No abstract

The microstructure of poly(1,3‐pentadiene) synthesized by cationic polymerization of 1,3‐pentadiene with tBuCl/TiCl4 initiating system is analyzed using one‐dimensional‐ and two‐dimensional‐NMR spectroscopy. It is shown that unsaturated part of chain contains only homo and mixed dyads with trans−1,4‐, trans−1,2‐, and cis−1,2‐structures with regular and inverse (head‐to‐head or tail‐to‐tail) enchainment, whereas cis−1,4‐ and 3,4‐units are totally absent. The new quantitative method for the calculation of content of different structural units in poly(1,3‐pentadiene)s based on the comparison of methyl region of 13C NMR spectra of original and hydrogenated polymer is proposed. The signals of tert‐butyl head and chloromethyl end groups are identified in a structure of poly(1,3‐pentadiene) chain and the new approaches for the quantitative calculation of number‐average functionality at the α‐ and ω‐end are proposed. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3297–3307

The cationic polymerization of 1,3-pentadiene using a tert -butyl chloride ( t BuCl)/TiCl 4 initiating system in CH 2 Cl 2 at different reaction conditions is reported. It is shown that the reaction rate increases with the increase of the t BuCl/TiCl 4 molar ratio, while the molecular weight distribution becomes narrower. Well-defi ned oligo(1,3-pentadiene)s (M n ≤ 3500 g mol − 1 ; M w /M n ≤ 3.0) are obtained at high t BuCl/TiCl 4 molar ratio (340) and low temperature (-78 °C). 1 H and 13 C NMR spectroscopy studies reveal the presence of tert -butyl head and -CH 2 -Cl end groups. The number-average functionalities ( F n s) at the α -and ω -ends are calculated to be F n ( t Bu) > 1 and F n (Cl) < 1, respectively. The general mechanism of 1,3-pentadiene polymerization is proposed.

Technology of industrial production of liquid rubber under trademark ''SKOP'' is based on the cationic polymerization of 1,3-penadiene (piperylene) in the presence of TiCl 4 or AlCl 3 -based catalytic systems. The disadvantage of these catalytic systems is the high probability of formation of branched and insoluble fractions due to the chain transfer to polymer. This deteriorates the useful qualities of SKOP. Here we propose the new initiating systems for the cationic polymerization of 1,3-pentadiene based on the homogeneous (dissolved in a minimal amount of diethyl ether) zinc halides (ZnCl 2 and ZnBr 2 ) as coinitiators and hydrochloric acid, tertbutyl chloride or trichloroacetic acid as initiators. These initiating systems allow to synthesize fully soluble low molecular weight (M n ¼ 1000-3000 g mol À1 ) poly(1,3-pentadiene)s with relatively narrow molecular weight distribution (M w /M n < 2.0), which do not contain any high molecular weight and insoluble fractions in the whole range of monomer conversion. The polymers synthesized in the presence of zinc halides possess the same microstructure that those prepared with TiCl 4 as coinitiator.