Günter Lieser

Structure, phase transitions and polymerizability of multilayers of some diacetylene monocarboxylic acids

Abstract The state of order and the packing of cadmium salts of long-chain diacetylene monocarboxylic acid in the form of Langmuir-Blodgett (LB) multilayers were investigated using electron diffraction and small angle X-ray techniques. The diacetylene moiety can be polymerized by exposure to UV light giving rise to the corresponding polymer without destruction of the LB assembly. Crystallinity in both the monomer and the polymer is restricted to the —(CH2)n—segments for which regular subcells have been worked out. No evidence for regular packing can be found in the regions where the cadmium ions and the carboxylate groups must be located. Some phase transitions in the monomer as well as in the polymer layers were observed. The crystallographical relationship between the different modifications and the mechanism of phase transformation are discussed in relation to the solid state polymerization mechanism.

Parameters influencing the polymerization and structure of long-chain diynoic acids in multilayers

Abstract Long-chain diynoic acids CH3(CH2)m−1CCCC(CH2)nCOOH with m = 9−16 and n = 0, 2 and 8 were investigated to determine the factors influencing their polymerization properties and morphology in Langmuir-Blodgett multilayers. The morphology of the films is described, as a function of the preparation conditions and the polymerization process. Effects in the photoreactivity are discussed, caused either by variations in the molecular chain lengths or by the formation of salts or mixtures of the acids.

Influences of the structure of long-chain diynoic acids on their polymerization properties in Langmuir—Blodgett multilayers

Abstract Acids of the general formula CH 3 − (CH 2 ) m −1 − CC − CC −(CH 2 ) n − COOH with m = 10, n = 8; m = 16, n = 2 and m = 16, n = 0 were investigated concerning their spreading behavior in monomolecular layers and their polymerizability in Langmuir—Blodgett multilayers. Influences of the aliphatic chain lengths m and n and the cadmium salt formation on their solid-state reactivity are discussed. Acids with the diacetylene unit amidst the aliphatic chain are highly photoreactive, but their monomolecular layers are of low stability. Acids with the diacetylene unit near the polar headgroup form more stable monolayers, but the packing is less favorable for a polymerization reaction. The cadmium salt formation in the multilayers can influence the reactivity and cause even photoinactivity, as shown for the acid with m = 16, n = 2.

Topochemical Reactions in Langmuir-Blodgett Multilayers

Abstract The topochemical polymerization of diacetylenes and.the dimerization of cinnamic acid derivatives have been studied in Langmuir-Blodgett-multilayers. The resulting polymer films are of controlled thickness and morphology and exhibit excellent stability. Structure, morphology and phase changes occuring in monomer and polymer films have been investigated using spectroscopic methods, electron and x-ray diffraction. Possible applications of the polymer films are discussed.

Polymerization of diacetylenes in mixed multilayers

Abstract Mixed multilayers of the Cd salts of pentacosa-10,12-diynoic acid and arachidic acid (mixture I) and tricosa-10,12-diynoic acid and tricosa-4,6-diynoic acid (mixture II) have been investigated with regard to their structure, miscibility, and polymerizability by the use of spectroscopic methods, X-ray and electron diffraction. In mixture I a phase separation into domains of the pure compounds is observed. Influences of the composition on the domain size and the maximum conversion to polymer are discussed. In mixture II a phase separation into domains of a 1: 1 mixture of both the compounds and into domains of the excess compound is observed. A structure model of the 1:1 complex phase is proposed.

New Routes to Conducting Polymers and New Insights into Structure-Properties Relations

Abstract The structure of conducting polymers is discussed in comparison to simple, so-called organic metals derived from naphthalene and similar arenes. In this context the conducting polymers are viewed as ion-radical salts of the backbone-units. This view is substantiated by recent results from X-ray investigations on electrochemically oxidized p-quaterphenyl as a model for poly(p-phenylene), poly-pyrrol salts of detergent ions and oxidized, highly oriented polyacetylene.

Structure of Doped Polymers

Abstract Studies of the synthesis, molecular weight, structure and morphology of polyacetylene (PA) indicate that the average length of linar chain segments between structural defects like crosslinks and chain folds is of the order of 20 units. Several models for the crystal structure of trans PA are given. The influence of the morphology on the mechanism of charge tranport is discussed. The doping is found to be inhomogeneous and the macroscopic conductivity is controlled by the topology of interlamellar contracts.

Morphology of Pristine Poly (Acetylene) Obtained by Luttinger's Catalyst

Abstract Poly (acetylene) was jprepared as freestanding mechanically stable film using Luttingers catalyst. The cis isomer formed initially is stable during storage at room temperature over many days. Electron micrographs show a loose conglomerate of irregularly shaped platelets with a diamjeter of several ten nanometers and a thickness of less than 10 nm. Electron diffraction on the cis form shows the chain axes perpendicular to the lamella surface. Annealing conver ts the polymer into the trans isomer. Morphological changes are not observed. The chanins however tilt in the course of the phase transition associated with the isomerization. Films of the material obtained by Luttingers cataltyst show essentially the same electrical and mechanical behavior as the ones prepared by a Shirakwa-technique.