Gaussian- to stretched-coil transition in block copolymer melts

Almdal, Kristoffer; Rosedale, Jeffrey H.; Bates, Frank S.; Wignall, G. D.; Fredrickson, Glenn H.

doi:10.1103/physrevlett.65.1112

Cited by 234 publications

(221 citation statements)

References 16 publications

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“…Experiments, however, have shown that deviations from a Gaussian chain conformation already occurs well above the ODT transition. 31 Theoretical extensions by Barrat and Fredrickson 32 and by Stepanow 33 qualitatively confirm the experimental results. The theory by Stepanow 33 going beyond the RPA approximation additionally proposes a stepwise increase of the coil size at the ODT transition in consistence with experiments by Stü hn et al; 34 on the other hand, in asymmetrical diblock copolymers a stepwise decrease of the coil was found by Ogawa et al 35 More quantitative results have been obtained from recent simulation studies by Fried and Binder; 36 a scaling behavior of Q m vs (ΓN) or 1/T at constant N was found with a maximum effective exponent ∆ν = -0.24 near the ODT transition instead of the predicted ∆ν ) 0 by the RPA.…”

Section: Pee-pdms Pee/ Pdmssupporting

confidence: 70%

“…It will be discussed separately as it gives more microscopic information about the size of the diblock copolymer; within the Leibler mean field theory and the Fredrickson-Helfand theory the radius of gyration follows the relationship R g Q m ) 1.945; e.g., assuming R g constant, Q m is expected to be constant with temperature and pressure. 7,9 Experiments, 31,34,35 extensions beyond the Fredrickson-Helfand theory, 32,33 and computer simulations, 36 however, have shown that the polymer is stretching if continuously approaching the ordering phase transition. The simulation studies have also shown that Q m does not only represent pure chain properties but also reflects cooperative effects.…”

Section: Analysis and Discussion Of The Sans Resultsmentioning

confidence: 99%

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Abnormal Pressure Dependence of the Phase Boundaries in PEE−PDMS and PEP−PDMS Binary Homopolymer Blends and Diblock Copolymers

et al. 2001

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Both polymer blends and diblock copolymers have been investigated with small-angle neutron scattering (SANS) in varying temperature and pressure fields. Four samples were studied: a polymer blend of near critical composition and the corresponding symmetric diblock copolymer of poly-(ethylethylene) (PEE) and poly(dimethylsiloxane) (PDMS) and two further symmetric diblock copolymers of poly(ethylenepropylene) (PEP) and PDMS differing in their molecular mass. From the SANS results the phase transition temperatures, the Flory-Huggins interaction parameter, the Ginzburg number, and the sizes of the chain were determined. As the transition temperature and the Flory-Huggins parameter are independently determined from the SANS data, the Clausius-Clapeyron equation offers a cross-check of the theoretical background used for SANS analysis. The resulting parameters showed for all samples qualitatively similar behavior. In particular, a quite unusual decrease of the phase boundaries in low increasing pressure regimes was observed. Analysis based on the Clausius-Clapeyron equation shows that the reason for this pressure-induced decrease of the phase boundary is a dominating increase of the entropic Flory-Huggins parameter. The Ginzburg parameter was found constant with pressure. The size of the diblock copolymer chains changes with temperature and pressure. Beyond the chain stretching observed near the ordering temperatures (T ODT) for both decreasing temperature and applied pressure, a discontinuous decrease of the chain size was consistently found at the TODT. The chain size vs temperature was found to follow a scaling behavior with slightly different exponents in the disordered and the ordered regimes consistent with former simulation calculations.

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Section: Pee-pdms Pee/ Pdmssupporting

confidence: 70%

Section: Analysis and Discussion Of The Sans Resultsmentioning

confidence: 99%

Abnormal Pressure Dependence of the Phase Boundaries in PEE−PDMS and PEP−PDMS Binary Homopolymer Blends and Diblock Copolymers

et al. 2001

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“…Experimentally, there are deviations from this power law because of chain stretching 34 . As shown in Fig.…”

Section: A Stability Limit -Rpa Resultsmentioning

confidence: 99%

Microphase separation in polyelectrolytic diblock copolymer melt: Weak segregation limit

Kumar

Muthukumar

2007

The Journal of Chemical Physics

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“…[1][2][3][4][5][6][7] The meso-structures of block copolymers in confinement systems are an important research area because of the fact that, compared with that in the bulk phase, the microphase structure can be controlled more easily. In the bulk phase, although the specific equilibrium structure can be adjusted by changing some parameters, the orientation of the structure is random while, if a symmetric diblock copolymer is confined between two parallel walls mainly two types of lamellar phase -perpendicular or parallel -appear, dependent on the width between the walls and the immiscibility of two blocks.…”

Section: Full Papermentioning

confidence: 99%

Mesophase Separation of Diblock Copolymer Confined in a Cylindrical Tube Studied by Dissipative Particle Dynamics

Feng

Liu

2006

Macro Theory & Simulations

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Summary: The morphologies of diblock copolymers confined in a cylindrical tube have been investigated by the dissipative particle dynamics (DPD) method. Results indicate that the morphology depends on the volume ratio of the immiscible blocks, the diameter of the cylindrical tube and the interactions between the blocks and between the confinement wall and blocks. For symmetric diblock copolymers, when the tube wall is uniform toward the two blocks, perpendicular lamellae or a stacked disk morphology are generally formed except when the diameter of the cylindrical tube is very small; in that case, a special bi‐helix morphology forms because of the entropy effect. When the tube wall is non‐uniform, as the diameter of the tube increases, perpendicular lamellae are first formed, then changing to parallel lamellae and, finally, back to perpendicular lamellae again. An intermediate morphology characterizing the transition between perpendicular and parallel lamellae is observed. If the non‐uniformity of the wall is further enhanced, only parallel lamellae can be found. In the case of asymmetric diblock copolymers, more complex morphologies can be obtained. Multi‐cylindrical micro‐domains and a multilayer helical phase as well as other complex pictures are observed. Generally, the morphologies obtained could find their counterparts from experiments or Monte Carlo simulations; however, differences do exist, especially in some cases of asymmetric diblock copolymers.Bi‐helix and stacked disks morphologies of A5B5 diblock copolymer confined in two different neutral nanocylinders.imageBi‐helix and stacked disks morphologies of A5B5 diblock copolymer confined in two different neutral nanocylinders.

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Gaussian- to stretched-coil transition in block copolymer melts

Cited by 234 publications

References 16 publications

Abnormal Pressure Dependence of the Phase Boundaries in PEE−PDMS and PEP−PDMS Binary Homopolymer Blends and Diblock Copolymers

Abnormal Pressure Dependence of the Phase Boundaries in PEE−PDMS and PEP−PDMS Binary Homopolymer Blends and Diblock Copolymers

Microphase separation in polyelectrolytic diblock copolymer melt: Weak segregation limit

Mesophase Separation of Diblock Copolymer Confined in a Cylindrical Tube Studied by Dissipative Particle Dynamics

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