Polymerization of Langmuir-Blodgett

Molecular-level fabrication of a conducting polymer matrix is an important hurdle to constructing molecular devices. Three approaches have been demonstrated (i) electrochemical polymerization of Langmuir-Blodgett (LB) multilayers, (ii) photo-patterning of conducting polymers [9], and (iii) depth profile control of conducting polymer multilayers. These are discussed in turn. 

A major achievement towards greater flexibility with respect to structural constraints of the reaction is the discovery of polymerization in Langmuir-Blodgett (LB)-films made by Wegner and coworkers These systems also allow introducing dye... 

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

Liquori et al. [23] first discovered that isotactic and syndiotactic PMMA chains form a crystalline stereocomplex. A number of authors have since studied this phenomenon [24]. Buter et al. [25,26] reported the formation of an in situ complex during stereospecific replica polymerization of methyl methacrylate in the presence of preformed isotactic or syndiotactic PMMA. Hatada et al. [24] reported a detailed study of the complex formation, using highly stereoregular PMMA polymers with narrow molecular weight distribution. The effect of tacticity on the characteristics of Langmuir-Blodgett films of PMMA and the stereocomplex between isotactic and syndiotactic PMMA in such monolayers at the air-water interface have been reported in a series of papers by Brinkhuis and Schouten [27,27a]. Similar to this system, Hatada et al. [28] reported stereocomplex formation in solution and in the bulk between isotactic polymers of / -(+)- and S-(—)-a-methylbenzyl methacrylates. 

The j Aiotochemistry of Langmuir-Blodgett multilayers has been discussed (83,84) as has that of phenazine-diacetylene caid nic acid con lezes (85). y-ray polymerization of the coraplesces and pure acids have also been studied The complexes are iinusual in that the initiation can occur via a fhotochemical reaction beti een the phenazinc and acid Thermal polymerization has been reported for bis( 1,3-penta-diynl mercury (88) and a nuniber of nitrophenoxy substituted monomers (8e-91) The thermal polymerization of hexadiynediol has also been reported (92) With the exception of the LB multilayers the kinetics were not analysed in detail ... 

Polymer monolayers. Polymeric spread films at the air-water interface are examples of polymers in pseudo-two-dimensional situations. The nature of such films is germane to the preparation of Langmuir-Blodgett films. 

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... 

Laschewsky A, Ringsdorf H and Schmidt G 1985 Polymerization of hydroxocarbon and fluorocarbon amphiphiles in Langmuir-Blodgett multilayers Thin Soiid Fiims 134 153-72... 

Laschewsky A and Ringsdorf H 1988 Polymerization of amphiphilic dienes in Langmuir-Blodgett multilayers Maoromoieouies 21 1936-41... 

Uchida M, Tanizaki T, Kunitake T and Ka]iyama T 1989 Surface stability and functional property of polymerized Langmuir-Blodgett type films Maoromoieouies 22 2381-7... 

Erdelen C, Laschewsky A, Ringsdorf H, Schneider J and Schuster A 1989 Thermal-behaviour of polymeric Langmuir-Blodgett multilayers Thin Solid Films S0 153-66... 

Orthmann E and Wegner G 1986 Preparation of ultrathin layers of molecularly controlled architecture from polymeric phthalocyanines by the Langmuir-Blodgett-technique 1986 Angew. Chem. Int. Edn. Engl. 25 1105-7... 

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. 

Ejaz, M., Yamamoto, S., Ohno, K., Tsujii, Y. and Fukuda, T. (1998) Controlled graft polymerization of methyl methacrylate on silicon substrate by the combined use of the Langmuir-Blodgett and atom transfer radical polymerization techniques. Macromolecules, 31, 5934-5936. 

Diacetylenes like [30o] after being laboriously prepared, are not polymerized either by heat or ultraviolet irradiation (Iwamura, 1990). Control of molecular packing in crystals is now needed. Introduction of the technology of liquid crystals or Langmuir-Blodgett membranes (Hupfer et al., 1981 Koch and Ringsdorf, 1981) may be of help. 

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