Radiation-induced and RAFT-mediated grafting of poly(hydroxyethyl methacrylate) (PHEMA) from cellulose surfaces Yasko Kodama a , Murat Barsbay b , Olgun Güven b,n a Instituto de Pesquisas Energeticas e Nucleares—IPEN-CNEN/SP, Av. Prof. Lineu Prestes 2242, Cidade Universitaria, 05508-000, Sao Paulo, Brazil b Department of Chemistry, Hacettepe University, 06800 Beytepe, Ankara, Turkey HIGHLIGHTS  Poly(hydroxyethylmethacrylate) was grafted from cellulose surface w/w a RAFT agent by gamma irradiation.  Control of molecular weight and distribution of grafted chains were achieved in RAFT-mediated grafting reactions.  Graft copolymers were characterized by FTIR-ATR, XPS, SEM, elemental analysis and contact angle measurements. article info Article history: Received 27 December 2012 Accepted 18 July 2013 Available online 25 July 2013 Keywords: RAFT mediated grafting 2-Hydroxyethyl methacrylate (HEMA) Cellulose γ-Irradiation abstract This paper presents the results of RAFT mediated free-radical graft copolymerization of 2-hydroxyethyl methacrylate (HEMA) onto cellulose fibers in a “grafting-from” approach under γ-irradiation. The effects of absorbed dose and monomer concentration on the graft ratios were investigated at different monomer (HEMA) to RAFT agent (cumyl dithiobenzoate, CDB) ratios. Cellulose-g-PHEMA copolymers with various graft ratios up to 92% (w/w) have been synthesized. The synthesized copolymers were characterized by ATR-FTIR spectro- scopy, X-ray photoelectron spectroscopy, elemental analysis and scanning electron microscopy. The results of various techniques confirmed the existence of PHEMA in the copolymer composition. & 2013 Elsevier Ltd. All rights reserved. 1. Introduction The modification of polymers through grafting has a bright future and the developments anticipated are practically boundless. In principle, graft co-polymerization is an attractive method to impart a variety of functional groups to a polymer and it can be initiated by chemical treatment, photo-irradiation, high-energy radiation, plasma-induced techniques, etc. (Nasef and Güven, 2012). In recent years, methods of controlled free-radical poly- merizations (CRP) were developed to open up new potential for grafting reactions especially using ionizing radiation (Barsbay and Güven, 2009). Well-defined graft copolymers via CRP methods are most frequently prepared by either a “grafting through” or a “grafting from” polymerization process. In the “grafting from” technique, the initiators are initially anchored or active sites are generated on the surface and then they subsequently used to initiate the polymerization of monomer from the surface. Because the diffusion of monomer is not strongly hindered by the existing grafted polymer chains, this technique is more promising to achieve high graft densities. (Li et al., 2008). Among the CRP techniques, RAFT (Reversible Addition/Frag- mentation Chain Transfer) polymerization is one of the most versatile ones for providing living characteristics to radical poly- merization (Barsbay et al., 2007; Moad et al., 2005). Advantages of RAFT polymerization include the ability to control polymerization of most monomers polymerizable by radical polymerization such as (meth)acrylates, (meth)acrylamides, acrylonitrile, styrenes, dienes, etc., tolerance of unprotected functionality in monomer and solvent, compatibility with reaction conditions (e.g., bulk, organic or aqueous solution, emulsion, mini-emulsion, and suspension) and ease of implementation and inexpensive relative to competitive technologies (Moad et al., 2005; Moad et al., 2009). RAFT polymerization at ambient temperature by means of γ-radiation has been successfully performed for a variety of monomers (Barsbay and Güven, 2009). In the course of γ- initiated RAFT mediated grafting; growing of both grafted polymer (on the surface) and free polymer (in the solution) are controlled by the same RAFT agent at the same time. Therefore, the molecular weights and molecular weight distributions of grafted and free polymers are almost the same when the grafting occurs on the surface of the substrate (Barsbay et al. 2007). In this study, RAFT-mediated free-radical graft polymerization of 2-hydroxyethyl methacrylate (HEMA) onto cellulose fibers in a Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/radphyschem Radiation Physics and Chemistry 0969-806X/$ - see front matter & 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.radphyschem.2013.07.016 n Corresponding author. Tel.: +90 312 297 7977; fax: +90 312 297 7973. E-mail addresses: yasko.kodama@gmail.com (Y. Kodama), mbarsbay@hacettepe.edu.tr (M. Barsbay), guven@hacettepe.edu.tr (O. Güven). URLS: http://www.ipen.br (Y. Kodama), http://www.polymer.hacettepe.edu.tr (M. Barsbay), http://www.polymer.hacettepe.edu.tr (O. Güven). Radiation Physics and Chemistry 94 (2014) 98–104