Micellar Interpolyelectrolyte Complexes with a Compartmentalized Shell

We investigate the formation of micellar interpolyelectrolyte complexes (IPECs) from multicompartment micelles (MCMs) of polybutadiene-<i>block</i>-poly­(1-methyl-2-vinylpyridinium methylsulfate)-<i>block</i>-poly­(methacrylic acid) (BVqMAA) triblock terpolymers and polycations of opposite charge. As cationic material, predominantly a polymer with a high charge density is used: quaternized poly­(2-((2-(dimethylamino)­ethyl)­methylamino)­ethyl methacrylate) (PDAMAq), which carries two positive net charges per monomer unit. Upon IPEC formation at different charge stoichiometries, particles with a compartmentalized IPEC shell are formed. These rather unusual structures even form when both BVqMAA micelles and PDAMAq are mixed at high salinity, followed by dialysis, indicating that the structures formed are not kinetically trapped. Whereas the nature of the polycation seems to play a minor role, our studies suggest that the length of the PMAA corona is the key factor for the formation of a compartmentalized IPEC shell

Counterion-Mediated Hierarchical Self-Assembly of an ABC Miktoarm Star Terpolymer

Directed self-assembly processes of polymeric systems represent a powerful approach for the generation of structural hierarchy in analogy to biological systems. Herein, we utilize triiodide as a strongly polarizable counterion to induce hierarchical self-assembly of an ABC miktoarm star terpolymer comprising a polybutadiene (PB), a poly(<i>tert</i>-butyl methacrylate) (P<i>t</i>BMA), and a poly(<i>N</i>-methyl-2-vinylpyridinium) (P2VPq) segment. Hereby, the miktoarm architecture in conjunction with an increasing ratio of triiodide <i>versus</i> iodide counterions allows for a stepwise assembly of spherical micelles as initial building blocks into cylindrical structures and superstructures thereof. Finally, micrometer-sized multicompartment particles with a periodic lamellar fine structure are observed, for which we introduce the term “woodlouse”. The counterion-mediated decrease in hydrophilicity of the corona-forming P2VPq block is the underlying trigger to induce this hierarchical structure formation. All individual steps and the corresponding intermediates toward these well-defined superstructures were intensively studied by scattering and electron microscopic techniques, including transmission electron microtomography

Counterion-Mediated Hierarchical Self-Assembly of an ABC Miktoarm Star Terpolymer

Directed self-assembly processes of polymeric systems represent a powerful approach for the generation of structural hierarchy in analogy to biological systems. Herein, we utilize triiodide as a strongly polarizable counterion to induce hierarchical self-assembly of an ABC miktoarm star terpolymer comprising a polybutadiene (PB), a poly(<i>tert</i>-butyl methacrylate) (P<i>t</i>BMA), and a poly(<i>N</i>-methyl-2-vinylpyridinium) (P2VPq) segment. Hereby, the miktoarm architecture in conjunction with an increasing ratio of triiodide <i>versus</i> iodide counterions allows for a stepwise assembly of spherical micelles as initial building blocks into cylindrical structures and superstructures thereof. Finally, micrometer-sized multicompartment particles with a periodic lamellar fine structure are observed, for which we introduce the term “woodlouse”. The counterion-mediated decrease in hydrophilicity of the corona-forming P2VPq block is the underlying trigger to induce this hierarchical structure formation. All individual steps and the corresponding intermediates toward these well-defined superstructures were intensively studied by scattering and electron microscopic techniques, including transmission electron microtomography

Counterion-Mediated Hierarchical Self-Assembly of an ABC Miktoarm Star Terpolymer

Directed self-assembly processes of polymeric systems represent a powerful approach for the generation of structural hierarchy in analogy to biological systems. Herein, we utilize triiodide as a strongly polarizable counterion to induce hierarchical self-assembly of an ABC miktoarm star terpolymer comprising a polybutadiene (PB), a poly(<i>tert</i>-butyl methacrylate) (P<i>t</i>BMA), and a poly(<i>N</i>-methyl-2-vinylpyridinium) (P2VPq) segment. Hereby, the miktoarm architecture in conjunction with an increasing ratio of triiodide <i>versus</i> iodide counterions allows for a stepwise assembly of spherical micelles as initial building blocks into cylindrical structures and superstructures thereof. Finally, micrometer-sized multicompartment particles with a periodic lamellar fine structure are observed, for which we introduce the term “woodlouse”. The counterion-mediated decrease in hydrophilicity of the corona-forming P2VPq block is the underlying trigger to induce this hierarchical structure formation. All individual steps and the corresponding intermediates toward these well-defined superstructures were intensively studied by scattering and electron microscopic techniques, including transmission electron microtomography

Template-Directed Mild Synthesis of Anatase Hybrid Nanotubes within Cylindrical Core–Shell–Corona Polymer Brushes

We demonstrate the synthesis of uniform one-dimensional (1D) titania hybrid nanotubes using core–shell–corona cylindrical polymer brushes (CPBs) as soft templates. The CPBs consist of a polymethacrylate backbone with densely grafted poly­(ε-caprolactone) (PCL) as the core, poly­(2<i>-</i>(dimethlamino)­ethyl methacrylate) (PDMAEMA) as the cationic shell, and poly­(oligo­(ethylene glycol) methyl ether methacrylate) (POEGMA) as the corona. The weak polyelectrolyte shell complexed an oppositely charged titania precursor, namely titanium­(IV) bis­(ammonium lactate) dihydroxide (TALH), and then acted as a nanoreactor for the hydrolysis and condensation of TALH, resulting in crystalline TiO₂. The POEGMA shell provides solubility in aqueous and organic solvents. The hybrid titania nanotubes containing anatase nanoparticles were characterized by atomic force microscopy (AFM), transmission electron microscopy (TEM), and scanning electrion microscopy (SEM). The phase purity of the crystalline nanostructures was verified by powder X-ray diffractometry (PXRD)

Multicompartment Micelles with Adjustable Poly(ethylene glycol) Shell for Efficient <i>in Vivo</i> Photodynamic Therapy

We describe the preparation of well-defined multicompartment micelles from polybutadiene-<i>block</i>-poly(1-methyl-2-vinyl pyridinium methyl sulfate)-<i>block</i>-poly(methacrylic acid) (BVqMAA) triblock terpolymers and their use as advanced drug delivery systems for photodynamic therapy (PDT). A porphyrazine derivative was incorporated into the hydrophobic core during self-assembly and served as a model drug and fluorescent probe at the same time. The initial micellar corona is formed by negatively charged PMAA and could be gradually changed to poly(ethylene glycol) (PEG) in a controlled fashion through interpolyelectrolyte complex formation of PMAA with positively charged poly(ethylene glycol)-<i>block</i>-poly(l-lysine) (PLL-<i>b</i>-PEG) diblock copolymers. At high degrees of PEGylation, a compartmentalized micellar corona was observed, with a stable bottlebrush-on-sphere morphology as demonstrated by cryo-TEM measurements. By <i>in vitro</i> cellular experiments, we confirmed that the porphyrazine-loaded micelles were PDT-active against A549 cells. The corona composition strongly influenced their <i>in vitro</i> PDT activity, which decreased with increasing PEGylation, correlating with the cellular uptake of the micelles. Also, a PEGylation-dependent influence on the <i>in vivo</i> blood circulation and tumor accumulation was found. Fully PEGylated micelles were detected for up to 24 h in the bloodstream and accumulated in solid subcutaneous A549 tumors, while non- or only partially PEGylated micelles were rapidly cleared and did not accumulate in tumor tissue. Efficient tumor growth suppression was shown for fully PEGylated micelles up to 20 days, demonstrating PDT efficacy <i>in vivo</i>