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Synthesis of Chain‐End Functionalized PP and Applications in Exfoliated PP/Clay Nanocomposites
Author(s) -
Wang Z.M.,
Han H.,
Chung T.C.
Publication year - 2005
Publication title -
macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 1022-1360
DOI - 10.1002/masy.200550710
Subject(s) - polymer chemistry , polypropylene , polymer , tacticity , polymerization , end group , molar mass distribution , materials science , styrene , functional group , chain transfer , reactivity (psychology) , nanocomposite , chemistry , copolymer , radical polymerization , nanotechnology , composite material , medicine , alternative medicine , pathology
This paper summarizes our research to the preparation of chain‐end functionalized isotactic polypropylene (i‐PP) having a terminal functional group, such as an OH and an NH 2 . The chemistry involves metallocene‐mediated propylene polymerization using the rac‐Me 2 Si[2‐Me‐4‐Ph(Ind)] 2 ZrCl 2 /MAO complex in the presence of styrene derivatives (St‐f) and hydrogen, which serve as the chain transfer agents. The molecular weight of the resulting i‐PP polymers with terminal OH or NH 2 groups (i.e., PP‐t‐OH and PP‐t‐NH 2 ) are inversely proportional to the molar ratio of [St‐f]/[propylene]. Despite the extremely low concentration of functional groups, the high molecular weight NH 3 + ‐terminated PP (PP‐t‐NH 3 + ) exhibits a distinctive advantage over other functional PP polymers containing side chain functional groups or long functional blocks. The terminal hydrophilic NH 3 + cation, with good mobility and reactivity, effectively ion‐exchanges the cations (Li + , Na + , etc.) located between the clay interlayers, and anchors the PP chain to the clay surfaces. On the other hand, the remaining rest of the unperturbed, end‐tethered, high molecular weight PP tail exfoliates the clay layers. This exfoliated structure is maintained even after further mixing of the PP‐bearing platelets with pure, neat PP polymers.