Solvent-Induced Morphological Transition in Core-Cross-Linked Block Copolymer Micelles

Abstract

Microwave-assisted polymerization has been utilized to synthesize amphiphilic poly(2-ethyl-2-oxazoline-block-2-"soy alkyl"-2-oxazoline) diblock copolymers (PEtOx-PSoyOx). The amphiphilic block copolymers have been used to prepare aqueous spherical micelles consisting of a PEtOx corona and a PSoyOx core, which have been further cross-linked by UV irradiation. The morphology of these cross-linked micelles has been shown to reversibly change from spheres to short rods referred to as rice grains whenever the micelles were transferred from water into acetone, a nonselective solvent for the constituent blocks. This morphological transition has been attributed to the swelling of the slightly cross-linked PSoyOx core.

Design Strategies for Functionalized Poly(2-oxazoline)s and Derived Materials

“…These micellar catalysts showed high catalytic activity during first experiments. Schubert, Gohy et al synthesized amphiphilic pEtOx-block-pSoy = = Ox that formed aqueous spherical micelles with a pEtOx corona and a pSoy = = Ox core [175]. The core of the micelles was slightly crosslinked by UV irradiation.…”

Bioinspired Poly(2-oxazoline)s

“…Furthermore, Hoogenboom and Schubert et al studied the micellization of PEtOx-b-NonOx block copolymers in water-ethanol mixtures revealing spherical micelles that increased in size with the addition of ethanol due to expansion of the PEtOx chains in the corona [36]. The self-assembly behavior of a block copolymer based on EtOx and a hydrophobic monomer with soy-bean fatty acid side chains was investigated by Schubert and Gohy et al revealing the formation of well-defined spherical micelles [61]. The oxidative crosslinking of the unsaturated fatty acid side chains was successfully exploited for cross-linking the micellar structures.…”

Poly(2‐oxazoline)s: Alive and Kicking

“…After this first proof of principle, an amphiphilic block copolymer that consists of a large pEtOx hydrophilic block and a short pSoyOx hydrophobic block has been synthesized under microwave irradiation as basis for the preparation of corecrosslinked micelles. [59] This amphiphilic block copolymer self-assembles into micelles after dissolution in acetone and gradually changing the solvent to water. UV irradiation of this micellar solution has been performed to prepare the core-crosslinked micelles.…”