Cyclic polymers micelles

Cyclic polymers should be an excellent substrate for the preparation of invertible unimolecular micelles (Figure 2). Traditional micelles are formed in solution as a thermodynamic minima resulting from the self-assembly of surfactant type amphiphilic molecules. Because of this self-assembly process, they are subject to two significant limitations ... 

Both of these problems limit their application for a range of biomedical applications, but can be addressed by using unimolecular micelles, micelle-like structures that are covalently linked to prevent disaggregation. In particular, if a bifurcated amphiphile is attached to each repeat unit of a cyclic polymer, (Figure 3) a unique architecture is afforded that will adapt to its environment. For... 

Amino acid-based norbomene random and block copolymers have been synthesized by Sanda, Masuda et al. [178]. The blocks were constructed with monomers containing either the ester or carboxyl amino acid forms, and C4 was used. While the random copolymers were partially soluble in acetone, the block copolymers were soluble through formation of reverse micelles (Scheme 24). Moreover, the diameter of these aggregates was around 100 nm as measured by DLS and AFM. Amino acid-based ROMP monomers with a different cyclic core, i.e., cyclobutenecarbonyl glycine methyl esters, were polymerized by Sampson et al., leading to head-to-tail-ordered polymers without stereocenters [179]. C6 was used and polydispersities between 1.2 and 1.6 were obtained. 

Kapui et al. prepared a novel type of polypyrrole films [168]. The film was impregnated by spherical styrene-methacrylic acid block copolymer micelles with a hydrophobic core of 18 nm and a hydrophilic corona of 100 nm. The properties of the micelle-doped polypyrrole films were investigated by cyclic voltammetry and SECM. It was found that the self-assembled block copolymer micelles in polypyrrole behave as polyanions and the charge compensation by cations has been identified during electrochemical switching of the polymer films. 

The majority of the polymers were soluble in water and formed micelles above a critical micelle concentration (cmc) of 10 to 10 M. Monomers were electrochemically polymerized on gold electrodes using cyclic voltammetry. Polymerization of the monomers failed when the concentration of the monomers fell below the critical micelle concentration. Above the... 

In the random copolymers shown in Scheme 1, hydrophobic associations occur completely in an intrapolymer mode [20-22] hence, the polymers form unimer micelles independent of the polymer concentration in water. The sequence distribution of electrolyte and hydrophobic monomer units in the polymer chain is a critical structural factor to determine whether the hydrophobic self-associations are an intra- or interpolymer mode. Block sequences of hydrophobic units have a strong tendency for interpolymer association, whereas random and alternating sequences tend to associate in an intrapolymer mode [20-22]. Even a subtle difference in the sequence distribution in random copolymers has a significant effect on the self-association mode [23]. If the sequence distribution is blocky in nature, there is a propensity for interpolymer association. Other important structural factors that induce polymers to form unimer micelles are that the hydrophobic groups should be bulky and have cyclic structures, such as cyclododecyl, adamantyl, and naphthyl groups, and their contents in the copolymers should be higher than about 30 mol%, as shown in Scheme 1 [20-22]. In addition. 

Direct dissolution of a functional molecule into the unimer micelle can be an alternative way to functionalization. For the unimer micelles formed from the polymers containing La groups at low concentrations in water, small molecules of amphiphilic nature can be localized in the La microdomain from aqueous solutions. However, hydrophobic microdomains in unimer micelles formed by cyclic hydrophobes, such as Cd, Ad, and 1-Np, are so tightly packed with the rigid hydrophobes that penetration of small mol-... 

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