Cylindrical Nanostructure of Rigid-Rod POSS-Containing Polymethacrylate from a Star-Branched Block Copolymer

Progress in the self-assembly of organic/inorganic polyhedral oligomeric silsesquioxane (POSS) hybrids

This Review describes recent progress in the self-assembly of organic/inorganic POSS hybrids derived from mono-, di-, and multi-functionalized POSS cages. We highlight the self-assembled structures and physical properties of giant surfactants and chain-end- and side-chain-type hybrids derived from mono-functionalized POSS cages; main-chain-type hybrids derived from di-functionalized POSS cages; and star-shaped hybrids derived from multi-functionalized POSS cages; with various polymeric attachments, including polystyrene, poly(methyl methacrylate), phenolic, PVPh, and polypeptides.

Polymethacrylates containing cage-silsesquioxanes in the side chains: effects of cage and linker structures on film properties

Polymers in which cage-silsesquioxanes were tethered through urethane linkers, were newly synthesized. The free-standing films were supported by the hydrogen bonding networks. Their properties were dependent on the cage structure.

Miktoarm Star Copolymers Prepared by Transformation from Enhanced Spin Capturing Polymerization to Nitroxide-Mediated Polymerization (ESCP-Ŧ-NMP) toward Nanomaterials

Reversible-deactivation radical polymerization (RDRP) serves as a powerful tool nowadays for the preparations of unique linear and non-linear macromolecules. In this study, enhanced spin capturing polymerizations (ESCPs) of styrene (St) and tert-butyl acrylate (tBA) monomers were, respectively, conducted in the presence of difunctional (1Z,1'Z)-1,1'-(1,4-phenylene) bis (N-tert-butylmethanimine oxide) (PBBN) nitrone. Four-arm (PSt)4 and (PtBA)4 star macroinitiators (MIs) can be afforded. By correspondingly switching the second monomer (i.e., tBA and St), miktoarm star copolymers (μ-stars) of (PSt)2-μ-(PtBA-b-PSt)2 and (PtBA)2-μ-(PSt-b-PtBA)2) were thus obtained. We further conducted hydrolysis of the PtBA segments to PAA (i.e., poly(acrylic acid)) in μ-stars to afford amphiphilic μ-stars of (PSt)2-μ-(PAA-b-PSt)2 and (PAA)2-μ-(PSt-b-PAA)2. We investigated each polymerization step and characterized the obtained two sets of "sequence-isomeric" μ-stars by FT-IR, 1H NMR, differential scanning calorimeter (DSC), and thermogravimetric analysis (TGA). Interestingly, we identified their physical property differences in the case of amphiphilic μ-stars by water contact angle (WCA) and atomic force microscopy (AFM) measurements. We thus proposed two microstructures caused by the difference of polymer chain sequences. Through this polymerization transformation (Ŧ) approach (i.e., ESCP-Ŧ-NMP), we demonstrated an interesting and facile strategy for the preparations of μ-stars with adjustable/switchable interior and exterior polymer structures toward the preparations of various nanomaterials.

Crystallization Induced Self-Assembly: A Strategy to Achieve Ultra-Small Domain Sizes

Achieving self-assembled nanostructures with ultra-small feature sizes (e. g., below 5 nm) is an important prerequisite for the development of block copolymer lithography. In this work, the preparation and self-assembly of a series of giant molecules composed of vinyl polyhedral oligomeric silsesquioxane (VPOSS) tethered with monodispersed oligo(L-lactide) chains are presented. Small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) results demonstrate that ultra-small domain sizes (down to 3 nm) of phase separated lamellar morphology are achieved in bulk, driven by the strong tendency and fast kinetics for crystallization of VPOSS moieties. Moreover, upon gamma ray radiation, VPOSS cages in the lamellar structure can be crosslinked via polymerization of the vinyl groups. After pyrolysis at high temperature, ultra-thin two-dimensional nano-silica sheets can be obtained.

Stretchable Conductive Hybrid Films Consisting of Cubic Silsesquioxane-capped Polyurethane and Poly(3-hexylthiophene)

We fabricated stretchable and electric conductive hybrids consisting of polyhedral oligomeric silsesquioxane (POSS)-capped polyurethane (PUPOSS) and doped poly(3-hexylthiophene) (P3HT). In order to realize robust films coexisting polar conductive components in hydrophobic elastic matrices, we employed POSS introduced into the terminals of the polyurethane chains as a compatibilizer. Through the simple mixing and drop-casting with the chloroform solutions containing doped P3HT and polyurethane polymers, homogeneous hybrid films were obtained. From the conductivity and mechanical measurements, it was indicated that hybrid materials consisting of PUPOSS and doped P3HT showed high conductivity and stretchability even with a small content of doped P3HT. From the mechanical studies, it was proposed that POSS promoted aggregation of doped P3HT in the films, and ordered structures should be involved in the aggregates. Efficient carrier transfer could occur through the POSS-inducible ordered structures in the aggregates.

Topology effects on protein–polymer block copolymer self-assembly

Bioconjugates made of the model red fluorescent protein mCherry and synthetic polymer blocks show that topology, i.e. the BA, BA₂, ABA and ABC chain structure of the block copolymers, where B represents the protein and A and C represent polymers, has a significant effect on ordering transitions and the type and size of nanostructures formed during microphase separation.

One-pot strategy for synthesis of open-cage silsesquioxane monomers

A novel synthetic strategy to access POSS monomers has been proposed; one reaction site of an open-cage POSS was capped, and the remaining two silanol groups were functionalized for polymerization. Importantly, the monomer can be obtained by one-pot synthesis without any troublesome isolation process.

Synthesis of a well-defined alternating copolymer of 1,1-diphenylethylene and tert-butyldimethylsilyloxymethyl substituted styrene by anionic copolymerization: toward tailored graft copolymers with controlled side chain densities

Well-defined alternating copolymers comprising 1,1-diphenylethylene (DPE) and styrene derivative having sterically bulky tert-butyldimethylsilyloxymethyl group at the meta position (St-TBS) were successfully synthesized.

Molecular and kinetic design for the expanded control of molecular weights in the ring-opening metathesis polymerization of norbornene-substituted polyhedral oligomeric silsesquioxanes

Rod-like POSS-containing polynorbornenes with high molecular weights were synthesized using ROMP with molecular and kinetic control.

Simultaneous fabrication of line and dot dual nanopatterns using miktoarm block copolymer with photocleavable linker

Block copolymers with various nanodomains, such as spheres, cylinders, and lamellae, have received attention for their applicability to nanolithography. However, those microdomains are determined by the volume fraction of one block. Meanwhile, nanopatterns with multiple shapes are required for the next-generation nanolithography. Although various methods have been reported to achieve dual nanopatterns, all the methods need sophisticated processes using E-beam. Here, we synthesized a miktoarm block copolymer capable of cleavage of one block by ultraviolet. Original cylindrical nanodomains of synthesized block copolymer were successfully transformed to lamellar nanodomains due to the change of molecular architecture by ultraviolet. We fabricated dual nanopatterns consisting of dots and lines at desired regions on a single substrate. We also prepared dual nanopatterns utilizing another phase transformation from spheres to cylinders in a block copolymer with higher interaction parameter. Since our concept has versatility to any block copolymer, it could be employed as next-generation nanolithography.

Precise Synthesis of Macromolecular Architectures by Novel Iterative Methodology Combining Living Anionic Polymerization with Specially Designed Linking Chemistry

This article reviews the development of a novel all-around iterative methodology combining living anionic polymerization with specially designed linking chemistry for macromolecular architecture syntheses. The methodology is designed in such a way that the same reaction site is always regenerated after the polymer chain is introduced in each reaction sequence, and this "polymer chain introduction and regeneration of the same reaction site" sequence is repeatable. Accordingly, the polymer chain can be successively and, in principle, limitlessly introduced to construct macromolecular architectures. With this iterative methodology, a variety of synthetically difficult macromolecular architectures, i.e., multicomponent μ-star polymers, high generation dendrimer-like hyperbranched polymers, exactly defined graft polymers, and multiblock polymers having more than three blocks, were successfully synthesized.

Synthesis and surface characterization of well-defined amphiphilic block copolymers composed of polydimethylsiloxane and poly[oligo(ethylene glycol) methacrylate]

A series of amphiphilic polydimethylsiloxane-b-poly[tri(ethylene glycol) methyl ether methacrylate] (PDMS-b-PM3) diblock copolymers were prepared with varying PM3 compositions.

Rh-catalyzed direct arylation of a polyhedral oligomeric silsesquioxane

Conjugation of a polyhedral oligomeric silsesquioxane (POSS) with the π-electrons of functional organic units has recently attracted much attention. This is the first example of catalytic direct arylation of a POSS.

Synthesis of diblock copolymers consisting of POSS-containing random methacrylate copolymers and polystyrene and their cross-linked microphase-separated structure via fluoride ion-mediated cage scrambling

POSS-containing diblock copolymers were synthesized for the formation of cross-linked microphase-separated structure.

Star Polymers

Recent advances in controlled/living polymerization techniques and highly efficient coupling chemistries have enabled the facile synthesis of complex polymer architectures with controlled dimensions and functionality. As an example, star polymers consist of many linear polymers fused at a central point with a large number of chain end functionalities. Owing to this exclusive structure, star polymers exhibit some remarkable characteristics and properties unattainable by simple linear polymers. Hence, they constitute a unique class of technologically important nanomaterials that have been utilized or are currently under audition for many applications in life sciences and nanotechnologies. This article first provides a comprehensive summary of synthetic strategies towards star polymers, then reviews the latest developments in the synthesis and characterization methods of star macromolecules, and lastly outlines emerging applications and current commercial use of star-shaped polymers. The aim of this work is to promote star polymer research, generate new avenues of scientific investigation, and provide contemporary perspectives on chemical innovation that may expedite the commercialization of new star nanomaterials. We envision in the not-too-distant future star polymers will play an increasingly important role in materials science and nanotechnology in both academic and industrial settings.

Facile synthesis of multiarmed and multicomponent star polymers by a new iterative methodology using (formyl-protected 1,3-dioxolane)-end-functionalized polymer anions

In this manuscript, we have developed a new and efficient iterative methodology using formyl-protected 1,3-dioxolane-end-functionalized polymer anions for the facile synthesis of multiarmed and multicomponent miktoarm star polymers.

POSS-derived mesoporous ionic copolymer–polyoxometalate catalysts with a surfactant function for epoxidation reactions

Novel mesoporous POSS-derived POM-paired polymeric hybrids were demonstrated to be highly efficient interfacial solid catalysts for the epoxidation of alkenes with H₂O₂.

Morphological dependence on the addition of a soft middle block segment to rigid POSS-containing triblock copolymers for forming cylindrical nanostructures

A series of novel polyhedral oligomelic silsesquioxane (POSS)-containing triblock copolymers that self-assemble into hexagonally-packed cylinders of the POSS domain in a polystyrene (PS) matrix was developed in this study.

POSS-derived solid acid catalysts with excellent hydrophobicity for highly efficient transformations of glycerol

New POSS-derived acid catalysts were synthesized, which proved to be highly efficient, and steadily reused for glycerol transformations.