Low cost bifunctional initiators for bidirectional living cationic polymerization of olefins. I. isobutylene

We describe the discovery of novel low cost bifunctional initiators 2,4,7,9‐tetramethyl‐tricyclo[6.2.0.0³⁶]deca‐1(8),2,6‐triene‐4,9‐diol (bBCB‐diOH) and 4,9‐dichloro,2,4,7,9‐tetramethyl‐tricyclo[6.2.0.0³⁶]deca‐1(8),2,6‐triene (bBCB‐diCl), for living cationic bidirectional polymerization of olefins, for example, isobutylene. bBCB‐diOH was quantitatively synthesized in one step by UV radiation of commercially available diacetyl durene (DAD) and bBCB‐diCl by hydrochlorination of bBCB‐diOH. These molecules, in conjunction with TiCl₄ coinitiator, initiate the living polymerization of isobutylene. Livingness was demonstrated by linear conversion versus molecular weight (MW) plots and narrow MW distributions. Polymerizations are slower than those initiated by the universally used “hindered” bifunctional initiator 5‐tert‐butyl‐1,3‐bis(1‐chloro‐1‐methyl)benzene and are suitable for rate studies. Herein, we report the synthesis, by the use of bBCB‐diCl, of relatively low MW (M _n < 3000 g mol^?1) allyl‐telechelic polyisobutylene (PIB) used for the synthesis of PIB‐based polyurethanes and that of relatively high MW (M _n > 30,000) living PIB telechelics for the synthesis of thermoplastic elastomers. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 3716–3724     

Synthesis of Novel Unsymmetrical and Symmetrical Diacetylenic Ketones

A convenient and efficient method for the preparation of unsymmetrical and symmetrical diacetylenic ketones bearing a carboxylate group.     

The Influence of Aluminum-Containing Lewis Acids on Polyisobutylene,Isobutylene-lsoprene Copolymers (Butyl Rubber), and Chlorinated Isobutylene-lsoprene Copolymer (Chlorobutyl)

The influence of aluminum-containing Lewis acids, e.g., AlCl₃, AlEtCl₂, AlEt₂Cl, AlEt₃, and AliBu₃, on polyisobutylene, isobutylene-isoprene copolymer (butyl rubber), and chlorinated butyl rubber has been investigated in nonpolar and polar solvents at various Lewis acid concentrations in the temperature range -10 to -78°C. Polyisobutylene does not degrade even under the most aggressive conditions employed (AlEtCl₂, -10°C). Butyl rubber degrades rapidly in the presence of AlEtCl₂ in the range -10 to -50°C. In contrast, no degradation occurs with the milder Lewis acid AlEt₂Cl; however, in conjunction with small amounts of a suitable Bronsted acid (i.e., HCl) immediate and extensive degradation takes place with AlEt₂Cl as well. Chlorobutyl rubber severely and very rapidly degrades in the presence of AlCl₃ and AlEtCl₂. With the less acidic AlEt₂Cl and AlEt₃, molecular weight breakdown can be prevented only when employing milder conditions, i.e., at low Lewis acid concentrations in nonpolar solvents at lowest temperatures. A comprehensive mechanism involving carbonium ions of these degradation processes is proposed.     

Quasiliving Carbocationic Polymerization. XV. Forced Ideal Copolymerization of Isobutylene-lsoprene

Forced ideal carbocationic copolymerization of isobutylene and isoprene has been achieved by continuous addition of monomer mixtures of different compositions to cumyl chloride/TiCl₄ charges at -50°C. The overall rate of copolymerization could be kept equal to that of addition rate with up to 10 mol% isoprene in the mixed monomer feed. In this monomer concentration range the composition of the copolymer was identical to that of the feeds. At higher diene concentrations in the feed, chain transfer to monomer and other side reactions (intramolecular cyclization, gel formation) could not be completely avoided. The number-average molecular weight of the copolymers increased almost linearly with the amount of consumed monomers at 10 mol% isoprene concentrations in the feed (i.e., in the quasiliving range). According to ¹H-NMR and ¹³C-NMR spectroscopy, the products are random copolymers.     

Contributions to the Mechanism of Isobutene Polymerization. VII. Effect of HCI and Chloroethyl Benzene and a Brief Summary of the Data

Der Einfluss von HCI und Chloräthylbenzol auf die Ausbeute und das Molekulargewicht von Polyisobutylen wurde untersucht. Es konnten keine sinnvollen Vergiftungs-und Übetrträgerkoeffizienten abgeleitet werden da HC1 als ausbeuteverbessernder Promotor wirkte und der Einfluss des Chloräthylbenzols sich als sehr komplex erwies. Die Molekulargewichte der Polyisobutylene waren geringer, je grösser die Menge der vorhandenen Halogenverbindungen war. Es wird postuliert, dass HC1 als Promotor und Überträger wirkt.

Die in dieser Untersuchungsreihe erhaltenen Ergebnisse wurden durch Auftragung des Vergiftungskoeffizienten jeder Verbindung gegen den ëbertragungskoeffizienten dargestellt. Die meisten der untersuchten Ver-bindungen sind sowohl Gifte als auch ëbertràger, nur wenige sind reine (oder fast reine) Gifte oder Ubertràger. Es wird betont, dass diese Eigen-schaften rein empirisch sind und dass diese Ergebnisse nur mit grösster Vorsicht verallgemeinert werden dürdrfen.     

Contributions to the Mechanism of Isobutene Polymerization. VI. Effect of Halides

The effects of various allyl chlorides and alkyl halides on the overall yield of polymerization and molecular weight of polyisobutene have been investigated and expressed quantitatively by poison and transfer coefficients. The poison and transfer coefficients of halides have been compared with those obtained previously for corresponding hydorcarbons. The poison coefficients of halides and hydrocarbons can be treated formally in a similar manner (1/W_p vs. [X] plots linear for both classes); however, the appropriate transfer coefficients indicate fundamentally dissimilar transfer mechanisms in these systems (1/MW_p vs. [X] plots linear for hydrocarbons, whereas 1/MW_p vs. [X]^1/2 plots linear for halides). These results are discussed in terms of the allylic termination mechanism.     

Olefin Polymerizations and Copolymerizations with Aluminum Alkyl-Cocatalyst Systems. V. The Molecular Weight and Molecular Weight Distribution of Polystyrene

Abstract

The polymerization of styrene with the cationic initiator system AlR₂Cl/RCl was investigated further. Earlier conclusions [1] were corroborated and expanded by an analysis of the number and weight average molecular weights. Alkyl halides with low (high) R?Cl bond dissociation energies are efficient (poor) coinitiators of the polymerization of styrene. In the presence of efficient RCl coinitiators, the molecular weights strongly decrease and the molecular weight distributions strongly increase with increasing conversions (Fig. 1). With poor cointiators, only low conversions are obtained even in the presence of large amounts of AlEt₂Cl. The data are discussed in terms of a previously proposed mechanism [1].     

Living Carbocationic Polymerization. XXIII. Analysis of Slow Initiation in Living Isobutylene Polymerization

The aim of this research was to develop a quantitative treatment of the consequences of relatively slow initiation on M _n and N (the number of molecules formed, W_p/M _n , where W_p =weight of polymer formed) in living carbocationic polymerizations, particularly for the case of the incremental monomer addition (IMA) technique. This has been achieved by analysis of the effect of initiator efficiency (I_eff (%) = 100N/[I ₀], where [I ₀] = initiator input) on M _n versus W_p , and N versus W_p plots. Three types of systems have been discerned: 1) I_eff equal to 100%; 2) I_eff constant but less than 100%; and 3) I_eff less than 100% but increasing with increasing number of monomer increments j by the IMA technique. Thus conditions can be found under which slowly initiating systems yield close to “ideal” product, i.e., one with M _n = [M₀ ]/[I₀ ] and narrow molecular weight distribution (M _w /M _n ≈ 1.1). The corresponding equations and plots can be used to diagnose the mechanism. Subsequently, this quantitative analysis was used to describe a novel living system, trans‐2,5‐diacetoxy‐2,5‐dimethyl‐3‐hexene (DiOAcDMH₆)/BCI₃/isobutylene/CH₃CI. This system produces linear t‐chlorine‐telechelic polyisobutylenes under homogeneous conditions. Surprisingly, cationation seems to be rate determining. This conclusion is illustrated by chemical equations.