Copolymerization of propylene with higher α‐olefins in the presence of the syndiospecific catalyst i‐Pr(Cp)(9‐Flu)ZrCl₂/MAO

Abstract

The catalyst system i‐Pr(Cp)(9‐Flu)ZrCl2/methylaluminoxane was used for the synthesis of random syndiotactic copolymers of propylene with 1‐hexene, 1‐dodecene, and 1‐octadecene as comonomers. An investigation of the microstructure by 13C NMR spectroscopy revealed that the stereoregularity of the copolymers decreased because of an increase in skipped insertions in the presence of the higher 1‐olefin. The melting temperature of the copolymers, as measured by differential scanning calorimetry (DSC), decreased linearly with increasing comonomer content independently of the comonomer nature. During the DSC heating cycle, an exothermic peak indicating a crystallization process was observed. The decrease in the crystallization temperature with higher 1‐olefin content, measured by crystallization analysis fractionation, indicated a small but significant dependence on the nature of the comonomer. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 40: 128–140, 2002

Nonisothermal crystallization and melting behavior of syndiotactic polypropylenes of different microstructure

“…The MDSC for sample sPPB3 are shown in Figure 3. It is seen that the exothermic process on heating is associated almost exclusively with a nonreversing process, and supports the conclusion that the exothermic peak found on heating for these samples is due to a cold crystallization process related to macromolecular segments that were not able to crystallize during cooling 24, 25. However, the subsequent melting process has both real and imaginary contributions20 and we suppose that the out‐of‐phase contribution is associated with a melt, recrystallization, and remelt process, associated with the small endothermic peak around 100 °C in the total heat flow in Figures 2 and 3.…”

“…Arranz‐javier et al24 found that the second melting of sPP homopolymer shows a cold crystallization around 45 °C, but when 1‐olefins (1‐hexene, 1‐octene, and 1‐octadecene) are incorporated into the sPP main chain this exothermic process disappears and the samples become amorphous under those crystallization conditions. Similar results are reported by Graef et al25 but in an opposite way, since the sPP homopolymers do not present any exothermic process on heating, but its copolymers with 1‐hexene showed an important cold crystallization. Therefore, more detailed studies need to be done to explain the complete crystallization and melting behavior of syndiotactic propylene/1‐olefin copolymers.…”

Syndiotactic polypropylene copolymer membranes and their performance for oxygen separation

“…1, and the prominent peaks around 20, 28 and 47 ppm correspond to the methyl, methine and methylene groups of propylene units. The corresponding assignments of the 13 C NMR spectra were made taking into account references [29][30][31]. Table 1 also presents the physical properties of the syndiotactic polypropylene and its copolymers with 1-hexene and 1-octadecene.…”

13Carbon nuclear magnetic resonance characterization of ethylene–propylene–1-octadecene terpolymers and comparison with ethylene–propylene–1-hexene and 1-decene terpolymers

“…A possible explanation to this fact it may be related with the polymerization temperature. Ethylene presents a better activity at higher temperatures (60 8C) [30] on the other hand propylene presents a better performance at 40 8C [13,31], the temperature in which these reactions were done. Table 8 also shows that the increase of propylene in the feed from 5 to 95% with respect to ethylene causes an increase in the catalytic activity for the copolymers of ethylene-propylene (column EP lines 2-8) as for the terpolymers with 1-hexene (column EPH, lines 2-8).…”