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The discovery of rubbery elastomers based on 1,3‐butadiene and its derivatives was made in 1926. I. G. Farben developed a process to use sodium polymerization on a commercial scale. The resulting polymer, Buna, made from butadiene and natrium, was tested in passenger car tires, and the results were fairly encouraging since it showed equivalent wear properties to natural rubber compounds. The work on emusion polymerization of butadiene and copolymerization of butadiene and styrene or acrylonitrile began in the 1920s in the United States under the government established Rubber Reserve program. Under this program, Gr‐s and SBR became general‐purpose rubbers even though their tire properties were inferior to natural rubber compounds. Great improvements were made in the emulsion polymerization of 1,3‐butadiene and isoprene, especially with the discovery of chain‐transfer agents used for molecular weight control. Nevertheless, the search for a natural rubber replacement continued in many research laboratories worldwide especially in the United States.
The discovery of rubbery elastomers based on 1,3‐butadiene and its derivatives was made in 1926. I. G. Farben developed a process to use sodium polymerization on a commercial scale. The resulting polymer, Buna, made from butadiene and natrium, was tested in passenger car tires, and the results were fairly encouraging since it showed equivalent wear properties to natural rubber compounds. The work on emusion polymerization of butadiene and copolymerization of butadiene and styrene or acrylonitrile began in the 1920s in the United States under the government established Rubber Reserve program. Under this program, Gr‐s and SBR became general‐purpose rubbers even though their tire properties were inferior to natural rubber compounds. Great improvements were made in the emulsion polymerization of 1,3‐butadiene and isoprene, especially with the discovery of chain‐transfer agents used for molecular weight control. Nevertheless, the search for a natural rubber replacement continued in many research laboratories worldwide especially in the United States.
Untersuchungen zur Mikrostruktur des Polybutadiens durch '3C-NMR-Spektroskopie wurden bisher von DUCH und GRANT'), MOCHEL') und ALAKI~) durchgefuhrt.Durch Interpretation der 13C-Spektren von Polybutadienen mit 1,4-und 1,2-Verknupfungen des Monomeren vermutete MOCHEL, da8 die Sequenzen von cis-1,4-und rrans-1,4-Struktureinheiten in Polybutadienen rnoglicherweise irnmer durch eine I ,2-verknupfte Butadieneinheit getrennt sind. Grund fur diese Annahme war, daB in den NMR-Spektren, die bisher bei 25,3 MHz aufgenornrnen wurden, keine Signale fur die Wechsel von cis-1,4-und trans-1,4-Einheiten gefunden wurden.
S U M M A R Y :The proton decoupled natural abundant I3C-NMR spectra of equibinary (cis-l,4-1,2)polybutadiene were measured. Assignments of spectra were made for all peaks of the aliphatic range using chemical shift corrective terms estimated for the present system together with GRANT'S parameters. Each peak was interpreted in terms of the diad or triad of cis-1,4 and 1,2 units. The relative intensities of the peaks were in good agreement with the calculated ones from the random assumption with respect to the distribution of cis-1,4 and 1,2 units. The gas-chromatographic analysis of the ozonolysis product of the polymers also showed that the sequence distribution of cis-1,4 and 1,2 units was random. Z U S A M M E N F A S S U N G :Die protonenentkoppelten 13C-Kernresonanzspektren (naturlichc Isotopenhaufigkeit) des aquibinaren (cis-1,4-1,2)-Polybutadiens wurden gemessen. Alle Resonanzen im aliphatischen Bereich wurden zugeordnet ; hierbei wurden geschatzte Korrekturterme fur die chcmischen Verschiebungen im vorliegenden System zusammen mit den GRANTSChen Parametern verwendet. Fur jeden Peak wurde aunerdem angegeben, ob er zu einer Diade oder Triade von cis-1,4-und 1,2-Einheitcn gehort. Die gemessencn relativen Intensitaten der Peaks stimmten mit den berechneten Intensitaten uberein; der Rechnung wurde eine regcllose Verteilung der cis-1,4-und der 1,2-Einheiten zugrunde gelegt. Die gaschromatographische Analyse der Ozonolyseprodukte der Polymere zeigte ebcnfalls eine regellose Vcrteilung der bciden Einhciten an.
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