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Depolarized light scattering from critical polymer blends
Author(s) -
Semenov Alexander N.,
Likhtman Alexei E.,
Vlassopoulos Dimitris,
Karatasos Kostas,
Fytas George
Publication year - 1999
Publication title -
macromolecular theory and simulations
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.37
H-Index - 56
eISSN - 1521-3919
pISSN - 1022-1344
DOI - 10.1002/(sici)1521-3919(19990501)8:3<179::aid-mats179>3.0.co;2-r
Subject(s) - scattering , light scattering , static light scattering , critical point (mathematics) , polymer , dynamic light scattering , structure factor , relaxation (psychology) , anisotropy , degree of polymerization , polymer blend , thermodynamics , materials science , molecular physics , chemistry , condensed matter physics , physics , polymerization , optics , mathematics , nuclear magnetic resonance , mathematical analysis , nanotechnology , psychology , social psychology , nanoparticle , copolymer
Depolarized light scattering of binary polymer blends in disordered state near the demixing critical point is considered both theoretically and experimentally. It is shown that the depolarized scattering in such systems is predominantly due to double scattering processes induced by composition fluctuations. For long enough polymer chains, this scattering is stronger than the contribution from intrinsic anisotropy fluctuations. The general equation for the static and dynamic double scattering function is obtained in terms of the system structure factor. The scattering functions are calculated both analytically and numerically (dynamic part) for polymer blends. We found that the depolarized intensity depends on the polymerization degree N and the relative distance from the critical point τ = 1 – χ */ χ (where χ is the Flory‐Huggins interaction parameter and χ * its critical value) as I vh ∼ N 2 / τ 2 , which is in good agreement with the experimental data. It is also shown that the dynamic scattering function is decaying non‐exponentially. We calculate the relaxation rate and the non‐exponentiality parameter as functions of the scattering angle and τ . These theoretical predictions are compared with experimental data for three chemically different blends.