The Effect of Hydrostatic Pressure on the Lower Critical Ordering Transition in Diblock Copolymers

Pollard, Michael; Russell, Thomas P.; Ruzette, Anne-Valérie; Mayes, Anne M.; Gallot, Yves

doi:10.1021/ma980316f

Cited by 85 publications

(130 citation statements)

References 17 publications

(33 reference statements)

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“…The net result is that Equation 9 is positive and the LCST/LDOT generally increases with increasing P, as has been confirmed experimentally [84][85][86] and theoretically. [86][87][88][89] This pressure dependence can be envisaged as "squeezing" the component polymers together, which counters the effect of thermally-weakened specific interactions or tempers the compressibility difference responsible for the LCST/LDOT behavior.…”

Section: Solvent and Pressure Effectssupporting

confidence: 66%

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Thermodynamics and Kinetic Processes of Polymer Blends and Block Copolymers in the Presence of Pressurized Carbon Dioxide

2008

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Environmentally‐responsible materials processing is becoming an important global consideration in a wide variety of technologies, especially those wherein volatile and/or residual organic solvents cannot be tolerated. In this context, polymer processing has benefited tremendously from advances achieved using high‐pressure CO2 as a viscosity modifier, plasticizing agent, foaming agent, and reaction medium. Pressurized CO2 is environmentally benign, inexpensive, sustainable, and versatile owing to its gas‐like viscosity and liquid‐like solubility, which can be tuned through judicious choice of temperature and pressure. The addition of high‐pressure CO2 to homopolymer blends and block copolymers can have a profound impact on polymer thermodynamics and kinetic processes since the number of interacting species increases. As a result, the compressibility as well as plasticization and intermolecular screening effects become non‐negligible. In this work, we review how these factors influence such polymeric systems, and discuss commercial polymer processes and applications that benefit from the use of high‐pressure CO2.

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Section: Solvent and Pressure Effectssupporting

confidence: 66%

“…The sorption of CO 2 preferentially occurs within the PnBMA block, wherein CO 2 exacerbates the existing free-volume effect and lowers the LDOT. As with the PS/PVME blend, exposure of a PS-b-PnBMA copolymer to hydrostatic pressure alone increases [85] the LDOT by ca. 1.5°C MPa…”

Section: Scco 2 -Modified Systemsmentioning

confidence: 97%

Thermodynamics and Kinetic Processes of Polymer Blends and Block Copolymers in the Presence of Pressurized Carbon Dioxide

2008

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“…This temperature is referred to as the order-to-disorder transition temperature (T ODT ). [15][16][17][18][19][20] Some block copolymers exhibit the disorder-to-order transition (LDOT) with increasing temperature, [21][22][23][24][25][26][27][28] and a very few show the closed-loop (or immiscibility loop) phase behavior. [29][30][31][32][33][34][35][36][37] Also, the order-toorder transition (OOT) has been reported for many block copolymers when temperature is changed.…”

Section: Introductionmentioning

confidence: 99%

Self-assembled block copolymers: Bulk to thin film

2008

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Block copolymers that two or more polymer chains are covalently linked have drawn much attention due to self-assembly into nanometer-sized morphology such as lamellae, cylinders, spheres, and gyroids. In this article, we first summarize the phase behavior of block copolymers in bulk and thin films and some applications for new functional nanomaterials. Then, future perspectives on block copolymers are described.

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“…Moreover, the v parameter often depends on composition and chain length as well. More recently the effect of pressure on the incompatibility v of homopolymer blends and the ordering in diblock copolymers has attracted attention 19) . (ii) According to the original mean field theory, the demixing temperature is independent of the molecular architecture.…”

Section: Introductionmentioning

confidence: 99%

Miscibility behavior and single chain properties in polymer blends: a bond fluctuation model study

Müller¹

1999

Macromol. Theory Simul.

106

113

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SUMMARY: Computer simulation studies on the miscibility behavior and single chain properties in binary polymer blends are reviewed. We consider blends of various architectures in order to identify important architectural parameters on a coarse grained level and study their qualitative consequences for the miscibility behavior. The phase diagram, the relation between the exchange chemical potential and the composition, and the intermolecular pair correlation functions for symmetric blends of linear chains, blends of cyclic polymers, blends with an asymmetry in cohesive energies, blends with different chain lengths, blends with distinct monomer shapes, and blends with a stiffness disparity between the components are discussed. For strictly symmetric blends the Flory-Huggins theory becomes quantitatively correct in the long chain length limit, when the v parameter is identified via the intermolecular pair correlation function. For small chain lengths composition fluctuations are important. They manifest themselves in 3D Ising behavior at the critical point and an upward parabolic curvature of the v parameter from small-angle neutron scattering close to the critical point. The ratio between the mean field estimate and the true critical temperature decreases like v p aqb 3 for long chain lengths. The chain conformations in the minority phase of a symmetric blend shrink as to reduce the number of energeticaly unfavorable interactions. Scaling arguments, detailed self-consistent field calculations and Monte Carlo simulations of chains with up to 512 effective segments agree that the conformational changes decrease around the critical point like 1a N p . Other mechanisms for a composition dependence of the single chain conformations in asymmetric blends are discussed. If the constituents of the blends have non-additive monomer shapes, one has a large positive chain-length-independent entropic contribution to the v parameter. In this case the blend phase separates upon heating at a lower critical solution temperature. Upon increasing the chain length the critical temperature approaches a finite value from above. For blends with a stiffness disparity an entropic contribution of the v parameter of the order 10 -3 is measured with high accuracy. Also the enthalpic contribution increases, because a back folding of the stiffer component is suppressed and the stiffer chains possess more intermolecular contacts. Two aspects of the single chain dynamics in blends are discussed: (a) The dynamics of short non-entangled chains in a binary blend are studied via dynamic Monte Carlo simulations. There is hardly any coupling between the chain dynamics and the thermodynamic state of the mixture. Above the critical temperatures both the translational diffusion and the relaxation of the chain conformations are independent of the temperature. (b) Irreversible reactions of a small fraction of reactive polymers at a strongly segregated interface in a symmetric binary polymer blend are investigated. End-functionalized homopolymers of different...

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The Effect of Hydrostatic Pressure on the Lower Critical Ordering Transition in Diblock Copolymers

Cited by 85 publications

References 17 publications

Thermodynamics and Kinetic Processes of Polymer Blends and Block Copolymers in the Presence of Pressurized Carbon Dioxide

Thermodynamics and Kinetic Processes of Polymer Blends and Block Copolymers in the Presence of Pressurized Carbon Dioxide

Self-assembled block copolymers: Bulk to thin film

Miscibility behavior and single chain properties in polymer blends: a bond fluctuation model study

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