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Precise hierarchical self-assembly of multicompartment micelles.

Gröschel AH, Schacher FH, Schmalz H, Borisov OV, Zhulina EB, Walther A, Müller AH - Nat Commun (2012)

Bottom Line: This directed self-assembly leads to a step-wise reduction of the degree of conformational freedom and dynamics and avoids undesirable kinetic obstacles during the structure build-up.It yields a general concept for homogeneous populations of well-defined multicompartment micelles with precisely tunable patchiness, while using simple linear ABC triblock terpolymers.We further demonstrate control over the hierarchical step-growth polymerization of multicompartment micelles into micron-scale segmented supracolloidal polymers as an example of programmable mesoscale colloidal hierarchies via well-defined patchy nanoobjects.

View Article: PubMed Central - PubMed

Affiliation: Makromolekulare Chemie II, Universität Bayreuth, Bayreuth, Germany.

ABSTRACT
Hierarchical self-assembly offers elegant and energy-efficient bottom-up strategies for the structuring of complex materials. For block copolymers, the last decade witnessed great progress in diversifying the structural complexity of solution-based assemblies into multicompartment micelles. However, a general understanding of what governs multicompartment micelle morphologies and polydispersity, and how to manipulate their hierarchical superstructures using straightforward concepts and readily accessible polymers remains unreached. Here we demonstrate how to create homogeneous multicompartment micelles with unprecedented structural control via the intermediate pre-assembly of subunits. This directed self-assembly leads to a step-wise reduction of the degree of conformational freedom and dynamics and avoids undesirable kinetic obstacles during the structure build-up. It yields a general concept for homogeneous populations of well-defined multicompartment micelles with precisely tunable patchiness, while using simple linear ABC triblock terpolymers. We further demonstrate control over the hierarchical step-growth polymerization of multicompartment micelles into micron-scale segmented supracolloidal polymers as an example of programmable mesoscale colloidal hierarchies via well-defined patchy nanoobjects.

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Mesoscale polymerization of linear MCMs and subunit exchange of spherical MCMs promoted by changing the corona volume.The red corona chains emerge from the black compartments, but are mostly omitted for clarity (TEM images, OsO4-staining except (b) RuO4, acetone/isopropanol fractions are given in v/v). (a) Scheme for reversible mesoscale colloidal polymerization (SBM9). Note that the branching points are composed of (SBS)3 centres. (b) SBS-refined subunits in acetone/isopropanol (90/10), (c) (SBS)2 'double burgers' formed by two SBS in acetone/isopropanol (80/20) and their polymerization (d) in acetone/isopropanol (50/50). (e) Scheme for reversible exchange of refined subunits in spherical MCMs (SBM3). (f–h) In situ switching of spherical MCMs. (f) 'Hamburgers' and refined subunits successively merge into (g) 'clovers' and (h) 'footballs' triggered by reduction of the solvent quality for the corona (addition of isopropanol from 90/10 to 60/40 to 50/50). Refined subunits clearly reappear upon the expansion of the corona (addition of acetone from 50/50 to 90/10). Scale bars are 200 nm and 50 nm in insets.
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f5: Mesoscale polymerization of linear MCMs and subunit exchange of spherical MCMs promoted by changing the corona volume.The red corona chains emerge from the black compartments, but are mostly omitted for clarity (TEM images, OsO4-staining except (b) RuO4, acetone/isopropanol fractions are given in v/v). (a) Scheme for reversible mesoscale colloidal polymerization (SBM9). Note that the branching points are composed of (SBS)3 centres. (b) SBS-refined subunits in acetone/isopropanol (90/10), (c) (SBS)2 'double burgers' formed by two SBS in acetone/isopropanol (80/20) and their polymerization (d) in acetone/isopropanol (50/50). (e) Scheme for reversible exchange of refined subunits in spherical MCMs (SBM3). (f–h) In situ switching of spherical MCMs. (f) 'Hamburgers' and refined subunits successively merge into (g) 'clovers' and (h) 'footballs' triggered by reduction of the solvent quality for the corona (addition of isopropanol from 90/10 to 60/40 to 50/50). Refined subunits clearly reappear upon the expansion of the corona (addition of acetone from 50/50 to 90/10). Scale bars are 200 nm and 50 nm in insets.

Mentions: Figure 5 depicts the growth of linear (SBM9) and spherical (SBM3) MCMs by changing the solvent quality for the corona block. In DMAc, the initial subunits of SBM9 showed a weakly phase-separated PS/PMMA corona (Fig. 3a)30. Dialysis into acetone/isopropanol (90/10) induces a contraction of PS and a refinement of the structure as visible by the grey patches on the opposite sides of the PB core (Fig. 5b), that is, the formation of SBS 'inverse hamburger' MCMs (refined subunit). The increasing solvophobicity of the PS domains of these symmetrical building blocks and the concomitant contraction of the PMMA corona trigger the following dimerization and step-growth polymerization. Upon addition of further non-solvent (80/20) 'double-burger' dimers, (SBS)2, are formed as dominant species (Fig. 5c). A distribution of oligomers cannot be found here and thus we attribute their intermediate stability to a rearranged corona that is large enough to protect the terminal PS compartments, suppressing further growth (compare Fig. 4e). At higher isopropanol content (70/30), slightly extended 1D oligomers are formed, followed by several μm long (60/40) and increasingly branched colloidal polymers (50/50; Fig. 5d). Branches and kinks are caused by fusion/assembly of three SBS 'inverse hamburgers' into an (SBS)3 branching point with one common PS domain in the centre. The drop in solvent quality contracts the corona and corresponds to an increase of the equilibrium association constant, K, as expressed in equation (4) and explains the formation of longer mesoscale colloidal polymers (DLS in Fig. 3c and Supplementary Fig. S4). Even higher isopropanol contents result in network formation and precipitation, caused by the increasing end-to-side addition, possible at stronger corona contraction. The polymerization is fully reversible by changing the solvent quality, for example, from 80/20 to 50/50 and back. Loosely related are results from Lodge and Hillmyer43 who observed that addition of diblock copolymer micelles to MCM worms can induce a shortening of the worms via fusion/fission event.


Precise hierarchical self-assembly of multicompartment micelles.

Gröschel AH, Schacher FH, Schmalz H, Borisov OV, Zhulina EB, Walther A, Müller AH - Nat Commun (2012)

Mesoscale polymerization of linear MCMs and subunit exchange of spherical MCMs promoted by changing the corona volume.The red corona chains emerge from the black compartments, but are mostly omitted for clarity (TEM images, OsO4-staining except (b) RuO4, acetone/isopropanol fractions are given in v/v). (a) Scheme for reversible mesoscale colloidal polymerization (SBM9). Note that the branching points are composed of (SBS)3 centres. (b) SBS-refined subunits in acetone/isopropanol (90/10), (c) (SBS)2 'double burgers' formed by two SBS in acetone/isopropanol (80/20) and their polymerization (d) in acetone/isopropanol (50/50). (e) Scheme for reversible exchange of refined subunits in spherical MCMs (SBM3). (f–h) In situ switching of spherical MCMs. (f) 'Hamburgers' and refined subunits successively merge into (g) 'clovers' and (h) 'footballs' triggered by reduction of the solvent quality for the corona (addition of isopropanol from 90/10 to 60/40 to 50/50). Refined subunits clearly reappear upon the expansion of the corona (addition of acetone from 50/50 to 90/10). Scale bars are 200 nm and 50 nm in insets.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC3293418&req=5

f5: Mesoscale polymerization of linear MCMs and subunit exchange of spherical MCMs promoted by changing the corona volume.The red corona chains emerge from the black compartments, but are mostly omitted for clarity (TEM images, OsO4-staining except (b) RuO4, acetone/isopropanol fractions are given in v/v). (a) Scheme for reversible mesoscale colloidal polymerization (SBM9). Note that the branching points are composed of (SBS)3 centres. (b) SBS-refined subunits in acetone/isopropanol (90/10), (c) (SBS)2 'double burgers' formed by two SBS in acetone/isopropanol (80/20) and their polymerization (d) in acetone/isopropanol (50/50). (e) Scheme for reversible exchange of refined subunits in spherical MCMs (SBM3). (f–h) In situ switching of spherical MCMs. (f) 'Hamburgers' and refined subunits successively merge into (g) 'clovers' and (h) 'footballs' triggered by reduction of the solvent quality for the corona (addition of isopropanol from 90/10 to 60/40 to 50/50). Refined subunits clearly reappear upon the expansion of the corona (addition of acetone from 50/50 to 90/10). Scale bars are 200 nm and 50 nm in insets.
Mentions: Figure 5 depicts the growth of linear (SBM9) and spherical (SBM3) MCMs by changing the solvent quality for the corona block. In DMAc, the initial subunits of SBM9 showed a weakly phase-separated PS/PMMA corona (Fig. 3a)30. Dialysis into acetone/isopropanol (90/10) induces a contraction of PS and a refinement of the structure as visible by the grey patches on the opposite sides of the PB core (Fig. 5b), that is, the formation of SBS 'inverse hamburger' MCMs (refined subunit). The increasing solvophobicity of the PS domains of these symmetrical building blocks and the concomitant contraction of the PMMA corona trigger the following dimerization and step-growth polymerization. Upon addition of further non-solvent (80/20) 'double-burger' dimers, (SBS)2, are formed as dominant species (Fig. 5c). A distribution of oligomers cannot be found here and thus we attribute their intermediate stability to a rearranged corona that is large enough to protect the terminal PS compartments, suppressing further growth (compare Fig. 4e). At higher isopropanol content (70/30), slightly extended 1D oligomers are formed, followed by several μm long (60/40) and increasingly branched colloidal polymers (50/50; Fig. 5d). Branches and kinks are caused by fusion/assembly of three SBS 'inverse hamburgers' into an (SBS)3 branching point with one common PS domain in the centre. The drop in solvent quality contracts the corona and corresponds to an increase of the equilibrium association constant, K, as expressed in equation (4) and explains the formation of longer mesoscale colloidal polymers (DLS in Fig. 3c and Supplementary Fig. S4). Even higher isopropanol contents result in network formation and precipitation, caused by the increasing end-to-side addition, possible at stronger corona contraction. The polymerization is fully reversible by changing the solvent quality, for example, from 80/20 to 50/50 and back. Loosely related are results from Lodge and Hillmyer43 who observed that addition of diblock copolymer micelles to MCM worms can induce a shortening of the worms via fusion/fission event.

Bottom Line: This directed self-assembly leads to a step-wise reduction of the degree of conformational freedom and dynamics and avoids undesirable kinetic obstacles during the structure build-up.It yields a general concept for homogeneous populations of well-defined multicompartment micelles with precisely tunable patchiness, while using simple linear ABC triblock terpolymers.We further demonstrate control over the hierarchical step-growth polymerization of multicompartment micelles into micron-scale segmented supracolloidal polymers as an example of programmable mesoscale colloidal hierarchies via well-defined patchy nanoobjects.

View Article: PubMed Central - PubMed

Affiliation: Makromolekulare Chemie II, Universität Bayreuth, Bayreuth, Germany.

ABSTRACT
Hierarchical self-assembly offers elegant and energy-efficient bottom-up strategies for the structuring of complex materials. For block copolymers, the last decade witnessed great progress in diversifying the structural complexity of solution-based assemblies into multicompartment micelles. However, a general understanding of what governs multicompartment micelle morphologies and polydispersity, and how to manipulate their hierarchical superstructures using straightforward concepts and readily accessible polymers remains unreached. Here we demonstrate how to create homogeneous multicompartment micelles with unprecedented structural control via the intermediate pre-assembly of subunits. This directed self-assembly leads to a step-wise reduction of the degree of conformational freedom and dynamics and avoids undesirable kinetic obstacles during the structure build-up. It yields a general concept for homogeneous populations of well-defined multicompartment micelles with precisely tunable patchiness, while using simple linear ABC triblock terpolymers. We further demonstrate control over the hierarchical step-growth polymerization of multicompartment micelles into micron-scale segmented supracolloidal polymers as an example of programmable mesoscale colloidal hierarchies via well-defined patchy nanoobjects.

Show MeSH