Giant Surfactants Research Articles

Directed Self-Assembly of Polystyrene-Block-Polyhedral Oligomeric Silsesquioxane Monolayer by Nano-Trench for Nanopatterning.

This work pioneers to combine fast self-assembly of polyhedral oligomeric silsesquioxanes (POSS) nanocage-based giant surfactants with high etching contrast and directed self-assembly for reliable long-range lateral order to create well-aligned sub-10nm line nanopatterns via reactive ion etching (RIE). Polystyrene-block-oligo(dimethylsiloxane) substituted POSS (PS-b-oDMS7POSS) with seven oligo(dimethylsiloxane) at the corners of the POSS nanocage and one polystyrene (PS) tail is designed and synthesized as a giant surfactant with self-assembly behaviors like block copolymer (BCP). In contrast to BCP, oDMS7POSS gives a volume-persistent "nanoatom" particle with higher mobility for fast self-assembly and higher segregation strength with PS for smaller feature size. By taking advantage of directed self-assembly using nano-trench fabricated by electron beam lithography, well-ordered nanostructured monolayer with well-aligned parallel oDMS7POSS cylinders can be formed by confined self-assembly within the nano-trench. With the optimization of the RIE treatment using O2 as an etchant, the high etching contrast from the oDMS7POSS and PS gives the formation of well-defined line nanopatterns with sub-10nm critical dimension that can serve as a mask for pattern transfer in lithography. These results demonstrate a cost-effective approach for nanopatterning by utilizing a creatively designed giant surfactant with sub-10nm feature size and excellent etching contrast for modern lithographic applications.

From Frank-Kasper, Quasicrystals, and Biological Membrane Mimics to Reprogramming In Vivo the Living Factory to Target the Delivery of mRNA with One-Component Amphiphilic Janus Dendrimers.

This Perspective is dedicated to the 25th Anniversary of Biomacromolecules. It provides a personal view on the developing field of the polymer and biology interface over the 25 years since the journal was launched by the American Chemical Society (ACS). This Perspective is meant to bridge an article published in the first issue of the journal and recent bioinspired developments in the laboratory of the corresponding author. The discovery of supramolecular spherical helices self-organizing into Frank-Kasper and quasicrystals as models of icosahedral viruses, as well as of columnar helical assemblies that mimic rodlike viruses by supramolecular dendrimers, is briefly presented. The transplant of these assemblies from supramolecular dendrimers to block copolymers, giant surfactants, and other self-organized soft matter follows. Amphiphilic self-assembling Janus dendrimers and glycodendrimers as mimics of biological membranes and their glycans are discussed. New concepts derived from them that evolved in the in vivo targeted delivery of mRNA with the simplest one-component synthetic vector systems are introduced. Some synthetic methodologies employed during the synthesis and self-assembly are explained. Unraveling bioinspired applications of novel materials concludes this brief 25th Anniversary Perspective of Biomacromolecules.

Self-assembly of three-component bolaform giant surfactants with branched architectures

Branched architecture profoundly influences the physical properties of polymers, making it an important topic in the field of polymer science. Herein, we report a facile synthetic strategy to introduce one site-specific side chain at the junction point to fabricate a series of bolaform giant surfactants with branched architecture. By tuning the volume fraction and the ratio between the linking chain and side chain, various phases have been identified, including three-phase-four-layer lamellae, graphene-like honeycombs, tetragonally packed cylinders, and two-phase lamellae. Notably, the lattice dimension of obtained columnar structures is ∼12 nm, corresponding to sub-10 nm cylinder diameters. As revealed by temperature-dependent small-angle X-ray scattering profiles, a branched architecture significantly decreases the order-disorder transition temperature by ∼90 °C. We also use semi-quantitative calculations to analyze the thermodynamic properties of the observed phases and build rational connections between phase behaviors and the corresponding branching ratios. This study shed light on fine-tuning the macromolecular assembly via molecular topology engineering.

Three-Component Bolaform Giant Surfactants Forming Lamellar Nanopatterns with Sub-5 nm Feature Sizes

Nanopatterns with a sub-5 nm line width are of great interest due to their potential applications in nanotechnology. Herein, we report the design and synthesis of three-component bolaform giant surfactants that can assemble into three-phase-four-layer lamellar (LAM3) structures with sub-5 nm feature sizes. These samples consist of central linear polystyrene (PS) chains with oligodimethylsiloxane-functionalized polyhedral oligomeric silsesquioxane (SiPOSS) at one end and perfluoroalkyl-functionalized POSS (FPOSS) at the other end. Phase separation occurs among three mutually incompatible components, leading to LAM3 structures with relatively sharp interfaces and d-spacings of 12–19 nm. While the lamellar periodicity can be facilely tuned by changing the chain length of PS, the pitch widths of the POSS domains remain largely constant. Energy-dispersive X-ray spectroscopy (EDS) and electron energy loss spectroscopy (EELS) were used to analyze the elemental distribution of the LAM3 structures. After oxygen plasma treatment, the morphology converts into a hierarchical lamellar structure with extremely small Si-rich layers (∼2 nm in thickness). This work suggests that these bolaform giant surfactants are versatile counterparts of traditional triblock copolymers capable of undergoing rapid and strong phase separation at relatively low molecular weights toward unconventional nanostructures with small feature sizes.

Dynamic co-assembly behaviors of polyoxometalates and giant surfactants in dual solvents

Inorganic-organic hybridization is a widely used method to develop new functional materials involving polyoxometalates (POMs), affording them with unique synergistic physical and chemical properties. As one of the core topics in hybrid materials, the study of their assembly structures is critical for the optimization of their performances.In the present work, dynamic co-assembly behaviors of several giant surfactants XPOSS-PS (X, POSS and PS denote different polar groups, polyhedral oligomeric silsesquioxane and polystyrene, respectively) and Keggin-type silicotungstic acid H4SiW12O40 (H4SiW for short) were investigated. We designed and synthesized three series of giant surfactants that possess heads bearing cationic (NPOSS-PS, N for ammonium group), neutral (DPOSS-PS, D for dihydroxyl group) and anionic charges (APOSS-PS, A for carboxylic acid group), respectively. The different charge types of POSS heads lead to different electrostatic interactions with the anionic POM clusters, resulting in different co-assembly structures in dual mixed solvents. Moreover, we found the POM's loading content and PS chain length are another two important factors that can determine the morphology of co-assembly structures. This work expands the scope of co-assembled structures of POM-based hybrid materials, and provides a platform for the study of the basic physical principles of their co-assembly behaviors.

ABC-Type, Bola-Form Giant Surfactants: Synthesis and Self-Assembly.

Due to the fast phase separation kinetics and small feature size, the self-assembly of giant molecules has attracted lots of attention. However, there is not much study on multicomponent giant surfactants. In this work, through a modular synthetic strategy, different polyhedral oligomeric silsesquioxane (POSS)-based molecular nanoparticles are installed with diverse functionalities (hydrophobic octavinyl POSS (VPOSS), hydrophilic dihydroxyl-functionalized POSS (DPOSS), and omniphobic perfluoroalkyl-chain-functionalized POSS (FPOSS)) on the ends of one polystyrene (PS) chain to build up a series of triblock bola-form giant surfactants denoted as XPOSS-PSn -FPOSS (X represents V or D). The target molecules are prepared by a combination of atom transfer radical polymerization (ATRP), esterification, as well as Cu(I)-catalyzed azide-alkyne cycloaddition(CuAAC) and thiol-ene "click" reactions. These macromolecules are thoroughly characterized by combined technologies including nuclear magnetic resonance(NMR), size exclusion chromatography (SEC), and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) analyses. It is revealed by small angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) that VPOSS-PSn -FPOSS adopts a two-phase separation scenario where VPOSS and POSS are segregated in one phase. DPOSS-PSn -FPOSS with a third hydrophilic DPOSS shows a three-phase separation scenario, where highly ordered phase structures are difficult to develop owing to the competition of mutual phase separation processes and may be trapped in kinetically metastable states.

Solvent-Free Templated Synthesis of Core-Crosslinked Star-Shaped Polymers in Supramolecular Body-Centered Cubic Phase.

This study reports the exploration of a solvent-free supramolecular templated synthesis strategy toward highly core-cross-linked star-shaped polymers (CSPs). To achieve this, a kind of cross-linkable giant surfactant, based on a functionalized polyhedral oligomeric silsesquioxanes (POSS) head tethered with a diblock copolymer tail containing reactive benzocyclobutene groups, is designed and prepared. By varying the volume fraction of linear block copolymer tail, these giant surfactants can self-assemble into a body-centered cubic (BCC) structure in bulk, in which the supramolecular spheres are composed of a core of POSS cages, a middle shell of crosslinkable poly(4-vinylbenzocyclobutene) (PBCB) blocks, and a corona of inert polystyrene (PS) blocks. The solvent-free thermally induced cross-linking reaction of the benzocyclobutene groups can be finished in 5min upon heating, resulting in well-defined polymeric spheres with over 90 linear chains surrounding the cross-linked cores. The outer PS blocks serve as the protection corona to ensure that cross-linking of giant surfactants occurs in each supramolecular spherical domain. Given the modular design and diversity of the POSS-based giant surfactants, it is believed that the strategy may enable access to a wide range of CSPs.

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.

Phase Behaviors of Multi‐tailed B2AB2‐Type Regio‐isomeric Giant Surfactants at the Columnar‐Spherical Boundary†

Main observation and conclusionWe report herein the precision synthesis and phase behaviors of multi‐tailed B2AB2‐type regio‐isomeric giant surfactants consisting of a hydrophilic polyhedral oligomeric silsesquioxane (POSS) head tethered with four hydrophobic polystyrene (PS) tails. The synthesis was accomplished through two sequential “click” reactions to give a series of regio‐isomeric giant surfactants S2DS2 (where S is short for PS tails and D for hydroxyl‐functionalized POSS) in para‐, meta‐, and ortho‐configurations. Their phase structures and phase behaviors at the columnar‐spherical boundary were investigated with a single PS tail molecular weight of 1.4 kDa. Specifically, the para‐ and meta‐isomers show hexagonally packed cylinders phases with slightly different order‐disorder transition temperatures (~120 °C and ~130 °C) and the ortho‐isomer exhibits an order‐order transition from a kinetically favored, metastable dodecagonal quasi‐crystal phase to a thermodynamically stable sigma phase at ~120 °C, as well as a further transition into the disordered state at ~140 °C. The phase diagram was constructed and their differences were rationalized based on the calculated interfacial area per molecule. This work demonstrates that tiny structural disparity could not only lead to unconventional phase formation in single‐component macromolecules, but also render dynamic and rich phase behaviors in these macromolecular assemblies.

Tadpole‐like Copolymer for Fabrication of Silica‐encapsulated Polysulfide Microspheres

AbstractA novel giant surfactant, possessing a well‐defined hydrophilic tail and a hydrophobic head with rigid multiple conjugate chains, tadpole‐like copolymer with polyhedral oligomeric silsesquioxane core (P9‐1), had been designed and synthesized via aminolysis/addition, interfacial oxidation polymerization. It was used to form complex micelles with polysulfides (PSL) for constructing the silica microspheres with micrometer dimensions in a simplified one‐pot synthesis. The characterization results for the morphologies of the complex micelles and the resulting microspheres indicated that the introduction of conjugated segments and steric hindrance of hybrid cage contributes to promote the stability and provide larger core space of the self‐assembled micelle to accommodate more PSL. With increasing the PSL/P9‐1 feed ratio, the size of microspheres and the content of PSL in the resulting microsphere were increased due to the PSL droplets providing a soft‐template for silica particles to build larger‐sized silica microspheres with PSL cores. And the growth mechanism of microstructures was also proposed in evaporation synthetic procedures, especially for special hollow morphology.

Phase Behaviors of Giant Surfactants with Different Numbers of Fluorinated Polyhedral Oligomeric Silsesquioxane "Heads" and One Poly(ethylene oxide) "Tail" at the Air-Water Interface.

Giant surfactants with different numbers of aryl-trifluorovinyl ether-functionalized polyhedral oligomeric silsesquioxane (FVPOSS) heads and one poly(ethylene oxide) (PEO) tail, (FVPOSS)n-PEO227, are precisely synthesized. The phase behaviors of (FVPOSS)n-PEO227 at the air-water interface were investigated through surface pressure measurements (isotherm and hysteresis experiments) and the Brewster angle microscopy. Upon increasing the number of FVPOSS heads, the interfacial behaviors of these giant surfactants greatly change. More phase transitions occur during the compression as the number of FVPOSS heads increased from one to two and three. The evolution of morphologies of Langmuir films and compression-expansion hysteresis curves further illustrate phase transitions at the air-water interface. Furthermore, molecular mechanisms to describe phase transitions of (FVPOSS)n-PEO227 at the interface are put forward. This study deepens the understanding of interfacial phase behaviors of special giant surfactants and provides knowledge of nanostructure design and construction at the interface.

Towards achieving a large-area and defect-free nano-line pattern via controlled self-assembly by sequential annealing

Utilizing the controlled self-assembling of a giant surfactant, a bottom-up method for constructing line gratings with sub-10 nm resolution has been developed. Via a simple solvent vapor annealing procedure, the giant surfactant comprised of an oligomeric silsesquioxane (DPOSS) and polystyrene (PS) tail (i.e., DPOSS-PS) has been precisely self-assembled into perpendicularly oriented lamellae structures. A follow-up thermal annealing further significantly promotes the long-range ordering, giving rise to highly oriented and defect-free sub-10 nm line patterns (up to areas of several µm2). The solvent evaporation and thermal annealing process, together with the strong segregation strength (χN) of DPOSS-PS, play crucial roles in the self-orientation and width-reduction of the line patterns. This simple processing of the easy-accessed giant surfactants results in a facile and more economic approach for large-scale nano-sized line grating fabrication.

Ordered Mesoporous Silica Pyrolyzed from Single-Source Self-Assembled Organic-Inorganic Giant Surfactants.

We report the preparation of hexagonal mesoporous silica from single-source giant surfactants constructed via dihydroxyl-functionlized polyhedral oligomeric silsesquioxane (DPOSS) heads and a polystyrene (PS) tail. After thermal annealing, the obtained well-ordered hexagonal hybrid was pyrolyzed to afford well-ordered mesoporous silica. A high porosity (e.g., 581 m2/g) and a uniform and narrow pore size distribution (e.g., 3.3 nm) were achieved. Mesoporous silica in diverse shapes and morphologies were achieved by processing the precursor. When the PS tail length was increased, the pore size expanded accordingly. Moreover, such pyrolyzed, ordered mesoporous silica can help to increase both efficiency and stability of nanocatalysts.

Self-organisation of rhombitruncated cuboctahedral hexagonal columns from an amphiphilic Janus dendrimer

Frank-Kasper phases are available in both hard and soft complex matter. They have been discovered in metal alloys and subsequently in self-organisations of supramolecular spheres from self-assembling dendrons, dendrimers and dendronized polymers. Recently, they were found in block copolymers, lipids, surfactants, giant surfactants, nanoparticles, DNA particles and even in condensed small molecules such as N2, O2, and CO. Here we report the discovery of an amphiphilic Janus dendrimer, that self-assembles in water into vesicles known as dendrimersomes, self-organised also in bulk state into helical columns and spheres forming columnar hexagonal and a Frank-Kasper A15 phase known as Pm n. These self-organisations display a supramolecular orientational memory (SOM) effect that is induced by an epitaxial nucleation at the transition from columns to spheres and during the reverse process. This SOM effect is mediated by the closed contact supramolecular spheres from the A15 phase. In this case a rhombitruncated cuboctahedral hexagonal columnar arrangement, that to the best of our knowledge is not known in biology or synthetic chemistry, was self-organised. We believe that the addition of amphiphilic Janus dendrimers to the classes of molecules displaying Frank-Kasper phases and the SOM effect will broaden our ability to discover additional complex soft condensed matter morphologies.

Open and Closed Layered Nanostructures with Sub-10 nm Periodicity Self-Assembled from Hydrophilic [60]Fullerene-Based Giant Surfactants.

Giant surfactants have been identified as good candidates to produce sub-10 nm elaborate nanostructures, which could potentially realize complex functions in nanofabrication fields. Our theoretical simulation demonstrates the formation of open layered (pupa-like micelles) and closed layered (onion-like micelles) nanostructures, self-assembled from giant surfactants with comparably sized hydrophilic heads tethered by oligomers in solution. Directed by these simulation results, we synthesized giant surfactants consisting of hydrophilic [60]fullerene heads and oligostyrene (OS7) tails and produced the predicted nanostructures with periods of 9.5, 8.3, and 7.5 nm, experimentally. Adjusting the polarity of the solvent and corresponding concentration changed the nanostructures from onion-like micelles with closed layers to pupa-like micelles with open layers. The different morphologies and periods were caused by solvent inclusion and the overlap of OS chains. The above layered nanostructures remained stable after annealing at 120 °C. This work provides insights that computer simulation can play an important role in assisting the design and construction of complicated nanostructures in giant surfactant systems.

Discovery of Structural Complexity through Self-Assembly of Molecules Containing Rodlike Components.

Hierarchical structures are important for transferring and amplifying molecular functions to macroscopic properties of materials. In this regard, rodlike molecules have emerged as one of the most promising molecular building blocks to construct functional materials. Although the self-assembly of conventional molecules containing rodlike components generally results in nematic or layered smectic phases, due to the preferred parallel arrangements of rodlike components, extensive efforts have revealed that rational molecular design provides a versatile platform to engineer rich self-assembled structures. Herein, first successes achieved in polyphilic liquid crystals and rod-coil block systems are summarized. Special attention is paid to recent progress in the conjugation of rodlike building blocks with other molecular building blocks through the molecular Lego approach. Rod-based giant surfactants, sphere-rod conjugates, and dendritic rodlike molecules are covered. Future perspectives of the self-assembly of molecules containing rodlike components are also provided.

Fine-tuned order-order phase transitions in giant surfactants via interfacial engineering

Thermotropic order-order phase transitions (OOTs) in block copolymers are not commonly observed in the strong segregation region. Phase separation of giant surfactants composed of hydrophilic molecular nanoparticles (MNPs) as heads and hydrophobic flexible polymer chains as tails occurs generally in the strong segregation region. By introducing a rigid molecular segment at the junction point of the giant surfactants, the interface between the MNPs and polymer tails could be delicately manipulated, resulting in the occurrence of thermotropic OOTs that are sensitively dependent on the properties of those junction segments. For samples with hydrophilic junction segments, no thermal-induced OOT has been observed. However, for samples with hydrophobic junction segments, complicated thermotropic OOTs between as many as four different ordered phases in a single giant surfactant system, from lamellae (LAM) to hexagonally perforated layer structure (HPL), double gyroids (DG), and finally to hexagonally packed cylinders (HEX), have been observed with increasing temperature. These results demonstrated that interfacial engineering could be used to regulate the self-assemble behavior of macromolecules at the nanometer scales.

Fluorinated polyhedral oligomeric silsesquioxanes end-capped poly(ethylene oxide) giant surfactants: precise synthesis and interfacial behaviors

Interfacial behavior of giant surfactants with precisely tethered molecular nanoparticles (MNPs) is an important topic. In this article, by the combination of hydrosilylation, esterification, and CuAAC ‘‘click’’ chemistry, poly(ethylene oxide) (PEO) chains were end-capped with particle-like aryl-trifluorovinyl ether functionalized polyhedral oligomeric silsesquioxane (FVPOSS) to construct “one-head one-tail” and “bola-form” giant surfactants. The giant surfactants are spread at air/water interface, and surface pressure-area (π-A) isotherms reveal their interfacial behaviors under compression. Atomic force microscope (AFM) images indicate that the giant surfactants show fractal growth behavior after transferred to the silicon substrate at different surface pressure through the procedure of Langmuir-Blodgett (LB) film deposition. The results are useful for understanding the assembly of giant surfactants at the interface and developing of nanostructured functional materials.

Versatile Construction of Single-Tailed Giant Surfactants with Hydrophobic Poly(ε-caprolactone) Tail and Hydrophilic POSS Head.

Giant surfactants refer to a new kind of amphiphile by incorporating functional molecular nanoparticles with polymer tails. As a size-amplified counterpart of small-molecule surfactants, they serve to bridge the gap between small-molecule surfactants and amphiphilic block copolymers. This work reports the design and synthesis of single-tailed giant surfactants carrying a hydrophobic poly(ε-caprolactone) (PCL) as the tail and a hydrophilic cage-like polyhedral oligomeric silsesquioxane (POSS) nanoparticle as the head. The modular synthetic strategy features an efficient “growing-from” and “click-modification” approach. Starting from a monohydroxyl and heptavinyl substituted POSS (VPOSS-OH), a PCL chain with controlled molecular weight and narrow polydispersity was first grown by the ring-opening polymerization (ROP) of ε-CL under the catalysis of stannous octoate, leading to a PCL chain end-capped with heptavinyl substituted POSS (VPOSS-PCL). To endow the POSS head with adjustable polarity and functionality, three kinds of hydrophilic groups, including hydroxyl groups, carboxylic acids, and amine groups, were installed to the periphery of POSS molecule by a high-efficiency thiol-ene “click” reaction. The compounds were fully characterized by NMR, gel permeation chromatography (GPC), MALDI-TOF mass spectrometry, and TGA analysis. In addition, the preliminary self-assembly study of these giant surfactants was also investigated by TEM and dynamic laser light scattering (DLS), which indicated that they can form spherical nanoparticles with different diameters in aqueous solution. This work affords a straightforward and versatile way for synthesizing single-tailed giant surfactants with diverse head surface functionalities.

Self-assembly of giant bottlebrush block copolymer surfactants from luminescent organic electronic materials.

Bottlebrush copolymers have shown promise as building blocks for self-assembled nanomaterials due to their reduced chain entanglement relative to linear polymers and their ability to self-assemble with remarkably low critical micelle concentrations (CMCs). Concurrently, the preparation of bottlebrush polymers from organic electronic materials has recently been described, allowing multiple optoelectronic functions to be incorporated along the length of single bottlebrush strands. Here we describe the self-assembly of bottlebrush surfactants containing soluble n-butyl acrylate blocks and carbazole-based organic semiconductors, which self-assemble in selective solvent to give spherical micelles with CMCs below 54 nM. These narrowly dispersed structures were stable in solution at high dilution over periods of months, and could further be functionalized with fluorescent dyes to give micelles with quantum yields of 100%. These results demonstrate that bottlebrush-based nanostructures can be formed from organic semiconductor building blocks, opening the door to the preparation of fluorescent or redox-active micelles from giant polymeric surfactants.