ION-PAIRING POLYMERIZATION

Abstract

This account describes the development of a new type of polymerization catalysis termed ion-pairing polymerization (IPP). IPP utilizes compatible and dually active transition-metal cation–main-group anion ion pairs in which both the cation and the anion can independently catalyze the polymer chain growth in a single polymerization reaction. Furthermore, cations and anions of ion pairs can exhibit different stereoselectivity and growing chains at the cationic and anionic sites can undergo infrequent exchange between the two sites, thereby covalently linking the polymer chains produced at both sites to afford functionalized vinyl polymers with unique stereomultiblock microstructures.

Keywords:

• ion-pairing polymerization
• living polymerization
• metallocene catalysts
• stereomicrostructure
• stereospecific polymerization

Abbreviations:

• at (it, sb, st)-, atactic (isotactic, stereoblock, syndiotactic)
• BHT, butylated hydroxytoluene
• BMA, n-butyl methacrylate
• CD, circular dichroism
• CGC, Me₂Si(η⁵-Me₄C₅)(t-BuN)
• Cp, η⁵-cyclopentadienyl
• DMAA, N,N-dimethyl acrylamide
• DPAA, N,N-diphenyl acrylamide
• DSC, differential scanning calorimetry
• EBI, C₂H₄(η⁵-Ind)₂
• FG, functional group
• Flu, η⁵-fluorenyl
• GPC, gel-permeation chromatography
• mm (rr, mr), isotactic (syndiotactic, heterotactic) triad
• MMA, methyl methacrylate
• M _n (M _w), number (weight) average molecular weight
• MWD, molecular weight distribution
• P, growing polymer chain
• PDI, polydispersity index (M _w/M _n)
• PMMA, poly(MMA)
• RT, room temperature
• SBI, Me₂Si(η⁵-Ind)₂
• T _g (T _m), glass (melting) transition temperature

ACKNOWLEDGMENTS

The author is indebted to his students and co-workers whose names appear in the cited references for their invaluable contributions to the research described in this account. Acknowledgment is made to National Science Foundation, Petroleum Research Fund, Alfred P. Sloan Foundation, and Colorado State University for support of this research.