Chemistry

Better Grafting

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Science  27 May 2005:
Vol. 308, Issue 5726, pp. 1227
DOI: 10.1126/science.308.5726.1227c

Polyolefins, such as polyethylene and polypropylene, have many uses, including shopping bags and hip replacements. To improve the solvent resistance or to make them more adhesive to polar surfaces, it is advantageous to graft polar groups onto the polymer backbone. However, current approaches to adding polar groups are either much slower than commercial polyolefin polymerization methods or are initiated by radicals at high temperatures and pressures because they are not compatible with the use of metal catalysts. Ideally, one would like to add side groups in a controlled secondary process, something that is easy to do for polymers with unsaturated bonds in the backbone, but is much more challenging for polyolefins. Díaz-Requejo et al. examined a copper-based catalytic system, which they had used to functionalize alkanes under mild conditions. For poly(2-butene), which can be thought of as polyethylene with a methyl branch at every third carbon, grafting occurred at the tertiary carbons. For random copolymers of ethylene and 1-octene, grafting occurred primarily at the secondary carbons and was controlled by the ratio of polymer to graft monomer. The authors also showed that they could also functionalize polypropylene, primarily at the secondary carbons, without any of the chain scission problems that plague the traditional radical-initiated methods. — MSL

Macromolecules 10.1021/ma050626f (2005).

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