsion method, and in vivo specific delivery of aniticancer... 

Keywords Amphiphilic polymer Cell adhesion Chimeric protein Islet of Langerhans Self-assembled monolayer Stem cell... 

Cell Surface Modifications with Amphiphilic Polymers. 187... 

Inui O, Teramura Y, Iwata H (2010) Retention dynamics of amphiphilic polymers PEG-lipids and PVA-Alkyl on the cell surface. ACS Appl Mater Interfaces 2 1514—1520... 

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. 

The problems related to the colloidal stability of amphiphilic polymers in water are reviewed by Aseyev, Tenhu, and Winnik in the first chapter of volume 196. The focus is on the derivatives of thermally responsive smart macromolecules - both on copolymers and homopolymers - which are present in a solution as stable micelles potentially having various applications. 

McCormick CL (ed) (2001) Stimuli-responsive water-soluble and amphiphilic polymers. ACS symposium series 780. American Chemical Society, Washington, DC... 

Aseyev, V. O., Tenhu, H. and Winnik, F. M. Temperature Dependence of the Colloidal Stability of Neutral Amphiphilic Polymers in Water. Vol. 196, pp. 1-86. 

The rheological properties of a fluid interface may be characterized by four parameters surface shear viscosity and elasticity, and surface dilational viscosity and elasticity. When polymer monolayers are present at such interfaces, viscoelastic behavior has been observed (1,2), but theoretical progress has been slow. The adsorption of amphiphilic polymers at the interface in liquid emulsions stabilizes the particles mainly through osmotic pressure developed upon close approach. This has become known as steric stabilization (3,4.5). In this paper, the dynamic behavior of amphiphilic, hydrophobically modified hydroxyethyl celluloses (HM-HEC), was studied. In previous studies HM-HEC s were found to greatly reduce liquid/liquid interfacial tensions even at very low polymer concentrations, and were extremely effective emulsifiers for organic liquids in water (6). 

C. Tribet, R. Audebert, J.-L. Popot (1997) Stabilisation of hydrophobic colloidal dispersions in water with amphiphilic polymers application to integral membrane proteins. Langmuir, 13 5570-5576... 

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