Synthesis and photocrosslinking of benzyl acrylate substituted polydimethylsiloxanes Cristina Iojoiu a,b , Marc J.M. Abadie b , Valeria Harabagiu a , Mariana Pinteala a , Bogdan C. Simionescu c, * a ``P. Poni'' Institute of Macromolecular Chemistry, 6600 Jassy, Romania b Montpellier 2 University, LEMP/MAO, 34095 Montpellier Cedex 05, France c ``Gh. Asachi'' Technical University, Department of Macromolecules, 6600 Jassy, Romania Received 16 August 1999; accepted 3 November 1999 Abstract This article deals with the synthesis of polydimethylsiloxanes (PDMSs) substituted with chain or end benzyl acrylate groups by the hydrosilation of appropriate hydro-siloxanes, followed by phase transfer catalysed reaction of chlo- romethylated aromatic groups with the sodium salt of acrylic acid. Dierential scanning photocalorimetry (DPC) was used to study the crosslinking behaviour of the mentioned functional PDMSs in the presence of dierent photoiniti- ators. The reaction rate, the ®nal conversion and the inhibition period characterizing the crosslinking were found to be dependent on reaction atmosphere, light intensity, nature and concentration of photoinitiator and on polymer func- tional groups content. Ó 2000 Elsevier Science Ltd. All rights reserved. Keywords: Functional polysiloxanes; Benzyl acrylate; Radical photocrosslinking 1. Introduction Polydimethylsiloxanes (PDMSs) present well-known peculiar characteristics such as very high thermal and chemical resistance, high ¯exibility and hydrophobicity, stability against dierent types of radiation. Polysilox- anes with dierent organofunctional substituents were synthesized and used as starting compounds in the preparation of polymeric materials with interesting properties and applications [1,2]. Photocrosslinking of functional polysiloxanes is one of the most ecient methods in rapidly producing siloxane based polymeric networks. PDMSs containing acrylic and methacrylic ester groups, linked to the siloxane chain as pendant units through aliphatic ether moieties, have been previously described in the literature [3±12]. These compounds combine the properties of silicones with the fast cross- linking ability of (meth)acrylates. Siloxane-based net- works have been used for metal coating and for the protection of glass or optical ®bres [11±16] owing to their transparent nature. Our previous contributions proposed the attachment of dierent photoactive groups (benzoin [17], glycidyl ether [18] or cyclohexene oxide [19]) to the siloxane backbone by the hydrosilation method. This article deals with the synthesis of PDMSs containing chain or end benzyl acrylate functionalities by chemical transforma- tion of the appropriate precursors. The photocrosslink- ing behaviour of these functional polymers is also considered. The aim of this study is to report on the in¯uence of photoinitiator nature, reaction atmosphere and polymer characteristics (functionality and molecular weight) on photocrosslinking parameters. European Polymer Journal 36 (2000) 2115±2123 * Corresponding author. Tel.: +40-32-140287; fax: +40-32- 211-299. E-mail address: bcsimion@poni.ichpp.tuiasi.ro (B.C. Simio- nescu). 0014-3057/00/$ - see front matter Ó 2000 Elsevier Science Ltd. All rights reserved. PII: S 0 0 1 4 - 3 0 5 7 ( 9 9 ) 0 0 2 8 7 - 6