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gem ‐Dimethyl Effects in the Thermal Behavior of Polyethylene
Author(s) -
Schwendeman John E.,
Wagener Kenneth B.
Publication year - 2005
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/macp.200500078
Subject(s) - tacticity , polyethylene , polymerization , polymer chemistry , polymer , amorphous solid , ethylene , coordination polymerization , steric effects , macromolecule , materials science , backbone chain , chemistry , metathesis , radical polymerization , organic chemistry , biochemistry , catalysis
Summary: Polyethylene can be rendered completely amorphous via the insertion of regularly spaced gem ‐dimethyl defects along its backbone, where frequency of insertion is the deciding factor in achieving the totally amorphous state. Accurate placement of defects along polyethylene's backbone is achieved with step polymerization metathesis chemistry (the ADMET reaction) rather than using chain polymerization techniques. These gem ‐dimethyl polyethylene macromolecules, when compared with other ADMET ethylene‐based model materials, demonstrate that steric bulk, frequency, and distribution of the defect along the polymer backbone are more important than stereoregularity (tacticity) when the defects are spaced nine carbon atoms or more apart. Comparisons are made between gem ‐dimethyl “defects” and methyl “defects” in a polyethylene backbone.Synthetic scheme for the ADMET‐made gem ‐dimethyl model polyethylenes ( 14a–c ).