Visible Light-Induced Grafting from Polyolefins Mustafa Ciftci, † Pınar Batat, ‡ A. Levent Demirel, ‡ Guangjuan Xu, § Michael Buchmeiser, §,∥ and Yusuf Yagci* ,†,⊥ † Department of Chemistry, Istanbul Technical University, Maslak, TR-34469, Istanbul, Turkey ‡ Koc University, Chemistry Department, Rumelifeneri Yolu, Sariyer,TR-34450, Istanbul, Turkey § Institute of Polymer Chemistry, University of Stuttgart, Pfaffenwaldring 55, 70569, Stuttgart, Germany ∥ Institute of Textile Chemistry and Chemical Fibers, Kö rschtalstr. 26, D-73770 Denkendorf, Germany ⊥ Center of Excellence for Advanced Materials Research (CEAMR) and Chemistry Department, Faculty of Science, King Abdulaziz University, PO Box 80203, Jeddah, 21589, Saudi Arabia ABSTRACT: Polyethylene-graft-poly(tert-butylacrylate) (PE-g- PtBA) copolymers were prepared by using a combination of ring-opening metathesis polymerization (ROMP), hydrobromi- nation, and visible light-induced free radical polymerization. First, cis-cyclooctene was polymerized via ROMP in the presence of a chain transfer agent and quantitatively hydrobrominated. Poly- (tert-butyl acrylate) (PtBA) chains were then grown via a grafting from approach from the Br-substituted linear poly(ethylene) (PE) backbone using dimanganese decacarbonyl (Mn 2 (CO) 10 ) under visible light. The effect of Mn 2 (CO) 10 concentration and irradiation time on the grafting density and efficiency was evaluated. The tert-butyl acrylate (tBA) esters of the graft copolymers were hydrolyzed into acrylic acid functionalities by acidolysis to obtain hydrophilic polyolefins. The precursor polymer, graft copolymer, and hydrolyzed polymer were characterized by 1 H and 13 C NMR, Fourier transform infrared, atomic force microscopy, and contact angle measurements. ■ INTRODUCTION Graft copolymers, a class of segmented copolymers, exhibit improved physical and chemical properties fulfilling endless demands of the industry for various applications. In many cases, such improvements cannot be achieved by simple blending of respective homopolymers due to their incompatibility resulting in the formation of heterogeneous mixtures. 1 In recent years, in need of preparing graft copolymers displaying improved physical and chemical properties, a number of strategies have been developed to solve that problem. Particularly, time and efforts have been devoted to the block and graft copolymers through recently developed controlled/living polymerization strategies and their combinations, as summarized by our group. 2 Polyolefins have broad industrial utility on a huge scale as from packaging to building materials and automotive parts. 3 Although they exhibit excellent resistance to harsh environment arising from the aliphatic nature, their relatively low compatibility and adhesion with other classes of polymers limits their broader applicability. Among the various strategies, the use of graft copolymers as compatibilizers is an elegant way to overcome these limitations by improving interfacial adhesion between two immiscible components. However, due to their inert chemical structure, grafting process can only be achieved by the incorporation of polar functionalities. 4 Radical polymer- ization at high temperature, 5 chemical- 6 and photografting, 7 and γ-radiation functionalization 8 are some of the methods used for fabricating polyolefins with polar functionalities. However, these processes either require severe conditions or the use of harsh reagents or give products without control of structure and compositions. For the obtainment of polyolefin graft copolymers with controlled structure and molecular weight, atom transfer radical polymerization (ATRP) seemed to be the most suitable route due to its simplicity and applicability to a wide range of monomers. 9 Reports relating to the preparation of polyolefin graft copolymers by ATRP comprise in the first step the introduction of activated halide functionalities to the polyolefin. Recent studies focused on either acyclic diene metathesis (ADMET) or ring-opening metathesis polymerization (ROMP) using polar comonomers and post functionalization reactions. 10 In the approaches involving ATRP as the grafting method, the polyolefins should possess activated halides such as α-bromocarboxylic esters since their carbon-halide bonds are weaker and facilitates homolytic cleavage more easily in the presence of Cu(I) ligands. Recently, Buchmeiser and co-workers 11 reported a simple modification by ROMP derived poly(cis-cyclooctene), poly- (COE), and poly(cyclopentene), poly(CPE), to yield a fully Received: July 10, 2013 Revised: July 31, 2013 Published: August 16, 2013 Article pubs.acs.org/Macromolecules © 2013 American Chemical Society 6395 dx.doi.org/10.1021/ma401431h | Macromolecules 2013, 46, 6395−6401