Structure and design of polymeric surfactant-based drug delivery systems.

Nano-engineering block copolymer aggregates for drug delivery

Crew-cut micelle-like aggregates of various morphologies prepared from polystyrene-b-poly(acrylic acid), PS-b-PAA, diblock copolymers under near-equilibrium conditions, were studied by transmission electron microscopy (TEM). The insoluble block (PS) contents in the copolymers ranged from 80 to 98 wt %. In spherical micelles, the micelle cores, formed by aggregation of the PS blocks, were generally monodisperse. A comparison between star and crew-cut micelles showed that the latter are distinguished by a low density of corona chains on the core surface and a low degree of stretching of the PS blocks in the cores. As the PAA content in block copolymer decreased, the morphology of the aggregates changed progressively from spheres to cylinders, to bilayers (both vesicles and lamellae), and eventually to compound micelles consisting of an assembly of inverted micelles surrounded by a hydrophilic surface. The compound micelles are believed to be a new morphology for block copolymers. The addition of homopolysty...

Multiple Morphologies and Characteristics of “Crew-Cut” Micelle-like Aggregates of Polystyrene-b-poly(acrylic acid) Diblock Copolymers in Aqueous Solutions

The addition of ions in micromolar (CaCl2 or HCl) or millimolar (NaCl) concentrations can change the morphology of "crew-cut" aggregates of amphiphilic block copolymers in dilute solutions. In addition to spherical, rodlike, and univesicular or lamellar aggregates, an unusual large compound vesicle morphology can be obtained from a single block copolymer. Some features of the spontaneously formed large compound vesicles may make them especially useful as vehicles for delivering drugs and as models of biological cells. Gelation of a dilute spherical micelle solution can also be induced by ions as the result of the formation of a cross-linked "pearl necklace" morphology.

https://science.sciencemag.org/content/sci/272/5269/1777.full.pdf

Ion-Induced Morphological Changes in “Crew-Cut” Aggregates of Amphiphilic Block Copolymers

Polymeric micelles as new drug carriers

Block copolymer micelles formed by diblock and triblock copolymers of styrene and methacrylic acid were characterized in solution in a mixed solvent with 80 vol% of dioxane and 20 vol% of water. No unattached unimer molecules were observed. Three independent methods were employed for obtaining micellar weights. They agreed well with each other. No anomalous behavior was observed by any method. The micellar solutions were shown to contain almost exclusively single micelles; only a few samples (those producing the largest micelles) contained micellar clusters. The micelles behaved hydrodynamically and thermodynamically as impermeable spheres

Polystyrene-poly(methacrylic acid) block copolymer micelles

: Block copolymers of styrene and methacrylic acid dissolved in water/ dioxane mixtures form spherical micelles with polystyrene cores and poly(methacrylic acid) shells. When two micellar solutions containing micelles made from two different copolymers are mixed, the micelles may hybridize. The hybridization was followed by the method of sedimentation velocity. The rate of hybridization was found to be a very sensitive function of the architecture of both copolymers and of the thermodynamic properties of the solvent mixture. In many instances this rate is imperceptible slow; it may be totally frozen when the solvent is very poor with respect to the micellar core. The analysis of the hybridization of numerous micellar pairs provided new insights into the dynamics and thermodynamics of unimer/micelle equilibria. (Author)

Hybridization of Block Copolymer Micelles

Excess volumes of mixing were measured at 20 o C for mixtures of three linear alkanes (hexane, heptane, and octane) and cyclohexane with five alkyl acetates (methyl, ethyl, propyl, butyl, and amyl acetates) and two ketones (acetone and 2-butanone). The whole composition range was studied for all 28 binary systems. For a given alkane, the excess volume decreases with the increasing size of the carbonyl compound. For a given carbonyl compound, the excess volume increases with the size of the alkane

Excess volumes of mixtures of alkanes with carbonyl compounds

Excess volumes of mixing were measured at 20 C for mixtures of four aromatic hydrocarbons (benzene, toluene, ethylbenzene, and p-xylene) with five alkyl acetates (methyl, ethyl, propyl, butyl, and amyl acetates) and two ketones (acetone and 2-butanone). The whole composition range was studied for all 28 binary systems. Specific interactions between the carbonyl and aromatic systems lead to rather small excess volumes, frequently even negative ones. Ketones interact more strongly than alkyl acetates

Excess volume of mixtures of selected alkyl esters and ketones with aromatic hydrocarbons

Excess volumes were calculated from measured densities of binary mixtures of five linear alkanols (methanol, ethanol, 1-propanol, 1-butanol, and 1-pentanol) with five n-alkyl acetates (methyl, ethyl, propyl, butyl, and pentyl acetates) and with two ketones (acetone and 2-butanone) at 20 °C. The whole composition range was studied for all thirty-five binary systems. For a given alcohol, the ∆ V /φ 1 ϑ 2 value decreases with increasing size of the carbonyl compound. For a given carbonyl compound, it increases with the length of the alkanol. Systems with methyl acetate as one component have relatively large ∆ V /φ 1 ϑ 2 values, while systems with methanol display different compositional dependency in respect to systems with other alcohols.

Anwei Qin

Papers

Polystyrene-poly(methacrylic acid) block copolymer micelles

Hybridization of Block Copolymer Micelles

Excess volumes of mixtures of alkanes with carbonyl compounds

Excess volume of mixtures of selected alkyl esters and ketones with aromatic hydrocarbons

Excess Volumes of Mixtures of Some Alkyl Esters and Ketones with Alkanols