Effect of composition fluctuations on tracer diffusion in symmetric diblock copolymers

1998 ◽  
Vol 108 (11) ◽  
pp. 4634-4639 ◽  
Author(s):  
Rangaramanujam M. Kannan ◽  
Jie Su ◽  
Timothy P. Lodge
Keyword(s):  
Diblock Copolymers ◽  
Tracer Diffusion ◽  
Composition Fluctuations

Pressure and Temperature Effects in Homopolymer Blends and Diblock Copolymers

1997 ◽  
Vol 30 (5) ◽  
pp. 696-701 ◽  
Author(s):  
H. Frielinghaus ◽  
D. Schwahn ◽  
K. Mortensen ◽  
L. Willner ◽  
K. Almdal
Keyword(s):  
Interaction Parameter ◽  
Diblock Copolymers ◽  
Mean Field ◽  
Three Dimensional ◽  
Thermal Fluctuation ◽  
Thermal Fluctuations ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
Phase Boundaries ◽  
Composition Fluctuations

Thermal composition fluctuations in a homogeneous binary polymer blend and in a diblock copolymer were measured by small-angle neutron scattering as a function of temperature and pressure. The experimental data were analyzed with theoretical expressions, including the important effect of thermal fluctuations. Phase boundaries, the Flory–Huggins interaction parameter and the Ginzburg number were obtained. The packing of the molecules changes with pressure. Therefore, the degree of thermal fluctuation as a function of packing and temperature was studied. While in polymer blends packing leads, in some respects, to a universal behaviour, such behaviour is not found in diblock copolymers. It is shown that the Ginzburg number decreases with pressure sensitively in blends, while it is constant in diblock copolymers. The Ginzburg number is an estimation of the transition between the universality classes of the `mean-field' approximation and the three-dimensional Ising model. The phase boundaries in blends increase with pressure, while the phase boundary of the studied block copolymer shows an unusual shape: with increasing pressure it first decreases and then increases. Its origin is an increase of the entropic and of the enthalpic parts, respectively, of the Flory–Huggins interaction parameter.

Intermediate Wavelength Composition Fluctuations in Diblock Copolymers:  Modification of the Diffusive Mode near the Ordering Transition

2002 ◽  
Vol 35 (2) ◽  
pp. 522-528 ◽  
Author(s):  
K. Chrissopoulou ◽  
L. Papoutsakis ◽  
S. H. Anastasiadis ◽  
G. Fytas ◽  
G. Fleischer ◽  
...  
Keyword(s):  
Diblock Copolymers ◽  
Composition Fluctuations ◽  
Ordering Transition

Dynamics of the Most Probable Composition Fluctuations of “Real” Diblock Copolymers near the Ordering Transition

2001 ◽  
Vol 34 (7) ◽  
pp. 2156-2171 ◽  
Author(s):  
K. Chrissopoulou ◽  
V. A. Pryamitsyn ◽  
S. H. Anastasiadis ◽  
G. Fytas ◽  
A. N. Semenov ◽  
...  
Keyword(s):  
Diblock Copolymers ◽  
Composition Fluctuations ◽  
Ordering Transition

Rich Dynamics in Diblock Copolymers

2004 ◽  
Vol 856 ◽  
Author(s):  
G. Fytas
Keyword(s):  
Phase Diagram ◽  
Structure Factor ◽  
Diblock Copolymers ◽  
Photon Correlation Spectroscopy ◽  
Dynamic Structure ◽  
High Molecular Mass ◽  
Correlation Spectroscopy ◽  
Dynamic Structure Factor ◽  
Photon Correlation ◽  
Composition Fluctuations

ABSTRACTThe dynamic structure factor S(q, t) of ultra-high molecular mass diblock copolymers BC in a common solvent was systematically investigated by photon correlation spectroscopy in different regimes of the phase diagram. Through proper probing of the composition fluctuations in symmetric and asymmetric BC the different relaxation mechanisms were identified and the influence of the disorder to order (ODT) transition was assessed. In the disordered regime, S(q, t) sensitively depends on the composition polydispersity of BC and the proximity to ODT complementing the real phase morphology of BC. The dynamic response of BC is therefore predictable.

Composition fluctuations in homopolymer blends and diblock copolymers

2000 ◽  
Vol 276-278 ◽  
pp. 375-376
Author(s):  
H Frielinghaus ◽  
K Mortensen ◽  
K Almdal
Keyword(s):  
Diblock Copolymers ◽  
Homopolymer Blends ◽  
Composition Fluctuations

Morphological behavior of compatibilized ternary blends prepared by mechanical mixing

1993 ◽  
Vol 51 ◽  
pp. 1200-1201
Author(s):  
S.D. Smith ◽  
R.J. Spontak ◽  
D.H. Melik ◽  
S.M. Buehler ◽  
K.M. Kerr ◽  
...  
Keyword(s):  
Interfacial Adhesion ◽  
Diblock Copolymers ◽  
Ternary Blends ◽  
Mechanical Mixing ◽  
Design Considerations ◽  
Covalently Bonded ◽  
Homopolymer Blends ◽  
Emulsifying Agent ◽  
Surface Active ◽  
Low Entropy

When blended together, homopolymers A and B will normally macrophase-separate into relatively large (≫1 μm) A-rich and B-rich phases, between which exists poor interfacial adhesion, due to a low entropy of mixing. The size scale of phase separation in such a blend can be reduced, and the extent of interfacial A-B contact and entanglement enhanced, via addition of an emulsifying agent such as an AB diblock copolymer. Diblock copolymers consist of a long sequence of A monomers covalently bonded to a long sequence of B monomers. These materials are surface-active and decrease interfacial tension between immiscible phases much in the same way as do small-molecule surfactants. Previous studies have clearly demonstrated the utility of block copolymers in compatibilizing homopolymer blends and enhancing blend properties such as fracture toughness. It is now recognized that optimization of emulsified ternary blends relies upon design considerations such as sufficient block penetration into a macrophase (to avoid block slip) and prevention of a copolymer multilayer at the A-B interface (to avoid intralayer failure).

Triply-periodic nanostructures in surfactant, block copolymer, and biomembrane systems, and simulation of TEMs

1993 ◽  
Vol 51 ◽  
pp. 884-885
Author(s):  
David M. Anderson ◽  
Tomas Landh
Keyword(s):  
Liquid Crystalline ◽  
Diblock Copolymers ◽  
Cubic Phase ◽  
List Type ◽  
Interpenetrating Networks ◽  
Triply Periodic ◽  
Wide Range ◽  
Bicontinuous Cubic ◽  
Phase Liquid ◽  
Dividing Surface

First discovered in surfactant-water liquid crystalline systems, so-called ‘bicontinuous cubic phases’ have the property that hydropnilic and lipophilic microdomains form interpenetrating networks conforming to cubic lattices on the scale of nanometers. Later these same structures were found in star diblock copolymers, where the simultaneous continuity of elastomeric and glassy domains gives rise to unique physical properties. Today it is well-established that the symmetry and topology of such a morphology are accurately described by one of several triply-periodic minimal surfaces, and that the interface between hydrophilic and hydrophobic, or immiscible polymer, domains is described by a triply-periodic surface of constant, nonzero mean curvature. One example of such a dividing surface is shown in figure 5.The study of these structures has become of increasing importance in the past five years for two reasons:1)Bicontinuous cubic phase liquid crystals are now being polymerized to create microporous materials with monodispersed pores and readily functionalizable porewalls; figure 3 shows a TEM from a polymerized surfactant / methylmethacrylate / water cubic phase; and2)Compelling evidence has been found that these same morphologies describe biomembrane systems in a wide range of cells.

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