PS Block Research Articles

Tunable Assembly of Block Copolymer Tethered Particle Brushes by Surface-Initiated Atom Transfer Radical Polymerization.

A strategy to synthesize SiO2-g-PMMA/PMMA-b-PS mono- and bimodal block copolymer particle brushes by surface-initiated atom transfer radical polymerization (SI-ATRP) from silica particles is presented. First, PMMA blocks were prepared by normal ATRP with controlled degree of polymerizations and grafting density. In a second step, the PS block was synthesized through a chain extension using low parts per million of Cu catalyst. Variation of the SiO2-g-PMMA-Br macroinitiator concentration had a pronounced effect on the modality of the chain extension product. In the limit of small concentration, partial termination resulted in bimodal brush architectures, while more uniform brush architectures were observed with increasing concentration of macroinitiator. Brush nanoparticles with bimodal architectures assembled into string-like aggregates that bore a resemblance to structures found in systems comprised of sparse (homopolymer) brush particles. The unexpected effect of modality on structure formation points to opportunities in controlling microstructures in brush particle materials.

Stabilization of complex morphologies in highly disperse AB diblock copolymers

Block copolymers have the unique property to self-assemble into ordered microstructures with well-defined periodicity. Among the various attainable microdomain morphologies, complex morphologies with inherent structural connectivity are highly desirable. While such structures are difficult to obtain in monodisperse block copolymers, they may be stabilized by increasing block dispersity. In this study, we prepare poly (styrene-b-methyl methacrylate) (PS-b-PMMA) diblock copolymers where dispersity of both PS and PMMA blocks are varied independently. Morphology examination of the diblocks reveals that at fixed block composition, dispersity dictated phase transition is observed. In particular, in the case where dispersity of both blocks are high, the polymers are found to exhibit perforated lamellae and disordered bicontinuous morphologies. Dissipative particle dynamics (DPD) simulations are also carried out to confirm the stability of the observed morphologies. These results show that control of block dispersity can effectively stabilize energetically disfavored complex morphologies in block copolymers.

Nanostructure- and Orientation-Controlled Resistive Memory Behaviors of Carbohydrate-block-Polystyrene with Different Molecular Weights via Solvent Annealing.

We report the resistive electrical memory characteristics controlled by the self-assembled nanostructures of maltoheptaose-block-polystyrene (MH-b-PS) block copolymers, where the MH and PS blocks provide the charge-trapping and the insulating tunneling layer, respectively. A simple solvent annealing process, with various annealing conditions, were introduced for MH-b-PS thin films to achieve disordered, orientated cylinders and ordered-packed spheres morphologies. More details about the self-assembled MH-b-PS nanostructures, coupled with different volume fractions between MH and PS blocks, were investigated using atomic force microscopy and grazing-incidence small-angle X-ray scattering analyses. Moreover, various electrical memory behaviors including nonvolatile write-once-read-many-times (WORM) and Flash, and volatile dynamic-random-access-memory (DRAM) could be obtained by the same material (MH-b-PS3k). This study establishes a detailed relationship between the nanostructure of the MH-b-PS-based block copolymers and their memory behavior of the resistive memory devices.

Confined Crystallization of Spin‐Crossover Nanoparticles in Block‐Copolymer Micelles

AbstractNanoparticles of the spin‐crossover coordination polymer [FeL(bipy)]n were synthesized by confined crystallization within the core of polystyrene‐block‐poly(4‐vinylpyridine) (PS‐b‐P4VP) diblock copolymer micelles. The 4VP units in the micellar core act as coordination sites for the Fe complex. In the bulk material, the spin‐crossover nanoparticles in the core are well isolated from each other allowing thermal treatment without disintegration of their structure. During annealing above the glass transition temperature of the PS block, the transition temperature is shifted gradually to higher temperatures from the as‐synthesized product (T1/2↓=163 K and T1/2↑=170 K) to the annealed product (T1/2↓=203 K and T1/2↑=217 K) along with an increase in hysteresis width from 6 K to 14 K. Thus, the spin‐crossover properties can be shifted towards the properties of the related bulk material. The stability of the nanocomposite allows further processing, such as electrospinning from solution.

Confined Crystallization of Spin-Crossover Nanoparticles in Block-Copolymer Micelles.

Nanoparticles of the spin‐crossover coordination polymer [FeL(bipy)]n were synthesized by confined crystallization within the core of polystyrene‐block‐poly(4‐vinylpyridine) (PS‐b‐P4VP) diblock copolymer micelles. The 4VP units in the micellar core act as coordination sites for the Fe complex. In the bulk material, the spin‐crossover nanoparticles in the core are well isolated from each other allowing thermal treatment without disintegration of their structure. During annealing above the glass transition temperature of the PS block, the transition temperature is shifted gradually to higher temperatures from the as‐synthesized product (T 1/2↓=163 K and T 1/2↑=170 K) to the annealed product (T 1/2↓=203 K and T 1/2↑=217 K) along with an increase in hysteresis width from 6 K to 14 K. Thus, the spin‐crossover properties can be shifted towards the properties of the related bulk material. The stability of the nanocomposite allows further processing, such as electrospinning from solution.

Key Factors for Template‐Oriented Porous Titania Synthesis: Solvents and Catalysts

AbstractVarious types of titania nanostructures are synthesized with a polymer‐templated sol–gel method based on the amphiphilic diblock copolymer polystyrene‐b‐polyethylene oxide (PS‐b‐PEO) in combination with selective incorporation of the titania precursor titanium tetraisopropoxide. Custom tailoring of different types of titania morphologies is realized by changing the phase separation behavior of the PS‐b‐PEO template. Particularly, application of solvents from different categories is found to have a major impact upon the phase separation behavior of PS‐b‐PEO and the final titania film morphology. The amount of available hydrochloric acid catalyst during the gelation process is seen as an additional key factor to induce controllable morphological changes. Scanning electron microscopy and grazing incidence small angle X‐ray scattering measurements are carried out to study the surface and inner structure of porous titania films. Systematic analysis and comparison of different characterization results allow attributing the following three factors to the respectively formed titania nanostructure: the surface energy between PS blocks and surrounding solvent, the aggregation behavior of the titania nanoparticles, and the block‐specific selectivity of the used solvent. For all synthesized titania thin films, an anatase‐type crystallization is confirmed through X‐ray powder diffraction.

Micellization of Polystyrene-b-Polyglycidol in Dioxane and Water/Dioxane Solutions.

In this work, the self-assembly of a series of amphiphilic polystyrene-b-polyglycidol (PS-b-PGL) diblock copolymers in dioxane and dioxane/water mixtures is presented. The PS-b-PGL have an average degree of polymerization (DP) of PS block equal to 29 units and varied degrees of polymerization for the glycidol segments with DPs of 13, 42, 69 and 117. In dioxane, amphiphilic diblock copolymers form micelles with the hydrophilic PGL placed in the core. Critical micelle concentration (CMC) was determined based on the intensity of scattered light vs. concentration. The micelle size was measured by dynamic light scattering and transmission electron microscopy. Also, the behaviour of the copolymer was studied in water/dioxane solutions by following the changes of scattered light intensity with the addition of water to the system. Critical water content (CWC) of the studied systems decreased as the initial PS-b-PGL concentration in dioxane increased. This process was accompanied by a decrease in the size of aggregate formed. For a given initial copolymer concentration, the size of copolymer aggregates decreased linearly with increasing the length of the PGL block

Self-assembly of amphiphilic poly(styrene-b-acrylic acid) on magnetic latex particles and their application as a reusable scale inhibitor.

The deposition of scale on membranes or container and pipe surfaces (clogging the system) is a costly issue in water treatment processes or water-cooling systems. To effectively cope with this issue, magnetic polymeric nanoparticles (MPNPs) have been developed and applied as promising scale inhibitors, due to their high surface-area-to-volume ratio, surface modifiability, and magnetic separation ability. Carboxylated MPNPs, having a monodisperse size distribution (236 ± 26 nm) with a high magnetic content of 70 wt% and superparamagnetic properties, were fabricated by using a 2-step process: (i) formation of clusters of hydrophobic magnetic nanoparticles stabilized by oleic acid (OA-MNPs), and (ii) self-assembly of the amphiphilic block copolymer of poly(styrene27-b-acrylic acid120) (PS27-b-PAA120) onto the cluster surfaces. With application of ultrasonication to 12.0 wt% OA-MNPs, a three-dimensional network was formed by particle–particle interactions, suppressing coalescence, and then creating stable magnetic clusters. The cluster surfaces were then adsorbed by amphiphilic PS27-b-PAA120via the attractive force between hydrophobic PS blocks. This moves longer hydrophilic PAA blocks containing carboxylic acid groups into the water phase. The formulated MPNPs acted as a nanosorbent for calcium ion (Ca2+) removal with a removal efficiency of 92%. The MPNPs can be effectively reused for up to 4 cycles. Based on the electrostatic interactions between the negatively-charged polymer and the hydrated Ca2+, the resulting precipitation leads to the prevention of calcium carbonate scale formation. Insights into this mechanism open up a new perspective for magnetic-material applications as effective antiscalants.

PSI-28 Effect of supplementation with low-moisture, sugarcane molasses-based block on intake and ruminal volatile fatty acid profile on steers fed low quality forage

Abstract We evaluated the effects of supplementation of molasses based on low moisture molasses (LMB) on steers fed low quality forage in DM intake and ruminal VFA. Six rumen cannulated Nellore steers (23 months, 350 ± 10 kg) were distributed in a 3 × 3 double Latin square design. The treatments were composed of Brachiaria brizantha cv. Marandu ad libtum as an exclusive source of bulks (93.65% DM, 3.97% CP and 81.76% NDF) and supplements: complete mineral blend with urea [UR, (urea, salt, mineral-vitamin premix)], a commercial protein supplement [PS, (corn grain, soybean meal, urea, salt, and mineral- vitamin premix)] or protein block based on low-moisture cooked sugarcane molasses [LMB, (cane molasses, cottonseed meal, soybean oil, urea, salt and mineral-vitamin premix)]. Before subsequent feeding, samples of orts were collected to monitor the daily intake. After 14-d adaptation period, rumen fluid samples were collected in each experimental period at 0, 2, 4, 6, 8, 10, 12 and 14 h after feeding, to evaluate concentrations of VFA, which was determined by gas chromatography. The data were analyzed using Software R, with measures repeated in time for VFA and having as fixed effect the treatments and as animal random effect, period, Latin square and error. The intake of hay (P = 0.024), total DM (g/day, P = 0.001), NDF (P = 0.027) and supplement (P < 0.001) was higher for animals supplemented with PS. The total VFA and acetate ratio were not affected by the treatment (P > 0.05). The propionate ratio was higher for LMB (P = 0.016). The butyrate ratio (P = 0.005), valerate (P = 0.010) and A:P ratio (P = 0.017) was higher when the animals were supplemented with PS. The results indicate that the use of LMB improves propionate ratio and decrease the acetate:propionate ratio for steers fed low quality forage.

Dual Nanopatterns Consisting of Both Nanodots and Nanoholes on a Single Substrate

Block copolymers (BCPs) with various nanostructures such as spheres, cylinders, gyroid, and lamellae, have received great attention for their application in nanolithography through nanopattern transfer to substrates. However, the fabrication of diverse geometries, shapes and sizes of nanostructure on a single substrate at the desired position could not be achieved because the nanostructure based on BCPs is mainly determined by the volume fraction of one block. Here, we synthesize polystyrene-hv-poly(methyl methacrylate) copolymer (PS-hv-PMMA), which contains a photocleavable linker at the junction point between PS and PMMA blocks. After vertically oriented PMMA cylindrical nanodomains in a thin film on a substrate were obtained, dual nanopatterns composed of high-density array of nanodots and nanoholes were successfully fabricated at the desired area on a single substrate using selective irradiation with a mask. The dual nanopatterns could be used to prepare metal (or metal oxide) nanostructure arrays consisting of both nanodots and nanoholes, which are utilized for smart sensors capable of simultaneously detecting two independent molecules on nanodots and nanoholes.

Iodine‐transfer polymerization and CuAAC “click” chemistry: A versatile approach toward poly(vinylidene fluoride)‐based amphiphilic triblock terpolymers

ABSTRACTThis study presents the synthesis and properties of linear PVDF‐based amphiphilic triblock terpolymers with PS and PEO, [PVDF‐b‐PS‐b‐PEO], by adopting a procedure that involves: (a) iodine‐transfer polymerization (ITP) of VDF with 1‐iodoperfluorohexane (C6F13I) serving as chain‐transfer agent (CTA) to afford C6F13‐PVDF‐I, (b) ITP of styrene with the C6F13‐PVDF‐I macromolecular‐CTA to obtain C6F13‐PVDF‐b‐PS‐I diblock copolymer, (c) end‐group exchange from iodo‐ to azido‐group by nucleophilic substitution reaction with NaN3, and (d) copper‐catalyzed azide‐alkyne cycloaddition (CuAAC) with alkyne‐terminated PEO to achieve C6F13‐PVDF‐b‐PS‐b‐PEO triblock terpolymers. The 1H and 19F NMR spectroscopy confirmed the presence of all blocks, while gel permeation chromatography traces showed the living nature of ITP technique. The self‐assembly of these terpolymers was investigated in films (atomic force microscopy and DSC), as well as in aqueous and organic solvents (DLS). The analysis of crystalline phases based on the FTIR spectroscopy indicated the conversion of PVDF α‐phase into α + β‐phases and β + γ‐phases upon the incorporation of PS and PEO blocks, respectively. The synthesized amphiphilic copolymers were evaluated (fluorescence spectroscopy) as carriers of small hydrophobic molecules in water. © 2019 Wiley Periodicals, Inc. J. Polym. Sci. 2020, 58, 163–171

Aggregation Behavior of the Blends of Homo-PS and PS-b-PEO-b-PS at the Air/Water Interface.

Aggregation behaviors of the blended Langmuir monolayers of a homopolymer polystyrene (h-PS) and a triblock copolymer polystyrene-b-poly(ethylene oxide)-b-polystyrene (PS-b-PEO-b-PS) were studied by the Langmuir film balance technique, and the morphologies of their Langmuir-Blodgett (LB) films were studied by atomic force microscopy. The isotherms of the h-PS/PS-b-PEO-b-PS blends shift to small areas with the increase of h-PS content, and a pseudoplateau appears as h-PS content is below 60 wt %. It is worth noting that the blended isotherms appear at the left of their corresponding ideal ones, which means that the blended monolayers are a little more condensed due to attractive interactions between the two components. Hysteresis phenomena exist in all of the blended monolayers, and the higher the PS-b-PEO-b-PS content, the larger the hysteresis degree becomes because of the stronger looped-PEO entanglements. All the blended LB films of h-PS and PS-b-PEO-b-PS prepared under low pressure exhibit the mixed structures of small and large isolated circular aggregates. The small aggregates are the copolymer micelle cores and the large ones are attributed to coalescence of the local h-PS chains and some PS blocks. Upon further compression, the aggregates in the blended LB films become a little denser as h-PS content is below 60 wt %, whereas those become totally close-packed with decreased size as h-PS content is 80 wt %.

The Location-influenced Fluorescence of AIEgens in the Microphase-separated Structures

The fluorescent probe techniques have been widely applied. When the fluorescence probes are selectively located in nano-structures, the fluorescence properties are highly influenced by the environment. Here, we systematically studied the location-influenced fluorescence of AIEgens in the microphase-separated structures. The AIEgen tetraphenylethene (TPE) was doped into polystyrene-b-polyisoprene (PS-{tib}-PI). TPE was selectively located in the PS nanodomains. The TPE fluorenscence was affected by the structural relaxation of PS when investigated in a wide range of temperatures, including the glass transiton and secondary transiton. When TPE groups were selectively located in the PI nanodomains, the fluorenscence was affected by the glass transitons of PI and PS blocks. Amphiphilic TPE derivative was located at the interface of the assembly. The fluorescence emission was influenced by the main transition and secondary transiton of PS blocks, as well as the main transition of PI blocks. These results would give new understanding of the interrelation between fluorescence probes and the nanostructures.

The Impact of Selectively Plasticized Poly (ethylene oxide) (PEO) Block in Nanostructured Polystyrene−PEO−Polystyrene Triblock Copolymer Electrolytes

All polymer electrolytes, including block polymer (BP) electrolytes exhibit low ionic conductivity compared to liquid electrolytes. For homopolymer electrolytes, the ionic conductivity can be increased by incorporating plasticizer into the polymer network. However, the subsequent weakened mechanical structure of the network precludes its use in many practical applications. In this work, we selectively plasticize the PEO block in a polystyrene PS-PEO-PS triblock copolymer electrolyte using a PEO-like plasticizer: tetraethylene glycol dimethyl ether (TEGDME). Unlike its homopolymer (PEO) electrolyte counterpart, the mechanical properties of the PS-PEO-PS triblock copolymer electrolyte are not drastically degraded by this plasticizer because it is immiscible in the nonpolar PS block domains. Polymer electrolyte membranes were cast from lithium trifluoromethanesulfonate (LiTFS) solutions with the corresponding polymers. The molar ratio of ethylene oxide to Li+ is 16 for all electrolytes (nEO:nLi = 16:1). The ionic conductivity of the PS-PEO-PS electrolyte at 80 °C is about one order of magnitude lower than that of the homopolymer (PEO) counterpart at the same temperature. However, the shear modulus (G’) of the PS-PEO-PS electrolyte is about three orders of magnitude higher than the homopolymer, indicating the mechanical properties of the copolymer electrolyte is primarily dominated by the PS phase. The addition of TEGDME plasticizer to the PEO homopolymer electrolyte resulted in a ~10% increase in conductivity. The addition of same amount of TEGDME to the PS-PEO-PS electrolyte resulted in ~100% increase in conductivity. Compared to the dry electrolyte counterpart, the low isothermal frequency (ω = 0.1 rad/s) elastic modulus, G’ of the TEGDME plastized PS-PEO-PS was reduced to half at 80 °C (on the order of 106 Pa). Surprisingly, G’ of the plastized membrane surpassed its dry PS-PEO-PS counterpart at higher frequency values (17 < ω < 100 rad/s). This counter intuitive result is further explored using: 1) Fourier-transform infrared spectroscopy (FTIR) to elucidate the salt solvation and coordination to ether oxygens, and 2) small angle X-ray scattering (SAXS) to decipher the domain spacing of the adjacent copolymer blocks. Acknowledgment This work is supported by Dr. Imre Gyuk, Manager, Energy Storage Program, Office of Electricity Delivery and Reliability, Department of Energy. CC acknowldge partial financial support by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division.

Structural hierarchy in blends of amphiphilic block copolymers self-assembled at the air-water interface

We present a concurrent self-assembly strategy for patterning hierarchical polymeric surface features by depositing variable-composition blends of polystyrene-block-poly(ethylene oxide) (PS-b-PEO) and polybutadiene-block-poly(ethylene oxide) (PB-b-PEO) block copolymers at the air-water interface. Hierarchical strand networks of hydrophobic PS/PB blocks anchored via PEO blocks to the water surface, with an internal phase-separation structure consisting of periodic domains of PS blocks surrounded and connected by a matrix of PB blocks, are generated by the interplay of interfacial amphiphilic block copolymer aggregation and polymer/polymer phase separation. In contrast to the cylinder-in-strand structures previously formed by our group in which interfacial microphase separation between PS and PB blocks was constrained by chemical connectivity between the blocks, in the current system phase separation between PS and PB is not constrained by chemical connectivity and yet is confined laterally within surface features at the air-water interface. Investigations of multi-component polymer systems with different connectivities constraining repulsive and attractive interactions provides routes to new hierarchical surface patterns for a variety of applications, including photolithography masks, display technology, surface-guided cell growth and tissue engineering.

Mixed morphology in low molar mass fluorinated block copolymers

New low molar mass (Mn ~ 20 kg mol−1) polystyrene-b-poly(methyl methacrylate-co-perfluorohexylethyl acrylate) (PS-b-P(MMA-co-FA)) block copolymers were synthesized all consisting of ~70 mol% PS block and ~30 mol% P(MMA-co-FA) block. The amount of FA counits in the latter block was increased (0.5, 1, 3 and 4 mol%) in order to enhance the incompatibility between the two blocks and to form different self-assembled nanostructures. The block copolymers were thermally annealed by Rapid Thermal Processing (RTP) over wide ranges of temperatures and times. Complementary SEM and AFM analyses evidenced that the introduction of FA counits above a critical content (~2 mol%) drove a self-assembly process through mixed morphologies. These were formed at a distance from the polymer–air interface and consisted of perpendicular cylinders of P(MMA-co-FA) in a PS matrix laying at the substrate– polymer interface, and surmounted PS stripes and PS dots. Modification by low amounts of FA produced block copolymer samples that self-assembled in new, mixed nanostructures, even though they possessed much lower molar masses than those of analogous well established PS-b-PMMA block copolymers.

Orientation control of high-χ triblock copolymer for sub-10 nm patterning using fluorine-containing polymeric additives

Directed self-assembly (DSA) of block copolymers (BCPs) is one of the most promising techniques to tackle the ever-increasing demand for sublithographic features in semiconductor industries. BCPs with high Flory–Huggins parameter (χ) are of particular interest due to their ability to self-assemble at the length scale of sub-10 nm. However, such high-χ BCPs typically have imbalanced surface energies between respective blocks, making it a challenge to achieve desired perpendicular orientation. To address this challenge, we mixed a fluorine-containing polymeric additive with poly(2-vinylpyridine)-<italic>block</italic>-polystyrene-<italic>block</italic>-poly(2-vinylpyridine) (P2VP-<italic>b</italic>-PS-<italic>b</italic>-P2VP) and successfully controlled the orientation of the high-χ triblock copolymer. The additive selectively mixes with P2VP block through hydrogen bonding and can reduce the dissimilarity of surface energies between PS and P2VP blocks. After optimizing additive dose and annealing conditions, desired perpendicular orientation formed upon simple thermal annealing. We further demonstrated DSA of this material system with five times density multiplication and a half-pitch as small as 8.5 nm. This material system is also amenable to sequential infiltration synthesis treatment to selectively grow metal oxide in P2VP domains, which can facilitate the subsequent pattern transfer. We believe that this integration-friendly DSA platform using simple thermal annealing holds the great potential for sub-10 nm nanopatterning applications.

A Self‐Assembly Process for the Immobilization of N‐Modified Au Nanoparticles in Ordered Mesoporous Carbon with Large Pores

AbstractA self‐assembly approach has been developed for the immobilization of nitrogen‐modified gold nanoparticles in an ordered mesoporous carbon matrix with large pores. Self‐assembly of the polystyrene‐block‐poly(4‐vinylpyridine) (PS‐b‐P4VP) diblock copolymer template coordinated with gold ions and a low‐polymerized phenolic resin leads to a face‐centered cubic mesostructure with F mm symmetry. Characterization with X‐ray photoelectron spectroscopy and transmission electron microscopy shows that after pyrolysis at 600 °C, monodispersed N‐modified gold nanoparticles approximately 4 nm in size are encapsulated in the ordered mesoporous carbon matrix with open and large pores. The aggregation of Au nanocatalysts into large particles is inhibited due to the coordination between gold and pyridine. The pore size can be tuned from 6 to 12 nm by changing the molecular weight of the PS block. The N‐modified gold catalyst is active in converting benzyl alcohol to benzoic acid using O2 as a green oxidant.

Controllable Self-Assembly of Amphiphilic Tadpole-Shaped Polymer Single-Chain Nanoparticles Prepared through Intrachain Photo-cross-linking.

We report the use of intramolecular cross-linking chemistry as a tool to control the self-assembly of amphiphilic diblock copolymers (di-BCPs). Two amphiphilic di-BCPs of poly( N, N'-dimethylacrylamide)- block-polystyrene (PDMA- b-PS) with photo-cross-linkable cinnamoyl groups in either hydrophobic or hydrophilic blocks were prepared using reversible addition-fragmentation chain transfer polymerization. Intramolecular photo-cross-linking of cinnamoyl groups led to the formation of tadpole-shaped polymer single-chain nanoparticles (SCNPs) consisting of a self-collapsed block as the "head" and an un-cross-linked block as the "tail". When intramolecular photo-cross-linking was carried out in hydrophobic PS blocks, a clear morphological transition from branched cylindrical micelles (for the linear di-BCP) to completely spherical micelles at a dimerization degree of ∼63% was observed. A pattern of morphological transitions from cylindrical micelles to spherical micelles is observed through stepwise downsizing the length of cylindrical micelles when increasing the self-collapse degree of PS blocks, whereas, in case of photo-cross-linking carried out in hydrophilic PDMA blocks, the size of micelles showed a dramatic increase due to the shift of hydrophobic-to-hydrophilic balance. When the cross-linking degree of PDMA blocks reached >60%, tadpole-shaped SCNPs assembled into nonconventional aggregates with a nonsmooth surface. Our results illustrate the impact of chain topologies on the self-assembly outcomes of amphiphilic di-BCPs, which likely opens a door to control the micellar morphologies from just one parent linear di-BCP, rather than resynthesizing BPCs with different volume fractions of the two blocks.

Study of the perpendicular self-assembly of a novel high-χ block copolymer without any neutral layer on a silicon substrate.

A novel type of high-χ block copolymer, polystyrene-block-polycarbonate (PS-b-PC), which contains an active –NH– group on the polymer backbone between the PS block and the PC block, has been successfully synthesized. Vertical micro-phase separation can be successfully achieved on Si substrates with neutral-layer-free materials with a pitch of 16.8 nm. Water contact angle experiments indicate that PS and PC have approximate surface energy values on Si substrates. A hydrogen bond mechanism has been proposed for the formation of a periodic and lamella-forming phase separation structure, with the domains oriented perpendicular to the substrate. A combination of both theory and experimental verification proves that the hydrogen bonding plays a dominant role as a real driving force to promote vertical micro-phase separation in the absence of a neutral layer. Subsequently, the study of a novel block copolymer on four different types of substrate without any neutral layer further confirms that the newly synthesized material enables greater flexibility and potential applications for the fabrication of various nanostructures and functional electronic devices in a simple, cost-effective and efficient way, which is of considerable importance to contemporary and emerging technology applications.