Control of Corona Composition and Morphology in Aggregates of Mixtures of PS-b-PAA and PS-b-P4VP Diblock Copolymers: Effects of pH and Block Length

Abstract

The corona compositions and morphologies in aggregates of mixtures of amphiphilic polystyrene-block-poly(acrylic acid) (PS-b-PAA) and polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) diblock copolymers are influenced by controllable assembly parameters such as the hydrophilic block length and solution pH. The morphologies and corona compositions of the aggregates were investigated by transmission electron microscopy and electrophoretic mobility, respectively. When mineral acids or bases are present during aggregate formation, they can exert a strong influence on the corona composition. Morphology changes were also seen with changing pH, as well as changes in corona composition, specifically for vesicles. Because of complications introduced by the presence of ions, the general hypothesis that the external corona of the vesicles is composed of the longer chains, while the shorter chains form the inner corona, which is valid only in mixtures containing only nonionic chains without any additives (no acids or bases) or within a well-defined narrow pH range. In addition to the numerical block lengths and the pH, the solubility of the hydrophilic blocks can also influence the morphology and as well as the interfacial composition of vesicles; as the numerically longer chains become less soluble, they can contract and move to the interior, while the numerically shorter but more soluble chains go to the external corona. A remarkable morphological feature of the pH continuum is that for some compositions vesicles are observed in four distinct pH regions, separated by pH ranges in which other morphologies dominate. The effect of pH and microion content on coil dimensions of the PVP and PAA chains in the block copolymers is most likely responsible for the observed behavior.

Controllable Multigeometry Nanoparticles via Cooperative Assembly of Amphiphilic Diblock Copolymer Blends with Asymmetric Architectures

“…[17][18][19] Through a unique design with respect to block architecture, chemistry and solvent property, block copolymer blends can be successfully directed to selforganize into nanostructures with complex geometries. [20][21] The ability to kinetically trap different copolymers into nanoparticles provides an excellent opportunity to construct complex, multi-geometry nano-objects for multifunctional and hierarchical materials. [22][23][24][25][26][27][28][29] For blends of identical block lengths but different block chemistry, we have previously reported a versatile strategy for the preparation of spherical and cylindrical multi-compartment micelles with controllable core and corona structures.…”

Self‐Assembled Asymmetric Block Copolymer Membranes: Bridging the Gap from Ultra‐ to Nanofiltration

“…The assembly in solution as well as the final membrane morphology are more complex. Vyhnalkova24, 25 et al. recently reported a detailed investigation of the morphology of PS‐ b ‐P4VP/PS‐ b ‐PAA mixtures in relatively diluted solutions containing water.…”

Controllable multicompartment morphologies from cooperative self-assembly of copolymer–copolymer blends

“…Such structures can also be obtained from the cooperative self-assembly of block copolymer blends, such as AB/B [23][24][25][26] , AB/AC [27][28][29][30] , AB/CB 12,[31][32][33][34][35][36][37] and AB/BAB 38,39 . Such structures are the focus of the study here.…”

“…This approach represents a powerful and straightforward way to systematically tune the resulting micellar structures without having to synthesize even more complex multiblock copolymers 18 . Concentric core-shell corona 34,35 and nonconcentric 47 nanostructures have been obtained by this approach. Zhu et al by combining blending and polymerization-induced self-assembly.…”

“…Even a slight change in environmental conditions (e.g., pH, temperature) can have a major effect on the micellar morphology 34,35 . Experimentally, modification of the repulsions can be realized by adopting stimuli-responsive block copolymer 52 , in-situ reaction of copolymers 53 , or modifying solution parameters 29 .…”