Characterization of diblock copolymer monolayers at the liquid-air interface by neutron reflectivity and surface tension measurements

We report simultaneous measurements of the concentration profile and the free energy of the submerged PS blocks of PDMS-PS diblock copolymers spread as monolayers at the air surface of ethyl benzoate as a function of surface concentration. A parabolic concentration profile is found to give the best...

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Bibliographic Details
Published in:Macromolecules 1992-11, Vol.25 (23), p.6240-6247
Main Authors: Kent, Michael S, Lee, Lay Theng, Farnoux, Bernard, Rondelez, Francis
Format: Article
Language:English
Subjects:
Applied sciences
Exact sciences and technology
Inorganic and organomineral polymers
Physical Sciences
Physicochemistry of polymers
Polymer Science
Properties and characterization
Science & Technology
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Summary:We report simultaneous measurements of the concentration profile and the free energy of the submerged PS blocks of PDMS-PS diblock copolymers spread as monolayers at the air surface of ethyl benzoate as a function of surface concentration. A parabolic concentration profile is found to give the best fit to neutron reflectivity curves among the set of two-parameter models examined. The maximum extension h*/R(g) is comparable to previously reported values obtained from a variety of techniques for similar values of the reduced surface density sigma* and indicates some stretching perpendicular to the surface. As sigma* increases from 1.3 to 4.2, the energy per PS block (obtained from surface tension measurements) increases sharply while the dependence of h* on sigma* is much weaker than the 1/3 power law dependence predicted for the strongly stretched regime. Thus, the energy required to stretch the chains for this system appears to be much larger than predicted by current theories.
ISSN:0024-9297
1520-5835
DOI:10.1021/ma00049a021