A New Macroinitiator for the Synthesis of Triblock Copolymers PA12-b-PDMS-b-PA12 R. Rached, 1 S. Hoppe, 1 A. Jonquieres, 2 P. Lochon, 2 F. Pla 1 1 Laboratoire des Sciences du Ge ´nie Chimique, Unite ´ Propre de Recherche 6811 CNRS, Groupe ENSIC, 1 rue Grandville, B.P. 451, 54001 Nancy Cedex, France 2 Laboratoire de Chimie Physique Macromole ´culaire, Unite ´ Mixte de Recherche CNRS-INPL 7568, Groupe ENSIC, 1 rue Grandville, B.P. 451, 54001 Nancy Cedex, France Received 19 September 2005; accepted 31 March 2006 DOI 10.1002/app.24547 Published online in Wiley InterScience (www.interscience.wiley.com). ABSTRACT: A new PDMS macroinitiator is proposed for the anionic ring-opening polymerization of lactams. This a,o-dicarbamoyloxy caprolactam PDMS macroinitiator was readily obtained in quantitative yield, by an original syn- thesis scheme in two steps, which involved the scarcely reported reaction of isocyanates with silanol groups. It was then shown that this bifunctional macroinitiator enabled to synthesize triblock copolymers PA12-b-PDMS-b-PA12 by polymerization of lauryl lactam (LL) at high temperature (2008C) in inert atmosphere under conditions compatible with reactive extrusion processes. Another related high molar weight a,o-diacyllactam PDMS macroinitiator was also successfully used in the polymerization of LL under the same conditions, therefore overcoming the limitations formerly reported for this type of macroinitiators during the polymerization e-caprolactam (e-CL) at a much lower temperature (808C). Triblock copolymers with a wide range of PA12 /molar weights (M n :  10,800–250,000 Da) were eventually obtained by using both types of macroinitiators. DMTA and DSC analyses showed that their thermal pro- perties were strongly dependent upon their respective contents in soft and hard blocks. Such triblock copolymers already appear very promising for the highly effective in situ compatibilization of PA12/PDMS blends as shown by recent complementary results obtained in our labo- ratory. Ó 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2818–2831, 2006 Key words: ring-opening polymerization; lactam; macro- initiator INTRODUCTION Thermoplastic elastomers represent an important class of materials that are widely used for different tech- nical applications. Their excellent properties due to their two-phase morphology (i.e., soft and hard phases) can be varied over a wide range by the control of the amount and the nature of these two phases. Block copolymers with hard segments based on poly- urethanes, polyamides, polycarbonate, or polystyrene and a soft phase made of polybutadiene, polyisobu- tylene, or polydimethylsiloxane 1–5 allow achieving improved properties generally not available with ei- ther of both homopolymers. They often play the role of compatibilizing agent at the interface of immisci- ble polymers. 6–8 The increasing interest in multiphase copolymers based on polydimethylsiloxane (PDMS) is mainly due to their unique combination of properties, which is re- lated to their chemical structure and macromolecular architecture. Several works 9–13 have already reported the synthesis of block copolymers composed of PDMS and various polyamides (PA). A key finding towards success 11,14 was the design of new activating systems capable of polymerizing e-caprolactam (e-CL) without the concurrent nucleophilic degradation of the PDMS block, which had been observed in the early work of Lefebvre et al. 15 However, little information is avail- able about the successful synthesis of PDMS/PA block copolymers with fairly long PDMS blocks, which would be highly interesting to improve partic- ular properties of polyamides (e.g., toughness, pre- vention of moisture absorption) or silicones (e.g., weak mechanical properties). This work is part of a general project aimed at developing new PA12/PDMS blends by anionic po- lymerization of lauryl lactam (LL: monomer of PA12) by reactive extrusion. One key factor for good com- patibilization is the in situ synthesis of block copoly- mers PDMS-PA12 during melt processing. It has been shown that in situ block copolymer formation during melt processing is a very fast, easy, and cost- effective alternative to classical compatibilization methods. Moreover, anionic polymerization has pro- ven to be a valuable method for preparing block copolymers from a functional polymer containing active species at its ends (a macroinitiator), which can allow the polymerization of another monomer. Correspondence to: F. Pla (fernand.pla@ensic.inpl-nancy.fr). Journal of Applied Polymer Science, Vol. 102, 2818–2831 (2006) V V C 2006 Wiley Periodicals, Inc.