Living carbocationic copolymerization of isobutylene with styrene

Abstract

The carbocationic copolymerization of isobutylene (IB) and styrene (St), initiated by 2‐chloro‐2,4,4‐trimethylpentane/TiCl4 in 60/40 (v/v) methyl chloride/hexane at −90 °C, was investigated. At a low total concentration (0.5 mol/L), slow initiation and rapid monomer conversion were observed. At a high total comonomer concentration (3 mol/L), living conditions (a linear semilogarithmic rate and Mn–conversion plots) were found, provided that the St concentration was above a critical value ([St]0 ∼ 0.6 mol/L). The breadth of the molecular weight distribution decreased with increasing IB concentration in the feed, reaching Mw/Mn ∼ 1.1. St homopolymerization was also living at a high total concentration, yielding polystyrene with Mn = 82,000 g/mol, the highest molecular weight ever achieved in carbocationic St polymerization. An analysis of this system by both the traditional gravimetric–NMR copolymer composition method and FTIR demonstrated penultimate effects. IB enrichment was found in the copolymers at all feed compositions, with very little drift at a high total concentration and above the critical St concentration. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1778–1787, 2007

Advanced Monte Carlo Model for Arborescent Polyisobutylene Production in Batch Reactor

“…Puskas et al, have shown that there are two paths whereby the LA can cap and uncap the chloride end groups (see Figure ). Path A involves only one LA molecule, while path B requires two.…”

“…Path A is dominant when LA concentration is lower that initiator; Path B is dominant when LA concentration is higher that initiator. Note I is initiator and M is monomer …”

Monte Carlo Model for Arborescent Polyisobutylene Production in the Batch Reactor

“…The number of possible combinations between different chloride end groups and different vinyl groups is 6, which leads to 6 true propagation rate constants, i.e., k p II , k p IM , k p MI , k p MM , k p SI , k p SM , where the first subscript after k p represents the type of chloride end group and the second is the type of vinyl group that is consumed. In this living polymerization, when any chloride end group is uncapped by Lewis acid to produce a carbocation, several propagation steps may occur before the carbocation returns to its dormant state by capping with chloride . An interesting feature of this polymerization is that every polymer molecule that is produced has exactly one V I group, assuming that intra‐molecular reactions do not occur.…”

“…This model consists of dynamic material balances on polymer species containing different numbers of inimer units and chloride end groups. Two paths (path A and path B in Figure ) were considered for chain propagation . Based on the restrictive set of assumptions in Table , only four lumped parameters, whose estimated values are shown in Table , were required to conduct the simulations.…”

A Kinetic Model for Non‐Oxidative Thermal Degradation of Nylon 66

“…Parameters appear near the bottom of the list because they have little influence on the model predictions, because their effects are correlated with those of parameters that appear higher on the list, or because their values are already precisely known. Estimability analysis has been used successfully to rank parameters in models for a number of different chemical and biological reaction systems 22–28…”