Oil-Based versus Bio-Based C8 Alkyl Chain (Meth)Acrylates in Emulsion Polymerization: Kinetics and Microstructure

Abstract

2-Octyl acrylate (2-OA) is a very promising bio-based monomer that is a great candidate to substitute the widely used (but oil-based) 2-ethylhexyl acrylate (2-EHA). In this work, the homopolymerization of these two monomers along with their methacrylic analogues (2-octyl methacrylate, 2-OMA and 2-ethylhexyl methacrylate, 2-EHMA) is compared to analyze their performance in detail. Very similar polymerization kinetics are observed, both in conversion and particle size. However, there are important differences in the microstructure (molar mass distribution, gel content, and degree of branching). Both acrylates form high amounts of gel (2-OA higher than 2-EHA) while the methacrylates do not form any. It is found that the most likely reason for the higher amount of gel on 2-OA lies on the second abstractable labile hydrogen in the side chain presented in this monomer, that is more reactive in 2-OA than in 2-EHA. This is supported by the molar mass distributions, that show that 2-octyl esters have higher molar mass than their respective 2-ethylhexyl counterparts (both in acrylates and methacrylates), as a result of a higher amount of long chain branches.