Polyisobutylene‐containing block polymers by sequential monomer addition. I. The living carbocationic polymerization of styrene

Abstract

The living carbocationic polymerisation of styrene (St) has been investigated by the 2‐chloro‐2,4,4‐trimethylpentane (TMPCI)/TiCl4 initiating system in the presence of various additives such as electron pair donors (EDs) and the proton trap 2,6‐di‐tert‐butylpyridine (DtBP) by the use of the mixed solvent CH3Cl/methyl‐cyclohexane (MCHx) (40/60 v/v) at −80°C under conventional laboratory conditions. The TMPCl/TiCl4 system in the absence of additives produces ill‐defined bimodal molecular weight distribution (MWD) polymers. Much better defined polystyrenes (PSt) can be obtained in the presence of EDs, such as N,N‐dimethylacetamide (DMA) and hexamethylphosphoramide (HMPA). Monomer depletion should be avoided to prevent intra‐ or intermolecular alkylation yielding indanyl end groups or branched polymers, respectively. In the combined presence of an ED and the proton trap, i.e., DMA + DtBP, the living polymerization of St has been achieved and thus the foundations for the carbocationic synthesis of PSt block polymers by sequential monomer addition have been laid.

Macromolecular Engineering via Carbocationic Polymerization: Branched Structures, Block Copolymers and Nanostructures

“…[32,46,47,58] For isobutylene, the effectiveness of electron pair donors in preventing side reactions such as protic initiation, or electrophilic aromatic substitution and improving initiator efficiencies by reducing the overall propagation rate relative to initiation when aromatic initiators are used, were shown to increase with increasing Gutmann donor numbers. [36,59] The proton trap, 2,5-di-tert-butylpyridine, was found to cause proton elimination and subsequent chain coupling. [50,52] The exact mechanisms and kinetics of various carbocationic polymerizations exhibiting living behavior remain debated.…”

Cationic copolymerization of 1,1‐diphenylethylene with p‐substituted styrenes

“…First, the copolymerization was performed using TiCl 4 or GaCl 3 as well as EtAlCl 2 /SnCl 4 in conjunction with IBEA or IBVE-HCl as an initiator at 0 C. TiCl 4 -induced polymerization of styrene derivatives is known to yield controlled polymers. 10 We have demonstrated living cationic copolymerization of benzaldehydes and vinyl ethers with GaCl 3 as mentioned earlier. 7,8 Quite recently, GaCl 3 has been shown to be effective for controlling cationic polymerization of hydrocarbon monomers such as vinylcyclohexane.…”

Cationic polymerization of styrene in the presence of added base: Living nature of the propagating species and synthesis of poly(vinyl alcohol)-graft-polystyrene

“…As a cationogen, 1-(isobutoxy)ethyl acetate [CH 3 CH(OiBu)OCOCH 3 ; 1] was prepared by the treatment of isobutyl vinyl ether with acetic acid at 60°C for 3 h and was distilled over calcium hydride under reduced pressure. The styryltype cationogen 1-phenylethyl trifluoroacetate [CH 3 CH(Ph)OCOCF 3 ; 2] was prepared by the treatment of 1-phenethyl alcohol with trifluoroacetic anhydride in pyridine at room temperature for 3 h and was distilled over calcium hydride under reduced pressure.…”

“…A preliminary investigation into the effect of solvents on the rate of polymerization in the presence of Cl 2 CHCOOCH 3 Figure 2 as a function of styrene conversion. In each initiating system, the polymer molecular weight was directly proportional to conversion.…”