Living Anionic Polymerization of 1,4-Diisopropenylbenzene

Abstract

The anionic polymerization of diisopropenylbenzene (DIPB) derivatives was conducted in THF at −78°C with a specially designed initiator system prepared from oligo(α-methylstyryl)lithium and an excess potassium tert-butoxide (KOBu t ) (2.7−5.0 equiv to the Li salt). Among the ortho-, meta-, and para-isomers of DIPB derivatives, it was found that the para-isomer (p-DIPB) successfully underwent the living polymerization in a selective manner through one of the two isopropenyl groups under the above stated conditions. With this living polymerization system, soluble polymers with controllable M n values ranging from 7620 to 31 500 g/mol and near monodisperse distributions (M w /M n ≤ 1.03) were obtained for the first time. The obtained living polymers were stable at −78°C even after 168 h and at −40°C after 6 h, in which the intermolecular addition reaction of the chain-end anion to the pendant isopropenyl group could be completely suppressed. In contrast, the living polymerization of either the ortho-or metaisomer was not successful under the same conditions. The block copolymerization of p-DIPB with either styrene (S), 2-vinylpyridine (2VP), or tert-butyl methacrylate ( t BMA) by the sequential addition of such monomers was conducted. Four new PS-block-P(p-DIPB), P2VP-block-P(p-DIPB), P(p-DIPB)-block-P2VP, and P(p-DIPB)-block-P t BMA containing reactive P(p-DIPB) segments were synthesized. On the basis of the block copolymerization results, it is understood that p-DIPB is comparable to 2VP and located between S and t BMA in monomer reactivity. The reactivity increases as follows: S < 2VP ∼ p-DIPB < t BMA, while the nucleophilicity of the living chain-end anion decreases in the following order: PS − > P2VP − ∼ P(p-DIPB) − > P( t BMA) − . ■ INTRODUCTIONIt is known that the intermolecular addition reaction of the chain-end anion to the pendant CH 2 CH bond significantly occurs during the polymerization of 1,4-divinylbenzene (p-DVB). Such the addition reaction results in the formation of highly cross-linked polymers insoluble in solvents. Therefore, p-DVB is generally used as a cross-linking agent to prepare microand macro-gels, but not considered as a typical monomer. 1−9 In 2011, we successfully found that the oligo(α-methylstyryl)-lithium (αMSLi)-initiated anionic polymerization of p-DVB proceeds in a living manner by adding an excess potassium tertbutoxide (KOBu t ) (10 equiv or more). 10 In this polymerization, one of the two CH 2 CH bonds selectively participated the polymerization to quantitatively give the soluble poly(p-DVB)s with predictable M n values up to 60 500 g/mol and near monodisperse distributions (M w /M n ≤ 1.05). 11 The living nature of this system was also guaranteed by the quantitative formation of poly(p-DVB)-block-poly(2-vinylpyridine) and poly(p-DVB)-block-poly(tert-butyl methacrylate) by the sequential addition of p-DVB and then 2-vinylpyridine or tert-butyl methacrylate to the above initiator system. 12The success of the living anionic polymerization of p-DVB may possibly be attributed by ...

Rheological and thermal degradation properties of hyperbranched polyisoprene prepared by anionic polymerization

“…The molecular weight and dispersity index for the linear and the branched polymers are presented table 2. The branched polymers and the linear (LP-02) possess higher dispersity index due to addition of TMEDA, which is absent in the case of the linear polymer (LPI-01) [48,49]. The 1 H NMR spectrum is presented in figure 1.…”

Identity of Low-Molecular-Weight Species Formed in End-To-End Cyclization Reactions Performed in THF

“…A common solvent for both polymerizations, leading to linear precursors and post-polymerization transformation reactions, is tetrahydrofuran (THF). This solvent is compatible with all the cyclization reactions listed above, while also being a compatible polymerization medium for anionic techniques [13,14] and reversible activation/deactivation radical polymerization (RDRP) methods such as atom transfer radical polymerization (ATRP) [15,16] and nitroxide-mediated polymerization (NMP) [17]. The success of cyclization reactions is almost always evaluated, at least in part, using gel permeation chromatography (GPC), with the shift to longer elution times indicative of the topological transformation from linear to cyclic [18,19].…”

Synthesis of amphiphilic diblock copolymers of isotactic polystyrene-block-isotactic poly(p-hydroxystyrene) using a titanium complex with an [OSSO]-type bis(phenolate) ligand and sequential monomer addition

“…However, this method requires that the same catalytic or initiating species can initiate the living polymerization of both monomers, and that the conversion of the rst monomer must be quantitative. [13][14][15][16][17][18][19][20][21] Macroinitiators were prepared from end-functionalized polymers available, which initiate or catalyze living polymerizations of desired monomers to obtain welldened diblock copolymer. [22][23][24][25][26] Moreover, click coupling reaction of two end-functionalized macromolecular chains has been employed to synthesize diblock copolymers in recent years.…”