Perpendicular Orientation Control without Interfacial Treatment of RAFT-Synthesized High-χ Block Copolymer Thin Films with Sub-10 nm Features Prepared via Thermal Annealing

Self-Assembly of Hierarchical High-χ Fluorinated Block Copolymers with an Orthogonal Smectic-within-Lamellae 3 nm Sublattice and Vertical Surface Orientation

Hierarchical structure-within-structure assemblies offer a route toward increasingly complex and multifunctional materials while pushing the limits of block copolymer self-assembly. We present a detailed study of the self-assembly of a series of fluorinated high-χ block copolymers (BCPs) prepared via postmodification of a single poly(styrene)-block-poly(glycidyl methacrylate) (S-b-G) parent polymer with the fluorinated alkylthiol pendent groups containing 1, 6, or 8 fluorinated carbons (termed trifluoro-ethanethiol (TFET), perfluoro-octylthiol (PFOT), and perfluoro-decylthiol (PFDT), respectively). Bulk X-ray scattering of thermally annealed samples demonstrates hierarchical molecular assembly with phase separation between the two blocks and within the fluorinated block. The degree of ordering within the fluorinated block is highly sensitive to synthetic variation; a lamellar sublattice was formed for S-b-GPFOT and S-b-GPFDT. Thermal analyses of S-b-GPFOT reveal that the fluorinated block exhibits liquid crystal-like ordering. The complex thin-film self-assembly behavior of an S-b-GPFOT polymer was investigated using real-space (atomic force microscopy and scanning electron microscopy) and reciprocal-space (resonant soft X-ray scattering (RSoXS), grazing incidence small- and wide-angle scattering) measurements. After thermal annealing in nitrogen or vacuum, films thicker than 1.5 times the primary lattice spacing exhibit a 90-degree grain boundary, exposing a thin layer of vertical lamellae at the free interface, while exhibiting horizontal lamellae on the preferential (polystyrene brush) substrate. RSoXS measurements reveal the near-perfect orthogonality between the primary and sublattice orientations, demonstrating hierarchical patterning at the nanoscale.

Light-Mediated Polymerization Catalyzed by Carbon Nanomaterials

Carbon nanomaterials, specifically carbon dots and carbon nitrides, play a crucial role as heterogeneous photoinitiators in both radical and cationic polymerization processes. These recently introduced materials offer promising solutions to the limitations of current homogeneous systems, presenting a novel approach to photopolymerization. This review highlights the preparation and photocatalytic performance of these nanomaterials, emphasizing their application in various polymerization techniques, including photoinduced i) free radical, ii) RAFT, iii) ATRP, and iv) cationic photopolymerization. Additionally, it discusses their potential in addressing contemporary challenges and explores prospects in this field. Moreover, carbon nitrides, in particular, exhibit exceptional oxygen tolerance, underscoring their significance in radical polymerization processes and allowing their applications such as 3D printing, surface modification of coatings, and hydrogel engineering.

Epitaxial Growth of Surface Perforations on Parallel Cylinders in Terraced Films of Block Copolymer/Homopolymer Blends

Due to incommensurability between initial thickness and interdomain distance, thermal annealing inevitably produces relief surface terraces (islands and holes) of various morphologies in thin films of block copolymers. We have demonstrated three kinds of surface terraces in blend films: polygrain terraces with diffuse edges, polygrain terraces with step edges, and pseudo-monograin terraces with island coarsening. The three morphologies were obtained by three different thermal histories, respectively. The thermal histories were imposed on blend films, which were prepared by mixing a homopolystyrene (hPS, 6.1 kg/mol) with a weakly segregated, symmetry polystyrene-block poly(methyl methacrylate) (PS-b-PMMA, 42 kg/mol) followed by spin coating. At a given weight-fraction ratio of PS-b-PMMA/hPS = 75/25, the interior of the blend films forms parallel cylinders. Nevertheless, the surface of the blend films is always dominated by a skin layer of perforations, which epitaxially grow on top of parallel cylinders. By oxygen plasma etching at various time intervals to probe interior nanodomains, the epitaxial relationship between surface perforations and parallel cylinders has been identified by a scanning electron microscope.

Block Copolymer Nanopatterning for Nonsemiconductor Device Applications

Block copolymer (BCP) nanopatterning has emerged as a versatile nanoscale fabrication tool for semiconductor devices and other applications, because of its ability to organize well-defined, periodic nanostructures with a critical dimension of 5-100 nm. While the most promising application field of BCP nanopatterning has been semiconductor devices, the versatility of BCPs has also led to enormous interest from a broad spectrum of other application areas. In particular, the intrinsically low cost and straightforward processing of BCP nanopatterning have been widely recognized for their large-area parallel formation of dense nanoscale features, which clearly contrasts that of sophisticated processing steps of the typical photolithographic process, including EUV lithography. In this Review, we highlight the recent progress in the field of BCP nanopatterning for various nonsemiconductor applications. Notable examples relying on BCP nanopatterning, including nanocatalysts, sensors, optics, energy devices, membranes, surface modifications and other emerging applications, are summarized. We further discuss the current limitations of BCP nanopatterning and suggest future research directions to open up new potential application fields.

Si containing block copolymers quickly assemble into sub-6 nm domains

The directed self-assembly (DSA) of block copolymers (BCPs) is a potential patterning technology for sub-7 nm lithography.

From macromonomers to bottlebrush copolymers with sequence control: synthesis, properties, and applications

Bottlebrush polymers (BBPs) are a type of comb-like macromolecules with densely grafted polymeric sidechains attached to the polymer backbones, and many intriguing properties and applications have been demonstrated due to...

Sub-3-Nanometer Domain Spacings of Ultrahigh-χ Multiblock Copolymers with Pendant Ionic Groups

We investigated the temperature-dependent phase behavior and interaction parameter of polyethylene-based multiblock copolymers with pendant ionic groups. These step-growth polymers contain short polyester blocks with a single Li⁺SO₃^- group strictly alternating with polyethylene blocks of x-carbons (PESxLi, x = 12, 18, 23). At room temperature, these polymers exhibit layered morphologies with semicrystalline polyethylene blocks. Upon heating above the melting point (∼130 °C), PES18Li shows two order-to-order transitions involving Ia3̅d gyroid and hexagonal morphologies. For PES12Li, an order-to-disorder transition accompanies the melting of the polyethylene blocks. Notably, a Flory-Huggins interaction parameter was determined from the disordered morphologies of PES12Li using mean-field theory: χ(T) = 77.4/T + 2.95 (T in Kelvin) and χ(25 °C) ≈ 3.21. This ultrahigh χ indicates that the polar ionic and nonpolar polyethylene segments are highly incompatible and affords well-ordered morphologies even when the combined length of the alternating blocks is just 18-29 backbone atoms. This combination of ultrahigh χ and short multiblocks produces sub-3-nm domain spacings that facilitate the control of block copolymer self-assembly for various fields of study, including nanopatterning.

Self-Assembled Lamellar Films of Comb-Shaped Copolymers by Segregation between Hydrophobic Side Chains and the Main Chain with Hydrophilic Comonomers

Self-assembled lamellar films of poly(N-dodecyl acrylamide-stat-vinyl phosphonic acid) [p(DDA/VPA)] were formed via the segregation between the hydrophilic main chain and VPA and dodecyl side chains. p(DDA/VPA) copolymers were synthesized by free-radical copolymerization of DDA and VPA with VPA molar concentrations of 19% [p(DDA/VPA19)] and 64% [p(DDA/VPA64)]. Both copolymers exhibited a glass-transition temperature (T_g) and melting temperature for p(DDA/VPA19), but no crystalline or liquid-crystalline phase-transition temperatures, which suggests that both copolymers are amorphous. Thin films of the copolymers were prepared by spin coating, and the structure of the films was studied by X-ray diffraction (XRD) measurements. The as-cast films of the copolymers showed broad diffraction patterns, which suggested the formation of alkyl nanodomains similar to that observed in the pDDA homopolymers. On the other hand, the XRD patterns for both copolymer films showed a sharp Bragg diffraction in the low-q region after annealing at 60 °C. Furthermore, the p(DDA/VPA19) film showed first- and second-order Bragg diffractions with a ratio of 1:2. These XRD patterns suggest that the copolymer films form an ordered lamellar structure. We concluded that the main chain became more hydrophilic by the introduction of VPA, resulting in an increased segregation force relative to the hydrophobic dodecyl side chains, which induces the formation of lamellae. Moreover, doping a p(DDA/VPA64) film with imidazole increased the ordering and uniformity of the lamellar structures due to the increased segregation force by the formation of ion pairs in the hydrophilic comonomer. In their entirety, the results show that statistical copolymerization can be used as a new method to create self-assembled structures.

Local Orientation of Polystyrene at the Interface with Poly(methyl methacrylate) in Block Copolymer

The local conformation of polystyrene (PS) at the phase-separated lamellar interface with poly(methyl methacrylate) (PMMA) in their diblock copolymer (BCP) was examined by sum-frequency generation spectroscopy in conjunction with a full-atomistic molecular dynamics simulation. While PS phenyl groups of BCP were oriented in the interfacial region, they were random in the bulk. Such an interfacial orientation of phenyl groups was not clear for the corresponding blend of PS and PMMA. The PS backbone of BCP was in-plane oriented and folded near to the chemical junction point located in the interfacial region and the orientation became random at several nanometers distant. No evidence for the chain folding at the interface was found for the blend system.

Bicyclic Topology Transforms Self-Assembled Nanostructures in Block Copolymer Thin Films

Ongoing efforts in materials science have resulted in linear block copolymer systems that generate nanostructures via the phase separation of immiscible blocks; however, such systems are limited with regard to their domain miniaturization and lack of orientation control. We overcome these limitations through the bicyclic topological alteration of a block copolymer system. Grazing incidence X-ray scattering analysis of nanoscale polymer films revealed that bicyclic topologies achieve 51.3-72.8% reductions in domain spacing when compared against their linear analogue, which is more effective than the theoretical predictions for conventional cyclic topologies. Moreover, bicyclic topologies achieve unidirectional orientation and a morphological transformation between lamellar and cylindrical domains with high structural integrity. When the near-equivalent volume fraction between the blocks is considered, the formation of hexagonally packed cylindrical domains is particularly noteworthy. Bicyclic topological alteration is therefore a powerful strategy for developing advanced nanostructured materials for microelectronics, displays, and membranes.

Highly asymmetric lamellar nanostructures from nanoparticle-linear hybrid block copolymers

The highly asymmetric lamellar (A-LAM) nanostructure is one of the most important template geometries for block copolymer (BCP) lithography. However, A-LAM is unattainable from conventional BCPs, and there is no general molecular design strategy for A-LAM-forming BCP. Herein, a nanoparticle-linear hybrid BCP system is reported, which is designed based on the intramolecular crosslinking technique, as a remarkably effective platform to obtain the A-LAM morphology. The hybrid BCPs consisting of polystyrene single-chain nanoparticles and linear polylactide segments show a remarkable capability to form the A-LAM morphology in bulk, where a maximum width ratio of 4.1 between the two domains is obtained. This unusual phase behavior is attributed to the bulky and rigid characteristics of the nanoparticle block. Furthermore, the thin films of these hybrid BCPs show perpendicularly oriented A-LAM morphology on a chemically modified Si substrate, allowing promising application in the fabrication of asymmetric line-and-space nanopatterns.

High-Fidelity, Sub-5 nm Patterns from High-χ Block Copolymer Films with Vapor-Deposited Ultrathin, Cross-Linked Surface-Modification Layers

Despite their capability, sub-10 nm periodic nano-patterns formed by strongly segregating block copolymer (BCP) thin films cannot be easily oriented perpendicular to the substrate due to the huge surface energy differences of the constituent blocks. To produce perpendicular nano-patterns, the interfacial energies of both the substrate and free interfaces should be controlled precisely to induce non-preferential wetting. Unfortunately, high-performance surface modification layers are challenging to design, and different kinds of surface modification methods must be devised respectively for each neutral layer and top coat. Furthermore, conventional approaches, largely based on spin-coating processes, are highly prone to defect formation and may readily cause dewetting at sub-10 nm thickness. To date, these obstacles have hampered the development of high-fidelity, sub-5 nm BCP patterns. Herein, an all-vapor phase deposition approach initiated chemical vapor deposition is demonstrated to form 9-nm-thick, uniform neutral bottom layer and top coat with exquisite control of composition and thickness. These layers are employed in BCP films to produce perpendicular cylinders with a diameter of ≈4 nm that propagate throughout a BCP thickness of up to ≈60 nm, corresponding to five natural domain spacings of the BCP. Such a robust approach will serve as an advancement for the reliable generation of sub-10 nm nano-patterns.

Metallopolymer-block-oligosaccharide for sub-10 nm microphase separation

The novel high-χ BCPs comprising poly(vinyl ferrocene) and oligosaccharides formed hexagonal cylinder morphology with d values of ∼8 nm. Lamellar morphology with d values of ∼9 nm was also realized by mixing these polymers and glucose.

Block copolymers containing stable radical and fluorinated blocks with long-range ordered morphologies prepared by anionic polymerization

We report a facile synthetic approach to create stable radical block copolymers containing a secondary fluorinated block via anionic polymerization using a bulky, sterically hindered countercation composed of a sodium ion and di-benzo-18-crown-6 complex. The synthetic conditions described in this report allowed for controlled molecular weights and dispersity (<1.3) of both homopolymers: poly(2,2,6,6-tetramethyl-1-piperidinyloxy-methacrylate) (PTMA) and poly(2,2,2-trifluoroethyl methacrylate) (PTFEMA) as well as their block copolymers (PTMA-b-PTFEMA). The stable radical concentration of the polymers was determined by electron spin resonance (ESR) and showed radical content above 70%. An analysis of the microphase morphologies in PTMA-b-PTFEMA thin films via atomic force microscopy (AFM) and grazing incidence small angle X-ray scattering (GISAXS) showed clear evidence of long-range ordering of lamellar and cylindrical morphologies with 32 and 36 nm spacing, respectively. The long-range ordering of the morphologies was developed with the aid of two separate neutral layers: PTMA-ran-PTFEMA-ran-poly(hydroxyl ethyl methacrylate) (PHEMA) and poly(isobutyl methacrylate) (PiBMA)-ran-PTFEMA-ran-PHEMA, which helped us corroborate, along with the Zisman method, the surface energy estimation of PTMA to be 30.1 mJ/m2.

Dynamic Ordering in High-χ Block Copolymer Lamellae Based on Cross-Sectional Orientational Alignment

Further development of next-generation block copolymer (BCP) lithography processes is contingent on comprehensive studies of the ordering dynamics of high-χ BCPs that can form sub-10 nm features on thin films. However, quantitative analyses of the degree of ordering on the surface and cross sections of thin films have been difficult to execute. To tackle this challenge, we employ a perpendicular lamella-forming high-χ BCP, poly(polyhedral oligomeric silsesquixone-block-2,2,2-trifluoroethyl methacrylate) (PMAPOSS-b-PTFEMA), and reveal that the high-χ PMAPOSS-b-PTFEMA requires three times the activation energy (E_a) compared to that of poly(styrene-block-methyl methacrylate) (PS-b-PMMA) for defect annihilation, at E_a = 2600 ± 420 kJ mol^-1, and a transition from a fast ordering regime with a growth exponent of Φ = 0.30 at lower orientational order parameters (ψ₂ < 0.36) to a slow ordering regime with Φ < 0.05 at ψ₂ > 0.36, where well-aligned lamellae restrict defect annihilations to enthalpically unfavorable glide mechanisms that require BCP intermixing.

5 nm Ordered Structures Self-Assembled by C2 -Symmetric Hybrids with Polyhedral Oligomeric Silsesquioxane and Hexa-peri-Hexabenzocoronene

Hybrids consisting of polyhedral oligomeric silsesquioxane (POSS) and hexa-peri-hexabenzocoronene (HBC) with a dumbbell topology and C₂ symmetry were designed and synthesized. They self-assemble into 5 nm ordered structures. In particular, the increased steric effect with increasing POSS units stabilizes a square columnar phase (Col_squ ) which is important in nanotemplating. These hybrids containing discotic liquid crystal HBC and POSS units have an excellent etching contrast and present an approach to obtain 5 nm nanopatterns.

Chemically tailored high-χ block copolymers for perpendicular lamellae via thermal annealing

A chemically tailored high-χ block copolymer (BCP), polystyrene-block-poly[2-hydroxy-3-(2,2,2-trifluoroethylsulfanyl)propyl methacrylate] (PS-b-PHFMA), was designed to incorporate tailored surface affinities and chemical incompatibilities for engineering perpendicular lamellae using thermal annealing. PS-b-PHFMA was synthesized via the sequential anionic polymerization of styrene and glycidyl methacrylate and the post-polymerization functionalization of the glycidyl moieties with 2,2,2-trifluoroethanethiol. The bulk studies revealed lamellae with a minimum domain spacing of 9.6 nm and a large effective Flory-Huggins interaction parameter (χeff) of 0.191 at 25 °C. Furthermore, atomic force microscopy and scanning electron microscopy showed perpendicular lamellae of the PS-b-PHFMA prepared on thermally-annealed thin films. The introduction of hydrophobic trifluoroethyl moieties onto the hydrophilic glycidyl moieties successfully balanced the surface affinity of the PHFMA block relative to PS, while simultaneously increasing the strength of segregation. Thus, χeff of the chemically tailored BCP increased, and a perpendicular orientation was facilitated on the thin films using thermal annealing.

Synthesis of a Fluoromethacrylate Hydroxystyrene Block Copolymer Capable of Rapidly Forming Sub-5 nm Domains at Low Temperatures

A series of poly(pentadecafluorooctyl methacrylate)-block-polyhydroxystyrene (PPDFMA-b-PHS) block copolymers (BCPs) were synthesized via reversible addition-fragmentation chain-transfer polymerization and subsequent deprotection. Because of the high incompatibility between hydroxyl groups and fluoro groups, the interaction parameter (χ) of these BCPs, determined by temperature-resolved small-angle X-ray scattering (SAXS), was extremely high. The χ value of PPDFMA-b-PHS was 0.48 at 150 °C, 16× larger than the χ of polystyrene-block-poly(methyl methacrylate). The microphase behavior of PPDFMA-b-PHS with various volume fractions of PHS block was determined by SAXS, yielding ordered lamellar morphologies with different sizes of domain spacing (d), and further confirmed by transmission electron microscopy. The minimum d obtained was 9.8 nm annealed at a mild temperature for a short time (80 °C for 1 min) by SAXS analysis, indicating the width of each lamellar domains was <5 nm.

Downsizing feature of microphase-separated structures via intramolecular crosslinking of block copolymers

A novel strategy for downsizing the feature of microphase-separated structures was developed via the intramolecular crosslinking reaction of block copolymers (BCPs) without changing the molecular weight. A series of BCPs consisting of poly[styrene-st-(p-3-butenyl styrene)] and poly(rac-lactide) (SBS-LA) was subjected to Ru-catalyzed olefin metathesis under highly diluted conditions to produce intramolecularly crosslinked BCPs (SBS(cl)-LAs). Small-angle X-ray scattering measurement and transmission electron microscopy observation of the SBS(cl)-LAs revealed feature size reduction in lamellar (LAM) and hexagonally close-packed cylinder (HEX) structures in the bulk state, which was surely due to the restricted chain dimensions of the intramolecularly crosslinked SBS block. Notably, the degree of size reduction was controllable by varying the crosslink density, with a maximum decrease of 22% in the LAM spacing. In addition, we successfully observed the downsizing of the HEX structure in the thin film state using atomic force microscopy, indicating the applicability of the present methodology to next-generation lithography technology.

Thermal Approaches to Perpendicular Block Copolymer Microdomains in Thin Films: A Review and Appraisal

Block copolymer thin films are highly versatile and accessible materials capable of producing nanofeatures in the size regime of a few to hundreds of nanometers by a simple spin-coating-and-anneal process. Unfortunately, this simple protocol usually leads to parallel microdomains, which limits the applicability of such nanofeatures. A great deal of effort has been put into achieving perpendicular microdomains, but those that incorporate thermal annealing are arguably the most practical and reproducible in the lab and industry. This review discusses the recent ongoing efforts on various thermal approaches to achieving perpendicular microdomains in order to provide the readers with a toolbox to work with.

Diblock Polymer Brush (PHEAA- b-PFMA): Microphase Separation Behavior and Anti-Protein Adsorption Performance

In this paper, a series of amphiphilic diblock polymers of poly(hydroxyethylacrylamide)- b-poly(1H,1H-pentafluoropropyl methacrylate) (PHEAA- b-PFMA) were grafted from silicon wafer via surface-initiated atom transfer radical polymerization (SI-ATRP). Surface wettability and chemical compositions of the modified surfaces were characterized by contact angle goniometer and X-ray photoelectron spectroscopy (XPS) respectively. Molecular weight and polydispersity of each block were measured using gel permeation chromatography (GPC). The topography and the microphase separation behavior of PHEAA- b-PFMA surfaces were investigated by atomic force microscope (AFM). The results show that only when the grafting density (σ) and thickness of PHEAA brush were in the range of 0.9-1.3 (chain/nm²) and 6.6-15.1 nm, respectively, and the ratio of PFMA/PHEAA varied from 89/42 to 89/94, could the diblock copolymer phase separate into nanostructures. Further, the antiprotein adsorption performance of the modified surfaces against BSA, fibrinogen, and lysozyme was studied. The results indicated the modified surfaces could reduce the protein adsorption compared to the pristine silicon wafer. For Fibrinogen, the antiadsorption effect of PHEAA- b-PFMA-modified surfaces with microphase segregation was better than that of corresponding PHEAA modified surfaces. The results provide further evidence that surface composition and microphase segregation of fluorinated moieties of block copolymer brushes significantly impact protein adsorption behaviors.

Directed Self-Assembly of High χ Poly(styrene-b-(lactic acid-alt-glycolic acid)) Block Copolymers on Chemical Patterns via Thermal Annealing

We demonstrated the synthesis and directed self-assembly (DSA) of poly(styrene-b-(lactic acid-alt-glycolic acid)) (PS-b-PLGA). Lamellae-forming PS-b-PLGAs with a range of molecular weights were synthesized by ring-opening polymerization (ROP) of LGA (d,l-3-methyl-1,4-dioxane-2,5-dione) from hydroxy-terminated polystyrene (PS-OH) with stannous octoate as the catalyst and characterized by ¹H NMR spectroscopy, GPC, DSC, TGA, SAXS, and rheometry. The order-disorder transition temperatures (T_ODT) of four PS-b-PLGA block copolymers were determined by temperature sweep measurements and verified by variable-temperature SAXS, which were used to determine the temperature dependence of χ. The χ value of PS-b-PLGA is twice as large as that of poly(styrene-b-racemic lactide) (PS-b-PDLLA) at 150 °C, while the surface energies (γ) of PS and PLGA are nearly equal. Thin films of PS-b-PLGA were successfully directed to assemble on stripe chemical patterns with a range of pattern periods (L_S) upon thermal annealing. SEM analysis of the assembled films revealed that long-range ordered perpendicularly oriented lamellae were registered on chemical patterns with 2× density multiplication. These results qualify PS-b-PLGA as an attractive candidate for next-generation lithography with sub-10 nm resolution.

Recent Advances in RAFT Polymerization: Novel Initiation Mechanisms and Optoelectronic Applications

Reversible addition-fragmentation chain transfer (RAFT) is considered to be one of most famous reversible deactivation radical polymerization protocols. Benefiting from its living or controlled polymerization process, complex polymeric architectures with controlled molecular weight, low dispersity, as well as various functionality have been constructed, which could be applied in wide fields, including materials, biology, and electrology. Under the continuous research improvement, main achievements have focused on the development of new RAFT techniques, containing fancy initiation methods (e.g., photo, metal, enzyme, redox and acid), sulfur-free RAFT system and their applications in many fields. This review summarizes the current advances in major bright spot of novel RAFT techniques as well as their potential applications in the optoelectronic field, especially in the past a few years.

Self-Assembly of Hierarchical Structures Using Cyclotriphosphazene-Containing Poly(substituted methylene) Block Copolymers

The cyclotriphosphazene-substituted diazoacetate homopolymer (polyPNDA') (PNDA' = hexaphenoxy-substituted phosphazene-containing methylene) and a novel poly(substituted methylene) block copolymer, polyPNDA'-block-poly(hexyloxycarbonylmethylene) (polyPNDA'-b-polyHDA'), were synthesized, and the self-assembly behavior of these polymers was studied in detail. A hexagonally packed aggregated structure was observed in the self-assembled structure of polyPNDA', whereas a lamellar structure was observed in the microphase-separated nanoassembly of polyPNDA'-b-polyHDA'. These results indicate that a hierarchical structure composed of highly regular polyPNDA' nanoaggregates and the long-range microphase-separated polyPNDA' and polyHDA' domains had formed.

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.

Synthesis of POSS-functionalized liquid crystalline block copolymers via RAFT polymerization for stabilizing blue phase helical soft superstructures

A study of the phase transition behaviors of blue phase liquid crystals containing different amounts of POSS-functionalized LC BCPs.

Molecular Tailoring of Poly(styrene-b-methyl methacrylate) Block Copolymer Toward Perpendicularly Oriented Nanodomains with Sub-10 nm Features

We demonstrate a novel approach for fabricating vertically orientated, sub-10 nm, block copolymer (BCP) nanodomains on a substrate via molecular tailoring of poly(styrene-b-methyl methacrylate) (PS-b-PMMA) BCP, one of the most widely used BCPs for nanopatterning. The idea is to incorporate a short middle block of self-attracting poly(methacrylic acid) (PMAA) between the PS and PMMA blocks, where the PMAA middle block promotes phase separation between PS and PMMA, while maintaining the domain orientation perpendicular to the substrate. The designed PS-b-PMAA-b-PMMA triblock copolymers, which were synthesized via well-controlled anionic polymerization, exhibited order-disorder transition temperatures higher than that of pristine PS-b-PMMA BCPs, indicating the promotion of phase separation by the middle PMAA block. For PS-b-PMAA-b-PMMA BCPs with total molecular weights of 21 and 18 kg/mol, the domain spacing corresponds to 19.3 and 16.7 nm, respectively, allowing us to fabricate sub-10 nm nanodomain structures. More importantly, it was demonstrated that the PMAA middle block, which has a higher surface energy than PS and PMMA, does not significantly alter lateral concentration fluctuations, which are responsible for phase-separation in the lateral direction. This enabled the vertical orientation of microdomains with sub-10 nm feature size on a PS-r-PMMA neutral surface without an additional neutral top layer. We anticipate that this approach provides an important platform for next-generation lithography and nanopatterning applications that require sub-10 nm features over large areas with simple process and reduced cost.