Polymerization of Allyltrimethylisilane and 4-Methyl-1-Pentene by Using Metallocene Catalysts

Area of Science:

• Polymer Chemistry
• Materials Science
• Catalysis

Background:

• Higher olefin polymers are crucial in biomedical applications like extracorporeal membrane oxygenation (ECMO), especially for severe COVID-19 patients.
• Single-site catalysts, such as metallocenes, offer enhanced performance in polymer synthesis.
• Allyltrimethylsilane (ATMS) and 4-methyl-1-pentene (4M1P) are key monomers for advanced polymer development.

Purpose of the Study:

• To investigate the homo- and co-polymerization of ATMS and 4M1P using syndiospecific and isospecific metallocene catalysts.
• To characterize the resulting polymers' molecular weight, stereotacticity, and copolymer formation.
• To analyze the thermal and crystalline properties of the synthesized polymers.

Main Methods:

• Ziegler-type polymerization utilizing syndiospecific (cat 1) and isospecific (cat 2) metallocene catalysts.
• ¹³C-NMR spectroscopy for determining polymer stereotacticity and confirming copolymer structure.
• Differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD) for thermal and crystallization analysis.

Main Results:

• Syndiospecific catalyst (cat 1) yielded low conversions and high molecular weight polymers, while the isospecific catalyst (cat 2) showed the opposite.
• ¹³C-NMR confirmed the formation of true ATMS/4M1P copolymers.
• Synthesized polymers exhibited high melting temperatures and low melting enthalpies; isotactic 4M1P-rich copolymers formed an unusual crystal form I.

Conclusions:

• Metallocene catalysts enable controlled synthesis of ATMS and 4M1P copolymers with tunable properties.
• The stereochemistry of the catalyst significantly impacts polymer molecular weight and conversion.
• The unusual crystal form observed in isotactic 4M1P-rich copolymers warrants further investigation for potential applications.