¹H NMR study of monomer sequence distributions in some commercial acrylonitrile‐butadiene copolymers

Abstract

A ratio of acrylonitrile groups (A) and 1,2‐ and 1,4‐bonded butadiene (B) in SKN‐18, SKN‐26 and SKN‐40 nitrile rubbers has been determined by means of a 250 MHz NMR spectrometer. The amounts of the corresponding units in mol% were as follows: 20; 28; 39 for A and 12; 7‐9; 4‐3 for B1.2. Block‐bonded acrylonitrile has been detected only in SKN‐40 where the ratio of the triad sequences AAB and BAB is 3:97. Quantitative data on the BBB, BBA and ABA triads of 1,4‐butadiene have been obtained by using the signals of the double bond methine protons at 5‐20‐5‐67 ppm. A clearly outlined decreasing trend of the proportion of the Btrans:Btrans sequence with respect to both the Btrans:Bcis and Bcis:Bcis dyads in the order SKN‐18, SKN‐26 and SKN‐40 was found. It was suggested that the signals located in the ‐02‐5‐20ppm region relate to the AB1.2B and probably to the AB1.2A triad sequences.

Homogeneous Hydrogenation Art of Nitrile Butadiene Rubber: A Review

“…[77][78][79][80] The degree of hydrogenation can be calculated using the following equation The polymerization of BD usually gives rise to products which have a mixture of 1,4 and 1,2 olefinic units, and the 1,4 addition products consist of trans and cis isomers, whereas 1,2 addition may result in isomers with isotactic, syndiotactic, and atactic structural units. Table 6 presents the chemical shifts of the proton in different microstructures of NBR and HNBR, respectively.…”

Nanoscale heterogeneous structure of polyacrylonitrile-co-butadiene with different molecular mobilities analyzed by spin–spin relaxation time

“…Thus, according to equation (7), R gi can be calculated from the slope of the plot of ln(I(q)) vs q 2 , the so-called Guinier plot. The relationship between the slope (S i ) and R gi and the relationship between R gi and the particle radius (R i ) are described by equations (10) and (11), respectively. The mass ratio of components with R gi can be calculated by equation 12: 17…”

Evolution of the Nanostructure and Viscoelastic Properties of Nitrile Rubber upon Mechanical Rejuvenation and Physical Aging

“…Anachkov et al assigned the peaks at 5.20− 5.43, 5.46−5.48, and 5.50−5.65 ppm to the BBB, BBA, and ABA triads of the cis-and trans-1,4-butadiene units and those at 4.88−5.02 and 5.02−5.20 ppm to the triads of the 1,2butadiene units. 36 Based on this peak assignment, the butadiene units of NBR have primarily 1,4-regiochemistry and are contained in the polymer chains predominantly within BBB triads. Thus, NBR is not a random copolymer with Bernoullian statistics along the polymer chain even if it results from the one-pot copolymerization of acrylonitrile and butadiene.…”

“…Anachkov et al . assigned the peaks at 5.20–5.43, 5.46–5.48, and 5.50–5.65 ppm to the BBB, BBA, and ABA triads of the cis - and trans -1,4-butadiene units and those at 4.88–5.02 and 5.02–5.20 ppm to the triads of the 1,2-butadiene units . Based on this peak assignment, the butadiene units of NBR have primarily 1,4-regiochemistry and are contained in the polymer chains predominantly within BBB triads.…”