High-temperature structural transition of polybutadienes

The Structure of Polybutadienes and Butadiene-Acrylonitrile Copolymers

“…In SKDL containing almost equal amounts of cis-1,4-and trans-1,4-isomers, the effective activation energy of radical rotation is 17.5 kJ/mol at temperatures below the transition temperature (308 K). The obtained transition temperature agrees with [11].…”

“…Hence, only cis-1,4unit-1,2-unit-trans-1,4-unit joints are present in it. cis-1,4 and trans-1,4-isomers form fluctuation structures [11]. Thus, the regions with the lowest order are enriched with 1,2-units located between cis-1,4-and trans-1,4-isomers.…”

“…The mechanism governing the molecular mobility of the microblocks consists in their formation and decomposition through the fluctuation attachment and detachment of segments as individual kinetic units [7]. Moreover, the thermomechanical analysis, the energy parameters of dissolution and diffusion of low-molecularmass substances, and IR spectroscopy data suggest the existence of fluctuation structures in elastomers [8][9][10][11][12].…”

“…The molecular dynamics of polymer chain fragments located in a structural defect depends on the mobility of regular chain fragments comprising ordered structures. The transitions are explained by the unfreezing of the molecular mobility in fluctuation structures composed of units occurring in the prevailing configuration and by their rearrangements [7][8][9][10][11][12][13].…”

The Influence of the Structural Organisation of Nitrile Butadiene Rubbers on their Vulcanisation

“…According to data of NMR spectroscopy [19], macromolecules of this rubber consist of microblocks of cis-1,4-and trans-1,4-butadiene units separated by isolated 1,2-units. According to data of IR spectroscopy [7] and the diffusion method [20], microblocks of units of the same type selectively aggregate, forming in SKDL two types of nanoformation. Here, the nanoformations of trans-1,4-butadiene units are stronger and break down entirely in the region of 120°C [20].…”