Rheological Anomalies of Syndiotactic Polystyrene
Syndiotactic polystyrene (SPS) was polymerized by a Cp* TiCl<SUB>3</SUB> (Pentamethyl cyclopentadienyl titanium trichloride)/MAO (Methylaluminoxane) catalyst system, and its rheological properties in the melt state were compared with commercial atactic polystyrene (APS) in view of the tacticity effect. The rheological properties of SPS/APS blends were also investigated. The storage and loss modulus of SPS/APS blends decreased with an increasing of APS contents in the terminal region at the same temperature and frequency. To compare rheological properties of APS with those of SPS and SPS/APS blends in the fully-melted state, the shift factor, a<SUB>T</SUB>, of APS was estimated in the high temperature range (>T<SUB>m</SUB> of SPS) by using the Arrhenius-like equation. The shift factor of SPS/APS blends decreased by increasing APS contents at 285°C and 300°C. The reason is that the sydiotactic chains have slower relaxation times due to their rotational hindrance and also more have interaction with each other. In the LogG′ vs. LogG″ plot, SPS containing samples had slopes smaller than 2 and this trend was vivid in SPS. Thus one can say that even though this system is chemically homogeneous, it is inhomogeneous in tacticity. Further work on molecular dynamics remains untouched.
日本レオロジー学会誌 25(1), 25-29, 1997-03-15