Tannic Acid-Mediated Aggregate Stabilization of Poly(N-vinylpyrrolidone)-b-poly(oligo (ethylene glycol) methyl ether methacrylate) Double Hydrophilic Block Copolymers.

Al Nakeeb Al Nakeeb,Schmidt Schmidt,Nischang Nischang

doi:10.3390/nano9050662

Abstract

The self-assembly of block copolymers in aqueous solution is an important field in modern polymer science that has been extended to double hydrophilic block copolymers (DHBC) in recent years. In here, a significant improvement of the self-assembly process of DHBC in aqueous solution by utilizing a linear-brush macromolecular architecture is presented. The improved self-assembly behavior of poly(N-vinylpyrrolidone)-b-poly(oligo(ethylene glycol) methyl ether methacrylate) (PVP-b-P(OEGMA)) and its concentration dependency is investigated via dynamic light scattering (DLS) (apparent hydrodynamic radii ≈ 100–120 nm). Moreover, the DHBC assemblies can be non-covalently crosslinked with tannic acid via hydrogen bonding, which leads to the formation of small aggregates as well (apparent hydrodynamic radius ≈ 15 nm). Non-covalent crosslinking improves the self-assembly and stabilizes the aggregates upon dilution, reducing the concentration dependency of aggregate self-assembly. Additionally, the non-covalent aggregates can be disassembled in basic media. The presence of aggregates was studied via cryogenic scanning electron microscopy (cryo-SEM) and DLS before and after non-covalent crosslinking. Furthermore, analytical ultracentrifugation of the formed aggregate structures was performed, clearly showing the existence of polymer assemblies, particularly after non-covalent crosslinking. In summary, we report on the completely hydrophilic self-assembled structures in solution formed from fully biocompatible building entities in water.

Highlights

Block copolymer self-assemblies play a prominent role in current polymer science [1,2]
The self-assembly of block copolymers in aqueous solution is an important field in modern polymer science that has been extended to double hydrophilic block copolymers (DHBC) in recent years
We could show an apparent improvement in the self-assembly process of double hydrophilic block copolymers in aqueous solution by non-covalent crosslinking with tannic acid (TA) and by utilizing a linear-brush macromolecular double hydrophilic architecture

Summary

Introduction

Block copolymer self-assemblies play a prominent role in current polymer science [1,2]. The formation of amphiphilic self-assembled structures was shifted to the polymerization process [18,19]. In such a way, the aforementioned and more complex structures can be accessed in one step via the adjustment of monomer conversion. Notwithstanding, self-assemblies of amphiphilic block copolymers in aqueous solution face some disadvantages, e.g., low permeability [20]. In the prospected applications of nanoreactors, permeability is a key property to enable efficient reaction progress. One solution to this problem is the introduction of artificial protein channels [21,22]. Another option is the implementation of stimuli-responsive blocks that allow selective swelling/deswelling of the hydrophobic domain [23,24]

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Results

Conclusion