Polymer International Polym Int 53:1219–1225 (2004) DOI: 10.1002/pi.1554 Synthesis and characterization of poly(p-phenylene)-graft-poly(ε -caprolactone) copolymers by combined ring-opening polymerization and cross-coupling processes Seda Yurteri, Ioan Cianga, † Mustafa Degirmenci and Yusuf Yagci ∗ Istanbul Technical University, Department of Chemistry, Maslak, Istanbul 34469, Turkey Abstract: 2,5-Dibromo-1,4-(dihydroxymethyl)benzene was used as initiator in ring-opening polymer- ization of ε-caprolactone in the presence of stannous octoate (Sn(Oct) 2 ) catalyst. The resulting poly(ε- caprolactone) (PCL) macromonomer, with a central 2,5-dibromo-1,4-diphenylene group, was used in combination with 1,4-dibromo-2,5-dimethylbenzene for a Suzuki coupling in the presence of Pd(PPh 3 ) 4 as catalyst or using the system NiCl 2 /bpy/PPh 3 /Zn for a Yamamoto-type polymerization. The poly(p- phenylenes) (PPP) obtained, with PCL side chains, have solubility properties similar to those of the starting macromonomer, ie soluble in common organic solvents at room temperature. The new polymers were characterized by 1 H and 13 C NMR and UV spectroscopy and also by GPC measurements. The thermal behaviour of the precursor PCL macromonomer and the final poly(p-phenylene)-graft-poly(ε- caprolactone) copolymers were investigated by thermogravimetric analysis and differential scanning calorimetry analyses and compared.  2004 Society of Chemical Industry Keywords: poly(p-phenylene); macromonomer; graft copolymer; poly(ε-caprolactone) INTRODUCTION Poly(para-phenylene) (PPP) and its derivatives are a promising class of high-performance polymers because of their excellent thermal and mechanical properties. Since the discovery that PPP conducts electricity when doped with oxidizing or reducing agents, 1 a great deal of research has gone into the study of this material and its derivatives. 2–4 Polyphenylene is used as a coating material in the packaging industry to protect integrated circuits from breakage, humidity and corrosion. Other interesting and important properties that PPPs exhibit include liquid crystallinity 5 and photo- and electroluminescence. 6 However, because of high crystallinity, insolubility and high melting temperature, the potential attractive properties are still under investigation. Several approaches to decrease the crystallinity of rigid conjugated polymers have been used. These approaches include introduction of bent or crank-shaped units into the main chain as well as lateral substitution and incorporation of flexible units as side chains. Substituted PPPs with flexible pendant moieties have received attention on account of their electrical and optical properties combined with solubility and fusibility. Current methodologies for the direct synthesis of derivatized PPPs are primarily based upon nickel- and palladium-mediated cross-coupling reactions largely because of their preservation of regiochemistry and nearly quantitative yields. 4–7 Taking in account the considerable interest not only in the synthesis of new types of plastic materials but also in the modification of the commodity polymers to improve their properties to meet the requirements for high-tech applications, polystyrene (PS) or poly(methyl methacrylate) (PMMA) were used, in which nanostructured photoactive conjugated oligo(phenylene vinylene) segments are attached as side chains to the backbone. 8,9 In recent years, the syntheses of architec- turally complex polymers have been reported by numerous research groups. Star, grafted and hyperbranched polymers are the most studied products 10 – 12 because of their specific solution and bulk properties and a growing number of diverse applications. The majority of these well- defined structures have been obtained by anionic polymerization 13 or more recently by controlled free radical polymerization. 14 ∗ Correspondence to: Yusuf Yagci, Department of Chemistry, Istanbul Technical University, Maslak, Istanbul 34469, Turkey † On leave from ‘Petru Poni’ Institute of Macromolecular Chemistry, Iasi, Romania Contract/grant sponsor: Tubitak (BDP Programme) Contract/grant sponsor: Gemsan AS (Received 29 July 2003; revised version received 28 October 2003; accepted 15 December 2003) Published online 1 June 2004  2004 Society of Chemical Industry. Polym Int 0959–8103/2004/$30.00 1219