Determination of low degrees of long-chain branching in polybutadiene by double-bond hydrogenation followed by 13C NMR and DEPT spectroscopies

Coordinative Chain Transfer Polymerization of Butadiene Using Nickel(II) Allyl Systems: A Straightforward Route to Branched Polybutadiene

“…A high-temperature quantitative dept 13 C NMR sequence enabled the detection and quantification of long chain branching (LCB) in polyethylene chains by observing the methine carbon signals of LCB (Figure ). The LCB density per sample was determined using eq by the peak areas of ethyl branch [EB, corresponding to a 1,2 regioselective insertion of butadiene, the only type of short chain branching (SCB) that can be seen here] or LCB per sample obtained from the high-temperature quantitative 13 C NMR, where a is the peak area of the methine carbons in branch (EB + LCB), b the peak areas of the methylene carbons (α, β, γ, and δ) present on the PE main chain, and c the peak area of the methine carbon of LCB. With this equation, we obtain the quantity of LCB per 1000 carbons in a sample, as well as the quantity of EB/1000C, by replacing c with the methine carbon of EB.…”

“…For polybutadiene, the possibility of either a tertiary carbon (methine) or a quaternary carbon typical of branching should be observed. However, owing to the complex nature of polybutadiene NMR analysis, the detection of such evidence is challenging, making hydrogenation of polybutadiene into polyethylene a more viable alternative for 13 C NMR analysis . A high-temperature quantitative dept 13 C NMR sequence enabled the detection and quantification of long chain branching (LCB) in polyethylene chains by observing the methine carbon signals of LCB (Figure ).…”

“…The NMR spectroscopy method to analyze hydrogenated polybutadiene was adapted from the literature: 70 mg of the PE sample was dissolved in a mixture of ortho -dichlorobenzene ( o -DCB)/C 6 D 6 (4/1, v/v) with a total volume of 0.70 mL at 80 °C in a NMR tube with a diameter of 5 mm. The samples were analyzed at 130 °C on an NMR spectrometer (Bruker AVANCE Neo 400).…”

“…However, owing to the complex nature of polybutadiene NMR analysis, the detection of such evidence is challenging, making hydrogenation of polybutadiene into polyethylene a more viable alternative for 13 C NMR analysis. 20 A high-temperature quantitative dept 13 C NMR sequence enabled the detection and quantification of long chain branching (LCB) in polyethylene chains by observing the methine carbon signals of LCB (Figure 6). 20 The LCB density per sample was determined using eq 1 by the peak areas of ethyl branch [EB, corresponding to a 1,2 regioselective insertion of butadiene, the only type of short chain branching (SCB) that can be seen here] or LCB per sample obtained from the high-temperature quantitative 13 C NMR, where a is…”

Hydrogenation of Polybutadiene at High Pressure

“…The hydrogenation of unsaturated polymers can be carried out in noncatalytic or catalytic systems. The conventional methodology to perform the reaction avoiding the use of catalysts is based on the generation of diimides from hydrazides. − This hydrogenation process does not require any special equipment since it is carried out at low pressure and moderate temperatures. On the other hand, this methodology shows numerous disadvantages at moderate temperatures, such as degradation of the polymer and presence of side reactions that can modify the molecular structure of the resulting polymer …”