1D 2D shape selectivity in the crystallization-driven self-assembly of polylactide block copolymers.

2D materials such as graphene, LAPONITE® clays or molybdenum disulfide nanosheets are of extremely high interest to the materials community as a result of their high surface area and controllable surface properties. While several methods to access 2D inorganic materials are known, the investigation of 2D organic nanomaterials is less well developed on account of the lack of ready synthetic accessibility. Crystallization-driven self-assembly (CDSA) has become a powerful method to access a wide range of complex but precisely-defined nanostructures.

Precision Epitaxy for Aqueous 1D and 2D Poly(ε-caprolactone) Assemblies.

The fabrication of monodisperse nanostructures of highly controlled size and morphology with spatially distinct functional regions is a current area of high interest in materials science. Achieving this control directly in a biologically relevant solvent, without affecting cell viability, opens the door to a wide range of biomedical applications, yet this remains a significant challenge. Herein, we report the preparation of biocompatible and biodegradable poly(ε-caprolactone) 1D (cylindrical) and 2D (platelet) micelles in water and alcoholic solvents via crystallization-driven self-assembly.

Form factor of asymmetric elongated micelles: playing with Russian dolls has never been so informative.

Scattering techniques (i.e., static light scattering, small angle neutron scattering,11 or small angle X-ray scattering) are excellent tools to study nanoscopic objects in solution.

Multi-armed micelles and block co-micelles via crystallization-driven self-assembly with homopolymer nanocrystals as initiators.

We report the preparation of multi-armed micelles and block co-micelles using the crystallization-driven self-assembly of crystalline-coil polyferrocenylsilane block copolymers from nanocrystals of the homopolymer. The resulting multi-armed micelles possessed hierarchical multipod structures with monodisperse and tunable arm lengths. The termini of the arms remained active to the addition of further block copolymer unimers, and multi-armed block co-micelles with segmented arm chemistries and variable segment sequences were prepared.

Self-seeding in one dimension: a route to uniform fiber-like nanostructures from block copolymers with a crystallizable core-forming block.

One-dimensional micelles formed by the self-assembly of crystalline-coil poly(ferrocenyldimethylsilane) (PFS) block copolymers exhibit self-seeding behavior when solutions of short micelle fragments are heated above a certain temperature and then cooled back to room temperature. In this process, a fraction of the fragments (the least crystalline fragments) dissolves at elevated temperature, but the dissolved polymer crystallizes onto the ends of the remaining seed fragments upon cooling. This process yields longer nanostructures (up to 1 μm) with uniform width (ca.

Evaluation of the cross section of elongated micelles by static and dynamic light scattering.

We describe simultaneous static (SLS) and dynamic light scattering (DLS) measurements on dilute solutions of a series of poly(ferrocenyldimethylsilane-b-isoprene) (PFS(50)-PI(1000)) block copolymer micelles of uniform length in tert-butyl acetate (tBA) and in decane. The subscripts in the term PFS(50)-PI(1000) refer to the mean degree of polymerization of each block. The SLS experiments show that in both solvents the micelles formed are elongated and rigid.

Reversible cross-linking of polyisoprene coronas in micelles, block comicelles, and hierarchical micelle architectures using Pt(0)-olefin coordination.

Previous work has established that polyisoprene (PI) coronas in cylindrical block copolymer micelles with a poly(ferrocenyldimethylsilane) (PFS) core can be irreversibly cross-linked by hydrosilylation using (HSiMe(2))(2)O in the presence of Karstedt's catalyst. We now show that treatment of cylindrical PI-b-PFS micelles with Karstedt's catalyst alone, in the absence of any silanes, leads to PI coronal cross-linking through Pt(0)-olefin coordination. The cross-linking can be reversed through the addition of 2-bis(diphenylphosphino)ethane (dppe), a strong bidentate ligand, which removes the platinum from the PI to form Pt(dppe)(2).

End-to-end coupling and network formation behavior of cylindrical block copolymer micelles with a crystalline polyferrocenylsilane core.

Cylindrical block copolymer micelles with a crystalline poly(ferrocenyldimethylsilane) (PFDMS) core and a long corona-forming block are known to elongate through an epitaxial growth mechanism on addition of further PFDMS block copolymer unimers. We now report that addition of the semicrystalline homopolymer PFDMS(28) to monodisperse short (ca. 200 nm), cylindrical seed micelles of PFDMS block copolymers results in the formation of aggregated structures by end-to-end coupling to form micelle networks.

Stimulus-responsive self-assembly: reversible, redox-controlled micellization of polyferrocenylsilane diblock copolymers.

In depth studies of the use of electron transfer reactions as a means to control the self-assembly of diblock copolymers with an electroactive metalloblock are reported. Specifically, the redox-triggered self-assembly of a series of polystyrene-block-polyferrocenylsilane (PS-b-PFS) diblock copolymers in dichloromethane solution is described. In the case of the amorphous polystyrene(n)-b-poly(ferrocenylphenylmethylsilane)(m) diblock copolymers (PS(n)-b-PFMPS(m): n = 548, m = 73; n = 71, m = 165; where n and m are the number-averaged degrees of polymerization), spherical micelles with an oxidized PFS core and a PS corona were formed upon oxidation of more than 50% of the ferrocenyl units by [N(C(6)H(4)Br-4)(3)][SbX(6)] (X = Cl, F).

Fiberlike micelles formed by living epitaxial growth from blends of polyferrocenylsilane block copolymers.

Poly(ferrocenyldimethylsilane) (PFS) block copolymers form fiberlike micelles by a seeded growth process. This paper describes the effect of adding similar amounts of PFS block copolymers, PFS-PDMS and PFS-PI, to a common micelle seed. The lengths of the micelles obtained were strongly influenced by the degree of polymerization of the corona-forming blocks.

Seeded growth and solvent-induced fragmentation of fiberlike polyferrocenylsilane-polyisoprene block copolymer micelles.

Addition of a concentrated solution of PI(1000) -PFS(50) dissolved in THF to a solution of PI(1000) -PFS(50) seed micelles in decane led to the formation of uniform elongated fiberlike micelles with a narrow length distribution. When additional THF (>10 vol.-%) was added to the micelles, the micelle length decreased and the contour-length distribution broadened.

Complex and hierarchical micelle architectures from diblock copolymers using living, crystallization-driven polymerizations.

Block copolymers consist of two or more chemically distinct polymer segments, or blocks, connected by a covalent link. In a selective solvent for one of the blocks, core-corona micelle structures are formed. We demonstrate that living polymerizations driven by the epitaxial crystallization of a core-forming metalloblock represent a synthetic tool that can be used to generate complex and hierarchical micelle architectures from diblock copolymers.