Two novel silyl-bridged C 2 -symmetric (2-methyl-4-aryl-7methoxy) substituted bisindenyl based ansa-hafnocene complexes of varied steric demand (I, II,-phenyl]) were synthesized and examined in the coordinative polymerization of propene. Both complexes enable a comparative study with the state of the art homogeneous metallocene catalyst (III, 4-[(3′,5′-tert-butyl)-phenyl]) for high melting ultrahigh molecular weight isotactic polypropylene. All three activated complexes exhibit extremely concise stereoregularity along with high molecular weights and high melting transitions at low to moderate polymerization temperatures. Increased sterical encumbrance of the 4-aryl substituent prevents the process of chain release reactions more effectively, especially due to enhanced reduction of β-methyl elimination. Accordingly, end group analysis disclosed the highest selectivity toward allylic chain ends as a result of β-methyl elimination with the less sterically encumbered complex I. Examination of the catalytic activity of I−III disclosed considerable impact of the varied 4-aryl substituents on the maximum productivity with respect to the applied polymerization conditions considering the combined influence of activation, monomer diffusion rate, catalyst deactivation, and rate of chain growth.

The C 1-symmetric metallocenes rac-[1-(9-η5-fluorenyl)-2-(5,6-cyclopenta-2-methyl-1-η5-indenyl)­ethane]­zirconium dichloride (1) and rac-[1-(9-η5-fluorenyl)-2-(5,6-cyclopenta-2-methyl-1-η5-indenyl)­ethane]­hafnium dichloride (2) are known to produce elastic polypropylene. They were investigated concerning their temperature stability during the polymerization of propene. After activation of these complexes with triisobutylaluminum (TIBA)/­[CPh3]­[B­(C6F5)4], first polymerization experiments (80–100 °C) afforded moderate to high activities. However, at these polymerization temperatures, the molecular weights of the produced polymers are significantly decreased, resulting in a waxy appearance and, therefore, a loss of the elastic behavior. The main reason for this behavior, especially for the more significant decrease of the molecular weight in the case of hafnocene 2 compared with zirconocene 1, was revealed to occur due to a fast β-methyl transfer reaction. Hence, hafnocene 2 can form polymer chains with a high selectivity toward allylic chain ends. These macromonomers can be used in the catalytic insertion polymerization for the formation of new grafted copolymers. Initial copolymerization experiments with ethene were conducted.

A series of poly(dialkyl vinylphosphonate)s (PDAVPs) have recently been reported to be available via rare earth metal-mediated group transfer polymerization (REM-GTP). We extend the existing portfolio of polyvinylphosphonates (PVPs) by presenting poly(ditolyl vinylphosphonate) (PDTVP) as the first example of a poly(diaryl vinylphosphonate) (PDArVP). Thermogravimetric analyses revealed that, for PDTVP, in contrast to the selected PDAVPs, side group cleavage does not occur. Instead, thermal decomposition takes place in a one-step mechanism at high temperatures above 350 °C. A series of PDAVPs and PDTVP were tested for their performance as flame-retardant additives (FRA) as well as flame-retardant coatings (FRC) for polycarbonate (PC). We thereby found that PDTVP is a promising FRA, because of its high thermal stability and its compatibility with polycarbonate. Poly(diisopropyl vinylphosphonate) (PDIVP) shows excellent performance as an FRC, because it forms a stable, blistered crust of poly(vinylphosphonic acid) (PVPA) upon flame treatment.

Phosphine-sulfonate)Pd(Me)(DMSO) catalyzed copolymerization of ethylene and 3,3,3-trifluoropropene (TFP) allows the synthesis of linear copolymers with high fluorine contents of up to 15 wt % (8.9 mol % TFP). 13 C and 19 F NMR analyses of the copolymers were performed, showing that most of the incorporated TFP is located in the polymer backbone. Copolymerization of ethylene-d 4 with TFP revealed that TFP is inserted into Pd-D bonds in 1,2-as well as in 2,1-mode, although 1,2-insertion is slightly preferred. Chain transfer after TFP insertion is exclusively observed following 2,1-insertion. With higher TFP incorporation, an increase in the ratio of internal to terminal double bonds was detected in the 1 H NMR spectra. This indicates that, in the case of 2,1-insertion of TFP, chain walking is facilitated relative to direct chain release after β-H transfer to the palladium center.

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