Polymerization Langmuir-Blodgett films

Photoconduction and absorption spectra of two different structural modifications of a PDA Langmuir-Blodgett film (polymerized tricosa-10,12-diin acid). From ref.(16). 

Rabe J P, Rabolt J F, Brown C A and Swalen J D 1982 Crder-disorder transitions in Langmuir-Blodgett films. 2. IR studies of the polymerization of Cd-octadecylfumarate and Cd-octadecylmaleate J. Chem. Phys. 84 4096-102... 

An example, Figure 9 is an SFM image of a Langmuir-Blodgett film. This film was polymerized with ultraviolet light, giving a periodicity of 200 A, which is seen in the associated Fourier transform. The low forces exerted by the SFM tip are essential for imaging such soft polymer surfaces. 

At the bulk level, molecular and polymeric materials also offer flexibility of fabrication in various forms such as crystals, films, fibers, as well as monolayer and multilayer Langmuir-Blodgett films. In addition, one can make composite structures to introduce multifunctionality at the bulk level. 

Seki, T., Tanaka, K., and Ichimura, K. Phototropic discrimination of the polymerization behavior of diacetylene Langmuir-Blodgett films by an azobenzene-containing monolayers. Adv. Mater., 9, 563 (1997). 

Langmuir-Blodgett films may have value in many applied areas of traditional interest to the industrial chemist, such as adhesion, encapsulation, and catalysis. The permeability characteristics of monolayer assemblies may also find application as synthetic membranes for ultrafine filtration, gas separation, and reverse osmosis. For example, Albrecht et al. (44) proved the eflSciency of polymeric diacetylene monolayers on semipermeable supports in reducing the flow of CH4. One interesting possibility lies in using LB monolayers as lubricants in magnetic tape technology. Unpublished reports have indicated that frictional coeflScients can be reduced markedly when the tape is coated with a few monolayers. In applications such as those listed previously, difiSculties may well be encountered with the mechanical stability of the films. To date, relatively little research has been carried out in this area. 

Photopolymerisation of Langmuir-Blodgett films continues to attract interest. Polymeric monolayer films of octadecyl methacrylate with methacrylamide con-... 

Many commercial applications of CPs involve coatings on various substrates and the most important method for processing CPs as coatings is the in situ polymerization of monomers on the surfaces of substrates. It is commonly used to coat fabrics and to fabricate Langmuir-Blodgett films. ... 

This paper presents studies of solid state polymerization aimed towards formulating a dynamic model of reactivity in the condensed phase. Phonon spectroscopy is successfully used to elucidate the mechanism of lattice control of the reaction. Novel concepts of phonon-assisted thermal and photochemical reactions are introduced, supported by experimental data. Non-linear laser spectroscopy is used to find the importance of biexcitonic processes in photopolymerization. Also, spectroscopic studies of reactions in Langmuir-Blodgett films and at gas-solid interface which produce ordered polymers are presented. 

Next, we discuss the concept of phonon-assisted reactions. In relation to thermal reactions, they can be assisted by phonon-mode softening leading to large-amplitude overdamped oscillations. In the case of a photochemical reaction, a strong electron-phonon coupling can assist in polymerization. Then some non-linear spectroscopic studies are discussed which illuminate on the dynamics of photopolymerization process. Then follows a discussion of results on reaction in a different kind of molecular assembly, the Langmuir-Blodgett films. Finally, some gas-solid interface reactions which produce polymers in a doped state are discussed. 

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