The formation of vesicular structures with average diameters from 200 to 300 nm consisting of double hydrophilic diblock copolymers pullulan-b-poly(N,N-dimethylacrylamide) (Pull-b-PDMA) and pullulan-bpoly(N-ethylacrylamide) (Pull-b-PEA) in aqueous solution is described. Bio-derived pullulan was depolymerized and functionalized with alkyne endgroups. Furthermore, azide end functionalized acrylamide blocks PDMA and PEA were synthesized via RAFT polymerization. Individual blocks were conjugated via copper catalyzed azide alkyne cycloaddition (CuAAC) to afford defined double hydrophilic block copolymers. Aqueous solutions of the synthesized block copolymers showed formation of completely hydrophilic vesicles that were observed via various techniques including dynamic light scattering (DLS), static light scattering (SLS), laser scanning confocal microscopy (LSCM), and cryogenic scanning electron microscopy (SEM). † Electronic supplementary information (ESI) available: Additional synthetic procedures, NMR, SEC, DLS and SLS data. See Scheme 2 RAFT polymerization procedure for the synthesis of azido terminated polyacrylamides.Scheme 3 CuAAC conjugation reaction scheme of pullulan alkyne and azide terminated acrylamides.
The formation of submicron particles consisting of double hydrophilic diblock copolymers of poly(ethylene oxide) and poly(N-vinylpyrrolidone) (PEO-b-PVP) in aqueous solution is described. Block copolymers were synthesized via reversible deactivation radical polymerization using a PEOxanthate as macro RAFT/MADIX chain transfer agent. Increasing polymer concentrations in aqueous solutions, the block copolymer is able to self-assemble into spherical structures with apparent hydrodynamic diameters in the range between 200 nm and 2 μm. The self-assembly was further improved by copolymerization with a more hydrophilic monomer, N-vinylimidazole (VIm). Submicron particles from PEO-b-P(VP-co-VIm) were preserved via cross-linking utilizing imidazolium formation with a dihalogenide. Thus, submicron double hydrophilic particles were obtained that are stable in organic solvents and under high dilution. Almost quantitative formation of submicron particles with an average diameter of 200 nm can be afforded by the self-assembly in the polar organic solvent DMF and subsequent crosslinking as well. Furthermore, the obtained particles show a promising ability to incorporate various molecules for delivery and release, here exemplified with simple dyes.
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.
The self-assembly of a novel double hydrophilic block copolymer (DHBC) architecture is presented. By combining linear biomacromolecule pullulan with biocompatible poly(oligo(ethylene glycol) methyl ether) methacrylate) (P(OEGMA))-brush blocks via copper(I) catalyzed azide alkyne cycloaddition, a novel DHBC linear-brush combination is obtained. Self-assembly in water was observed via optical microscopy and dynamic light scattering (DLS). Moreover, DLS investigations showed that self-assembly efficiency significantly relies on the degree of polymerization of the brush-block. Furthermore, the self-assembly of the formed particles was investigated with cryogenic scanning electron microscopy (cryo-SEM). To preserve the aggregates at lower concentrations, a biocompatible and FDA approved cross-linking agent, namely, sodium trimetaphosphate (STMP), was utilized for cross-linking. The reaction of STMP and pullulan was followed by P NMR, while the presence of the cross-linking agent within the particles could be detected via the combination cryo-SEM and energy dispersive X-ray spectroscopy.
Supramolecular hydrogels play a prominent role in contemporary research of hydrophilic polymers. Especially, hydrogels based on α-cyclodextrin/poly(ethylene glycol) (α-CD/PEG) complexation and crystal formation are studied frequently. Here, the effect of double hydrophilic block copolymers (DHBCs) on α-CD/PEG hydrogel properties is investigated. Therefore, a novel DHBC, namely poly(
N
-vinylpyrrolidone)-
b
-poly(oligo ethylene glycol methacrylate) (PVP-
b
-POEGMA), was synthesized via a combination of reversible deactivation radical polymerization and modular conjugation methods. In the next step, hydrogel formation was studied after α-CD addition. Interestingly, DHBC-based hydrogels showed a significant response to thermal history. Heating of the gels to different temperatures led to different mechanical properties after cooling to ambient temperature, i.e., gels with mechanical properties similar to the initial gels or weak flowing gels were obtained. Thus, the hydrogels showed thermoadaptive behavior, which might be an interesting property for future applications in sensing.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.