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 (Mn = 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 Am (m = 1 - 4).
Highlights
IntroductionLemon and other citrus oils are very attractive terpene based compounds. Terpenes are a class of natural products that typically contain carbon atom units built from isoprene molecules
Mandarin, lemon and other citrus oils are very attractive terpene based compounds
The major constituent of citrus oils is d-limonene with 74% for mandarin, 87% for lemon and 97% for orange oils
Summary
Lemon and other citrus oils are very attractive terpene based compounds. Terpenes are a class of natural products that typically contain carbon atom units built from isoprene molecules. The transformations of terpene based molecules using efficient catalysts are of great interest for the development of new applications for these biomass-derived compounds. In this perspective, metathesis transformations are becoming more attractive as the availability and choice of effective catalysts increased [4,5,6]. Metathesis transformations of several terpenoids such as citronellal, citronellol and citral using the Ru-alkylidene catalysts have been reported [8,9,10] Monoterpenes such as d-limonene and β-pinene have been used in the cross-metathesis reactions with cycloolefins [11,12,13] and natural rubber [14,15]. It was reported that the cyclodegradation of the alternating copolymer of butadiene and propene using classical metathesis catalysts can produce non-polymerizable via ring-opening metathesis polymerization 4-methylcyclo-
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