α,ω‐dichloropoly(2‐methylpropene) as an inifer: A modification to the Kennedy‐Smith mechanism

Abstract

Experimental details are given of attempts to enumerate the binary ionogenic equilibria (B.I.E.) of i-chloro-1-methylethylbenzene (l)/BC13, 1,4-bis(l-chloro-l-methylethyl)benzene (2)/BCI3 and 1,3,5-tris(l -chloro-I methylethy1)benzene (3)/BCI3 in CH2C12. Due to chemical reaction (dimerisation or polymerisation) no experimental values for the B.I.E. constants could be obtained. A Born-Haber cycle is constructed to estimate the relative sequence of the overall B.I.E. constants. A similar treatment for 2-chloro-2-methylpropane as a thermodynamic model for a,w-dichloropoly(2-methylpropene) (4) suggests that the overall B.I.E. constant for these polymers is somewhat smaller than those for 1 and 2 but greater than that for 3. Using 2/BCI3 as initiator for the polymerisation of 2-methylpropene(IB) it is shown, that the degree of polymerisation of 4 can be controlled within the limits 10 < DP < 100. It is shown that 4 can also act as an initiator for the polymerisation of IB, that these polymerisations involve only free ion propagation and, from a kinetic analysis of these polymerisations, that: (kp'y/kc = 12 1 . mol-' . s -' , kZt = 1,2~10-31.mol-'~s-',k,+[P,+] = 1,7.1O-,s-',andk,+/(k:~,5) = 102.Thesame analysis demonstrates that the self-ionisation of BCI, can be neglected in terms of any influence on the molar mass of the products. Experiments are also described which show that 2-chloro-2methylpropane is not suitable as a substitute initiator for IB, but that 2-chloro-2,4,4-trimethylpentane is a useful model for 4 as an initiator for the polymerisation of IB. CI transfer J via Zd -2c[.20) --------4 *) The nomenclature for the B.I.E. constants used here is based on that suggested by Grattan and Plescd).

Dimethylaluminum Chloride Catalyzed Living Isobutylene Polymerization

“…Rate depressions have been observed in other living isobutylene polymerization systems that use electron donors. 2,[20][21][22][23][24][25][26][27][28] Several hypotheses have been forwarded to explain the rate depressions observed in these systems. 2,20-28 A likely reason for the observed rate depression is a decrease in the effective concentration of Me 2 AlCl.…”

“…The magnitude of the rate depression is quite surprising, considering the amount of dimethyl phthalate added to the system. Rate depressions have been observed in other living isobutylene polymerization systems that use electron donors. ,− Several hypotheses have been forwarded to explain the rate depressions observed in these systems. ,− A likely reason for the observed rate depression is a decrease in the effective concentration of Me 2 AlCl. A similar explanation is used for observed rate depressions in TiCl 4 -based living isobutylene polymerizations carried out in the presence of Lewis bases …”

“…Both solvents are filtered before use. 5- tert -Butyl-1,3-bis(1-chloro-1-methylethyl)benzene and 2-chloro-2,4,4-trimethylpentane were prepared according to literature procedures. , Dimethyl phthalate (99+%), diethylaluminum chloride (97%), 2,6-di- tert -butylpyridine (97%) (all from Aldrich), and dimethylaluminum chloride (Albemarle, 98%) were used as received.…”

Stopped-Flow and 1H NMR Study of the Ionization of Cumyl Chloride by Boron Trichloride.

“…For instance, it was shown that 2-chloro-2,4,4-trimethylpentane (i.e. the hydrochlorinated dimer of isobutene) ionized with TiCl 4 was an efficient initiator in the cationic polymerization of isobutene. , The extent of ionization, i.e., the concentration of the initiating cation, depends also on the respective natures of Lewis acid and of the leaving group.…”

Kinetic Analysis of “Living” Polymerization Processes Exhibiting Slow Equilibria. 6. Cationic Polymerization Involving Covalent Species, Ion Pairs, and Free Cations

“…Puskas et al 4 concluded that ion pairs are the chain carriers in the living polymerization of isobutylene. Alternatively, Nuyken 7 regarded unpaired ions as the active species in his tertiary chloride/ BCl 3 system. Since the equilibrium constant of ionization (K i ) k ion /k c < 10 -5 L/mol) is regarded to be very low for isobutylene polymerization, the concentration of ionized species is also very low.…”