Citrus oils as chain transfer agents in the cross-metathesis degradation of polybutadiene in block copolymers using Ru-alkylidene catalysts

Araceli Martínez, Selena Gutiérrez, Mikhail A. Tlenkopatchev

Centro de Investigaciones Biológicas del Noroeste, CIBNOR, México City, México.
Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, México City, México.

DOI: 10.4236/ns.2013.57103                

Abstract

The cross-metathesis degradation of poly(styrene-co-butadiene) (styrene, 30 wt%) (SB-1) and poly(styrene-co-butadiene) (styrene, 21 wt%) (SB- 2) in the presence of essential oils and d-limo-nene as chain transfer agents (CTAs) using Rualkylidene catalysts (PCy₃)₂(Cl)₂Ru = CHPh (I) and (1,3-diphenyl-4,5-dihydroimidazol-2-ylidene) (PCy₃)Cl₂Ru=CHPh (II) was studied. Terpene-terminated butadiene oligomers and polystyrene blocks were obtained as products of the degradation of SB-1 and SB-2. Catalysts I and II showed high activity in the degradation of SB copolymers to produce the low molecular weight products (M_n = 276 - 335 g·mol^-1) and yields ranging from 91% - 95%. The cross-metathesis degradation of copolymers in organic solvents and in citrus oils (mandarin, orange and lemon oils) proceeded with similar efficiency and resulted in the same molecular weight butadiene oligomers. According to GS/MS (EI) analysis, the main products of the degradation of SB-1 copolymer with d-limonene were limonene-terminated oligomers of series A_m (m = 1 - 4).

Keywords

Metathesis Degradation; Polybutadiene in Block; Natural Oils; d-Limonene; Ru-Alkylidene Catalysts

Conflicts of Interest

The authors declare no conflicts of interest.

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