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.

Synthesis, Characterization and Structure Properties of Biobased Hybrid Copolymers Consisting of Polydiene and Polypeptide Segments

Novel hybrid materials of the PB-b-P(o-Bn-L-Tyr) and PI-b-P(o-Bn-L-Tyr) type (where PB: 1,4/1,2-poly(butadiene), PI: 3,4/1,2/1,4-poly(isoprene) and P(o-Bn-L-Tyr): poly(ortho-benzyl-L-tyrosine)) were synthesized through anionic and ring-opening polymerization under high-vacuum techniques. All final materials were molecularly characterized through infrared spectroscopy (IR) and proton and carbon nuclear magnetic resonance (1H-NMR, 13C-NMR) in order to confirm the successful synthesis and the polydiene microstructure content. The stereochemical behavior of secondary structures (α-helices and β-sheets) of the polypeptide segments combined with the different polydiene microstructures was also studied. The influence of the α-helices and β-sheets, as well as the polydiene chain conformations on the thermal properties (glass transition temperatures, thermal stability, α- and β-relaxation) of the present biobased hybrid copolymers, was investigated through differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and dielectric spectroscopy (DS). The obtained morphologies in thin films for all the synthesized materials via atomic force microscopy (AFM) indicated the formation of polypeptide fibrils in the polydiene matrix.

Functional Polyimide/Polyhedral Oligomeric Silsesquioxane Nanocomposites

The preparation of hybrid nanocomposite materials derived from polyhedral oligomeric silsesquioxane (POSS) nanoparticles and polyimide (PI) has recently attracted much attention from both academia and industry, because such materials can display low water absorption, high thermal stability, good mechanical characteristics, low dielectric constant, flame retardance, chemical resistance, thermo-redox stability, surface hydrophobicity, and excellent electrical properties. Herein, we discussed the various methods that have been used to insert POSS nanoparticles into PI matrices, through covalent chemical bonding and physical blending, as well as the influence of the POSS units on the physical properties of the PIs.

POSS Dental Nanocomposite Resin: Synthesis, Shrinkage, Double Bond Conversion, Hardness, and Resistance Properties

Nanocomposite dental resins with 0, 2, 5, and 10 wt % methacryl polyhedral oligomeric silsesquioxane (POSS) as filler in the resin matrix were prepared by a light curing method.The atomic force microscopy (AFM), fourier transform infrared spectroscopy (FTIR), nanoindentation, and nanoscratch tests were carried out to study the effect of POSS contents on the compatibility, double bond conversion, volumetric shrinkage, hardness, modulus, and resistance of the dental resins. POSS was very uniformly dispersed and showed a good compatibility with the matrix. The double bond conversion increased and the volume reduced with the addition of POSS. As the POSS addition increased, the mechanical properties increased initially. Small addition of POSS remarkably enhanced the hardness and scratch resistance of the resin matrix.

Superhydrophobic and slippery liquid-infused porous surfaces formed by the self-assembly of a hybrid ABC triblock copolymer and their antifouling performance

Superhydrophobic and slippery liquid-infused porous coatings were fabricated from a hybrid ABC triblock copolymer using a stepwise “bottom-up” strategy.

Using benzoxazine chemistry and bio-based triblock copolymer to prepare functional porous polypeptide capable of efficient dye adsorption

A functional porous PTyr with phenolic OH and amide units through the selective cancelation of the PCL-b-PEO block segment from PCL-b-PEO-b-PTyrBZ triblock copolymer and used for dye adsorption.

Supramolecular Interactions Induce Unexpectedly Strong Emissions from Triphenylamine-Functionalized Polytyrosine Blended with Poly(4-vinylpyridine)

In this study, we synthesized a triphenylamine-functionalized polytyrosine (PTyr-TPA) through living ring opening polymerization with 4,4′-diamino-4″-methoxytriphenylamine (TPA-NH₂) as an initiator, and used Fourier transform infrared (FTIR) and nuclear magnetic resonance spectroscopy to confirm the chemical structure. Photoluminescence spectroscopy revealed the photophysical properties of TPA-NH₂ and PTyr-TPA and suggested that TPA-NH₂ exhibited aggregation-caused quenching; in contrast, attaching the initiator to the rigid rod conformation of the PTyr segments caused PTyr-TPA to display aggregation-induced emission behavior. Differential scanning calorimetry revealed single glass transition temperatures for miscible PTyr-TPA/P4VP blends, the result of intermolecular hydrogen bonding between the pyridine units of P4VP and the phenolic OH units of PTyr-TPA, as confirmed through FTIR spectroscopic analyses. Furthermore, the chain behavior of PTyr-TPA transformed from a β-sheet conformation to random coils after blending with P4VP, as determined using wide-angle X-ray diffraction. These findings suggest that the decreased emission intensity of PTyr-TPA resulted from release of the restricted intramolecular rotation of the triphenylamine moiety in the polypeptide center.

Light-Up of Rhodamine Hydrazide to Generate Emissive Initiator for Polymerization and to Afford Photochromic Polypeptide Metal Complex

Ring-opening polymerization (ROP) of cyclic peptide monomer of γ-propargyl-l-glutamate N-carboxyanhydride (PLG⁻NCA) was originally initiated by non-emissive, ring-close rhodamine 6G hydrazide (R-C). However, instantaneously after adding PLG⁻NCA to R-C, the spirolactam ring of R-C was opened by PLG⁻NCA, rendering emissive, ring-open R-O to initiate ROP of PLG⁻NCA. The emissive R-O moiety therefore produced fluorescent R⁻PLG with aggregation-induced emission (AIE) properties. Moreover, R⁻PLG was found to exhibit photochromic properties with good fatigue resistance and long lifetime when forming metal complexes with Sn(II) and Fe(III). In the dark, irradiated metal complexes slowly (~50 min) restored to the initial state. This research provides foundation for the development of new photochromic materials with long lifetime.

POSS semitelechelic Aβ17–19 peptide initiated helical polypeptides and their structural diversity in aqueous medium

Polyhedral oligomeric silsesquioxane (POSS) semitelechelic Aβ_17–19 peptide which initiated polymerization of γ-benzyl l-glutamate N-carboxyanhydride (BLG-NCA) was studied to prepare peptide–polypeptide conjugates with α-helical conformation.

Influence of the secondary structure on the AIE-related emission behavior of an amphiphilic polypeptide containing a hydrophobic fluorescent terminal and hydrophilic pendant groups

AIE-related emission of polypeptide containing an AIE-active terminal is correlated with secondary structures (α-helix, β-sheet and random coil) of the peptide chains.

Hybrid Mesoporous Silicas and Microporous POSS-Based Frameworks Incorporating Evaporation-Induced Self-Assembly

We fabricated a series of mesoporous silicas and mesoporous organosilicates with hierarchical porosity through evaporation-induced self-assembly using Pluronic F127 as a template in this study. We could tailor the mesophase of each mesoporous silica sample by varying the weight ratio of its two silica sources: tetraethyl orthosilicate (TEOS) and triethoxysilane hydrosilylated octavinyl polyhedral oligomeric silsesquioxane (OV-POSS-SILY). The mesophases ranged from an ordered body-centered cubic (bcc) structure (TEOS alone) to ordered face-centered cubic (fcc) structure (10 and 20 wt.% of OV-POSS-SILY) and finally to disordered spherical pores (≥30 wt.% of OV-POSS-SILY). We used small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) to study the transformations of these mesophases, while N₂ isotherm sorption curves revealed the porosities of these mesoporous silicate samples. Moreover, ²⁹Si CP/MAS solid state nuclear magnetic resonance spectroscopy allowed us to analyze the compositions of the POSS-containing silicate frameworks. Such functional mesoporous silica samples incorporating microporous POSS building units have potential applications in various systems, including optical and electronic devices.

POSS-tethered fluorinated diblock copolymers with linear- and star-shaped topologies: synthesis, self-assembled films and hydrophobic applications

Polyhedral oligomeric silsesquioxane (POSS) tethered fluorinated diblock copolymers are synthesized using octakis(dibromoethyl)POSS and aminopropylisobutyl POSS initiation of methylmethacrylate and dodecafluoroheptylmethacrylate.

Strong emission of 2,4,6-triphenylpyridine-functionalized polytyrosine and hydrogen-bonding interactions with poly(4-vinylpyridine)

The emission intensity of Pyridine-PTyr decreased after blending with P4VP and underwent a hypsochromic shift from 536 to 489 nm due to the release of the restricted intramolecular rotation of the triphenyl pyridine unit in the center of the polymer.

Miscible polypeptide blends of polytyrosine and poly(γ-methyl l-glutamate) with rigid-rod conformations

A new miscible rod–rod polypeptide blend system comprising polytyrosine and poly(γ-methyl l-glutamate) from intermolecular hydrogen bonding between the phenolic OH groups of PTyr and the side chain CO groups of PMLG.

Self-assembly of an interacting binary blend of diblock copolymers in thin films: a potential route to porous materials with reactive nanochannel chemistry

Self-assembly of a binary mixture of poly(styrene)336-block-poly(4-vinyl pyridine)25 (PS336-b-P4VP25) and poly(ethylene glycol)113-block-poly(4-hydroxy styrene)25 (PEG113-b-P4HS25) is shown to give rise to a cylindrical morphology in thin films through pyridine/phenol-based hetero-complementary hydrogen bonding interactions between the P4VP and P4HS copolymer segments. Removal of the cylindrical phase (PEG-b-P4HS) allowed access to porous materials having a pore surface decorated with P4VP polymer blocks. These segments could be transformed into cationic polyelectrolytes through quaternization of the pyridine nitrogen atom. The resulting positively charged nanopore surface could recognize negatively charged gold nanoparticles through electrostatic interactions. This work, therefore, outlines the utility of the supramolecular AB/CD type of block copolymer towards preparation of ordered porous thin films carrying a chemically defined channel surface with a large number of reactive sites.

Alkylated cage silsesquioxane forming a long-range straight ordered hierarchical lamellar nanostructure

An alkylated cage silsesquioxane (1), targeting for a new class of bottom-up-type fabricating materials, was successfully synthesized, and its self-assembled structure is described and discussed herein. Through this, it was found that the intermolecular interaction of long alkyl chains of 1 could be manipulated by thermal annealing to form a long-range straight ordered hierarchical lamellar structure with a periodicity of around 5 nm. Subsequent transmission electron microscopy (TEM) clearly identified polyhedral oligomeric silsesquioxane (POSS) molecules of 1 arranged in a highly ordered fashion, with a "head-to-head" type bilayered structure. The observation of a sublayer structure measuring approximately 0.4 nm in width was attributed to the highly regular packing of isobutyl groups in POSS molecules identified by TEM analysis. Moreover, the formation of a long-range straight structure with sharp interfacial boundaries, which is difficult to achieve with traditional diblock copolymers, is considered to be of significant importance to developing new practical applications of self-assembled nanostructures.

Electrospun hybrid fibers with substantial filler contents formed through kinetically arrested phase separation in liquid jet

This study reports polyhedral oligomeric silsesquioxane (POSS)-based hybrid fibers of architectural hierarchy and compositional heterogeneity.

Star-shaped POSS diblock copolymers and their self-assembled films

This first example of 16-arm, star-shaped diblock copolymers s-POSS-PMMA_277.3-b-P(MA-POSS)_{5.8,16.4,25.4} can be used as solvent-dependent coatings.

Alkylated cage silsesquioxanes: a comprehensive study of thermal properties and self-assembled structure

Long-range straight ordered lamellar structures with controllable feature sizes at sub-10 nm scale are created by thoroughly choosing the aliphatic chain length and branch numbers of alkylated cage silsesquioxane.

Facile construction of hybrid polystyrene with a string of lantern shape from monovinyl-substituted POSS and commercial polystyrene via Friedel–Crafts reaction and its properties

Hybrid polystyrene was easily prepared from monovinyl-substituted POSS and commercial polystyrene (PS)viaa straightforward Friedel–Crafts reaction.

A chaperonin as protein nanoreactor for atom-transfer radical polymerization

The group II chaperonin thermosome (THS) from the archaea Thermoplasma acidophilum is reported as nanoreactor for atom-transfer radical polymerization (ATRP). A copper catalyst was entrapped into the THS to confine the polymerization into this protein cage. THS possesses pores that are wide enough to release polymers into solution. The nanoreactor favorably influenced the polymerization of N-isopropyl acrylamide and poly(ethylene glycol)methylether acrylate. Narrowly dispersed polymers with polydispersity indices (PDIs) down to 1.06 were obtained in the protein nanoreactor, while control reactions with a globular protein-catalyst conjugate only yielded polymers with PDIs above 1.84.

Pattern transfer using block copolymers

To meet the increasing demand for patterning smaller feature sizes, a lithography technique is required with the ability to pattern sub-20 nm features. While top-down photolithography is approaching its limit in the continued drive to meet Moore's law, the use of directed self-assembly (DSA) of block copolymers (BCPs) offers a promising route to meet this challenge in achieving nanometre feature sizes. Recent developments in BCP lithography and in the DSA of BCPs are reviewed. While tremendous advances have been made in this field, there are still hurdles that need to be overcome to realize the full potential of BCPs and their actual use.