The Influence of Back-Biting Interaction on the Polymerization of Conjugated Dienes in the Presence of Ziegler−Natta Catalysts

A New Family of Styrene/Diene Rubbers

“…Care has to be taken, however, since recent studies throw doubt on the existence of backbiting. [20] The single insertion is confirmed by the 13 C NMR spectra in the phenyl ipso carbon region represented in Figure 3d. The sharp singlet observed around 145.8 ppm is characteristic of a styrenic unit in a single and unique environment, in a similar way to poly(ethylenealt-styrene) [21] or isotactic (mm triads) and syndiotactic (rr triads, Figure 3c) polystyrene.…”

Diethylbis(2,2′-bipyridine)iron/MAO. A Very Active and Stereospecific Catalyst for 1,3-Diene Polymerization

“…According to some authors, backbiting plays an important role in determining the product of the polymerization. [21] In polymerizations with (Bipy) 2 FeEt 2 /MAO backbiting is quite improbable for the reasons set forth above and, hence, it cannot be considered essential for chemo-and stereoselectivity in diene polymerization.…”

Polymerization of 4‐Methyl‐1,3‐pentadiene with Catalysts Based on Cyclopentadienyl Titanium Chlorides: Effect of anti/syn Isomerism of the Allylic Group on the Chemoselectivity and the Role of Backbiting Coordination in 1,3‐Diene Polymerization

“…The high chemoselectivity in the homopolymerization has been attributed to backbiting, and the formation of 1,4 units in copolymerization to loss of backbiting caused by ethylene insertion. The effect of backbiting has been considered valid for catalysts other than CpTiCl 3 -MAO [9] and schemes based on backbiting have been presented in papers investigating the mechanism of chemo-and stereoselectivity of 1,3-diene polymerization. [10a,b] The influence of backbiting on the chemoselectivity appeared unconvincing for various reasons, but mainly because very high chemoselectivity can be obtained with catalysts for which backbiting is not possible for coordinative saturation at the transition metal.…”

“…[10a,b] The influence of backbiting on the chemoselectivity appeared unconvincing for various reasons, but mainly because very high chemoselectivity can be obtained with catalysts for which backbiting is not possible for coordinative saturation at the transition metal. [11][12][13] However, since various papers have recently appeared [9,10] stressing the importance of backbiting, we decided to reexamine this problem. We have investigated homopolymerization of MP and copolymerization of MP with some alkenes (ethylene, 1-pentene, 4-methyl-1-pentene), using as catalysts three homogeneous systems: CpTiCl 3 -MAO, Cp 2 TiCl 2 -MAO and Cp 2 TiCl-MAO.…”