Cationic polymerization of isoprene: Initiation by complexes of titanium chloride with halogenoacetic acids

Abstract

Polymerization of 2-methyl-1,3-butadiene (isoprene), initiated by titanium chloride in combination with trifluoro- and trichloroacetic acid and their t-butyl esters as coinitiators, was studied in benzene, 1,2-dichlorobenzene and heptane at 20 °C. Curves of the dependence polymerization rate vs coinitiator concentrations exhibit in the first two media a minimum and a maximum, those in heptane exhibit an inflex only. This is due to the fact that the acids and the esters are partly consumed to carboxylate TiCl4 and to form mono- and dicarboxylates of titanium chloride. Other products are either HCl or the corresponding alkylchlorides whose co-catalytic activity is very low. It follows from kinetic data and from electric conductivity and infrared spectra measurements that active centers in the polymerization are complexes of oligoesters of halogenoacetic acids with TiCl4 and its carboxylates, in which the ester bond is either considerably polarized or dissociated. Free ions are formed during the polymerization, too, contributing to changes of electric conductivity; however, they do not influence the polymerization rate directly.

A New Insight into the Mechanism of 1,3‐Dienes Cationic Polymerization III: Polymerization of 1,3‐Pentadiene with CF3COOD/TiCl4 Initiating System: Chain‐Ends Structure and Kinetics

“…In addition, the lower than quantitative initiator efficiency (Table ) can be explained by the side reaction involving initiator (CF 3 COOD) such as carboxylation of TiCl 4 with the formation of gaseous DCl. The similar reaction of TiCl 4 with CCl 3 COOH was reported by Matyska et al Poly(1,3‐pentadiene)s synthesized with CF 3 COOD/TiCl 4 initiating system are typically characterized by relatively low number‐average molecular weight, which is hardly changed with the increase of monomer conversion (Table ). This indicates that chain transfer to monomer is significant under these conditions .…”

Homogeneous polymerization of ethylene using an iron‐based metal catalyst system

“…This observation provides evidence that both initiation and propagation proceed via allylic carbocations in the cationic polymerization of IP. Similar polyisoprene structures were also obtained with different initiating systems such as BF 3 ,6, 7 SnCl 4 ,6, 7 AlCl 3 ,6, 7 AlEtCl 2 ,8 SnCl 4 /CCl 3 COOH,9 TiCl 4 /CCl 3 COOH or CF 3 COOH,10–14 and 1‐(4‐methoxyphenyl)ethanol/B(C 6 F 5 ) 3 15…”

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

“…A general feature of the cationic polymerization of 1,3‐dienes is the strongly pronounced unsteady‐state kinetics: the maximal rate is observed at the beginning of reaction and then the rate of polymerization is dramatically decreased (see curve 1 in Figure ). For the t BuCl/TiCl 4 initiating system, however, the decrease of thr reaction rate with increasing monomer conversion is less pronounced, especially in the case of using high t BuCl concentrations (curves 2 and 3, Figure ).…”

“…[ 1,[23][24][25][26] The main feature of TiCl 4 -based initiating systems is their low activity in the polymerization of 1,3-dienes in the absence of purposely added initiators such as water, hydrochloric acid, organic acids, and so on, while the addition to the system of protic compounds or cationogens allowed to increase the rate of polymerization of 1,3-dienes signifi cantly. [ 1 ] The TiCl 4 -co-initiated cationic polymerization of 1,3-dienes in conjunction with water, [ 1,19,[23][24][25][26][27] acetone, [ 28 ] trichloroacetic acid, [ 27,[29][30][31] trifl uoroacetic acid, [ 31 ] tert -butyl esters of these acids, [ 31 ] cumyl acetate, [ 32 ] cumyl methyl ether, [ 32 ] dimethylallyl bromide, [ 6 ] and dimethylallyl alcohol [ 7 ] has been investigated. The obtained poly(1,3-diene)s are characterized by reduced unsaturation that was explained either by intramolecular cyclization [11][12][13][14]23,33 ] or branching due to the chain transfer to polymer.…”

“…[ 1,19,[23][24][25] For example, for the cationic polymerization of 1,3-pentadiene with the trichloroacetic acid (CCl 3 COOH)/TiCl 4 initiating system, the maximal reaction rate is observed at a CCl 3 COOH/TiCl 4 molar ratio in the range of 2-10 ( Figure S1, Supporting Information), while for H 2 O/TiCl 4 system-at a H 2 O/TiCl 4 molar ratio between 0.35 and 0.5. [ 1,24,25 ] A general feature of the cationic polymerization of 1,3-dienes is the strongly pronounced unsteady-state kinetics: the maximal rate is observed at the beginning of reaction and then the rate of polymerization is dramatically decreased [ 1,24,25,[29][30][31] (see curve 1 in Figure 2 ). For the t BuCl/TiCl 4 initiating system, however, the decrease of thr reaction rate with increasing monomer conversion is less pronounced, especially in the case of using high t BuCl concentrations (curves 2 and 3, Figure 2 ).…”