Triazene Compound

Abstract: Organic triazene compounds are stable precursors to diazonium salts for functionalizing single-wall carbon nanotubes (SWNTs) in aqueous media. This method is particularly useful when a target molecule has functionality that will not tolerate diazotization conditions. We illustrate this by detailing the synthesis of a biotin-containing triazene followed by reaction with SWNTs.

Abstract: Triazene compounds have recently attracted attention due to a variety of interesting properties. The cytostatic activity discovered for several substituted triazenes *) has stimulated intense research efforts directed towards the development of triazene-based drugs3). In view of the importance of this field, several reviews on the synthesis of triazenes are available4-’). A second class of applications is based on the fact that the triazeno group is comparatively stable with respect to thermal decomposition, but undergoes facile photo-chemical cleavage releasing nitrogen. This property, which may lead to novel applications in photolithography and photoreproduction, is the motivation for the present study. Photopolymers which can be structured by light are important materials in the microelectronics industry. Laser ablation of polymers ‘3 ’) has been intensively investigated in this context; the laser treatment represents a dry processing technique, without the need for wet processing steps. Powerful XeC1*-excimer lasers emitting at 308 nm are available for reliable large-scale industrial operation, making it desirable to use this wavelength in polymer ablation. However, many polymers suitable for application in microelectronics do not absorb at this wavelength. Therefore, progress has been made recently in sensitizing these polymers for ablation at 308 nm, by the addition of low-molecular-weight chromophors. Acridine lo), benzophenone ‘ I ) , pyrene 12), porphyrines 1 3 ) and 1,3-diphenyltriazenes 143 15) have been tested for this purpose. Recently, we have successfully used and characterized several l-phenyl-3,3-dialkyltriazenes as dopants for the ablation of poly(methy1 methacrylate) (PMMA) at 308 nm 16). An attractive alternative to physical doping is the incorporation of the triazeno group into the polymer itself. Recently, polymer-analogous reactions have been used to synthesize a PMMA copolymer containing ca. 0,3 mol-Vo of triazene side chains ”). In the present communication, we are investigating the synthesis of another novel type of photopolymer which contains two triazeno groups per repeating unit. Synthesis is carried out by a polycondensation reaction in which a bis-diazonium salt and a

Abstract: The excimer laser-induced ablation of triazene polymers at a wavelength of 308 nm has been investigated as a function of laser fluence deposited on the surface in one or several pulses PMMA, which as a homopolymer can not be ablated at 308 nm, has been sensitized for ablation at this wavelength by synthesizing a copolymer in which 03 mol-% of the side chains contain the triazene functional groups The high ablated depths per pulse achieved in this manner are similar to the ones observed upon physical doping of PMMA with monomeric triazene compounds In an alternative approach, the triazene functional group is introduced once (polymer TP 1) or twice (TP 2) into each repeating unit of the polymer backbone by a polycondensation reaction Irradiation of TP 1 gives rise to ill-defined ablation profiles with sloping wall In contrast, clean circular ablation profiles are obtained with polymer TP 2, which are characterized by circular contours, steep edges, and flat bottoms of the ablated craters The origins of these differences are investigated A comparative study of excimer laser ablation of TP 2 at 248 and 308 nm shows that the latter wavelength is more effective; the plateau value of the ablated depth per pulse corresponds to ≈ 1 μm at 248 nm and ≈ 3 μm at 308 nm This dependence is attributed to the photolysis behaviour of the triazene compounds: nitrogen released upon photolytic bond cleavage acts as a driving gas which promotes the ablation As a consequence, no ‘incubation pulses’ are required for triazene polymer ablation in the investigated fluence range Die Ablation von Triazenpolymeren durch Exzimerlaserpulse mit einer Welenlange von 308 nm wird als Funktion der auf der Oberflache deponierten Energiedichte untersucht Um PMMA, welches als Homopolymeres keine Absorption bei 308 nm aufweist, fur die Ablation bei dieser Wellenlange zu sensitivieren, wird ein PMMA-Copolymeres synthetisiert, in welchem ein Anteil von 03 mol-% der Seitengruppen die Triazengruppe enthalt An diesem Material beabachtet man Abtragtiefen von bis zu ≈ 30μm pro Puls; das Ablationsverhalten des Copolymeren ist in dieser Hinsicht vergleichbar mit demjenigen von PMMA, welches durch Losen niedermolekularer Triazenverbindungen physikalisch dotiert wird Als Alternative zur Copolymerisation werden durch eine Polykondensationsreaktion Triazen-Hauptkettenpolymere mit einer bzw zwei Triazengruppen pro Wiederholungseinheit synthetisiert (Polymere TP 1 bzw TP 2) Wahrend die Bestrahlung von TP 1 in unbefriedigenden Ablationsprofilen mit geneigten Kraterwanden resultiert, erhalt man bei TP 2 gut definierte kreisformige Profile mit scharfen Kanten, senkrechten Wanden und ebenen Boden der Ablationskrater Ein Vergleich des Ablationsverhaltens von TP 2 bei 248 und 308 nm zeigt eine hohere Effizienz der Einstrahlung bei der groseren Wellenlange: Der Grenzwert der Abtragtiefe pro Plus fur hohe Laser-Energiedichten betragt 1 μm bei 248 nm, im Vergleich zu 3 μm bei 308 nm Diese Wellenlangenabhangigkeit wird auf dem Mechanismus der Ablation im vorliegenden System zuruckgefuhrt: Der bei der Photolyse der Triazene freigesetzte Stickstoff wirkt als ‘Treibgas’ fur die Ablation Als Konsequenz wird im Bereich der eingesetzten Laser-Energiedichten bereits beim ersten Plus Abtragung von Material beobachtet, d h es sind keine Inkubationspulse erforderlich