Functional polyisobutylenes via electrophilic cleavage/alkylation |
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Authors: | C. Garrett Campbell Robson F. Storey |
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Affiliation: | School of Polymers and High Performance Materials, The University of Southern Mississippi, Hattiesburg, Mississippi |
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Abstract: | Lewis‐acid catalyzed degradation of poly(isobutylene‐co‐isoprene) (butyl rubber) in the presence of an alkoxybenzene compound was studied as a new route toward low molecular weight multifunctional polyisobutylenes. Simultaneous cleavage and functionalization of butyl rubber was conducted at ?70 °C and ?40 °C under TiCl4 or AlCl3 catalysis in 60/40 hexane/methylene chloride cosolvents in the presence of (3‐bromopropoxy)benzene (BPB) for various times up to 24 h. The butyl rubber (EXXON? Butyl 365) possessed M n = 1.91 × 105 g/mol, PDI = 1.66 (GPC/MALLS), and 2.30 mol % isoprene units (nearly exclusively trans ?1,4). At ?70 °C with TiCl4, molecular weight was reduced to various values within the range 7 to 11 × 103 g/mol depending on conditions; lower BPB concentration produced lower molecular weight. However, the ratio of isobutylene repeat units to BPB units (IB/Q ) remained constant at about 43:1, which is approximately the same as the ratio of isobutylene to isoprene repeat units (IB/IP) in the starting butyl rubber (42.5:1). At ?40 °C with TiCl4, molecular weight was reduced to about 5 × 103 g/mol, and IB/Q was reduced below IB/IP, indicating nearly a difunctional telechelic structure. AlCl3 was a more active catalyst and produced results similar to TiCl4 at ?40 °C, even when used at seven times lower concentration. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 1991–1997 |
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Keywords: | alkoxybenzene electrophilic cleavage functionalization of polymers Friedel‐Crafts alkylation polyisobutylene polyolefins telechelics |
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