Preparation of bio-based styrene alternatives and their free radical polymerization

Jan Meuldijk,Koen Van Beurden,Jack Van Schijndel,Dennis Molendijk,Timothy Noël,Luiz Alberto Canalle

doi:10.1016/j.eurpolymj.2020.109534

Abstract

Three different bio-based styrene monomer alternatives, i.e., 4-vinylphenol derivatives, were synthesized starting from lignin building blocks. The synthetic route encompassed a green Knoevenagel condensation followed by two decarboxylation steps and acetylation. High isolated yields for the decarboxylation were obtained in a polar aprotic solvent, which prevented oligomerization. The polymerization of the three acetylated 4-vinylphenols was performed by free radical polymerization. The chain transfer constants of styrene and 4-acetoxy styrene 4c in toluene were evaluated in the Mayo procedure using the number-average molecular weight (Mn). After polymerization, the acetoxy group of the different polymers was efficiently hydrolyzed. The resulting phenol side groups of these polystyrene alternatives provide future opportunities to functionalize these bio-based polymers further.

Highlights

Styrene was first isolated in 1839 from the American sweetgum tree by the German pharmacist Eduard Simon [1]
The present study explores a novel, green synthesis of three styrene alternatives starting from bio-based building blocks with a focus on optimizing the second decarboxylation step
The synthesis of the bio-based styrene alternatives started with the derivatization of the ligno-phytochemicals 1a–1c, using the previously reported green Knoevenagel reaction with ammonium bicarbonate as catalyst under solvent-free conditions as shown in Table 1 [21]

Summary

Introduction

Styrene was first isolated in 1839 from the American sweetgum tree by the German pharmacist Eduard Simon [1]. He noticed that when the tree's gum resin was exposed to air, light, or heat, it gradually transformed at room temperature into a hard, and with heating a rubber-like substance known as polystyrene. Another component of the tree's resin, namely, cinnamic acid, could be decarboxylated in a laboratory resulting in styrene.

Methods

Results

Conclusion