Morphologies of Microphase-Separated A<sub>2</sub>B Simple Graft Copolymers

Pochan, Darrin J.; Gido, Samuel P.; Pispas, Stergios; Mays, Jimmy W.; Ryan, Anthony J.; Fairclough, J. Patrick A.; Hamley, Ian W.; Terrill, Nicholas J.

doi:10.1021/ma951696x

Cited by 131 publications

(189 citation statements)

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“…Furthermore, worm-like micelles are observed in the DPD simulations [24] in contrast to the sphere or cylindrical phase in the SCFT near the disorder-order transition around φ B = 0.8. Also, experiments by Pochan et al [20] show the existence of microphase separated structures (micellar) without any underlying lattice.…”

Section: Resultsmentioning

confidence: 99%

“…In the 1990s, systematic studies [19,20,21] aimed at elucidating the effect of branched architecture on the morphology and properties of block copolymers were initiated. Like the linear di-block copolymer melts, classical morphologies namely, lamellae, cylinders, spheres and gyroid, were observed in experiments [19,20,21] for the miktoarm star copolymers.…”

Section: Introductionmentioning

confidence: 99%

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Morphology diagrams forA₂Bcopolymer melts: real-space self-consistent field theory

Kumar

Sides

et al. 2012

J. Phys.: Conf. Ser.

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The standard Gaussian model for block copolymermelts M W Matsen -Stability of the fcc structure in block copolymer systems Makiko Nonomura -SCFT simulation and SANS study on spatial distribution of solvents in microphase separation induced by a differentiating non-solvent in a semi-dilute solution of an ultra-high-molecular-weight block copolymer K Ando, T Yamanaka, S Okamoto et al. Abstract. Morphology diagrams for A2B copolymer melts are constructed using real-space self-consistent field theory (SCFT). In particular, the effect of architectural asymmetry on the morphology diagram is studied. It is shown that asymmetry in the lengths of A arms in the A2B copolymer melts aids in the microphase separation. As a result, the disorder-order transition boundaries for the A2B copolymer melts are shown to shift downward in terms of χN, χ and N being the Flory's chi parameter and the total number of the Kuhn segments,respectively, in comparison with the A2B copolymers containing symmetric A arms. Furthermore, perforated lamellar (PL) and a micelle-like (M) microphase segregated morphologies are found to compete with the classical morphologies namely, lamellar, cylinders, spheres and gyroid. The PL morphology is found to be stable for A2B copolymers containing asymmetric A arms and M is found to be metastable for the parameter range explored in this work. IntroductionMicrophase separation in block copolymer melts [1,2,3,4,5,6,7] has motivated the scientific community over the last couple of decades. Delicate balance[3] of chain conformational entropy and repulsive interaction energy between unlike monomers allows block copolymers to readily self-assemble into a number of ordered morphologies. Typical morphologies [3,8,9] include lamellar, cylinder, sphere, gyroid and Fddd network phases, which have been proven to be equilibrium states.Experimentally, the balance of the energy and entropy can be tuned by a number of molecular characteristics such as molecular weight [3], chain architecture [10,11], conformational asymmetry [12,13], polydispersity [14,15,16,17,18] and temperature. A number of studies [1,2,3,4,5,6,7] have been done to elucidate the effects of molecular weight, polydispersity, conformational asymmetry and temperature on the mircophase separation in linear di-block copolymer melts. However, the effects of chain architecture are not that well established. On the computational side, this is primarily due to a large parameter space for the simulations and resulting large number of morphologies, which need to be compared in terms of their free-energy

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Morphology diagrams forA₂Bcopolymer melts: real-space self-consistent field theory

Kumar

Sides

et al. 2012

J. Phys.: Conf. Ser.

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“…Changing from simple linear diblock copolymers to graft copolymers can greatly alter the dependence of the morphologies on the component volume fractions. [1][2][3][4][5][6][7][8][9][10][11] It has been shown that complex graft copolymer architectures with multiple grafting points ( Figure 1) can be understood morphologically by analogy to fundamental building blocks defined as the average structure per junction point. 12,13 This fundamental component of a larger graft molecular architecture is referred to as the constituting block copolymer.…”

Section: Introductionmentioning

confidence: 99%

Morphology and Tensile Properties of Multigraft Copolymers with Regularly Spaced Tri-, Tetra-, and Hexafunctional Junction Points

Zhu¹,

Burgaz²,

Gido³

et al. 2006

Macromolecules

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123

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The effect of chain architecture on the morphological and tensile properties of series of multigraft copolymers, with regularly spaced tri-, tetra-, and hexafunctional junction points, was investigated using transmission electron microscopy (TEM), small-angle X-ray scattering (SAXS), and tensile testing. The materials were synthesized by coupling difunctional polyisoprene (PI) spacers and living polystyrene (PS) branches, made by anionic polymerization, with chlorosilanes of different functionalities. Since the coupling process is a step-growth polymerization, yielding polydisperse products, fractionation was utilized to separate each material into three fractions (high, middle, and low molecular weight), each of low polydispersity. All three fractions have the same chain architecture on a per junction point basis but differ in the number of junction point units per molecule. By applying the constituting block copolymer concept, the physical behavior of these molecules was compared with current theories. It was found that morphological behavior of these graft copolymers can be predicted using theoretical approaches and is independent on the number of junction points. The number of the junction points, however, greatly influences the long-range order of microphase separation. Additionally, two new parameters for adjusting mechanical properties of multigraft copolymers were found in this investigation: (1) functionality of the graft copolymerstri-, tetra-, or hexafunctionalsand (2) number of junction points per molecule. An increase in functionality causes a change in morphology, resulting in a high level of tensile strength for tetrafunctional (cylindrical) and hexafunctional (lamellae) multigraft copolymers, leading to about the twice the strength of the spherical trifunctional multigrafts of similar overall composition. Tetrafunctional multigraft copolymers show a surprisingly high strain at break, far exceeding that of commercial block copolymer thermoplastic elastomers (TPEs). Strain at break and tensile strength increase linearly with the number of junction points per molecule. Hysteresis experiments at about 300-900% deformation demonstrate that multifunctional multigraft copolymers have improved high elasticity as compared to commercial TPEs like Kraton or Styroflex.

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“…33,34 Unique morphologies were found in branched and star block copolymers that are not observed for linear block copolymers. [35][36][37][38][39] At the air-water interface, the hydrophobic chains collapse into globules while the hydrophilic chains spreads out to form a brush-like or a flat (pancake-like) structures. [40][41][42][43][44][45][46][47] Hyperbranched molecules possess a tree-like structure similar to that of dendrimers with the same enhancement in chemical and physical properties but at a great reduction in cost and time of synthesis when compared with dendrimers.…”

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Assembling hyperbranched polymerics

Peleshanko¹,

Tsukruk²

2011

J Polym Sci B Polym Phys

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A condensed overview discusses the existing grafting approaches and the surface behavior of various hyperbranched polymers. We focus on the recent strategies and corresponding characterization of the resulting surface morphologies and structures with a number of relevant recent results from the authors' own research and existing literature. Some results discussed here are important for prospective applications of hyperbranched polymers in biomedical fields, for resistive coatings, tough blends, and reinforced nanocomposites are briefly summarized as well. V C 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 50: 83-100, 2012 KEYWORDS: adsorption; hyperbranched; LB films; structural characterization; surfaces INTRODUCTION This publication presents a condensed overview of the existing grafting approaches as applied to hyperbranched polymers and discusses the surface morphologies of these polymers and corresponding composites and coatings. We mostly focus on the recent strategies and corresponding characterization of the resulting surface morphologies and structures developed in the authors' group with some relevant examples from current literature. A number of relevant results are also included here especially in relation to recent developments related to novel synthetic approaches of hyperbranched molecules as well as emerging applications of hyperbranched polymers and coatings for biomedical purposes, as resistive coatings, tough blends, and reinforced nanocomposites. Some comprehensive recent reviews on highly branched polymers, which are focused mainly on synthetic aspects can be found in literature.

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Morphologies of Microphase-Separated A₂B Simple Graft Copolymers

Cited by 131 publications

References 24 publications

Morphology diagrams forA₂Bcopolymer melts: real-space self-consistent field theory

Morphology diagrams forA₂Bcopolymer melts: real-space self-consistent field theory

Morphology and Tensile Properties of Multigraft Copolymers with Regularly Spaced Tri-, Tetra-, and Hexafunctional Junction Points

Assembling hyperbranched polymerics

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Morphologies of Microphase-Separated A2B Simple Graft Copolymers

Cited by 131 publications

References 24 publications

Morphology diagrams forA2Bcopolymer melts: real-space self-consistent field theory

Morphology diagrams forA2Bcopolymer melts: real-space self-consistent field theory

Morphology and Tensile Properties of Multigraft Copolymers with Regularly Spaced Tri-, Tetra-, and Hexafunctional Junction Points

Assembling hyperbranched polymerics

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Morphologies of Microphase-Separated A₂B Simple Graft Copolymers

Morphology diagrams forA₂Bcopolymer melts: real-space self-consistent field theory

Morphology diagrams forA₂Bcopolymer melts: real-space self-consistent field theory