Fluctuations, conformational asymmetry and block copolymer phase behaviour

Bates, Frank S.; Schulz, Mark F.; Khandpur, Ashish K.; Förster, Stephan; Rosedale, Jeffrey H.; Almdal, Kristoffer; Mortensen, K.

doi:10.1039/fd9949800007

Cited by 432 publications

(562 citation statements)

References 30 publications

(4 reference statements)

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“…The volume fraction of polyisoprene in the block copolymer is 0.26. On the basis of extensive characterization of polystyrene-block-polyisoprene copolymers, 20 we expect the sample to have a cylindrical microstructure at temperatures of interest, 124 -132°C. All of our experiments were conducted well above the spinodal temperature, which was estimated to be 87°C…”

Section: Methodsmentioning

confidence: 99%

Maximizing the grain growth rate during the disorder‐to‐order transition in block copolymer melts

Kim¹,

Garetz

Newstein³

et al. 2001

J Polym Sci B Polym Phys

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ABSTRACT:The factors controlling grain growth during the disorder-to-order transition in a polystyrene-block-polyisoprene copolymer melt were studied with time-resolved depolarized light scattering. The ordered phase consisted of hexagonally packed polyisoprene cylinders, and the order-disorder-transition temperature of the block copolymer (T ODT ) was 132 Ϯ 1°C. Our objective was to identify the temperature at which the grain growth rate was maximized (T max ) and compare it with theoretical predictions. We conducted seeded grain growth experiments, which comprised two steps. In the first step, which lasted for 43 min, the sample was cooled from the disordered state to 124°C. This resulted in the formation of a small number of ordered grains or seeds. This was followed by a second step in which the sample was heated to temperatures between 124 and 132°C and the seeds grew with time. Our objective was to study grain growth at different temperatures starting from the same initial condition. The value of T max obtained experimentally was 128°C. The theoretically predicted value of T max , based entirely on the rheological properties of the disordered sample and T ODT , was also 128°C.

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Section: Methodsmentioning

confidence: 99%

Maximizing the grain growth rate during the disorder‐to‐order transition in block copolymer melts

Kim¹,

Garetz

Newstein³

et al. 2001

J Polym Sci B Polym Phys

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“…As the composition is varied, morphologies analogous to the familiar diblock copolymer morphologies [7][8][9][10][11] are obtained. With increasing styrene content, these are styrene spheres in a bcc arrangement, followed by hexagonally packed styrene cylinders, a tricontinuous structure, and lamellae.…”

mentioning

confidence: 99%

Perpendicular Deformation of a Near-Single-Crystal Triblock Copolymer with a Cylindrical Morphology. 1. Synchrotron SAXS

et al. 2000

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A poly(styrene-block-isoprene-block-styrene) (SIS) triblock copolymer with a polystyrene (PS) cylinder morphology was processed via roll-casting to produce a near single-crystal texture. Deformation experiments normal to the cylinder axis were carried out using synchrotron small-angle X-ray scattering (SAXS) with the beam both parallel and perpendicular to the cylinder axis. In situ measurement of load and displacement enabled morphological information to be mapped to the stressstrain curve. Results indicate that the deformation proceeds in two stages. Deformation to strains of approximately 100-130% is nearly affine. The rubber matrix extends along the stretching direction (SD) while contraction occurs almost exclusively along the neutral direction due to the constraint imposed by the aligned PS cylinders. A measured Poisson's ratio of 0.9 compares favorably with a value of 1 expected for a perfect composite. At deformations beyond 130% an X-pattern is observed at perpendicular incidence. The angle between the arms of the X increases asymptotically, while the intercylinder spacing remains fairly constant. The initial hexagonal pattern undergoes a continuous distortion and provides further evidence for the deformation discontinuity in the rate of lateral contraction. The morphological observations in reciprocal space are interpreted in terms of a kinking instability in which the plane strain state imposed by the oriented cylinders is relieved by their kinking into a chevron pattern. The kinking transition strain is expected to be dependent on the degree of cylinder misorientation, the shear resistance of the rubber matrix, and the bending resistance of the PS cylinders.

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“…In conventional systems such as pure diblock copolymers and A-B/A blends, the ordered phase formed under such asymmetric conditions would undoubtedly be spherical. 23, 55 However, we note that, in their study of multicomponent blends with attractive and repulsive interactions, Jamieson et al also reported the formation of phase-inverted structures and flat interfaces in highly asymmetric blends. 30 It thus appears that the factors that govern the phase behavior of systems with both attractive and repulsive interactions are qualitatively different from those seen in diblock copolymers and A-B/A blends.…”

Section: Resultsmentioning

confidence: 96%

“…Even in the simple case of A-B diblock copolymers, unique values for the statistical segment lengths of both blocks cannot be determined from SANS data. While many groups assume that the statistical segment lengths of both blocks are identical, 55,60 it is well-known that other combinations of the statistical segment lengths give equally good fits. 60 We tried a number of approaches for arriving at the and l parameters (other than that described in the Appendix).…”

Section: Resultsmentioning

confidence: 99%

“…The ordered phase formed by a symmetric diblock copolymer is always lamellar, and it forms when N ≈ 5.25. [16][17][18]33,[55][56][57] In contrast, for the case of A-B/C blends with repulsive and attractive interactions, the effect of unequal statistical segment lengths in A-B/C mixtures cannot be expressed as an additive correction (eq 8). …”

Section: Theoretical Predictions For a Simplified A-b/c Systemmentioning

confidence: 99%

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Thermodynamics and Phase Behavior of Block Copolymer/Homopolymer Blends with Attractive and Repulsive Interactions

et al. 2002

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Small-angle neutron scattering (SANS) experiments were conducted on a 25 vol % blend of a poly(ethylene-block-head-to-head propylene) copolymer (PE-PP) in polyisobutylene (PIB). PE/PIB and PE/PP chains are incompatible (the Flory-Huggins interaction parameter > 0), while PIB and PP are compatible ( < 0) at low temperatures and incompatible ( > 0) at high temperatures. These interactions lead to an order-disorder transition at 150 ( 5°C and macrophase separation at 251 ( 5°C. The nature of the concentration fluctuations in the homogeneous state (155°C < T < 246°C) was studied by comparing the experimentally determined SANS profiles with theoretical calculations based on the multicomponent random phase approximation (RPA). Order formation at low temperatures is driven by two parameters:PE/PIB and lPP (the statistical segment length of the PP block). The other temperature-dependent parameters drive the system away from the ordering transition. At high temperatures, the RPA predicts microphase separation, while experimental data (neutron and light scattering) indicate macrophase separation. This discrepancy is mainly due to the inability of the RPA to correctly account for the large length scale concentration fluctuations.

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Fluctuations, conformational asymmetry and block copolymer phase behaviour

Cited by 432 publications

References 30 publications

Maximizing the grain growth rate during the disorder‐to‐order transition in block copolymer melts

Maximizing the grain growth rate during the disorder‐to‐order transition in block copolymer melts

Perpendicular Deformation of a Near-Single-Crystal Triblock Copolymer with a Cylindrical Morphology. 1. Synchrotron SAXS

Thermodynamics and Phase Behavior of Block Copolymer/Homopolymer Blends with Attractive and Repulsive Interactions

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