Stereoblock Polypropylenes Prepared by Efficient Chain Shuttling Polymerization of Propylene with Binary Zirconium Catalysts and iBu3Al

Preparation of Well-Controlled Isotactic Polypropylene-Based Block Copolymers with Superior Physical Performance via Efficient Coordinative Chain Transfer Polymerization

“…For the polymerization of propylene in this study, we used a well-known dimethyl­(pyridyl­amido)hafnium complex that plays a vital role in CSC and continuously produces ethylene-based block copolymers via CCTP in the presence of Et 2 Zn or (Oct) 3 Al. ,− In addition to its activity for copolymerization of ethylene and α-olefins, this complex, when activated by [Ph 3 C]­[B­(C 5 F 5 ) 4 ]/ i Bu 3 Al, also shows high activity for isoselective α-olefin polymerization ([mmmm] > 99%) to afford products with high molecular weights and narrow PDIs (∼2). − Because our preliminary experimental results showed that this catalyst is much more active for propylene polymerization than for ethylene polymerization under similar reaction conditions, we tried a one-pot approach for two- and three-step reactions to prepare well-controlled i PP-based diblock and triblock copolymers (Scheme ).…”

“…Although much of the research in the field of coordination polymerization has focused on suppressing chain transfer reactions, research conducted by the Dow Chemical Company has revealed that coordinative chain transfer polymerization (CCTP) can be useful for preparing olefin block copolymers. In one very successful example, ethylene/α-olefin multiblock copolymers with both hard and soft blocks were obtained by using a promising dual-catalyst chain shuttling copolymerization (CSC). − In the past decade, several promising multiblock copolymers composed of various semicrystalline (hard)/amorphous (soft) blocks that combine different physical properties have been successfully prepared via CSC. − We tried to synthesize stereoblock PP bearing isotactic and atactic PP segments via CSC of propylene with catalysis by binary zirconium complexes in the presence of i Bu 3 Al as a chain shuttling agent . The resulting multiblock copolymers showed complex regularity (iso-, syndio-, and atactic segments were present in the main chain), although their tensile properties were superior to those of physical blends of PPs obtained by the single catalyst system.…”

“…The resulting multiblock copolymers showed complex regularity (iso-, syndio-, and atactic segments were present in the main chain), although their tensile properties were superior to those of physical blends of PPs obtained by the single catalyst system. Evidently, the CSC approach has strict requirements not only for the two selective catalysts but also for a proper chain shuttling agent, and therefore i PP-based block copolymers with desired microstructures and properties have not yet been achieved. , Harney et al reported that PE-based block copolymers with a number-average molecular weight ( M n ) of 44 kDa and a PDI of 1.67 can be efficiently prepared via single-catalyst CCTP in continuously stirred tank reactors . Unlike ordinary living or quasi-living polymerization, continuous CCTP involves one catalyst that produces multiple chains, making this method suitable for the preparation of large quantities of block copolymers and thus potentially useful for industrial applications.…”

Synthesis and characterization of polyolefin thermoplastic elastomers: A review

“…A chain shuttling agent (CSA) is required in the chain shuttling polymerization to allow the connection of soft and hard segments to form the OBCs. [12,[80][81][82][83][84][85][86] Another approach is living coordination polymerization, which allows the successive growth of polymer chains to form the block structure. [66,87] 3.1 | Synthetic strategies…”

iPP/PE Multiblock Copolymers for Plastic Blend Recycling Synthesized by Coordinative Chain Transfer Polymerization

“…Note that in ref , where copolymers having a PE backbone with i PP side chains were reported, the macromonomer or side chain synthesis was accomplished in a nonliving fashion. Coordinative chain transfer polymerization (CCTP) is an economic alternative to living polymerization since an inexpensive metal alkyl, such as triethylaluminum (AlEt 3 ), diethylzinc, or dialkylmagnesium, acts as an initiator, , and an added polymerization catalyst mediates the chain growths of these alkyl groups successively in the presence of monomers, such as ethylene − and propylene. − One expensive catalyst molecule now forms numerous macromolecules in a highly controlled fashionliving polymerization multiplied.…”