Structural Characteristics of Amphiphilic Cyclic and Linear Block Copolymer Micelles in Aqueous Solutions

Abstract

The structural characteristics of aqueous micelles composed of amphiphilic cyclic poly(n-butyl acrylate-b-ethylene oxide) (cyclic PBA-b-PEO) or a linear analogue (i.e., linear poly(n-butyl acrylate-b-ethylene oxide-b-n-butyl acrylate) (linear PBA-b-PEO-b-PBA)) were examined for the first time using synchrotron X-ray scattering techniques and quantitative data analysis. The scattering data were analyzed using a variety of methodologies in a comprehensive complementary manner. These analyses provided details of the structural information about the micelles. Both micelles were found to consist of a core and a fuzzy shell; however, the cyclic block copolymer had a strong tendency to form micelles with core and shell parts that were more compact and dense than the corresponding parts of the linear block copolymer micelles. The PBA block of the cyclic copolymer was found to form a hydrophobic core with a density that exceeded the density of the homopolymer in the bulk state. The structural differences originated primarily from the topological difference between the cyclic and linear block copolymers. The elimination of the chain end groups (which introduced entropy and increased the excess excluded volume) from the amphiphilic block copolymer yielded more stable dense micelles in solution.

Well-defined and stable nanomicelles self-assembled from brush cyclic and tadpole copolymer amphiphiles: a versatile smart carrier platform

“…Further analysis of the X-ray scattering data were attempted by using two model-dependent methods from the literature: (i) spherical copolymer micelle model analysis 13,37,38 and (ii) spherical core-fuzzy shell model method 13,39 (the analytical schemes are described in the Supplementary Information). With these methods, however, the X-ray scattering data could not be analysed well; in particular, the scattering data in the region of q = 0.13~0.60 nm − 1 could not be fitted with the analytical schemes (for a representative of the data analysis results, see Supplementary Figure S3).…”

“…[1][2][3][4][5][6][7][8][9][10] In addition, cyclic block copolymers have received interest due to selfassembly characteristics that deviate from the typical behaviours of their linear analogues. 3,5,[11][12][13][14][15][16][17][18][19][20][21][22][23][24] In the case of micelle formation in solution, cyclic block copolymers were reported to form relatively more compact micelles than their linear analogues. [11][12][13]15,16,18,23 The cyclic block copolymer micelles, however, were very often evaluated qualitatively.…”

“…3,5,[11][12][13][14][15][16][17][18][19][20][21][22][23][24] In the case of micelle formation in solution, cyclic block copolymers were reported to form relatively more compact micelles than their linear analogues. [11][12][13]15,16,18,23 The cyclic block copolymer micelles, however, were very often evaluated qualitatively. 11,15,18,22,23 Their stabilities were relatively higher than those of their linear analogues but still limited to a certain extent.…”

“…11,15,18,22,23 Their stabilities were relatively higher than those of their linear analogues but still limited to a certain extent. 1,11,13,15,18,22,23 Thus, they have not yet been fully understood in the aspect of structural characteristics (shape, size, size distribution, structural components, density gradient, stability and so on). In fact, micelles have great potent for applications as a carrier system in various fields, such as drug delivery, biomedical imaging, foods, cosmetics, coatings, photonics and molecular electronics.…”

A study on emulsion stabilization induced with linear and cyclized polystyrene-poly(ethylene oxide) block copolymer surfactants

“…At the same time, X-ray structural analysis 17 showed that the cyclized block copolymer surfactants, 2, are more densely ordered to form a compact micelle in comparison with that by the linear counterparts, 1. Therefore, it is speculated that, at the higher surfactant concentration, 2 at the toluene-water interface area can be accommodated in a denser arrangement in comparison with 1, having free chain ends (Figure 4 (bottom), a and b).…”