Cationic polymerization of 1,3‐pentadiene coinitiated by zinc halides

Abstract

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.

A new insight into the mechanism of 1,3‐dienes cationic polymerization. II. Structure of poly(1,3‐pentadiene) synthesized with tBuCl/TiCl4 initiating system

“…We showed recently that the addition of tert ‐butyl chloride ( t BuCl) to the system allowed to increase significantly the rate of ZnBr 2 ‐ and TiCl 4 ‐co‐initiated cationic polymerization of 1,3‐pentadiene. Particularly, for adventitious H 2 O/TiCl 4 , initiating system of about 5% of monomer conversion was obtained in 1 h, whereas for t BuCl/TiCl 4 initiating system (at t BuCl:TiCl 4 = 340 mol/mol), the complete monomer conversion was attained for the same period of time .…”

A New Insight into the Mechanism of 1,3‐Dienes Cationic Polymerization I: Polymerization of 1,3‐Pentadiene with tBuCl/TiCl4 Initiating System: Kinetic and Mechanistic Study

“…Before the experiments, 1,3‐pentadiene was washed with water, dried on NaX molecular sieves, and then distilled over CaH 2 in argon flow. The content of traces impurities in 1,3‐pentadiene is reported in our previous work . CH 2 Cl 2 (99.9%, Biosolve) and t BuCl (>99.5%, Fluka) were distilled over CaH 2 under an argon atmosphere before use.…”

“…We showed recently that the use of excess of tert ‐butyl chloride ( t BuCl) toward Lewis acid (LA) ([ t BuCl]/[LA] = 10–1000 mol mol −1 ) allowed not only to increase significantly the reaction rate of 1,3‐dienes polymerization in the presence of zinc halides but also to synthesize well‐defined oligo(1,3‐diene)s ( ≤ 2000 g mol −1 ) with relatively narrow MWD (/ = 2–4), and without any IF . However, data concerning the influence of t BuCl on the activity of TiCl 4 ‐based initiating systems in the cationic polymerization of 1,3‐dienes are limited to describing two experiments on the isoprene polymerization with t BuCl/TiCl 4 initiating system at t BuCl to TiCl 4 molar ratio 0.9:1 and 1:1, respectively.…”

Living anionic polymerization of (E)-1,3-pentadiene and (Z)-1,3-pentadiene isomers

“…Considering the traditional cationic polymerization of 1,3‐pentadiene initiated by AlCl 3 –ED (electron donor) initiator system, it appears that EP shows much higher reactivity than ZP isomer . It is well known that the synthesized polypentadiene consists of both soluble and insoluble fractions, mainly relying on choices of solvents, various types of EDs and the isomer configurations.…”

“…In addition, the results of linear microstructure obtained from the Z / E mixture monomer indicate that contents of cis ‐1,4, cis ‐1,2, and 3,4‐units rely heavily on the concentration of ZP isomer. Recently, Rozentsvet and et al have tried much efforts to successfully achieve the relatively controlled poly(1,3‐pentadiene)s with low M n s and Ð min ≈ 1.9, however, up to date, living polymers with well‐defined structure (still have not been polymerized from either EP or ZP isomer via traditional cationic polymerization method …”