Nitroxide-Mediated Copolymerization of Itaconate Esters with Styrene

Sepehr Kardan,Adrien Métafiot,Milan Maric,Omar Garcia Valdez

doi:10.3390/pr7050254

Abstract

Replacing petro-based materials with renewably sourced ones has clearly been applied to polymers, such as those derived from itaconic acid (IA) and its derivatives. Di-n-butyl itaconate (DBI) was (co)polymerized via nitroxide mediated polymerization (NMP) to impart elastomeric (rubber) properties. Homopolymerization of DBI by NMP was not possible, due to a stable adduct being formed. However, DBI/styrene (S) copolymerization by NMP at various initial molar feed compositions fDBI,0 was polymerizable at different reaction temperatures (70–110 °C) in 1,4 dioxane solution. DBI/S copolymerizations largely obeyed first order kinetics for initial DBI compositions of 10% to 80%. Number-average molecular weight (Mn) versus conversion for various DBI/S copolymerizations however showed significant deviations from the theoretical Mn as a result of chain transfer reactions (that are more likely to occur at high temperatures) and/or the poor reactivity of DBI via an NMP mechanism. In order to suppress possible intramolecular chain transfer reactions, the copolymerization was performed at 70 °C and for a longer time (72 h) with fDBI,0 = 50%–80%, and some slight improvements regarding the dispersity (Ð = 1.3–1.5), chain activity and conversion (~50%) were observed for the less DBI-rich compositions. The statistical copolymers produced showed a depression in Tg relative to poly(styrene) homopolymer, indicating the effect of DBI incorporation.

Highlights

The limited supply of fossil resources has forced the exploration of renewable feedstocks as an alternative route to materials such as polymers [1]
We first attempted to determine the best conditions for the controlled polymerization of dialkyl itaconates, which is defined here as linear progression of degree of polymerization with monomer conversion, dispersity Ð (Mw /Mn ) < 1.5 and ability to reinitiate a second batch of monomer
dibutyl itaconate (DBI) was homopolymerized via conventional radical processes and reversible de-activation radical polymerization (RDRP) processes such as RAFT [32,33] and the related dimethyl itaconate (DMI) by atom transferreversible radical polymerization (ATRP) [34], DBI did not homopolymerize via nitroxide mediated polymerization (NMP) with no conversion after several hours at elevated temperatures of ~110 ◦ C

Summary

Introduction

The limited supply of fossil resources has forced the exploration of renewable feedstocks as an alternative route to materials such as polymers [1]. One such feedstock for polymers is itaconic acid (IA), which was first isolated from the pyrolysis of citric acid [2,3] and is made by fermentation from fungi [3,4]. Itaconic acid’s high availability, low cost, structural similarity with acrylates and methacrylates, and its dicarboxylic acid functionality have motivated research on the development of polymeric materials from IA and derivatives like dialkyl itaconates or β monoalkyl itaconates [9,10]. The dual functionality of IA is appealing as it makes it possible to polymerize it via free radical mechanisms

Methods

Results

Conclusion