Polymers periodic surfaces

Fig. 25 A striped surface is modeled by a periodic surface potential V(x) which defines the interaction between a polymer chain and the surface. Polymers deposited onto the substrate will concentrate in the lanes of higher affinity. If a chain changes from a lane of higher affinity to a lane of lower affinity, a potential barrier u has to be surmounted. On scales larger than the periodicity a of the stripe pattern the diffusivity becomes anisotropic. In our simulations we use 400 lanes with a period of 12 lattice units and a width of 6 lattice units per lane...

Even with resistant polymers, the surfaces of products can be contaminated by microorganisms if they become roughened or pitted, and they then remain moist for long periods. Also, they become discoloured if constituent additives are vulnerable. Other symptoms include black or pink staining, odour, and changes in electrical or mechanical properties. Affected plastics products attract and retain dirt more than unaffected ones. 

Qiu J, Wang Z, Yang L, Zhao J, Niu Y, Hsiao BS (2007) Deformation-induced highly oriented and stable mesomorphic phase in quenched isotactic polypropylene. Polymer 48 6934-6947 Rebollar E, Perez S, Hernandez JJ, Martin-Pabiani I, Rueda DR, Ezquerra TA, Castillejo M (2011) Assessment and formation mechanism of laser-induced periodic surface structures on polymer spin-coated films in real and reciprocal space. Langmuir 27 5596-5606 Reiter G, de Gennes PG (2001) Spin-cast, thin, glassy polymer films highly metastable forms of matter. Eur Phys J E 6 25... 

Pereira and Williams performed early ID large-area simulations of a symmetric AB diblock film on surfaces patterned with selective stripes where the stripe period was either shorter or longer than the lamellar period. At the same time, Chen and Chakrabarti carried out full 3D simulations of a symmetric AB diblock on a striped surface, observing strong epitaxial order when the stripe and polymer periods match but an onset of tilted lamellae for significantly longer period stripes. Kielhom and Muthukumar carried out early 3D simulations of a thick symmetric diblock film in the... 

Fluorine was first produced commercially ca 50 years after its discovery. In the intervening period, fluorine chemistry was restricted to the development of various types of electrolytic cells on a laboratory scale. In World War 11, the demand for uranium hexafluoride [7783-81-5] UF, in the United States and United Kingdom, and chlorine trifluoride [7790-91 -2J, CIF, in Germany, led to the development of commercial fluorine-generating cells. The main use of fluorine in the 1990s is in the production of UF for the nuclear power industry (see Nuclearreactors). However, its use in the preparation of some specialty products and in the surface treatment of polymers is growing. 

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