Comparative study of p-phenylenediamine antioxidant effectiveness in styrene-butadiene and polyisoprene rubber through NMR calculations. (July 2020)

• Record Type: Journal Article
• Authors: Jelemenská, Ingrid; Breza, Martin
• Is Part Of: Polymer degradation and stability. Volume 177(2020)
• Publication Date: 2020-07
• Subjects: DFT geometry optimization -- NMR shifts -- Antioxidant effectiveness -- Linear regression analysis; Polymers -- Deterioration -- Periodicals; Stabilizing agents -- Periodicals; Polymères -- Dégradation -- Périodiques; Stabilisants -- Périodiques; 668.9
• DOI: 10.1016/j.polymdegradstab.2020.109196
• Languages: English
• ISSNs: 0141-3910

Abstract

Abstract: Structures of six p -phenylenediamine (PPD) antioxidants were optimized and their NMR shifts were evaluated by B3LYP calculations. The dependences of experimental values of Antioxidant Effectiveness (AEX) and Molar Antioxidant Effectiveness (AEM) in styrene-butadiene (SBR) and polyisoprene (PIR) rubber on the calculated NMR chemical shifts of nitrogens, tertiary carbons and hydrogens bonded to them were investigated by means of a multiple linear regression analysis. Based on regression parameter values, the significance of the N centers between aromatic rings (A) seems to be higher than of the N centers between aromatic rings and aliphatic chains (B) except AEM data in PIR. The extent of shielding the A center activity by the cumyl group in ortho-position was estimated. Regression parameters obtained for SBR are significantly higher than for PIR. Highlights: DFT geometry optimization of six PPD antioxidants. GIAO calculations of NMR shifts. Linear regression of antioxidant effectiveness vs. NMR shifts. Sterical shielding estimation for the o-cumyl derivative. Different results for both rubber matrices.