Influence of 2,1‐erythro regiodefects on the crystallization behavior of isotactic polypropylene

Abstract

We produced isotactic polypropylene (iPP) samples with metallocene catalysts, containing 2,1‐erythro regiodefects between ∼0% and 3.4% and only trace amounts of stereodefects, and studied their thermal properties in order to quantify the influence of regiodefects on the crystallization behavior of iPP. Isothermal and nonisothermal experiments performed on these samples show that increasing the regiodefects content proportionally slows down crystallization rate, apparently without phase transitions or additional phenomena. The analysis of the rigid amorphous fraction and the mobile amorphous fraction however reveals a different behavior of samples containing more than ∼1.5% regiodefects, related to the inclusion of these defects in the lamellae. Additionally, the wide range of regiodefects and a novel calculation approach allowed us to estimate the equilibrium melting temperature of a fully iPP free of defects to be 206°C .

Microstructural details and polymorphs in poly(propylene‐ co ‐1‐nonene) copolymers synthesized at different polymerization temperatures

“…[25,28,31,74] Defects in general have a profound influence on the crystallization behavior of iPP. [75] Moreover, and as mentioned above, two components are observed for the two copolymers with the highest contents, attributed to crystalline and mesophase, with the mesophase line appearing at around 20 C below that of the crystal. Figures 7b and 8b, it follows that the effect of comonomer content on the variation of the peak crystallization temperature (around 90 C among the different copolymers) is considerably higher than that exhibited by the melting temperature, varying only around 60 C.…”

Influence of Temperature on the Regioselectivity of Highly Isospecific C2-Symmetric Zirconocenes in Propene Polymerization

“…The high content of isolated regiodefects in the iPP samples from 3 /MAO, coupled to the absence of mrrm or any other chain defect, provides an ideal set of samples for structure–property correlations studies on the effect of such regiodefects on iPP properties. This investigation is in progress in our laboratories and will be reported in due time …”

“…A thorough analysis of the thermal behavior of iPP with high amounts of regiodefects is currently being carried out and will be discussed elsewhere …”

Triptycene as a scaffold in metallocene catalyzed olefin polymerization

“…Spaleck-type selectivity would be <1% stereo-errors and 1-2% 2,1e regiodefects. 56 Resconi [56][57][58] has reported up to 3.4% 2,1 regioerrors in polymers produced with rac-Me 2 Si(2-Me-4-Ph-5-OMe-6-tBu-Ind) 2 ZrCl 2 . 55 The regioselectivity and 3,1-isomerization tendency of this catalyst is however tied to activation/immobiliz- Dalton Transactions Paper ation conditions.…”