Silicon-Modified Ziegler−Natta Polymerization. Catalytic Approaches to Silyl-Capped and Silyl-Linked Polyolefins Using “Single-Site” Cationic Ziegler−Natta Catalysts

Abstract

This contribution reports efficient and selective organotitanium-mediated silanolytic (PhSiH3, PhMeSiH2, Me2SiH2, Et2SiH2) chain transfer in the homogeneous polymerization and copolymerization of a variety of α-olefins. The result is several broad classes of silyl-capped and silyl-linked polyolefins which have been characterized by 1H/13C/29Si NMR and IR spectroscopy as well as by GPC. “Single-site” Ziegler−Natta catalysts effect this chain transfer with significant efficiency and scope. For [Me2Si(Me4C5)tBuN]TiMe+B(C6F5)4 --mediated propylene polymerization, the mechanism of chain transfer is supported by the observation that M n of the capped atactic polypropylenes produced at constant [catalyst], [PhSiH3], and [propylene] is inversely proportional to [PhSiH3]. Using the same catalyst, this process also efficiently produces silyl endcapped poly(1-hexene), ethylene + 1-hexene copolymers, ethylene + styrene copolymers (both with high degrees of comonomer incorporation), and (at low temperatures) polyethylene. In the case of rac-C2H4(Ind)2TiMe+B(C6F5)4 - + propylene and (Me5C5)TiMe2 +B(C6F5)4 - + styrene, PhH2Si-functionalized isotatic polypropylene and syndiotactic polystyrene, respectively, are produced. Using 1,4-disilabenzene and 1,3,5-trisilabenzene as chain-transfer agents in the presence of [Me2Si(Me4C5)tBuN]TiMe+B(C6F5)4 - + propylene, linear diblock and starlike atactic polypropylene structures, respectively, are produced. In addition to primary silanes, secondary silanes (PhMeSiH2, Me2SiH2, Et2SiH2) are efficient and selective chain-transfer agents in this organotitanium-mediated polymerization. In the presence of [Me2Si(Me4C5)tBuN]TiMe+B(C6F5)4 - + propylene, (Me5C5)TiMe2 +B(C6F5)4 - + propylene, and (Me5C5)TiMe2 +B(C6F5)4 - + styrene, PhMeHSi- or Me2HSi-capped atactic polypropylene and PhMeHSi-, Me2HSi-, or Et2HSi-capped syndiotactic polystyrene are produced, respectively. Using PhH2Si-capped polypropylene as a chain-transfer agent, an atactic polypropylene−syndiotactic polystyrene AB block copolymer is produced in the presence of (Me5C5)TiMe2 +B(C6F5)4 - + styrene.

Ethene homo- and ethene/propene copolymerization using a MAO activated cyclopentadienyl-amido half-sandwich complex

“…[1,[3][4][5] Even though these systems are efficiently activated with MAO, the effect of the MAO/M (M = Ti, Zr, Hf) molar ratio on the polymerization activity and on the polymer properties has only been studied in the case of bis-indenyl, bis-cyclopentadienyl or Cp-fluorenyl systems carrying chlorine and/or alkyl groups as additional ligands. [6,7] Furthermore, the catalytic behaviour of halfsandwich Cp-amido complexes investigated in the homogeneous catalytic polymerization until now contain a dialkylsilanediyl bridge, [1,2,4,8] whereas the systems analysed here contain a hydrocarbon bridge. [5,9,10] The new ((cyclopentadienyl)(N-ethylamido)ethylene) titanium di(diethylamino) complex was prepared in the present work.…”

Silyl‐Terminated Ethylene‐co‐Norbornene Copolymers by Organotitanium‐Based Catalysts

“…The Ph, SiCH 2 , copolymer backbone, and chain-end CH 3 moieties are assigned by comparison to literature data. [7] The overlap between the CH 3…”

“…As shown by Marks, organosilanes are effective chain-transfer agents in organotitanium-mediated polymerization processes, producing polyolefins having silanolytic chain-ends functionality. [7] Ethylene (E)-norbornene (N) copolymers [8,9] are thermoplastic materials that have recently received great attention because of their attractive properties such as high glass transition temperature (T g ), high optical transparency, excellent moisture barrier, biocompatibility, and chemical resistance. [10] These distinctive properties of the copolymers enable them for a large use in advanced packaging, engineering components, and optical applications.…”

“…The ''constrained geometry'' [Ti(h 4 ] active species exhibits high activity for silanolytic chain-transfer processes in a-olefin polymerization with no detectable silane dehydro-coupling products. [7] E-co-N copolymerizations with narrow polydispersities have been achieved with 1/MAO.…”

Synthesis and functionalization of ethylene/p-allyltoluene copolymer

“…Several reactive comonomers, such as borane [5], pmethylstyrene (p-MS) [6], diene [7] and silane [8], have been studied. Among them, p-MS showed outstanding properties that could be converted to various functional groups, such as -OH, -NH 2 , -COOH, halides [9] and maleic anhydride [10] at mild conditions with high degree of conversion.…”