Modeling the Free Radical Polymerization of Acrylates HAKAN GU ¨ NAYDIN, SEYHAN SALMAN, NURCAN S ¸ ENYURT TU ¨ ZU ¨ N, DUYGU AVCI, VI ˙ KTORYA AVI ˙ YENTE Chemistry Department, Bog ˘azici University, 34342 Istanbul, Turkey Received 21 July 2004; accepted 1 October 2004 Published online 8 February 2005 in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/qua.20480 ABSTRACT: Acrylates have gained importance because of their ease of conversion to high-molecular-weight polymers and their broad industrial use. Methyl methacrylate (MMA) is a well-known monomer for free radical polymerization, but its -methyl substituent restricts the chemical modification of the monomer and therefore the properties of the resulting polymer. The presence of a heteroatom in the methyl group is known to increase the polymerizability of MMA. Methyl -hydroxymethylacrylate (MHMA), methyl -methoxymethylacrylate (MC 1 MA), methyl -acetoxymethylacrylate (MAcMA) show even better conversions to high-molecular-weight polymers than MMA. In contrast, the polymerization rate is known to decrease as the methyl group is replaced by ethyl in ethyl -hydroxymethylacrylate (EHMA) and t-butyl in t-butyl -hydroxymethylacrylate (TBHMA). In this study, quantum mechanical tools (B3LYP/6-31G*) have been used in order to understand the mechanistic behavior of the free radical polymerization reactions of acrylates. The polymerization rates of MMA, MHMA, MC 1 MA, MAcMA, EHMA, TBHMA, MC 1 AN (-methoxymethyl acrylonitrile), and MC 1 AA (-methoxymethyl acrylic acid) have been evaluated and rationalized. Simple monomers such as allyl alcohol (AA) and allyl chloride (AC) have also been modeled for comparative purposes. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem 103: 176 –189, 2005 Key words: functionalized acrylates; DFT; chain transfer; rate of propagation; free radical polymerization Introduction A llyl monomers are usually reluctant to ho- mopolymerize, since the propagating radicals formed by the addition to the double bonds are highly reactive and can easily abstract one of the -methylene hydrogen atoms from the monomer to produce resonance stabilized allylic radicals [1– 4]. The hydrogen abstraction reaction may compete with the propagation reaction resulting in the for- mation of oligomers. The tendency of the hydrogen abstraction reaction from the monomer is known to dominate over the addition to the double bond due to the stability of the allylic radicals formed upon the abstraction of the -methylene hydrogen. These Correspondence to: V. Aviyente; e-mail: aviye@boun.edu.tr Contract grant sponsor: Bog ˘ azic ¸i U ¨ niversitesi Bilimsel Ara- s ¸tirma Projeleri (BAP). International Journal of Quantum Chemistry, Vol 103, 176 –189 (2005) © 2005 Wiley Periodicals, Inc.