The Synthesis of PHA-g-(PTHF-b-PMMA) Multiblock/ Graft Copolymers by Combination of Cationic and Radical Polymerization Hu ¨ lya Macit, 1 Baki Hazer, 1 Hu ¨ lya Arslan, 1 Isao Noda 2 1 Department of Chemistry, Zonguldak Karaelmas University, 67100 Zonguldak, Turkey 2 The Procter & Gamble Company, 8611 Beckett Road, West Chester, Ohio 45069 Received 10 October 2006; accepted 29 May 2008 DOI 10.1002/app.29254 Published online 19 November 2008 in Wiley InterScience (www.interscience.wiley.com). ABSTRACT: A new and promising method for the diversification of microbial polyesters based on chemical modifications is introduced. Poly(3-hydroxy alkanoate)- g-(poly(tetrahydrofuran)-b-poly(methyl methacrylate)) (PHA- g-(PTHF-b-PMMA)) multigraft copolymers were synthesized by the combination of cationic and free radical poly- merization. PHA-g-PTHF graft copolymer was obtained by the cationic polymerization of THF initiated by the carbonium cations generated from the chlorinated PHAs, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), and poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHx) in the presence of AgSbF 6 . Therefore, PHA-g- PTHF graft copolymers with hydroxyl ends were pro- duced. In the presence of Ce þ4 salt, these hydroxyl ends of the graft copolymer can initiate the redox polymeriza- tion of MMA to obtain PHA-g-(PTHF-b-PMMA) multi- graft copolymer. Polymers obtained were purified by fractional precipitation. In this manner, their c-values (volume ratio of nonsolvent to the solvent) were also determined. Their molecular weights were determined by GPC technique. The structures were elucidated using 1 H-NMR and FTIR spectroscopy. Thermal analyses of the products were carried out using differential scanning calorimeter (DSC) and thermogravimetric analysis (TGA). V C 2008 Wiley Periodicals, Inc. J Appl Polym Sci 111: 2308–2317, 2009 Key words: poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV); poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHx); bacterial polyesters; polytetrahydrofuran (PTHF); poly(methyl methacrylate) (PMMA); block and graft copolymers INTRODUCTION Poly(3-hydroxyalkanoate)s (PHAs) are originally natural aliphatic polyesters, which are distributed in biological systems and are produced within the cytoplasm of many prokaryotic organisms as intra- cellular carbon and energy sources. 1–4 By feeding bacteria with specific and unusual carbon com- pounds, it is possible to induce bacteria to produce polymers that are not usually produced in nature. In this structure, R is an alkyl side chain of naturally occurring PHAs depending on the substrates and the type of the bacteria. There are two types of PHAs according to the length of the R alkyl chain, that is, either a short-chain-length, sclPHA with an alkyl side chain having 1 to 2 carbon, produced by various bacteria, including Alcaligenes eutrophus (renamed Ralstonia eutropha, more recently changed again Wautersia eutropha 1 ) or a medium-chain-length, mclPHA with an alkyl side chain consisting of more than or equal to 3 carbon atoms, produced, for example, by Pseudomonas oleovorans. 4 The most well- known member of the sclPHAs, PHB is a 100% biodegradable and biocompatible polymer with the glass transition temperature ( T g ) of 0–10  C, the melting temperature (T m ) of 175–180  C, and the degradation temperature (T d ) of 252  C. It is also a water- and moisture-resistant thermoplastic poly- mer. 2,3 However, its highly crystalline and brittle structure, low impact strength, and nearly insoluble nature bring about shortcomings to use PHB in medical, pharmaceutical, and industrial areas. To improve the physical and chemical properties of PHB, there have been a lot of attempts to incorporate Correspondence to: B. Hazer (bkhazer@karaelmas.edu.tr). Contract grant sponsor: TU ¨ B _ IITAK; contract grant number: 104M128. Contract grant sponsor: Zonguldak Karaelmas University Research Fund. Journal of Applied Polymer Science, Vol. 111, 2308–2317 (2009) V C 2008 Wiley Periodicals, Inc.