Thin polymer ultra

While thin polymer films may be very smooth and homogeneous, the chain conformation may be largely distorted due to the influence of the interfaces. Since the size of the polymer molecules is comparable to the film thickness those effects may play a significant role with ultra-thin polymer films. Several recent theoretical treatments are available [136-144,127,128] based on Monte Carlo [137-141,127, 128], molecular dynamics [142], variable density [143], cooperative motion [144], and bond fluctuation [136] model calculations. The distortion of the chain conformation near the interface, the segment orientation distribution, end distribution etc. are calculated as a function of film thickness and distance from the surface. In the limit of two-dimensional systems chains segregate and specific power laws are predicted [136, 137]. In 2D-blends of polymers a particular microdomain morphology may be expected [139]. Experiments on polymers in this area are presently, however, not available on a molecular level. Indications of order on an... 

Grohens, Y, Hamon, L., Reiter, G., Soldera, A. and Holl, Y. (2002) Some relevant parameters affecting the glass transition of supported ultra-thin polymer films. Eur. Phys. J. E, 8, 217-224. 

Immobilization of bilayer membranes as ultra thin polymer films... 

Thin polymer films have many possible technical applications. Transistors and light-emitting diodes are the obvious ones. In ultra-thin films, one may even approach an electronics of molecular dimension. Molecular electronics will be a future challenge for basic and applied science. Nature applies it on a large scale in the reaction centers of the photosynthetic process, where photoinduced mobile charges are separated in some analogy to the separation of the photo-(p-n)-pair in the junction zone of a semiconductor (see Section 13.3.1). 

Myler S, Eaton S, Higson S. Poly(o-phenylenediamine ultra-thin polymer-film composite membranes for enzyme electrodes. Analytica Chimica Acta 1997, 357, 55-61. 

Jaeger, R., Bergshoef, M.M., Batlle, C.M.I., Schonherr, and Vancso, G.J., 1998. Electrospinning of ultra-thin polymer fibers, Macromol. Symp., ITl, pp. 141-150. 

X. Ma, D. Xu, and J. Lin, A Study of Dropwise Condensation on the Ultra-Thin Polymer Surfaces, Proc. 10th Int. Heat Transfer Conf, Brighton, 3, pp. 359-364,1994. 

Prucker, S. Christian, H. Bock, J. Ruehe, C.W. Frank, and W. KnoU, On the glass transition in ultrathin polymer films of different molecular architecture, Macromol. Chem. Phys. 199, 1435 (1998) J.N.D Amour, C.W. Frank, and U. Okoroanyanwu, Influence of substrate chemistry on the properties of ultra thin polymer films, Microelectron, Eng. 73 74, 209 217 (2004). 

However, direct investigation of the interphase properties inside an adhesive bond is very difficult, for experimental reasons. In contrast, ultra-thin polymer films on metal substrates provide access for a number of analytical techniques. Hence, to some extent, they are suited to monitoring of interphase properties and processes. By varying the film thickness, it is possible to discriminate the influence of the metal substrate on the aging behavior in the interphase. 

Solid polymer membranes for gas separations have been widely investigated for many years. In order to maximize fluxes, asymmetric versions of polymer membranes with a very thin ( 1 p.) membrane "skin" have been developed (JL2). Unfortunately these ultra-thin polymer membranes are still short of the flux n ed for many applications. Also, the selectivity of the membranes to gases is often poor and thus, limits their usefulness. 

The second problem with immobilized liquid membranes is that they are relatively thidr (25-150 1) conqnied to ultra-thin supported polymer membranes (0.1-2 p). Since flux is inversely proportional to membrane Uiickness, this reduces the total flux achievable. Although methods of fabricating suppcnled ultra-thin polymer membranes has been known for some time, there has been no method of preparing similar ultra-thin liquid membranes. 

ILMs can be fabricated with any any porous matrix in which the liquid phase wets the matrix material and the pores are sufficiently small. Since commerciidly available asymmetric membranes with thin (0.1 - 2pm) p us skins supported by a macroporous backing exist, it should be possible to fabricate liquid membrane versions of the supported ultra-thin polymer membranes figure 9). 

R. Silva, E.C. Muniz, A.F. Rubira, Multiple hydrophilic polymer ultra-thin layers covalently anchored to polyethylene films. Polymer 49, 4066 075 (2008)... 

Conducting polymer ultra-thin films with monomolecular thickness (mono-layers) having the minimum dimension and of built-up multilayers with anisotropic structures were constructed. The properties from the monolayers and the evaluation of functions of these films were investigated. The... 

Electrospinning can create surface textures needed for superhydrophobicity. Electrospinning is a widely used technique to make ultra-thin polymer fibers. In this process, a polymer solution is charged in a capillary tube and electrically biased with respect to a grounded collector surface located 10 cm from the needle. The polymer solution is then ejected from the capillary into a jet form and the solvent evaporates leaving polymer fibers. By electrospinning polymers with hydrophobic properties, one can easily produce superhydrophobic fiber mats on the collector [89-92]. Of course, the electrospinning can also be used to make porous fiber mats... 

Figure 6. Specular reflection FT-IR spectra of ultra-thin polymer films obtained at grazing angle using parallel polarized infrared radiation (26).

J.-U. Sommer and G. Reiter. Crystallization in ultra-thin polymer films morphogenesis and thermodynamical aspects. Thermochimica Acta, 432(2) 135-147, June 2005. 

Jagadeesh, B., Demco, D.E., and Bliimich, B. 2004. Surface induced order and dynamic heterogeneity in ultra thin polymer films A H multiple-quantum NMR study. Chem. Phys. Lett. 393 416-420. 

Polymer Conformations Confined into Thin and Ultra-Thin Films 394... 

The qualitative behavior of the polymer conformations in thin and ultra-thin films is sketched in Figure 6. In the simplest case of nonpreferential surfaces, Silberberg s argument suggests that the chains are reflected at the surface. As for a Gaussian chain the molecular extensions in different spatial directions are completely decoupled, the extension, J j., perpendicular to the surface is reduced but the lateral... 

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