Relative reactivity of cis‐ and trans‐1,3‐pentadiene in the cationic copolymerization with isobutene

Abstract

cis-1,3-Pentadiene (2) and trans-l,3-pentadiene (3) were copolymerized with isobutene (1) in the presence of (C2H5)2AIC1+(CH3)3CCI or (C2H5)2A1CI+CIz in the range of temperatures between -35 and -70°C. The reactivity ratios, determined at -55°C are: rl.2= 5.0 and r 1 . 3~ 2,3, while the chain transfer coefficients are K1.2= 50 and K,.1= 113. The activation energies are: Ea..2= -13,8 kJ/mol (-3,3 kcal/mol) and EU\..I= -16,7 kJ/mol(-4,0 kcal/mol). Spectroscopic analyses (IR, 'H-NMR) showed that in both copolymers the 1,4-trans structure is prevalent over the 1.2-trans-enchainment. The fact that 3 is more reactive than 2 can be correlated with a greater electron-density ( ' 'C-NMR data) on C-I in compound 3. ZUSAMMENFASSUNG:cis-1.3-Pentadien (2) und trcrns-1,3-Pentadien (3) wurden mit Isobuten ( I ) in Gegenwart von (C2H~)2AICI+(CH3)3CCI oder (C2HSj2AIC1+CI2 im Temperaturbereich von -35 bis -70°C copolymerisiert. Die Copolymerisationsparameter, bestimmt bei -55 "C. sind: r1,2=5,0 und rl,3=2,3; die Ubertragungskonstanten sind: K1.2=50 und K1.3= 113. Die Aktivierungsenergien betragen: E,g,,2 = -13.8 kJ/mol (-3,3 kcal/mol) und E,,.,= -16,7 kJ/mol ( -4,0 kcal/mol).Spektroskopische Analysen (IR, 'H-NMR) zeigten, daB in beiden Copolymeren die 1,4-trans-Struktur die 1,2-trans-Verkettung uberwiegt. Die hohere Reaktivitat von 3 im Vergleich mit 2 kann durch die hohere Elektronendichte (aus I3C-NMR-Daten) am C-l in der Verbindung 3 bedingt sein.

Dienes Polymerization: Where We Are and What Lies Ahead

“…Thus, polymerization in heptane−MeCl containing diethylaluminum chloride and (2chloroethoxy)tungsten pentachloride at −45 to 0°gave 1,3butadiene−cyclopentene−isobutene copolymer rubber of molecular weight 345000. 292 Heterogeneous titanium systems have been also studied in diene−olefin copolymerization, but the amount of butadiene inserted into the chains remained low. 293,294 Advances in the field of single-site catalysts have made possible the copolymerization of ethylene with butadiene by using group 4 metallocene/MAO catalysts.…”

Cationic copolymers of isobutylene. 5. Copolymerization of isobutylene and cis-1,3-pentadiene

“…The presence of the trans-1,2 unit must be the result of cis-trans isomerization. However, it would be of interest to learn whether the isomerization takes place (1) before the polymerization step (monomer isomerization), (2) during the polymerization, as a rearrangement of the last monomeric unit entering the growing chain, or (3) after polymerization (polymer isomerization).…”

Cationic Copolymers of Isobutylene. 3. Nuclear Magnetic Resonance Investigation of the Structure of Isobutylene-trans-1,3-Pentadiene Copolymer

“…As reported previously,2 the index G refers to the gemdimethyl group, the index M refers to the methyl group, the index 4 denotes that the substitution involves a quaternary carbon, at is the effect of a trans double bond, and <5« denotes a substitution in the position after a gemdimethyl substitution in the ß position. By means of a least-squares analysis we obtained the following set of parameter values (in ppm): (1) methylene carbon, do = 11.41, bgG = 3.28, fG = 0.26, = 0.76, /3m = 7.84, at = 3.60; (2) quaternary carbon, aG = 3.11, y4G = 2.18, eG = 0.25, r¡G = 0.24, 4 = 0.68; (3) methyl carbon, bG = 1.65, fG = 0.20, = 0.41. The base frequencies are 29.9 ppm (the resonance of the polyethylene) for the main-chain carbon atoms and 27.3 ppm (the resonance of an isolated gem-dimethyl group in a polyethylene chain)1 for the methyls.…”