The influence of the presence of different amounts m-methylstyrene (m-MS), in the composition range 4−21 mol %, on the polymorphic behavior of syndiotactic polystyrene (s-PS) is presented. A comparison with the effect of the presence of p-methylstyrene is also presented. The behavior of copolymers subjected to solvent extraction or annealing procedures indicates that the presence of m-MS stabilizes the γ form of s-PS, which remains stable in a large temperature range, up to 210−220 °C. The helical mesoporous δ form of s-PS has not been observed in copolymers with m-MS. The presence of low contents of m-MS induces crystallization of the β form from polymer solution (by casting at high temperatures), whereas high concentrations of m-MS tend to stabilize the γ form. The copolymer samples crystallize from the melt in α and β forms depending on the concentration of m-MS, which stabilizes the β form for composition around 11 mol %, and induces crystallization in the α form for lower (4 mol %) and higher (21 mol %) concentration. Moreover, even when the memory of the α form is maintained in the melt, the presence of m-MS in a concentration around 11 mol % induces the crystallization of the β form, whereas, even though no memory of the α form is present in the melt, samples with 4 and 21 mol % of m-MS crystallize in the α form. The α form obtained in these copolymers, by melt-crystallization or annealing of the γ form, does not correspond to neither the disordered α‘, nor the ordered α‘ ‘ modifications observed in s-PS. The presence of m-MS comonomeric units induces structural variation in the crystal packing of the trans-planar chains, and a new crystalline form is obtained.

Polymorphic Behavior of Copolymers of Syndiotactic Polystyrene with m-Methylstyrene.

CAPORASO, Lucia
2003-01-01

Abstract

The influence of the presence of different amounts m-methylstyrene (m-MS), in the composition range 4−21 mol %, on the polymorphic behavior of syndiotactic polystyrene (s-PS) is presented. A comparison with the effect of the presence of p-methylstyrene is also presented. The behavior of copolymers subjected to solvent extraction or annealing procedures indicates that the presence of m-MS stabilizes the γ form of s-PS, which remains stable in a large temperature range, up to 210−220 °C. The helical mesoporous δ form of s-PS has not been observed in copolymers with m-MS. The presence of low contents of m-MS induces crystallization of the β form from polymer solution (by casting at high temperatures), whereas high concentrations of m-MS tend to stabilize the γ form. The copolymer samples crystallize from the melt in α and β forms depending on the concentration of m-MS, which stabilizes the β form for composition around 11 mol %, and induces crystallization in the α form for lower (4 mol %) and higher (21 mol %) concentration. Moreover, even when the memory of the α form is maintained in the melt, the presence of m-MS in a concentration around 11 mol % induces the crystallization of the β form, whereas, even though no memory of the α form is present in the melt, samples with 4 and 21 mol % of m-MS crystallize in the α form. The α form obtained in these copolymers, by melt-crystallization or annealing of the γ form, does not correspond to neither the disordered α‘, nor the ordered α‘ ‘ modifications observed in s-PS. The presence of m-MS comonomeric units induces structural variation in the crystal packing of the trans-planar chains, and a new crystalline form is obtained.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11386/1867703
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