TY - JOUR
T1 - Synthesis and characterization of iPP-sPP stereoblock produced by a binary metallocene system
AU - Descour, C.D.
AU - Macko, T.
AU - Cavallo, D.
AU - Parkinson, M.
AU - Hubner, G.
AU - Spoelstra, A.B.
AU - Villani, M.
AU - Duchateau, R.
PY - 2014
Y1 - 2014
N2 - Stereoblock polypropylenes comprising of iPP and sPP segments are synthesized by polymerization of the following binary system of metallocenes: the Cs-symmetric [2,7-t-Bu2(Flu)2Ph2C(Cp)ZrCl2] and the C2-symmetric rac-Me2Si(2-Me-4-Ph-Ind)2ZrCl2. Blends of samples made either by each catalyst individually (solution blend) with materials obtained with the mixed catalyst system (reactor blend) are compared. The simultaneous presence of MAO and DEZ, enhancing fast and reversible transfer of the growing chains between the two active centers, leads to the formation of a stereoblock microstructure. In this case, low molecular weight polymers are obtained. The junction between the blocks is qualitatively observed in 13C NMR. When made in toluene, the stereoblock material consists of a majority of syndiotactic sequences, whereas the ratio is more equilibrated when the polymerization was conducted in the more polar chlorobenzene. This is confirmed by the results obtained with 13C NMR, CRYSTAF, HT HPLC, DSC, SSA, WAXD, and optical microscopy.
AB - Stereoblock polypropylenes comprising of iPP and sPP segments are synthesized by polymerization of the following binary system of metallocenes: the Cs-symmetric [2,7-t-Bu2(Flu)2Ph2C(Cp)ZrCl2] and the C2-symmetric rac-Me2Si(2-Me-4-Ph-Ind)2ZrCl2. Blends of samples made either by each catalyst individually (solution blend) with materials obtained with the mixed catalyst system (reactor blend) are compared. The simultaneous presence of MAO and DEZ, enhancing fast and reversible transfer of the growing chains between the two active centers, leads to the formation of a stereoblock microstructure. In this case, low molecular weight polymers are obtained. The junction between the blocks is qualitatively observed in 13C NMR. When made in toluene, the stereoblock material consists of a majority of syndiotactic sequences, whereas the ratio is more equilibrated when the polymerization was conducted in the more polar chlorobenzene. This is confirmed by the results obtained with 13C NMR, CRYSTAF, HT HPLC, DSC, SSA, WAXD, and optical microscopy.
U2 - 10.1002/pola.27127
DO - 10.1002/pola.27127
M3 - Article
SN - 0887-624X
VL - 52
SP - 1422
EP - 1434
JO - Journal of Polymer Science, Part A: Polymer Chemistry
JF - Journal of Polymer Science, Part A: Polymer Chemistry
IS - 10
ER -