Micelle forming block copolymers chemical structure

Fig. 7 Chemical structures of micelle-forming block copolymers used in drug delivery.

Figure 21.8 Structural models for lamellar PEP-fr-PEO-b-PHMA block copolymer-aluminosilicate composite morphologies with a small PEP block. In the absence of the PEP block, the PEO (black) and PHMA (light grey) chains stretch into their respective domains while the aluminosilicate particles (white) partition into the hydrophilic PEO domain (a). Possible domain structures discussed in the text are illustrated as follows In the balls-in-lamellae structure the small PEP block (dark grey) forms round micellar domains (b). Dimple structure with PEP micelles at the PHMA/PEO-aluminosilicate interface (c). In the pillared-lamellae structure the PEP domains form pillars spanning across the PEO-aluminosilicate domain (d).37 (Reprinted with permission fiomG.E. S.Toombesetal., Chem. Mater. 2008,20,3278-3287. Copyright 2008 American Chemical Society.)...

Micelle-like junction zones are formed by methylcel-lulose and polyethyloxylene polypropyloxylene block copolymers (poloxamers). Although the polymers differ in chemical structure, both have hydrophobic regions in their chains the di- and trimethyl-o-glucose residues of methylcellulose and the polypropyloxylene block of poloxamer. Another feature common to the... 

Surfactants as well as block copolymers form micelles [15-20] in dilute solutions. Due to the chemical structure of the blocks, block copolymers form micelles not only in polar solvents such as water, but also in very nonpolar media such as fluorinated hydrocarbons or supercritical CO2. Block copolymer micelles have a core consisting of the insoluble A-blocks and a shell or corona of the soluble B-blocks (Fig. 3). 

Cores of Block Copolymer Micelles. In selective solvents (a good solvent only for one block), amphiphilic block copolymers form micelles, the characteristics of which (size and shape) depend on the chemical structure and molecular weight of each block and on the solvent type [27-29]. If the coreforming block contains functional groups, which are able to react with metal... 

FIGURE 54.5 Preparation of disulfide cross-linked PIC micelles containing siRNA. (Reprinted with permission from Biomacromolecules, 12(9), Christie, R.J., Miyata, K., Matsumoto, Y., Nomoto, T., Menasco, D., Lai, T.ch., Pennisi, M. et al. Effect of polymer structure on micelles formed between siRNA and cationic block copolymer comprising thiols and amidines, 3174. Copyright 2011 American Chemical Society.)... 

Micelles are composed of amphiphilic block copolymers that self-assemble into spherical shapes of nanometer diameter due to energy minimization with the surrounding solvent. When exposed to a hydrophilic solvent the hydrophilic domains orient toward the solvent, while the hydrophobic domains orient toward the core and form a clump away from the solvent. In a similar manner, when amphiphilic molecules are exposed to a hydrophobic solvent they form micelles with a hydrophobic block on the surface and a hydrophilic block in the core. Micelles thus have a unique core-shell architecture composed of either hydrophobic or hydrophilic blocks depending on the chemical structures and the medium. The hydrophobic or hydrophilic core provides a reservoir for water-soluble or insoluble drugs and protects them from decomposition in order to maintain activity and stability. Stearic acid (SA)-grafted chitosan oligosaccharide (CSO-SA) formed... 

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