Journal of Molecular Catalysis A: Chemical 254 (2006) 174–179 Photosensitive polynorbornene containing the benzyl thiocyanate group—Synthesis and patterning Alexandra Lex, Gregor Trimmel ∗ , Wolfgang Kern, Franz Stelzer Institute for Chemistry and Technology of Organic Materials (ICTOS), Graz University of Technology, Streymayrgasse 16, 8010 Graz, Austria Available online 24 April 2006 Abstract In this paper, we report the synthesis of a new polymer based on polynorbornene containing the photosensitive benzyl thiocyanate group. The monomer (±)-endo,exo-bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic acid-bis-(4-thiocyanatomethyl)benzyl ester (2) was prepared from (4- thiocyanatomethyl)benzyl alcohol (1) and (±)-endo,exo-bicyclo[2.2.1]hept-5-ene-2,3-dicarbonyl dichloride as starting materials. Compound 2 was polymerised via ring opening metathesis polymerisation using the Grubbs type initiator [RuCl 2 (H 2 IMes)(3-bromo-pyridine) 2 (CHPh)] pro- viding a photoreactive polymer. The photoreactions of the low molecular compounds as well as of the polymer were investigated by FT-IR spectroscopy. The benzyl thiocyanate group undergoes photoisomerisation to the reactive benzyl isothiocyanate group when exposed to UV-light. Upon a post-modification process with gaseous propylamine, the isothiocyanate group is selectively transformed to the corresponding thiourea derivative. We show that these processes allow patterning of thin films of this polymer by lithographic techniques. © 2006 Elsevier B.V. All rights reserved. Keywords: Ring opening metathesis polymerisation; Photoreactive polymer; Photoisomerisation; Thiocyanate 1. Introduction Photolithography is a versatile tool for 2D-structuring of polymer films. Over the last few years, we have shown that polystyrene based photoactive polymers containing the benzyl thiocyanate group are excellent materials for applications in optics, optoelectronics and for immobilisation of (bio)molecules [1–9]. The basic reaction behind is an irreversible photoisomeri- sation of the benzyl thiocyanate group via a radical mechanism to the corresponding isothiocyanate group, as sketched in Scheme 1 [10–12]. Due to this isomerisation, the refractive index of the mate- rial changes. Using interference lithography, it is possible to inscribe refractive index gratings into the polymeric matrix that can be used for distributed feed back (DFB) lasers [3,6,13]. Recently, we have produced a mechanically tunable DFB laser by preparing an elastomeric copolymer of vinylbenzyl thio- cyanate, styrene and butadiene. The colour of the laser can be tuned continuously between 600 and 625 nm by mechani- cal force [2]. By incorporating benzyl thiocyanate groups into ∗ Corresponding author. Tel.: +43 316 873 4958; fax: +43 316 873 8951. E-mail address: gregor.trimmel@tugraz.at (G. Trimmel). conjugated polymers it is possible to inscribe a refractive index pattern into an electroactive material [1]. A second feature of this isomerisation reaction is the differ- ent reactivity of the thiocyanate and the isothiocyanate group. While the isothiocyanate unit reacts readily with amines, e.g. ammonia or propylamine to give derivatives of thiourea, the thiocyanate remains inert. Thus it is possible to immobilise amino-functionalised molecules onto the illuminated area. At the same time an increase in film thickness can be observed. This reaction has been applied for the generation of surface relief structures and for the preparation of bio-chips [4,6,7]. With exception of the electroactive polymer all investigations up to now were made on vinylbenzyl thiocyanate polymers and copolymers prepared by radical polymerisation. In this paper, we report for the first time the synthesis of a norbornene derivative carrying the benzyl thiocyanate group. Moreover, we wanted to investigate the possibility to polymerise this compound by ring opening metathesis polymerisation with ruthenium initiators. One crucial question is if the –SCN moiety is compatible with Ru, as it is known that CN-groups interact with the metal centre and hampers the reaction [14–16]. Using [RuCl 2 (H 2 IMes)(3-bromo-pyridine) 2 (CHPh)], the third gener- ation Grubbs initiator [17], and optimising the reaction condi- tions, it is possible to obtain a defined polymer in good yield. 1381-1169/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.molcata.2006.03.024