INTRODUCTION Polylactide (PLA) is one of the most readily available thermoplastic polyester that is derived from renewable resources such as corn, beet and sugar. Polylactide is 100 % biodegradable, can be recycled over 7-10 times 1-4 . Polylactide has been produced commercially and is used in packaging, agriculture, automotive, electronics sector, furniture, house ware sector, medical sector (absorbable sutures, in tissue engineering and controlled drug delivery) 5-6 . More research effort is being directed toward finding methods of addressing the weakness of PLA without compromising its biodegrad- ability. Theses polymers are appropriate in place of conven- tional plastics in large scale applications while exhibiting reduced environmental impact. Polylactide have high physico- mechanical properties which make it suitable for product development. Polylactide showing tensile strength, flexural strength and impact strength 50-70 MPa, 60-70 MPa and 2.6 to 2.7 Kj/m 2 , respectively 7-10 . Low molecular weight PLA can obtained by polyconden- sation and high molecular weight PLA can obtained by ring opening polymerization of lactide. Fig. 1 summarized the entire polymerization route. Ring opening polymerization of lactide can be carried out in melt, bulk, or in solution and by cationic, anionic and coordination-insertion mechanisms depending on the catalyst 11-13 . The choice of initiator system, Cyclometallic Zirconium Compound in Ring Opening Polymerization of L-Lactide to Biodegradable Polylactide RUHI HAQUE 1,* , MOHINI SAXENA 1 , S.C. SHIT 2 and ASOKAN PAPPU 1 1 CSIR-Advanced Materials and Processes Research Institute, Bhopal-462 064, India 2 Central Institute of Plastics Engineering and Technology, Plot No. 630, Phase-IV, GIDC, Vatva, Ahmedabad-382 445, India *Corresponding author: E-mail: ruhi_haq2003@yahoo.com (Received: 20 December 2012; Accepted: 1 October 2013) AJC-14199 Polylactide found potential as a substitute of non renewable resources. It is biodegradable and biocompatible polymer. Ring opening polymerization of polylactide has gained the importance in pharmacological, biomedical and environmental fields. In the present study, L-lactide was successfully polymerized with synthesized zirconium catalyst i.e., N-methyl benzyl amine zirconium chloride compound in bulk and in solution (THF) and the effect of monomer to catalyst ratio on the molecular weight of polymer were studied. Catalytic compound is an organometallic five membered cyclic compound, synthesized by cyclometallation process. It was observed that cyclometallic zirconium compound can effectively polymerize L-lactide to high molecular weight polylactide. Cyclometallic compound and polylactide was characterized by FT-IR, 1 H and 13 C NMR, CHNS techniques. Molecular weight was determined by GPC and thermal study was done by TGA-DSC. Surface morphology and shape was evaluated via FESEM. Key Words: Biodegradable polymer, Ring opening polymerization, Polylactide, Catalyst, Cyclometallation. co-initiator as chain control agent, catalyst concentration, monomer-to-initiator ratio and polymerization temperature and time significantly affect the polymer properties 14-18 . In the present study, organometallic cyclic compound was synthesized and used as catalyst for ring opening polymerization of L- lactide to polylactide at different monomer to catalyst ratio. The effect of different monomer to catalyst ratio in bulk and in solution on molecular weight distribution was also studied. Cyclometallation is a highly attractive and versatile synthetic method to produced organometallic compounds, because it permits to understand significant aspects of the metal-mediated activation of unreactive bonds mainly C-H bond. Cyclometallic compounds have been used in inorganic transformations and catalysis 19- 24 . They have been also utilized in other area of materials science for example in sensors, in anti- cancer agents and for other bioorganometallic applications 25-29 . Cyclometallation reaction can be achieved into two main steps, comprising the bonding of the metal center by the (hetero) atom N, P, O, etc. and the C-H bond activation. Influencing factors are metal precursor, donor group and C-H bond activation. Require- ment for a metal moeity is suitable for inducing cyclometallation i.e. providing a coordination site for atom bonding. Thus in the first step, attachment of the ligand via M-N interactions was occurred and in the second step, the C-H bond activation process is facilitated by strongly basic ligands at the metal moeity 30 . Asian Journal of Chemistry; Vol. 25, No. 17 (2013), 9434-9438 http://dx.doi.org/10.14233/ajchem.2013.14272