Photoinitiated Grafting of Maleic Anhydride Onto Polypropylene

Document Type

Article

Publication Date

4-15-2004

Department

Polymers and High Performance Materials

Abstract

The photoinitiated grafting of maleic anhydride (MAH) onto polypropylene with the use of benzophenone (BP) as the initiator has been investigated. In comparison with the process of thermally initiated grafting with peroxide as the initiator, photoinitiated grafting affords a higher grafting efficiency. The efficient photografting sensitized by BP can be explained by two possible mechanistic processes: the sensitization of the formation of the excited triplet state of MAH by BP and electron transfer followed by proton transfer between MAH and the benzopinacol radical, which may operate together. In the former case, the generated MAH excited triplet state abstracts a hydrogen from the polymer substrate to initiate grafting. A rate constant of 3.6 x 10(9) M (-1) s (-1) has been determined by laser flash photolysis for the process of quenching the excited triplet state of BP with ground-state MAH. In comparison, the rate constant for the quenching of the excited triplet state of BP by hydrogen abstraction has been determined to be 4.1 x 10(5) M (-1) S (-1). In a study of photografting using a model compound, 2,4-dimethylpentane, as a small-molecule analogue of polypropylene, the loss of BP was significantly reduced upon the addition of MAH, and this is consistent with the proposed mechanistic processes. (C) 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1953-1962, 2004.

Publication Title

Journal of Polymer Science Part A-Polymer Chemistry

Volume

42

Issue

8

First Page

1953

Last Page

1962

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