Functionalization of Micelles and Shell Cross-linked Nanoparticles Using Click Chemistry (original) (raw)
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Journal of Polymer Science Part A-polymer Chemistry, 2008
Double hydrophilic diblock copolymer, poly(N,N-dimethylacrylamide)-b-poly(N-isopropylacrylamide-co-3-azidopropylacrylamide) (PDMA-b-P(NIPAM-co-AzPAM), containing azide moieties in one of the blocks was synthesized via consecutive reversible addition-fragmentation chain transfer polymerization. The obtained diblock copolymer molecularly dissolves in aqueous solution at room temperature, and can further supramolecularly self-assemble into core-shell nanoparticles consisting of thermoresponsive P(NIPAM-co-AzPAM) cores and water-soluble PDMA coronas above the lower critical solution temperature of P(NIPAM-co-AzPAM) block. As the micelle cores contain reactive azide residues, core crosslinking can be facilely achieved upon addition of difunctional propargyl ether via click chemistry. In an alternate approach in which the PDMA-b-P(NIPAM-co-AzPAM) diblock copolymer was dissolved in a common organic solvent (DMF), the core-crosslinked (CCL) micelles can be fabricated via “click” crosslinking upon addition of propargyl ether and subsequent dialysis against water. CCL micelles prepared by the latter approach typically possess larger sizes and broader size distributions, compared with that obtained by the former one. In both cases, the obtained (CCL) micelles possess thermoresponsive cores, and the swelling/shrinking of which can be finely tuned with temperature, rendering them as excellent candidates as intelligent drug nanocarriers. Because of the high efficiency and quite mild conditions of click reactions, we expect that this strategy can be generalized for the structural fixation of other self-assembled nanostructures. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 860–871, 2008
Journal of the American Chemical Society, 2005
A new methodology for the preparation of well-defined core-shell nanoparticles was developed, based upon the employment of a multifunctional crosslinker to coincidently stabilize supramolecular polymer assemblies and imbed into the shell unique chemical functionalities. Amphiphilic diblock copolymers of poly(acrylic acid)80-b-poly(styrene)90 that had been assembled into micelles and partially functionalized throughout the corona with alkynyl groups were utilized as Click-readied nanoscaffolds for the formation of shell Click-crosslinked nanoparticles (SCCs). Divergently grown dendrimers of the zero, first, second, and third generations having increasing numbers of azide terminating groups (
Facile syntheses of surface-functionalized micelles and shell cross-linked nanoparticles
Journal of Polymer Science Part A: Polymer Chemistry, 2006
Scheme 3. Cross-linking of the hydrophilic shell in micelles 7 and 8 to afford SCK nanoparticles 17 and 9, respectively. Scheme 4. Fluorescent labeling of surface Click-readied nanoparticle, 17. Reagents and conditions for \Click" included CuSO 4 Á5H 2 O (0.25 equiv), Na ascorbate (5 wt % solution in water, 0.50 equiv), alkynyl dye (1.11 equiv to azido functionality), RT, 2 days, followed by dialysis against pH 7.3 phosphate-buffered saline, 10 days.
Poly(styrene-b-4-vinylpyridine) diblock copolymers PS404-b-P4VP76 and PS317-b-P4VP76 (the subscripts indicate the degree of polymerization) self-assemble into spherical ‘‘crew-cut’’ micelles with a PS core and P4VP corona when prepared in a mixture of chloroform and 2-propanol. When the micelles are formed in the presence of quantum dots (QDs), the nature of the structures formed depends upon the polymer and the type of QDs. In our previous report [Macromolecules, 2010, 43, 5066–5074], PS404-b-P4VP76 + CdSe QDs formed stable spherical hybrid micelles, but prolonged vigorous stirring of the solutions led to a rearrangement into wormlike networks and loss of photoluminescence (PL) from the QDs. Here we report that PS317-b-P4VP76 + CdSe/ZnS core–shell QDs behave differently. Partial loss of PL intensity occurred upon addition of 2-propanol to the chloroform solution of the components, and the rearrangement to a network structure occurred spontaneously. We describe two strategies for recovery of the PL intensity for the QDs within the network, photo-activation and chemical activation with elemental sulfur.
Polymer Chemistry, 2012
Functionally-responsive amphiphilic core-shell nanoscopic objects, capable of either complete or partial inversion processes, were produced by the supramolecular assembly of pH-responsive block copolymers, without or with covalent crosslinking of the shell layer, respectively. A new type of well-defined, dual-functionalized boronic acid-and amino-based diblock copolymer poly(3-acrylamidophenylboronic acid) 30 -block-poly(acrylamidoethylamine) 25 (PAPBA 30 -b-PAEA 25 ) was synthesized by sequential reversible addition-fragmentation chain transfer (RAFT) polymerization and then assembled into cationic micelles in aqueous solution at pH 5.5. The micelles were further cross-linked throughout the shell domain comprised of poly(acrylamidoethylamine) by reaction with a bis-activated ester of 4,15-dioxo-8,11-dioxa-5,14diazaoctadecane-1,18-dioic acid, upon increase of the pH to 7, to different cross-linking densities (2%, 5% and 10%), forming well-defined shell cross-linked nanoparticles (SCKs) with hydrodynamic diameters of ca. 50 nm. These smart micelles and SCKs presented switchable cationic, zwitterionic and anionic properties, and existed as stable nanoparticles with high positive surface charge at low pH (pH = 2, zeta potential ~ +40 mV) and strong negative surface charge at high pH (pH = 12, zeta potential ~ −35 mV). 1 H NMR spectroscopy, X-ray photoelectron spectroscopy (XPS), dynamic light scattering (DLS), transmission electron microscopy (TEM), atomic force microscopy (AFM), and zeta potential, were used to characterize the chemical compositions, particle sizes, morphologies and surface charges. Precipitation occurred near the isoelectric points (IEP) of the polymer/particle solutions, and the IEP values could be tuned by changing the shell cross-linking density. The block copolymer micelles were capable of full reversible morphological inversion as a function of pH, by orthogonal protonation of the PAEA and hydroxide association with the PAPBA units, whereas the SCKs underwent only reptation of the PAPBA chain segments through the crosslinked shell of PAEA as the pH was elevated. Further, these nanomaterials also showed D-glucose-responsive properties. Correspondence to: Karen L. Wooley, wooley@chem.tamu.edu. † Electronic Supplementary Information (ESI) available: [DLS Zeta potential and XPS characterization of non-cross-linked micelles and czaSCKs as a function of pH and concentration D-glucose]. See
The Journal of Physical Chemistry B, 2003
The structure and behavior of amphiphilic block copolymer micelles with partly hydrophobically modified polyelectrolyte shells were studied in 1,4-dioxane-water mixtures and in purely aqueous media by a combination of several experimental techniques. The studied hybrid micelles are formed by 20 wt % of a modified polystyrene-block-poly(methacrylic acid), PS-N-PMA-A, double-tagged by one pendant naphthalene between blocks and one anthracene at the end of the PMA block and by 80% of either nontagged PS-PMA or polystyrene-block-poly(ethylene oxide), PS-PEO. The cores of micelles contain pure PS, while the shells contain either PMA-A/PMA or PMA-A/PEO mixed chains. The double tagging by naphthalene and anthracene allows for a nonradiative energy transfer (NRET) study aimed at the estimate of donor-trap distances within one micelle. The fluorometric study suggests that the hydrophobic anthracene tag at the end of shell-forming PMA block tries to avoid the aqueous medium and is buried in the shell, forcing the PMA chain to loop back toward the core. Since the stability of hybrid micellar solutions is guaranteed by favorable interactions of stretched unmodified shell-forming chains (which are in excess in the system) with the aqueous solvent, the reduced entropy of the loop-forming chains does not play such an important role as in micelles with 100% tagging. Hence, we conclude that a higher fraction of the anthracene-tagged chains may return closer to the core-corona interface than in the case of 100% tagged micelles. † Part of the special issue "International Symposium on Polyelectrolytes".
Polymer Chemistry, 2022
We report the synthesis of redox-and pH-sensitive block copolymer micelles that contain chiral cores composed of helical poly(aryl isocyanide)s. Pentafluorophenyl (PFP) ester-containing micelles synthesised via nickel-catalysed coordination polymerisation-induced self-assembly (NiCCo-PISA) of helical poly(aryl isocyanide) amphiphilic diblock copolymers are modified post-polymerisation with various diamines to introduce cross-links and/or achieve stimulus-sensitive nanostructures. The successful introduction of the diamines is confirmed by Fourier-transform infrared spectroscopy (FT-IR), while the stabilisation effect of the cross-linking is explored by dynamic light scattering (DLS). The retention of the helicity of the core-forming polymer block is verified by circular dichroism (CD) spectroscopy and the stimuliresponsiveness of the nanoparticles towards a reducing agent (L-glutathione, GSH) and pH is evaluated by following the change in the size of the nanoparticles by DLS. These stimuli-responsive nanoparticles could find use in applications such as drug delivery, nanosensors or biological imaging.