Flow-induced alignment of lamellar block copolymer melts

Chen, Zhong‐Ren; Kornfield, Julia A.

doi:10.1016/s0032-3861(98)00136-0

Cited by 104 publications

(164 citation statements)

References 86 publications

Supporting

Mentioning

153

Contrasting

Order By: Relevance

“…It is well known that oscillatory shear can induce macroscopic alignment of lamellar microdomains in block copolymers [6]. This process was used to induce a single crystal-like "parallel" orientation in three copolymer samples.…”

Section: (Received 20 May 1999)mentioning

confidence: 99%

“…This process was used to induce a single crystal-like "parallel" orientation in three copolymer samples. In this parallel orientation the normal to the lamellae is aligned parallel to the velocity-gradient direction [6]. A poly(styrene-b-methyl methacrylate) diblock copolymer and two poly(styrene-b-ethylene propylene) diblock copolymers were examined, which we denote SMMA(36-29), SEP(38-62), and SEP(39-24), indicating the respective nominal average molecular weights of the blocks ͑3 10 3 g͞mol͒.…”

Section: (Received 20 May 1999)mentioning

confidence: 99%

See 1 more Smart Citation

Nature of Viscoelasticity in Lamellar Block Copolymers: Contraction Correlated to Strain Localization

et al. 1999

View full text Add to dashboard Cite

Section: (Received 20 May 1999)mentioning

confidence: 99%

Section: (Received 20 May 1999)mentioning

confidence: 99%

Nature of Viscoelasticity in Lamellar Block Copolymers: Contraction Correlated to Strain Localization

et al. 1999

View full text Add to dashboard Cite

“…On the other hand, when α 56 < 0, we have η ′ Parallel < η ′ Perpendicular , which is the case in PS-PI copolymers [Chen and Kornfield (1998); Gupta et al (1995)]. The viscosity coefficients α 1 and α 56 could be in principle measured in block copolymers under shear flows, with experimental setups possibly similar to those used in nematic liquid crystals [see, e.g., methods reviewed by de Gennes and Prost (1993)].…”

Section: Model a Governing Equationsmentioning

confidence: 99%

Stability of parallel/perpendicular domain boundaries in lamellar block copolymers under oscillatory shear

Huang

Viñals

2007

Journal of Rheology

View full text Add to dashboard Cite

SynopsisWe introduce a model constitutive law for the dissipative stress tensor of lamellar phases to account for low frequency and long wavelength flows. Given the uniaxial symmetry of these phases, we argue that the stress tensor must be the same as that of a nematic but with the local order parameter being the slowly varying lamellar wavevector. This assumption leads to a dependence of the effective dynamic viscosity on orientation of the lamellar phase. We then consider a model configuration comprising a domain boundary separating laterally unbounded domains of so called parallel and perpendicularly oriented lamellae in a uniform, oscillatory, shear flow, and show that the configuration can be hydrodynamically unstable for the constitutive law chosen. It is argued that this instability and the secondary flows it creates can be used to infer a possible mechanism for orientation selection in shear experiments.1

show abstract

“…Both alignments have been observed in nearly symmetric diblock copolymer systems such as poly(ethylenepropylene)-poly(ethylethylene) (PEP-PEE) [5] and polystyrene-polyisoprene (PS-PI) [6,7]. Which of these two possible alignments is selected in a given experiment depends on temperature, and shear strain amplitude and frequency [2,8,9]. A third alignment direction, the so called transverse orientation in which the lamellar normal is parallel to the shear direction, has been found to coexist with parallel orientation for entangled poly(styrene-b-ethylenepropylene) (S-EP) diblock copolymer at high frequency and in the strong segregation limit [10].…”

Section: Introductionmentioning

confidence: 99%

“…A third alignment direction, the so called transverse orientation in which the lamellar normal is parallel to the shear direction, has been found to coexist with parallel orientation for entangled poly(styrene-b-ethylenepropylene) (S-EP) diblock copolymer at high frequency and in the strong segregation limit [10]. Other studies have focused on the kinetics of global alignment and have shown that the ordering rate increases with shear frequency, strain amplitude, and temperature [8,11]. Experiments on PS-PI diblocks further show nonlinear effects of the strain amplitude on the alignment rate, and that the time scale for the development of alignment exhibits a power law dependence on the strain amplitude, with an exponent equal to −3 or −5 depending on the stage of alignment and in different frequency regimes [11].…”

Section: Introductionmentioning

confidence: 99%

Shear-induced grain boundary motion for lamellar phases in the weakly nonlinear regime

Huang

Viñals

2004

Phys. Rev. E

View full text Add to dashboard Cite

We study the effect of an externally imposed oscillatory shear on the motion of a grain boundary that separates differently oriented domains of the lamellar phase of a diblock copolymer. A direct numerical solution of the Swift-Hohenberg equation in shear flow is used for the case of a transverse/parallel grain boundary in the limits of weak nonlinearity and low shear frequency. We focus on the region of parameters in which both transverse and parallel lamellae are linearly stable.Shearing leads to excess free energy in the transverse region relative to the parallel region, which is in turn dissipated by net motion of the boundary toward the transverse region. The observed boundary motion is a combination of rigid advection by the flow and order parameter diffusion.The latter includes break up and reconnection of lamellae, as well as a weak Eckhaus instability in the boundary region for sufficiently large strain amplitude that leads to slow wavenumber readjustment. The net average velocity is seen to increase with frequency and strain amplitude, and can be obtained by a multiple scale expansion of the governing equations.

show abstract

Flow-induced alignment of lamellar block copolymer melts

Cited by 104 publications

References 86 publications

Nature of Viscoelasticity in Lamellar Block Copolymers: Contraction Correlated to Strain Localization

Nature of Viscoelasticity in Lamellar Block Copolymers: Contraction Correlated to Strain Localization

Stability of parallel/perpendicular domain boundaries in lamellar block copolymers under oscillatory shear

Shear-induced grain boundary motion for lamellar phases in the weakly nonlinear regime

Contact Info

Product

Resources

About