Micellar Morphologies of Poly(ε-caprolactone)-b-poly(ethylene oxide) Block Copolymers in Water with a Crystalline Core

Abstract

The self-assembly of poly(ε-caprolactone)-b-poly(ethylene oxide) block copolymers (PCL n PEO44 and PCL n PEO113) with narrow polydispersity in aqueous medium was studied using transmission electron microscopy. In this system, the formed micelles are composed of a crystalline PCL core and a soluble PEO corona. We demonstrated that the PCL-b-PEO block copolymers can form micelles with abundant morphologies, depending on the lengths of the blocks and composition. It is observed that for PCL n PEO44 the micellar morphology changes from spherical, rodlike, wormlike, to lamellar, as the length of the PCL block increases. In contrast, most of PCL n PEO113 (n = 21−147) block copolymers form spherical micelles, and only PCL232PEO113 exhibits mixed spherical and lamellar micellar morphologies. The effect of microstructure on micellar morphology was semiquantitatively interpreted in terms of reduced tethering density (σ). It is found that lamellar micelles are formed when σ is smaller than a critical value of between 3.0 and 4.8. A larger σ indicates crowding of the tethered chain, and spherical micelles tend to be formed.

An enzyme-catalysed access to amphiphilic triblock copolymer of PCL-b-PEG-b-PCL: synthesis, characterization and self-assembly properties

“…[4][5][6] In an aqueous system, the hydrophobic block aggregates to form a micellar core and the hydrophilic block constitutes the outer shell. [4][5][6] Fluorescence spectra based on selective emission of pyrene in hydrophobic phase against aqueous phase have been used with great success for the measurement of CMC. [13,18,19] The CMC is an effective parameter of micellar stability, and a low critical value is desired for stable micelles.…”

“…The PCLblock-PEG (PCL-b-PEG) copolymer, produced by introducing PEG chains into PCL, can be made into nanoscale micelles in proper solvents. [4][5][6] These drug-loaded nanomicelles can escape from being phagocytized by the reticuloendothelial system, retain for a long time in blood circulation and enrich continuously around the tumour location. [1,2] As a result, they can improve the curative effect of drugs and reduce the toxicity to normal cells.…”

How a Small Modification of the Corona-Forming Block Redirects the Self-Assembly of Crystalline–Coil Block Copolymers in Solution

“…6,9,10 The first rod-like micelles reported involved poly(ferrocenyldimethylsilane) (PFS) block copolymers. [11][12][13] Other more recent examples of rod-like micelles involve block copolymers with polyethylene (PE), 7,[14][15][16][17][18][19][20] polyacrylonitrile (PAN), 21 polyferrocenyldimethylgermane (PFG), 22 poly(e-caprolactone) (PCL), [23][24][25][26][27][28][29][30] poly(L-lactide) (PLLA), [31][32][33][34][35] and polythiophene, 36,37 as the crystalline core-forming block.…”

“…Under many sample preparation conditions and for a variety of different block ratios, multiple morphologies are observed. 28 One study of PCL-b-PEO showed that exposure of spherical micelles in water to high ionic strength led to a morphological transition to lower curvature structures such as rods and lamellae. 26 The authors explained that ionic strength promotes contraction of the PEO chains due to salting-out, and in this way induced the change in morphology.…”

Crystallization-induced aggregation of block copolymer micelles: influence of crystallization kinetics on morphology

“…The overall shape thus depends on the interplay between the interfacial energy of the crystalline block and the solvent, and the stretching within the amorphous block [4]. Thus, the micellar architecture is strongly influenced by the crystallization conditions, such as temperature [9], and composition of the block copolymers [3, 5-By changing composition, solvent, and structure of the crystalline block, spherical [7,[11][12][13], cylindrical [10,14,28], and lamellar micelles have been obtained [1,3,5,15,29]. Recently, Winnik et al reported the possibility to obtain cylindrical micelles with controlled dimensions and architectures of organometallic block copolymers containing the crystallizable polyferrocenyldimethylsilane as one block.…”