Synthesis of Biobased Hydroxyl-Terminated Oligomers by Metathesis Degradation of Industrial Rubbers SBS and PB: Tailor-Made Unsaturated Diols and Polyols

Abstract

Biobased hydroxyl-terminated polybutadiene (HTPB) was successfully synthesized in a one-pot reaction via metathesis degradation of industrial rubbers. Thus, polybutadiene (PB) and poly(styrene-butadiene-styrene) (SBS) were degraded via metathesis with high yields (>94%), using the fatty alcohol 10-undecen-1-ol as a chain transfer agent (CTA) and the second-generation Grubbs–Hoveyda catalyst. The identification of the hydroxyl groups (-OH) and the formation of biobased HTPB were verified by FT-IR and NMR. Likewise, the molecular weight and properties of the HTPB were controlled by changing the molar ratio of rubber to CTA ([C=C]/CTA) from 1:1 to 100:1, considering a constant molar ratio of the catalyst ([C=C]/Ru = 500:1). The number average molecular weight (Mn) ranged between 583 and 6580 g/mol and the decomposition temperatures between 134 and 220 °C. Moreover, the catalyst optimization study showed that at catalyst loadings as low as [C=C]/Ru = 5000:1, the theoretical molecular weight is in good agreement with the experimental molecular weight and the expected diols and polyols are formed. At higher ratios than those, the difference between theoretical and experimental molecular weight is wide, and there is no control over HTPB. Therefore, the rubber/CTA molar ratio and the amount of catalyst play an important role in PB degradation and HTPB synthesis. Biobased HTPB can be used to synthesize engineering design polymers, intermediates, fine chemicals, and in the polyurethane industry, and contribute to the development of environmentally friendly raw materials.

Recent Developments in Synthesis, Properties, Applications and Recycling of Bio-Based Elastomers

“…Polyols from polybutadiene (PB), polybutadiene rubber (BR), or SBS copolymer have been synthesized. BR has repeating butadiene units, which can be trans or cis -1,4-polybutadiene and are modified with another compound or reagent with hydroxyl (-OH)-terminated groups, which are called “hydroxy-terminated polybutadiene” (HTPB), hydroxy telechelic polybutadiene or polyols; these have been obtained by different methods such as oxidation or oxidolysis [ 67 , 68 ], anionic polymerization [ 69 ], via copolymerization [ 70 ], via nickel catalyst [ 71 ], and by olefin metathesis [ 72 , 73 ]. Other polyols have been obtained from natural rubber (NR), NR comes from the rubber tree, or from its synthetic form, polyisoprene rubber (IR), which has repeating isoprene units and can be trans or cis -1,4-polyisoprene [ 18 ].…”

“…Since natural and synthetic rubbers have a global consumption of more than 14 Mt in 2022 [ 73 ], the TPEs became more important since they possess a microphase-separated structure, avowing the use of reinforced fillers. This particularity is essential in terms of the recyclability of the material.…”

Recent developments in bio-based polyethylene: Degradation studies, waste management and recycling

“…Polymers like PE can undergo degradation through various mechanisms such as chemical processes (oxidation, hydrolysis, or systems involving catalysts), thermal processes (involving high temperatures), mechanical processes (grinding or trituration), or physical processes (ultrasonic radiation, microwave, or sunlight) [ 6 , 28 ]. These processes have the potential to break down the original polymer into smaller molecular weights, generating monomers, oligomers and oils that could serve as potential fuel sources ( Fig.…”

“…However, these degradation processes can come with certain drawbacks. These drawbacks encompass high energy consumption, the requirement of elevated temperatures and pressures, and the use of solvents and additives [ 6 , 30 ]. Additionally, in some cases where the isolation of degradation products is inadequate, polymer fragmentation can give rise to the formation of micro and nanoplastics [ 31 ].…”

“…Since most of the resources and raw materials used in PE production originate from oil, there is a predominant emphasis within the industry and scientific community on substituting these fossil-based materials with environmentally sustainable alternatives. Additionally, there is a significant focus on creating materials that can be effectively recycled or biodegraded after their product life cycle and bio-based compounds to produce new polymers and materials [ [5] , [6] , [7] , [8] ].…”