Physicochemical properties of pH-controlled polyion complex (PIC) micelles of poly(acrylic acid)-based double-hydrophilic block copolymers and various polyamines (original) (raw)
Related papers
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".
Langmuir, 2012
Hybrid polyion complex (HPIC) micelles are nanoaggregates obtained by complexation of multivalent metal ions by double hydrophilic block copolymers (DHBC). Solutions of DHBC such as the poly(acrylic acid)-block-poly(acrylamide) (PAA-b-PAM) or poly(acrylic acid)-block-poly(2-hydroxyethylacrylate) (PAA-b-PHEA), constituted of an ionizable complexing block and a neutral stabilizing block, were mixed with solutions of metal ions, which are either monoatomic ions or metal polycations, such as Al 3+ , La 3+ , or Al 13 7+. The physicochemical properties of the HPIC micelles were investigated by small angle neutron scattering (SANS) and dynamic light scattering (DLS) as a function of the polymer block lengths and the nature of the cation. Mixtures of metal cations and asymmetric block copolymers with a complexing block smaller than the stabilizing block lead to the formation of stable colloidal HPIC micelles. The hydrodynamic radius of the HPIC micelles varies with the polymer molecular weight as M 0.6. In addition, the variation of R h of the HPIC micelle is stronger when the complexing block length is increased than when the neutral block length is increased. R h is highly sensitive to the polymer asymmetry degree (block weight ratio), and this is even more true when the polymer asymmetry degree goes down to values close to 3. SANS experiments reveal that HPIC micelles exhibit a well-defined core−corona nanostructure; the core is formed by the insoluble dense poly(acrylate)/ metal cation complex, and the diffuse corona is constituted of swollen neutral polymer chains. The scattering curves were modeled by an analytical function of the form factor; the fitting parameters of the Pedersen's model provide information on the core size, the corona thickness, and the aggregation number of the micelles. For a given metal ion, the micelle core radius increases as the PAA block length. The radius of gyration of the micelle is very close to the value of the core radius, while it varies very weakly with the neutral block length. Nevertheless, the radius of gyration of the micelle is highly dependent on the asymmetry degree of the polymer: if the neutral block length increases in a large extent, the micelle radius of gyration decreases due to a decrease of the micelle aggregation number. The variation of the R g /R h ratio as a function of the polymer block lengths confirms the nanostructure associating a dense spherical core and a diffuse corona. Finally, the high stability of HPIC micelles with increasing concentration is the result of the nature of the coordination complex bonds in the micelle core.
Journal of Fluorescence, 1998
Properties of the interracial region between the nonpolar core and the polar shell in polystyreneblock-poly(methacrylic acid) micelles were studied by fluorescence techniques using 5-(N-octadecanoyl) aminofluorescein (OAF) as a probe for rnicrofluidity and local pH. The block copolymer used was tagged between blocks by one 9,10-diphenylanthracene (DPA) group, which allowed us to study binding of OAF at the interface by means of nonradiative energy transfer between DPA and OAF. A shift in the pK~ of OAF and appreciable changes in anisotropy and quenching efficiency due to immobilization of the fluorophore head-group in hydrophobic poly(methacrylie acid) domains were observed after binding of the probe at the interface.
Characterizing the Structure of pH Dependent Polyelectrolyte Block Copolymer Micelles
Macromolecules, 1999
We use fluorescence spectroscopy, dynamic light scattering (DLS), and small-angle neutron scattering (SANS) to characterize the structure of 2-(dimethylamino)ethyl methacrylate/2-(diethylamino)ethyl methacrylate (DMAEMA/DEAEMA) block copolymer micelles. The copolymers exhibit a strong pH dependence, where protonation of the tertiary amines along the side chains cause the blocks to be soluble in water. Fluorescence results show a critical degree of protonation below which single chains aggregate to form micelles. This critical degree of protonation depends on the copolymer concentration and solution ionic strength. Dynamic light scattering experiments provide unimer and micelle size distributions, and the measured critical degrees of protonation are consistent with the fluorescence data. The micelle hydrodynamic radius measured from DLS depends on the solution ionic strength, because of the polyelectrolyte nature of the protonated copolymers. Small-angle neutron scattering experiments in conjunction with a starlike micelle model provide additional insights into the micellar structures.
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
Macromolecules
Thermosensitive and pegylated polyion complex (PIC) micelles were formed by coassembly of oppositely and permanently charged poly(sodium 2-acrylamido-2-methylpropanesulfonate)-block-poly(N-isopropylacrylamide), PAMPS-b-PNIPAAM, and poly[(3-acrylamidopropyl)-trimethylammonium chloride]-block-poly(ethylene oxide), PAMPTMA-b-PEO, block copolymers under stoichiometric charge neutralization conditions and polyelectrolyte chain length matching. PAMPTMA-b-PEO block copolymers with different block lengths were prepared for the first time by atom transfer radical polymerization (ATRP) using a PEO macroinitiator. PIC micelles were characterized by 1H NMR, static light scattering (SLS), dynamic light scattering (DLS), and transmission electron microscopy (TEM). At room temperature, spherical almost monodisperse PIC micelles, consisting of a mixed PAMPTMA/PAMPS coacervate core and a mixed PEO/PNIPAAM shell, were formed, with size of about 80−110 nm. The PIC micelles completely dissociated to un...
Polyion complex micelles with gradient pH-sensitivity for adjustable intracellular drug delivery
Polym. Chem., 2015
A series of poly(amino acid)-containing copolymers with gradient pH-sensitive side groups were synthesized through ring-opening reaction of succinic anhydride (SA), cis-cyclohexene-1,2-dicarboxylic anhydride (CDA), cis-aconitic anhydride (CA), and dimethylmaleic anhydride (DMMA) initiated by the amino groups in methoxy poly(ethylene glycol)-block-poly(L-lysine). Subsequently, four pH-responsive polyion complex (PIC) micelles (denoted as SAD, CDAD, CAD and DMMAD) were prepared through the electrostatic interaction between pH-responsive negatively charged copolymers and positively charged doxorubicin for adjustable intracellular drug delivery. Due to the differences among the acid-sensitive side amide bonds, these micelles were proved to have gradient pH-sensitivity in the following order: SAD < CDAD < CAD < DMMAD. The in vitro drug release rate was consistent with the sensitivity order of the micelles. The intracellular DOX release behaviors and cytotoxicities of the PIC micelles could also be adjusted by the sensitivities of copolymers. All these different characters among the PIC micelles would be further applied for "on demand" intracellular targeting chemotherapy in clinics. † Electronic supplementary information (ESI) available. See Scheme 1 Schematic mechanism of pH-sensitive drug delivery systems for malignancy treatment.
Towards a structural characterization of charge-driven polymer micelles
The European Physical Journal E, 2009
Light scattering and small-angle neutron scattering experiments were performed on comicelles of several combinations of oppositely charged (block co)polymers in aqueous solutions. Fundamental differences between the internal structure of this novel type of micelle -termed complex coacervate core micelle (C3Ms), polyion complex (PIC) micelle, block ionomer complex (BIC), or interpolyelectrolyte complex (IPEC)-and its traditional counterpart, i.e., a micelle formed via self-assembly of polymeric amphiphiles, give rise to differences in scaling behaviour. Indeed, the observed dependencies of micellar size and aggregation number on corona block length, N corona, are inconsistent with scaling predictions developed for polymeric micelles in the star-like and crew-cut regime. Generic C3M characteristics, such as the relatively high core solvent fraction, the low core-corona interfacial tension, and the high solubility of the coronal chains, are causing the deviations. A recently proposed scaling theory for the cross-over regime, as well as a primitive first-order self-consistent field (SCF) theory for obligatory co-assembly, follow our data more closely.
Block-copolymer micelles with a interpolyelectrolyte crown
Polymer Science, Series C
The dispersion stability, structure, and properties of polymer micelles with the hydrophobic core and the interpolyelectrolyte crown in dilute water-salt solutions are studied by turbidimetry, velocity sedimentation, static and dynamic light scattering, fluorescence spectroscopy, and electron microscopy, as well as by measuring the electrophoretic mobility of the particles. The micelles are obtained by mixing diblock copolymers PS-blockpoly(N-ethyl-4-vinylpyridine bromide) and PS-block-poly(acrylic acid) by a specially developed technique of water introduction in the mixture of copolymers in a nonselective organic solvent. It is found that the dispersion stability and the structural and physicochemical characteristics of micelles with the interpolyelectrolyte crown depend on the balance of electrostatic interactions of similarly and oppositely charged units in the crown. In turn, this balance is determined by the composition of the interpolyelectrolyte crown as well as by the pH and ionic strength of solution. It is shown that the micelles with the interpolyelectrolyte crown can be considered to be a special type of polyelectrolyte nanoparticles combining the properties of polyelectrolyte micelles and interpolyelectrolyte complexes. The unique ability of such micelles to electrostatically bind similarly charged polyions with a high linear charge density to the crown is demonstrated. It is first found that such a binding can be selective.
Advances in the Structural Design of Polyelectrolyte Complex Micelles
The Journal of Physical Chemistry B
Polyelectrolyte complex micelles (PCMs) are a unique class of self-assembled nanoparticles that form with a core of associated polycations and polyanions, microphase-separated from neutral, hydrophilic coronas in aqueous solution. The hydrated nature and structural and chemical versatility make PCMs an attractive system for delivery and for fundamental polymer physics research. By leveraging block copolymer design with controlled self-assembly, fundamental structure−property relationships can be established to tune the size, morphology, and stability of PCMs precisely in pursuit of tailored nanocarriers, ultimately offering storage, protection, transport, and delivery of active ingredients. This perspective highlights recent advances in predictive PCM design, focusing on (i) structure−property relationships to target specific nanoscale dimensions and shapes and (ii) characterization of PCM dynamics primarily using time-resolved scattering techniques. We present several vignettes from these two emerging areas of PCM research and discuss key opportunities for PCM design to advance precision medicine.