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Dielectric investigation of molecular dynamics of blends: III. Effect of molecular weight in TMPC/PS blends
Author(s) -
Mansour Ashraf A.,
Madbouly Samy A.,
Höhne Günther W. H.
Publication year - 1996
Publication title -
polymer international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.592
H-Index - 105
eISSN - 1097-0126
pISSN - 0959-8103
DOI - 10.1002/(sici)1097-0126(199612)41:4<395::aid-pi628>3.0.co;2-g
Subject(s) - glass transition , polystyrene , materials science , polycarbonate , relaxation (psychology) , dielectric , molecular dynamics , volume fraction , polar , volume (thermodynamics) , thermodynamics , molar mass distribution , polymer , polymer chemistry , composite material , chemistry , computational chemistry , psychology , social psychology , physics , optoelectronics , astronomy
Dielectric and calorimetric measurements have been carried out for tetramethyl polycarbonate/polystyrene (TMPC/PS) blends with different compositions. The effect of varying the molecular weight of the weakly polar component (PS) on the molecular dynamics of the polar segments of TMPC has been thoroughly studied over wide ranges of frequency (10 −2 −10 5 Hz), temperature (50–220°C) and number average molecular weight, M̄ n , (6500–560 000 g mol −1 ). All blends were found to be compatible regardless of the composition ratio and the molecular weight of PS. Some new and interesting experimental findings have been observed concerning the effect of molecular weight on the glass temperature and on the broadness of the glass transition and relaxation. Neither the kinetics nor the distribution of relaxation times of the local process observed in pure TMPC was affected by blending with PS, regardless of the composition ratio or the molecular weight of PS. It has been concluded that the mixing of the polymeric components to form a homogeneous single phase (compatible blend) does not take place on a segmental level but on a structural one. The size of this structural level has been suggested to have the same volume as the cooperative dipoles, which is assumed to be the minimum volume responsible for a uniform glass transition (10–15 nm). The molecular weight dependence of the relaxation characteristics of the glass process and temperature could be attributed to the variation in the size and packing of the structural units.