Block Copolymer Blends Research Articles

Confinement effects on the miscibility of block copolymer blends.

Thin films of long and short symmetric AB diblock copolymers are examined using self-consistent field theory (SCFT). We focus on hard confining walls with a preference for the A component, such that the lamellar domains orient parallel to the film with an even number ν of monolayers. For neat melts, confinement causes the lamellar period, D, to deviate from its bulk value, Db, in order to be commensurate with the film thickness, i.e., L = νD/2. For blends, however, the melt also has the option of macrophase separating into ν(l) large and ν((s)) small monolayers so as to provide a better fit, where L = ν(l)D(l)/2 + ν(s)D((s))/2. In addition to performing full SCFT calculations of the entire film, we develop a semi-analytical calculation for the coexistence of thick and thin monolayers that helps explain the complicated interplay between miscibility and commensurability.

Toward Cell Selective Surfaces: Cell Adhesion and Proliferation on Breath Figures with Antifouling Surface Chemistry.

We report the preparation of microporous functional polymer surfaces that have been proven to be selective surfaces toward eukaryotic cells while maintaining antifouling properties against bacteria. The fabrication of functional porous films has been carried out by the breath figures approach that allowed us to create porous interfaces with either poly(ethylene glycol) methyl ether methacrylate (PEGMA) or 2,3,4,5,6-pentafluorostyrene (5FS). For this purpose, blends of block copolymers in a polystyrene homopolymer matrix have been employed. In contrast to the case of single functional polymer, using blends enables us to vary the chemical distribution of the functional groups inside and outside the formed pores. In particular, fluorinated groups were positioned at the edges while the hydrophilic PEGMA groups were selectively located inside the pores, as demonstrated by TOF-SIMS. More interestingly, studies of cell adhesion, growth, and proliferation on these surfaces confirmed that PEGMA functionalized interfaces are excellent candidates to selectively allow cell growth and proliferation while maintaining antifouling properties.

Self-organization of homopolymer brush- and mixed homopolymer brush-grafted silica nanoparticles in block copolymers and polymer blends

In this report, hierarchical self-organization of poly(tert-butyl acrylate) (PtBA) brush- and mixed PtBA/polystyrene (PS) brush-grafted silica nanoparticles (NPs) in PtBA-b-PS block copolymer and PtBA/PS polymer blend matrices having different molecular weights was investigated using transmission electron microscopy (TEM). Driven by the entropic interactions between the brushes and the polymer matrices (i.e., wet- and dry-brush effects), various morphologies were observed. First, PtBA brush-grafted 67 nm silica NPs could induce an onion-like structure in a low molecular weight block copolymer matrix because of the wet-brush effect, low particle curvature, and low bending rigidity of the block copolymer lamellae. On the contrary, PtBA brush-grafted 23 nm silica NPs could not induce the onion-like structure, primarily owing to the high particle curvature and high bending penalty of the block copolymer lamellae. Second, the attempt to use ordered block copolymer lamellae to direct microphase separation of mixed homopolymer brushes with a goal of achieving ordered nanopatterns was unsuccessful, likely because the mixed PtBA/PS brushes on NPs underwent microphase separation prior to the ordering of block copolymers during the solution-casting process. Third, in polymer blends, the wet- and dry-brush entropic effects played an important role. In the wet-brush regime, the hairy NPs were uniformly distributed in the preferred polymer phase. In the dry-brush regime, the hairy NPs were driven to the interfaces of immiscible PtBA/PS domains. The knowledge gained on hierarchical self-organization of homopolymer brush- and mixed homopolymer brush-grafted NPs in block copolymer and polymer blend matrices will help us design better polymer nanocomposites with precisely controlled locations of NPs.

Asymmetric block copolymer membranes with ultrahigh porosity and hierarchical pore structure by plain solvent evaporation.

Membranes with a hierarchical porous structure could be manufactured from a block copolymer blend by pure solvent evaporation. Uniform pores in a 30 nm thin skin layer supported by a macroporous structure were formed. This new process is attractive for membrane production because of its simplicity and the lack of liquid waste.

Topology and Shape Control for Assemblies of Block Copolymer Blends in Solution

We study binary blends of asymmetric diblock copolymers (AB/AC) in selective solvents with a mesoscale model. We investigate the morphological transitions induced by the concentration of the AC block copolymer and the difference in molecular weight between the AB and AC copolymers, when segments B and C exhibit hydrogen-bonding interactions. To the best of our knowledge, this is the first work modeling mixtures of block copolymers with large differences in molecular weight. The coassembly mechanism localizes the AC molecules at the interface of A and B domains and induces the swelling of the B-rich domains. The coil size of the large molecular weight block copolymer depends only on the concentration of the short block copolymer (AC or AB), regardless of the B–C interactions. However, the B–C interactions control the morphological transitions that occur in these blends.

Effect of the Degree of Hydrogen Bonding on Asymmetric Lamellar Microdomains in Binary Block Copolymer Blends

ADVERTISEMENT RETURN TO ISSUEPREVNoteNEXTEffect of the Degree of Hydrogen Bonding on Asymmetric Lamellar Microdomains in Binary Block Copolymer BlendsJongheon KwakJongheon KwakNational Creative Research Initiative Center for Smart Block Copolymers, Department of Chemical Engineering, Pohang University of Science and Technology, Pohang, Kyungbuk 790-784, Republic of KoreaMore by Jongheon Kwak, Sung Hyun HanSung Hyun HanNational Creative Research Initiative Center for Smart Block Copolymers, Department of Chemical Engineering, Pohang University of Science and Technology, Pohang, Kyungbuk 790-784, Republic of KoreaMore by Sung Hyun Han, Hong Chul MoonHong Chul MoonNational Creative Research Initiative Center for Smart Block Copolymers, Department of Chemical Engineering, Pohang University of Science and Technology, Pohang, Kyungbuk 790-784, Republic of KoreaMore by Hong Chul Moon, Jin Kon Kim*Jin Kon KimNational Creative Research Initiative Center for Smart Block Copolymers, Department of Chemical Engineering, Pohang University of Science and Technology, Pohang, Kyungbuk 790-784, Republic of Korea*E-mail [email protected] (J.K.K.).More by Jin Kon Kim, Victor PryamitsynVictor PryamitsynDepartment of Chemical Engineering, University of Texas at Austin, Austin, Texas 78712, United StatesMore by Victor Pryamitsyn, and Venkat GanesanVenkat GanesanDepartment of Chemical Engineering, University of Texas at Austin, Austin, Texas 78712, United StatesMore by Venkat GanesanCite this: Macromolecules 2015, 48, 17, 6347–6352Publication Date (Web):August 18, 2015Publication History Received13 July 2015Revised10 August 2015Published online18 August 2015Published inissue 8 September 2015https://doi.org/10.1021/acs.macromol.5b01546Copyright © 2015 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views1626Altmetric-Citations29LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (7 MB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information SUBJECTS:Copolymers,Morphology,Noncovalent interactions,Transmission electron microscopy,X-ray scattering Get e-Alerts

Self-Assembly of Binary Mesocrystals from Blends of BABCB Multiblock Copolymers and ABC Triblock Copolymers

The phase behavior of binary blends composed of BABCB-type pentablock terpolymers and ABC-type triblock copolymers is investigated using the self-consistent field theory in the grand canonical ensemble. Specifically, the study is focused on how the simpler copolymers regulate the phase behavior of two sphere-forming multiblock copolymers of the type B1AB2CB1 and AB2CB3. For certain compositions, these two multiblock copolymers self-assemble to form mesocrystalline phases composed of binary A and C spheres with the ZnSC and ReO3 structures, respectively. It is discovered that the addition of symmetric ABC triblocks or AB diblocks to the two multiblock copolymers leads to the formation of different binary crystalline phases including symmetric binary crystalline phase of NaCl type for the A/C-component symmetric blends and asymmetric Cu2O, SnI4, TiO2, and CaF2 phases for the A/C-component asymmetric blends. In particular, the binary mesocrystals of the Cu2O and SnI4 structures observed in the blends of the tail-symmetric B1AB2CB1 terpolymers and the AB diblock copolymers are new stable phases which have not been observed in the B1AB2CB3 terpolymers melts. The theoretical results demonstrate that blending of block copolymers with specially designed multiblock terpolymers could provide an efficient route to fabricate binary mesocrystals.

Boundary Tension Between Coexisting Phases of a Block Copolymer Blend

Self-consistent field theory (SCFT) is used to evaluate the excess free energy per unit area (i.e., tension) of different boundaries (or interfaces) between the coexisting phases of a block copolymer blend. In this first study of its kind, we focus on the boundaries separating the short- and long-period lamellar phases that form in mixtures of small and large symmetric diblock copolymers of polymerizations Ns and Nl, respectively, when Ns ≪ Nl. According to strong-segregation theory (SST), the tension is minimized when both sets of lamellae orient parallel to the boundary, but experiments [Hashimoto, , Macromolecules 1994, 27, 1562] tend to observe kink boundaries instead, where the domains of one lamellar phase evolve continuously into those of the other lamellar phase. Our more refined SCFT calculations, on the other hand, do predict a lower tension for the kink boundary consistent with the experimental observations. For completeness, we also examine the boundaries that form when the short-period lamellar phase disorders, and again the SCFT results are in agreement with experiment.

Hierarchically Self-Assembled Block Copolymer Blends for Templating Hollow Phase-Change Nanostructures with an Extremely Low Switching Current

Phase change memory (PCM) is one of the most promising candidates for next-generation nonvolatile memory devices because of its high speed, excellent reliability, and outstanding scalability. However, the high switching current of PCM devices has been a critical hurdle to realize low-power operation. Although one solution is to reduce the switching volume of the memory, the resolution limit of photolithography hinders further miniaturization of device dimensions. In this study, we employed unconventional self-assembly geometries obtained from blends of block copolymers (BCPs) to form ring-shaped hollow PCM nanostructures with an ultrasmall contact area between a phase-change material (Ge2Sb2Te5) and a heater (TiN) electrode. The high-density (approximately 0.1 terabits per square inch) PCM nanoring arrays showed extremely small switching current of 2–3 μA. Furthermore, the relatively small reset current of the ring-shaped PCM compared to the pillar-shaped devices is attributed to smaller switching volume, which is well supported by electro-thermal simulation results. This approach may also be extended to other nonvolatile memory device applications such as resistive switching memory and magnetic storage devices, where the control of nanoscale geometry can significantly affect device performances.

Solution Self-Assembly of Blends of Crystalline-Coil Polyferrocenylsilane-block-polyisoprene with Crystallizable Polyferrocenylsilane Homopolymer

The self-assembly of block copolymers in solution leads to micellar structures with various morphologies. One way to modify the morphology of these micelles is to blend the block copolymer with a homopolymer corresponding to the core-forming block. Although the self-assembly of blends of amorphous homopolymers and block polymers has been extensively studied, there are few examples of solution self-assembly of blends of a core-crystalline block copolymer with a semicrystalline homopolymer. Here we describe a systematic study of the assembly in decane of blends of a polyferrocenylsilane-block-polyisoprene sample (PFS48-b-PI264) with two different PFS homopolymer samples (PFS50 and PFS20). We examine the structures formed as a function of blend composition and compare them to the structures formed from the individual components. PFS48-b-PI264 itself forms long cylindrical micelles, while the two homopolymer samples form stacks of lamellar crystals. Self-assembly of block copolymer mixtures leads to structures with an elongated planar core and fiber-like protrusions from the ends. The details of the structure vary in an interesting and systematic way as the ratio of homopolymer/block copolymer is increased, with important differences seen for the PFS50 and PFS20 homopolymer samples. This study demonstrates that cocrystallization plays a crucial role in determining the structures formed from these mixtures.

Computational study of directed self-assembly for contact-hole shrink and multiplication

We use three-dimensional self-consistent field theory (SCFT) to study the directed self-assembly (DSA) of cylinder-forming block copolymers in a peanut-shaped (also called egg-box) prepattern. The design of the prepattern shape will target the pitch reduction of the contact holes. The idea is that the DSA of block copolymers will not only lead to reduced critical dimensions relative to the template but will also repair defects in the guiding prepatterns and produce defect-free contact holes. We also study blends of block copolymers and homopolymers with various lengths and volume fractions. Using SCFT simulations, we establish the effects of the added homopolymer on defectivity, the process window, and the properties of the formed cylinders. In an attempt to quantify the effect of thermal fluctuations on the placement of the cylinders, we resort to complex Langevin simulations and perform a stochastic sampling of the assembled morphologies.

Characterization of polypropylene/hydrogenated styrene-isoprene-styrene block copolymer blends and fabrication of micro-pyramids via micro hot embossing of blend thin-films

Polypropylene (PP)/hydrogenated styrene-isoprene-styrene block copolymer (HYBRAR) blends were proposed as a new material for the fabrication of optical thin-films with regular micro-pyramids via the micro hot embossing of blend thin-films.

Tailoring mechanical response through coronal layer overlap in tethered micelle hydrogel networks.

Tethered micelle hydrogel networks based on the solution assembly of amphiphilic ABA-type block copolymers are prevalent throughout the hydrogel literature. However, the mechanical response of such systems is often determined largely by the integrity of the micellar core produced during solution assembly, not by the elements of the network structure upon which it is based. Using a solvent-free fabrication method based on the melt-state self-assembly of sphere-forming polystyrene-b-poly(ethylene oxide) (SO) diblock and SOS triblock copolymers blends, we have been able to produce tethered micelle hydrogel networks with fully vitrified cores that enable the elements of the network structure to determine the mechanical response. Here, we explore the impact of using PEO midblocks of different lengths within the SOS tethers, in an effort to elucidate the role played by water content, tether concentration, and tether length in mechanical property determination. In doing so, we were able to establish coronal layer overlap as the primary contributing factor in regulating the dynamic elastic moduli exhibited by tethered micelle systems. Variation of either tether concentration or tether length could be used to tune the degree of coronal layer overlap, enabling direct and accurate control over hydrogel mechanical response. While such control is likely a unique feature of the melt-state fabrication approach applied here, the conclusions with respect to the role of coronal layer overlap and tether (bridging) concentration in determining the mechanical potential of the network should be applicable to all ABA-type tethered micelle systems, regardless of fabrication methodology.

Tailored pore sizes in integral asymmetric membranes formed by blends of block copolymers.

A simple way to generate isoporous membranes with tailored pore sizes is shown. Block copolymers of different compositions are blended in solution, and membranes are obtained by solution casting followed by nonsolvent-induced phase separation. This enables the preparation of integral asymmetric membranes with a defined pore size for given sets of block copolymers just by choosing the right blend composition.

Baroplastic behavior of miscible block copolymer blends

Pressure dependence of various phase transitions for the miscible block copolymer (BCP) blends was evaluated by depolarized light scattering (DPLS) and small-angle neutron scattering (SANS) measurements, in which the blends consist of a polystyrene-b-poly(n-butyl methacrylate) (PS-b-PnBMA) and a deuterated polystyrene-b-poly(n-hexyl methacrylate) (dPS-b-PnHMA). Excellent baroplasticity was observed in nearly symmetric blends of PS-b-PnBMA/dPS-b-PnHMA, leading to the most outstanding pressure coefficients, |dT/dP|, in a closed-loop type phase behavior between a lower disorder-to-order transition (LDOT) and an order-to-disorder transition (ODT) type phase behavior. Together with the estimated pressure coefficients based on the values of enthalpic and volumetric changes at phase transitions, we demonstrate that the entropic compressibility for the miscible BCP blends is a baroplastic indicator, which was characterized by the negative volume change on mixing (ΔVmix) at transitions.

Melt rheology and properties of compatibilized recycled poly(ethylene terephthalate)/(styrene‐ethylene‐ethylene‐propylene‐styrene) block copolymer blends

Blends of recycled poly(ethylene terephthalate) (R‐PET) and (styrene‐ethylene‐ethylene‐propylene‐styrene) block copolymer (SEEPS) compatibilized with (maleic anhydride)‐grafted‐styrene‐ethylene‐butylene‐styrene (SEBS‐g‐MAH) were prepared by melt blending. The compatibilizing effects of SEBS‐g‐MAH were investigated systematically by study of the morphology, linear viscoelastic behavior, and thermal and mechanical properties of the blends. The results show that there is good agreement between the results obtained by rheological measurement and morphological analysis. The rheological test shows that the melt elasticity and melt strength of the blends increase with the addition of SEBS‐g‐MAH. The Cole‐Cole plots and van Gurp‐Palmen plots confirm the compatibilizing effect of SEBS‐g‐MAH. However, the Palierne model fails to predict the linear viscoelastic properties of the blends. The morphology observation shows that all blends exhibit a droplet‐matrix morphology. In addition, the SEEPS particle size in the (R‐PET)/SEEPS blends is significantly decreased and dispersed uniformly by the addition of SEBS‐g‐MAH. Differential scanning calorimeter analysis shows that the crystallization behavior of R‐PET is restricted by the incorporation of SEEPS, whereas the addition of SEBS‐g‐MAH improves the crystallization behavior of R‐PET compared with that of uncompatibilized (R‐PET)/SEEPS blends. The Charpy impact strength of the blends shows the highest value at SEBS‐g‐MAH content of 10%, which is about 210% higher than that of pure R‐PET. J. VINYL ADDIT. TECHNOL., 22:342–349, 2016. © 2014 Society of Plastics Engineers

Self-assembled phases of block copolymer blend thin films.

The patterns formed by self-assembled thin films of blended cylindrical and lamellar polystyrene-b-poly(methyl methacrylate) block copolymers can be either a spatially uniform, single type of nanostructure or separate, coexisting regions of cylinders and lamellae, depending on fractional composition and molecular weight ratio of the blend constituents. In blends of block copolymers with different molecular weights, the morphology of the smaller molecular weight component more strongly dictates the resulting pattern. Although molecular scale chain mixing distorts microdomain characteristic length scales from those of the pure components, even coexisting morphologies exhibit the same domain spacing. We quantitatively account for the phase behavior of thin-film blends of cylinders and lamellae using a physical, thermodynamic model balancing the energy of chain distortions with the entropy of mixing.

Control of multilayered core–shell dispersed particles in HPP/EPR/EbP blends and its influences on crystallization and dynamic mechanical behavior

According to a two-step preparation technique consisting of temperature-gradient extraction fractionation (TGEF) and subsequent solution-mixing, a series of polypropylene/ethylene-propylene random copolymer/ethylene-propylene block copolymer (HPP/EPR/EbP) blends containing multilayered core–shell dispersed particle with bridges were prepared to explore the influences of dispersed phase on crystallization and dynamic mechanical behavior. The inner core of the core–shell dispersed particles was mainly composed of EbP with long ethylene chain segment, and the intermediate layer was EPR and outer layer was EbP with long propylene chain segment. The size and layer thickness of the core–shell dispersed particle could be regulated by varying the ratio of EPR/EbP. With the decrease of EbP content, the outer interfacial thickness of core–shell structure decreases and the blends presented elevated melting points, which might be ascribed to enhanced nucleation ability. Meanwhile, the special simultaneous depression of glass-transition temperatures (Tg) of HPP and EPR was observed in all HPP/EPR/EbP blends compared with the Tgs of neat components, which was attributed to the enlarging free volume by imperfect co-crystals and infiltration of long ethylene chain segments of EbP component at interface.

Rheological behavior of a LDPE/PS/SBS blending melt

The dynamic rheological behaviors are measured by small amplitude oscillatory shear on a rotational rheometer for a low-density polyethylene (LDPE)/polystyrene (PS)/styrene–butadiene–styrene (SBS) block copolymer blend with the tool of cole–cole plot. The morphology of the blend is measured by scanning electron microscope (SEM) micrograph, the storage moduli–angular frequency (G′–ω) data are fit by the Palierne model, and the relaxation time spectrum is investigated. The storage modulus and loss modulus of the LDPE/PS/SBS blend at low frequency increase when the weight ratio LDPE/PS increases from 10/90, reaches a maximum of 30/70, and drops thereafter. The cole–cole plots of some blends (10/90/3, 70/30/3, 90/10/3 and 100/0/3) have only one main arc due to compatibilizing effect of the SBS, and those of other blends (0/100/3, 30/70/3 and 50/50/3) have a second arc or a long tail besides the main arc probably due to phase separation. The SEM micrographs of the LDPE/PS/SBS = 10/90/3, 30/70/3, 50/50/3 show sea-island, semi-co-continuous and co-continuous structure, respectively. G′–ω curve of two LDPE/PS/SBS = 30/70/3 and 50/50/3 blends shows a power law, and the power index is much lower than one (0.748 and 0.817), respectively, showing a co-continuous morphology also verified by the SEM micrographs. The experimental data of G′–ω curve of the LDPE/PS/SBS blends are fit by Palierne model, the deviation between the fit line and the experimental data increases gradually as the LDPE/PS weight ratio decreases from 90/10 to 10/90. For the LDPE/PS/SBS blends, the weighted relaxation spectra τH (τ)–τ show a main as well as a second arc or tail; the former corresponding to the relaxation of PS phase and the latter corresponding to that of LDPE phase. Due to the compatibilizing effect of SBS the relaxation time and spectrum strength of LDPE/PS = 50/50 (wt) blends are both increased.

Morphology and properties of polypropylene/ethylene-octene copolymer/clay nanocomposites with double compatibilizers

The influence of nanoclay on the morphology and properties of the polypropylene (PP)/ethylene–octene block copolymer (EOC) blend with double compatibilizers of maleated PP (PP-g-MA) and maleated EOC (EOC-g-MA) was investigated and compared with the nanocomposites containing either PP-g-MA or EOC-g-MA as a compatibilizer. X-ray diffraction, transmission electron microscopy, and scanning electron microscopy were utilized for morphological characterization in conjunction with dynamic mechanical thermal analysis, mechanical testing, and rheological evaluation of these nanocomposites. The results suggested that in the nanocomposite including both compatibilizers of PP-g-MA and EOC-g-MA, clay was dispersed as a mixed structure of intercalation and exfoliation in both phases of the polymer blend. Comparing the mechanical properties of the studied nanocomposite with nanocomposites of PP/EOC/PP-g-MA/clay and PP/EOC/EOC-g-MA/clay also indicated that the nanocomposite containing mixed compatibilizers displayed higher tensile modulus, tensile strength, and complex viscosity because of the better dispersion of clay in both phases. The results also confirmed the increased structural stability and reduced dispersed phase size of PP/EOC/PP-g-MA/EOC-g-MA blend in the presence of clay that proposed the compatibilization role of clay in this nanocomposite. Copyright © 2014 John Wiley & Sons, Ltd.