Polymer micelles hydrophobic segments

PIPAAm-PBMA block copolymers form a micellar structures by selfassociation of the hydrophobic PBMA segments in water, a good solvent for PlPAAm chains below the LCST but a nonsolvent for the PBMA chains. This amphiphilic system produces stable and monodispersed micelles from polymer/A-ethylacetamide (good solvent for the both polymer blocks) solutions dialyzed against water. Hydrophobic dmgs can be physically incorporated into the iimer micelle cores with PBMA chains by hydrophobic interactions between the hydrophobic segments and dmgs. 

At very low concentrations, the polymers only exist as single chains. As the concentration increases to reach a critical value, called the critical micelle concentration (CMC), polymer chains start to associate to form micelles in such a way that the hydrophobic segment of the copolymer will avoid contact with the aqueous media in that the polymer is diluted. At the CMC, a signiLcant amount of solvent may still be found inside the micellar core and micelles are described as loose aggregates that exhibit largersize than micelles formed at higher concentrations (Gao and Eisenberg,... 

Hemoglobin and many enzymes are covalent polymers with a globular shape. This shape is enforced by the tendency of hydrophobic amino acids to form a hydrophobic droplet in aqueous solutions solubilized by hydrophilic side-chains around them. The same is true for synthetic block polymers made of hydrophobic and hydrophilic segments. " Spherical biopolymers thus usually appear as micelles, with a core made of organic material. Covalency allows the construction of fully organized micelles, e.g. dendrimeric spheres, where one half has a hydrophilic, the other a hydrophobic surface. Block polymers may not only form micelles, but they may also arrange to form vesicles which entrap a water volume. Such spheres have a thick polymer wall." Both the polymer micelles and vesicles can be removed from solution without collapsing. 

PBLG), and poly(N-hexyl stearate L-aspartamide), and non-biodegradable hydrophobic polymers like poly(propylene oxide) (PPO) and poly(vinyl) derivatives. The hydrophobic segment can be inert or can possess reactive groups for postfunctionalization. A special group of micelles can finally be obtained from lipid conjugates such as PEG-phosphatidyl ethanolamine (PEG-PE). ... 

In addition, polymer micelles have been demonstrated to be more stable and also have a significantly lower cmc than surfactant micelles. Further discussion of surfactant micelles is beyond the scope of this review, and, instead, the reader is directed to a recent review article by Armes. In fact, the polymer building blocks need not be amphiphilic and such phase-separated nanostructures can be formed from completely hydrophobic or lipophilic diblock copolymers that contain two segments with differing solubility (such as polystyrene- -polyisoprene) and hence can undergo phase separation in selective solvents. One example of such completely hydrophobic phase-separated micelles are those reported by Wooley and coworkers, which can be obtained from toluene and acetone solutions of a [polystyrene-a/f-poly(maleic anhydride)]-fc-polyisoprene Iriblock. Conversely, inverse structures are also accessible and are known as reverse micelles. These can be formed by adding a nonsolvent for the hydrophilic block to afford the opposite of a conventional micelle, for which the hydrophilic core is surrounded by a hydrophobic shell in a hydrophobic surrounding media. There have been a handful of reports on the application of these reverse micelles, for example, as nanoreactors and for the extraction of water-soluble molecules. ... 

Amphiphilic block copolymers are polymers that can self-assemble into diverse structures in aqneons media above a critical micellization concentration (CMC) or critical aggregation concentration (CAC). Snch block copolymers contain hydrophilic and hydrophobic segments. The amphi-philicity of these block copolymers may be tnned by incorporating stimuli-responsive blocks, which allow a dynamic micellization process (Fig. 3.6). 

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