Binary Block Copolymer Blends Research Articles

Tetragonally Packed Inverted Cylindrical Microdomains from Binary Block Copolymer Blends with Enhanced Hydrogen Bonding

Tetragonally Packed Inverted Cylindrical Microdomains from Binary Block Copolymer Blends with Enhanced Hydrogen Bonding

Hydrogen bonding induced microphase and macrophase separations in binary block copolymer blends

This study investigated the macrophase and microphase transitions of blends comprising polystyrene-block-poly(ethylene oxide) (PS-b-PEO) and polystyrene-block-poly(acrylic acid) (PS-b-PAA). PEO and PAA molecules formed hydrogen bonds that enabled the two block copolymers to organize into a single microphase-separated morphology composed of two PS block chains in a common PS microdomain and PEO and PAA block chains in a coexisting PEO/PAA microdomain. Increasing temperature weakened the hydrogen-bonding interaction through the formation of PAA monomers and anhydride, causing the blends to macrophase separate into PS-b-PEO-rich and PS-b-PAA-rich phases. Further increasing the temperature weakened the repulsive interactions between both the PS and PEO segments and the PS and PAA segments, inducing order-to-disorder transitions in the PS-b-PEO-rich and PS-b-PAA-rich phases. However, the increasing repulsive interaction between the PEO and PAA segments with increasing temperature prevented the blends from forming an isotropic phase. The unique phase transformation of each block copolymer in the blend with an upper critical ordering transition (UCOT)-type interaction parameter, which caused the formation of a lower-critical-solution-temperature-type phase diagram, was attributed to the hydrogen-bonding interaction between PEO and PAA, which outweighed the UCOT behaviors of PS-b-PEO and PS-b-PAA and reversed the phase behaviors of their blends.

Inverted Cylindrical Microdomains from Binary Block Copolymer Blends Capable of Hydrogen Bonding

Inverted Cylindrical Microdomains from Binary Block Copolymer Blends Capable of Hydrogen Bonding

Morphology Evolution of Block Copolymer Blend Thin Films Induced by Solvent Vapor Annealing

ABSTRACT Self-assembly of binary block copolymer blends in thin film induced by solvent vapor annealing has been systematically studied. The diblock copolymers polystyrene-b-poly(2-vinylpyridine) with different molecular weights and volume fractions were blended with different molar ratios to cast thin films on silica substrate by spin coating. The films were annealed separately in the vapor of ethanol or toluene over time to induce morphology transformations from spheres, gyroids, and bicontinuous nanostructures, depending on the blending ratio, solvent selectivity, and annealing time, as investigated by atomic force microscopy and X-ray photoelectron spectroscopy. The formation and transformation mechanism of the self-assembly structure are discussed in the context of solvent-copolymer interactions. This study provides new insights into the simple manipulation of self-assembled nanostructures of block copolymer thin films.

Visualizing Nanoscale Coronal Segregation in Rod-Like Micelles Formed by Co-Assembly of Binary Block Copolymer Blends.

Mixed micelles formed by co-assembly of pairs of block copolymers (BCPs) can develop novel morphologies and generate useful properties not accessible from homomicelles. For micelles consisting of two different polymers in the corona, identifying the location of the corona chains is a critical part of morphology characterization. Coronal segregation in mixed micelle is often characterized by transmission electron microscopy in combination with selective staining of individual polymers. In this study, Karstedt's catalyst is used for selective Pt(0)-olefin coordination staining of polyisoprene (PI) and poly(methylvinylsiloxane) (PMVS) corona chains in the presence of poly(dimethylsiloxane) (PDMS) corona chains in cylindrical mixed micelles with a crystalline poly(ferrocenyldimethylsilane) (PFS) core. Previous experiments using OsO4 as a stain did not enable visualization of nanoscale coronal segregation in mixed micelles obtained from co-assembly of PFS-b-PI and PFS-b-PDMS, as well as PFS-b-PMVS and PFS-b-PDMS.

Multiple phase transitions in block copolymer blends and pressure effects on these transitions

We sought to identify an evident enthalpic-driven transition below an entropic-driven closed-loop phase transition by studying the phase behavior in miscible binary block copolymer (BCP) blends of a polystyrene-b-poly (n-butyl methacrylate) (PS-b-PnBMA) and a deuterated polystyrene-b-poly (n-hexyl methacrylate) (dPS-b-PnHMA), using small-angle x-ray scattering (SAXS) and depolarized light scattering (DPLS). Intriguingly, an order-to-disorder transition (ODT) below the closed-loop transition consisting of a lower disorder-to-order transition (LDOT) and an upper order-to-disorder transition (UODT) was observed in the BCP blends of an asymmetric (PS-rich) PS-b-PnBMA and a symmetric dPS-b-PnHMA. Multiple phase transitions, previously undiscovered in BCP system, were attributed to a delicate balance in the free energy of the dispersive intermolecular interactions, the entropic compressibility, and the combinatorial entropy of mixing at an experimental temperature range between the glass transition temperature (Tg) and degradation temperature (Td). We also characterized the effects of hydrostatic pressure on the transition temperatures to determine the thermodynamic origins of each phase transition.

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

Various Phase Behaviors of Weakly Interacting Binary Block Copolymer Blends

We investigated the phase behaviors of block copolymer (BCP) blends composed of the weakly interacting (with no specific interaction) polystyrene-b-poly(n-butyl methacrylate) (PS-b-PnBMA) and polystyrene-b-poly(n-hexyl methacrylate) (PS-b-PnHMA), using small-angle neutron scattering (SANS), small-angle X-ray scattering (SAXS), and depolarized light scattering (DPLS). A miscible phase between the PnBMA and PnHMA blocks in the BCP blends allows the various composition-dependent phase behaviors, which display a lower disorder-to-order transition (LDOT) to an order-to-disorder transition (ODT) on heating as the blend composition varies from PS-b-PnBMA to PS-b-PnHMA. In between these two extremes, intriguingly, the miscible PS-b-PnBMA/PS-b-PnHMA blends display a closed-loop phase transition consisting of a LDOT and an upper order-to-disorder transition (UODT).

Dynamic mechanical and rheological properties of binary S–(S/B)–S triblock copolymer blends

AbstractThe rheology and dynamic mechanical properties of binary block copolymer blends consisting of a symmetrical triblock copolymer with thermoplastic elastomeric behavior (LN4) and an asymmetrical thermoplastic triblock copolymer (LN3) were investigated. TEM images of the blends show a systematic variation in the morphologies from worms (∼20–0 wt % LN3) to cylinders (∼60–30 wt % LN3) to lamellae (100–70 wt % LN3) as a function of LN3 content. DMA analysis has revealed that the increase in LN3 content leads to a decrease in miscibility between the PS end blocks and the S/B middle block. The frequency and temperature dependence of the storage modulus (G′), loss modulus (G″), and complex viscosity (|η*|) has been studied for LN4 (weakly segregated) and LN3 (strongly segregated) from their master curves. By comparing the rheological properties of these blend compositions at low‐frequency regime, it is observed that with the increase in LN3 content the shear modulus and complex viscosity increase. Blend compositions with 70–100 wt % of LN3 show nonterminal behavior at reduced frequencies due to the presence of highly ordered microdomains when compared to blends with ∼0–20 wt % of LN3 content. van Gurp–Palmen plots were constructed to observe the transition from liquid‐ to solid‐like behavior in the vicinity of order‐to‐disorder transition (ODT) temperature. ODT temperature increases as the thermoplastic LN3 content increases which are also confirmed by the Han plots. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 329–343, 2008

Fracture Behaviour of Binary Styrene/Butadiene Block Copolymer Blends

Morphology and fracture behavior of binary block copolymer blends (triblock and star block copolymers being made up of styrene and butadiene) have been studied via transmission electron microscopy (TEM) and instrumented Charpy impact testing. The toughness of the ductile blends has been characterized by dynamic crack resistance curves (R-curves). The lamellar star block copolymer shows nearly elastic behavior of small scale yielding and unstable crack growth. Addition of 20 wt % of a triblock copolymer comprising polystyrene domains dispersed in rubbery matrix leads to a strong increase in toughness. The mechanism of toughness modification, based on the nanophase-separated structures, represents a specific morphology-toughness correlation which differs fundamentally from toughening mechanisms observed in conventional polymer blends.DOI: 10.3126/jncs.v22i0.523Journal of Nepal Chemical Society Vol. 22, 2007, pp. 55-66

Morphology and micromechanical deformation behavior of styrene–butadiene block copolymers. IV. Structure–property correlation in binary block copolymer blends

AbstractThe structure–property correlation in blends consisting of styrene/butadiene block copolymers forming alternating polystyrene (PS) and polybutadiene (PB) lamellae, and PS domains in rubbery matrix was investigated by different microscopic techniques (transmission electron microscopy, scanning force microscopy, and scanning electron microscopy), uniaxial tensile testing, and dynamic mechanical analysis. Unlike the pure lamellar block copolymer, the blends showed predominantly disordered wormlike morphology formed by the intermolecular mixing. These structures allowed a precise control of stiffness/toughness ratio of the blends over a wide range. The blends showed a gradual transition from predominantly viscoplastic to elastomeric behavior with increasing triblock copolymer content. The results demonstrated that the binary block copolymer blends provide the unique possibility of tailoring mechanical properties on the basis of nanostructured polymeric materials. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 1219–1230, 2004

Relating microhardness to morphology in styrene/butadiene block copolymer/polystyrene blends

The microhardness behaviour of binary blends comprising a styrene/butadiene star block copolymer and polystyrene homopolymer (hPS) over a wide composition range is investigated. In particular, the interrelation between the morphology, tensile properties (such as yield stress σ Y and the Young's modulus, E) and the microhardness H is explored. As in the case of microphase separated block copolymers and binary block copolymer blends, as reported in preceding publications, a clear deviation in the microhardness behaviour from the additivity law is observed. The lamellar block copolymer system is compared with the nanostructure of semicrystalline polymers having a lamellar morphology. A dependence of H upon PS lamellar thickness is found. For the samples with lamellar morphology the hardness value was found to correlate with the mechanical parameters obtained by uni-axial tensile testing according to: H/ σ Y∼2.2 and E/ H∼22.

Morphology and crack resistance behavior of binary block copolymer blends

Fracture behavior of binary blends comprising of styrene–butadiene block copolymers having star and triblock architectures was studied via instrumented Charpy impact test. The toughness of the ductile blends was characterized by dynamic crack resistance curves ( R-curves). This study represents a systematic investigation of crack resistance behavior of nanometer structured binary block copolymer blends and the development of a new material with a combination of high toughness and transparency, usually not observed in incompatible polymer blends. While the lamellar star block copolymer shows an elastic behavior (small-scale yielding and unstable crack growth), adding of 20 wt% of the triblock copolymer leads to a stable crack growth and at 60 wt% of the triblock copolymer the strong increase of toughness values indicate a tough/high-impact transition, demonstrating the existence of novel toughening concepts for polymers based on nanometer structured materials.

Energy Transfer Studies of Binary Block Copolymer Blends. 1. Effect of Composition on the Interface Area per Chain and the Lamellar Size

Binary blends of polyisoprene−poly(methyl methacrylate) PI−PMMA diblock copolymers with a common PMMA length and different lengths of polyisoprene blocks were prepared from samples containing a single fluorescent dye, either phenanthrene (donor) or anthracene (acceptor), at the junction point. The two pure block copolymers and their mixtures were studied by the direct energy transfer (DET) technique. All experiments point to intimate mixing of the samples over the entire composition range. These DET experiments yield the interphase volume per junction vj and/or the ratio R/δ of the microdomain size R to the interphase thickness δ, as a function of the composition of the block copolymer mixture. Since, for these strongly segregated chains, the interface thickness is invariant with chain length and should also be constant for this set of mixtures, we can calculate from vj and R/δ the interface area per chain and the period spacing R. Here we find that addition of up to 25 mol % of the second polymer has no ...

Phase separation in binary block copolymer blends

The well defined poly(styrene(S)-b-isoprene(I)) and poly(S-b-2-vinylpyridine(2VP)) diblock copolymers were prepared by sequential anionic addition. Binary poly(S-b-I)/poly(S-b-2VP) diblock copolymer blend films were prepared by solution casting, varying the volume fraction of the three-block sequences. Morphological results were obtained by transmission and scanning electron microscopy (TEM and SEM). The three-phase separated microdomains formed depended strongly on the volume fraction of binary block sequences and casting conditions.