Polyisobutylene containing covalently bound antioxidant moieties
2019
Parada, Corey M. | Parker, Grace L. | Storey, R. F. (Robson F.)
Polyisobutylene (PIB) bearing covalently bound antioxidants is reported. TiCl₄‐catalyzed cleavage/alkylation reactions were conducted on poly(isobutylene‐co‐isoprene) (EXXON® Butyl 068; M¯n = 3.37 × 10⁵ g/mol, (Ð) = 1.29, and 1.08 mol % isoprene) at −70 °C in 60/40 hexane/dichloromethane in the presence of 2,6‐di‐tert‐butylphenol (DTP). Resulting PIB M¯n s ranged from 30,000 to 85,300 g/mol and number average DTP functionalities (Fₙ) ranged from 4.3 to 12.0. ¹H NMR showed that 25%–40% of the DTP moieties underwent de‐tert‐butylation to form mono‐tert‐butyl phenol moieties. DTP‐functionalized and nonfunctionalized control PIBs were subjected to thermogravimetric analysis in nitrogen and in air. In nitrogen, commercial control PIBs (olefinic end groups) showed delayed onset of thermal degradation (T₁₀ = 380–381 °C) relative to both control PIBs produced by living polymerization (tert‐chloride end groups) and DTP‐functionalized PIBs (T₁₀'s all within the range of 366–370 °C). All PIBs showed lower degradation temperatures in air compared to nitrogen. Various control PIBs suffered 90% weight loss in air at temperatures ranging from 372 °C to 410 °C; DTP‐functionalized PIBs did not suffer 90% weight loss in air until 412–414 °C. Oxidative induction time analysis showed that all control PIBs suffered catastrophic degradation within 6 min, and most within 1 min, but DTP‐functionalized PIBs resisted degradation for >100 min. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1836–1846
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