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. 2017 Jul 20;9(7):293.
doi: 10.3390/polym9070293.

Self-Assembly of Double Hydrophilic Poly(2-ethyl-2-oxazoline)-b-poly(N-vinylpyrrolidone) Block Copolymers in Aqueous Solution

Jochen Willersinn  1 , Bernhard V K J Schmidt  2
Affiliations

Self-Assembly of Double Hydrophilic Poly(2-ethyl-2-oxazoline)-b-poly(N-vinylpyrrolidone) Block Copolymers in Aqueous Solution

Jochen Willersinn et al. Polymers (Basel). .

Abstract

The self-assembly of a novel combination of hydrophilic blocks in water is presented, namely poly(2-ethyl-2-oxazoline)-b-poly(N-vinylpyrrolidone) (PEtOx-b-PVP). The completely water-soluble double hydrophilic block copolymer (DHBC) is formed via copper-catalyzed polymer conjugation, whereas the molecular weight of the PVP is varied in order to study the effect of block ratio on the self-assembly process. Studies via dynamic light scattering, static light scattering as well as microscopy techniques, e.g., cryo scanning electron microscopy or laser scanning confocal microscopy, show the formation of spherical particles in an aqueous solution with sizes between 300 and 400 nm. Particles of the DHBCs are formed without the influence of external stimuli. Moreover, the efficiency of self-assembly formation relies significantly on the molar ratio of the utilized blocks. The nature of the formed structures relies further on the concentration, and indications of particular and vesicular structures are found.

Keywords: double hydrophilic block copolymers; polymer interface; self-assembly; water soluble polymers.

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Conflict of interest statement

The authors declare no conflict of interest. The founding sponsors had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, and in the decision to publish the results.

Figures

Scheme 1
Scheme 1
Overview of block copolymer synthesis and self-assembly in aqueous solution.
Scheme 2
Scheme 2
Synthesis route for the formation of PEtOx-b-PVP block copolymers via RAFT/MADIX polymerization, CROP and CuAAc.
Figure 1
Figure 1
(a) SEC traces of PVP14k, PEtOx22k and PEtOx22k-b-PVP14k block copolymer recorded in acetate buffer with 20% MeOH and (b) 1H-NMR spectrum of PEtOx22k-b-PVP14k recorded at 400 MHz in CDCl3.
Figure 2
Figure 2
Intensity weighted particle size distribution curves obtained via DLS at various concentrations in water at 25 °C: (a) PEtOx22k-b-PVP10k; (b) PEtOx22k-b-PVP14k and (c) PEtOx22k-b-PVP32k.
Figure 3
Figure 3
(a,b) optical microscopy images of PEtOx22k-b-PVP14k at a concentration of 20 wt % in water at 25 °C and (c,d) overlay of LSCM/DIC images from PEtOx22k-b-PVP14k at a concentration of 2.5 wt % in water stained with Rhodamine B at 25 °C.
Figure 4
Figure 4
Cryo SEM images of block copolymers at a concentration of 0.5 wt % in water: (a) PEtOx22k-b-PVP10k; (b,c) PEtOx22k-b-PVP14k and (d) PEtOx22k-b-PVP32k.
See this image and copyright information in PMC

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