Thin oligomer films

Response of Thin Oligomer Films to Steady and Transient Shear... 

Horowitz G, Peng XZ, Fichou D, Gamier F (1992) Role of the semiconductor insulator interface in the characteristics of Pi-conjugated-oligomer-based thin-film transistors. Synth Met 51 419 24... 

Marrocchi and co-workers at the University of Perugia have reported initial experiments to incorporate [2.2]paracyclophane-containing conjugated oligomers in thin film devices (Fig. 48). Their work includes the development of methods to fabricate and pattern thin films and the demonstration of photocurrents from devices that contain oligo(arylene ethynylene)s, shown below [183-185]. 

Polythiophene can be synthesized by electrochemical polymerization or chemical oxidation of the monomer. A large number of substituted polythiophenes have been prepared, with the properties of the polymer depending on the nature of the substituent group. Oligomers of polythiophene such as (a-sexithienyl thiophene) can be prepared by oxidative linking of smaller thiophene units (33). These oligomers can be sublimed in vacuum to create polymer thin films for use in organic-based transistors. 

ABA type poly(hydroxyethyl methacrylate) (HEMA) and PDMS copolymers were synthesized by the coupling reactions of preformed a,co-isocyanate terminated PDMS oligomers and amine-terminated HEMA macromonomers312). Polymerization reactions were conducted in DMF solution at 0 °C. Products were purified by precipitation in diethyl ether to remove unreacted PDMS oligomers. After dissolving in DMF/toluene mixture, copolymers were reprecipitated in methanol/water mixture to remove unreacted HEMA oligomers. Microphase separated structures were observed under transmission electron microscope, using osmium tetroxide stained thin copolymer films. 

It is interesting to note that the most critical spectral changes occur at the initial stages of photo-oxidation. On further exposure of the samples (as a thin film on KBr) to UV light, a certain stabilization of chemical changes in the structure of the oligomers studied takes place along with a decrease in the intensity of the major absorption bands. 

Bushnell and co-workers [117] employed extensive molecular modelling to understand the nature of cis and trans isomerism in tetrahedral p-phenylene vinylene oligomers, and to aid the interpretation of time of flight mass spectrometry and ion mobility studies. Molecules such as T4R, shown in Figure 18, with four equivalent arms can be used to control the crystallinity in thin films. The authors reported the observation of a species in the mass spectrum resulting from the loss of an arm from the central carbon. This species will be referred to as P4R. 

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