Poly dense film preparation

This chapter will focus mainly on the development of chemically modified poly (2, 6 - dimethyl - 1, 4 - phenylene oxide) (PPO) membranes for gas separation applications. Gas separation characteristics of dense films from PPO and modified PPO will be described. Formation of integrally skinned asymmetric membranes as well as thin film composite (TFC) membranes from PPO and modified PPO along with gas transport through these membranes will also be discussed. A brief discussion on the effect of the molecular weight of PPO on the mechanical and gas transport properties of the membranes prepared from PPO and modified PPO will also be included. 

The expansion and contraction of the polymer chain which accompanies the redox of Cu ions can also be visually confirmed by means of the mechanochemical system proposed by Kuhn161), as illustrated in Fig. 31. A film is prepared with a poly(vinylalcohol)-Cu(II) complex and is suspended with a sinker in water. The film is extended by about 20% on the reduction of Cu(II) to Cu(I) and shrinks back to its original length on the oxidation of Cu(I). The poly(vinylalcohol) chain is densely crosslinked by the extremely stable Cu(II) chelate, but is loosened when Cu ion forms the unstable Cu(I) chelate. This change is reversible as may be observed. 

Another commercial membrane prepared by stretching is GoreTex (Fig. 4.6). The polymer here is poly(tetrafluorethylene), which makes the membrane extremely inert and thus convenient for processing even harsh streams. Processing PTFE is only possible by paste extrusion. In paste forming the polymer is mixed with a lubricant such as odorless mineral spirits naphtha or kerosene. The lubricant component is removed by heating to 327 °C. Above this temperature, sintering would lead to a dense PTFE film. 

Montague, F, Polesel-Maris, J. R., Pugin, R., Heinzelmann, H. (2008). Poly (N-isopropylacrylamide) thin films densely grafted onto gold surface preparation, characterization, and dynamic AFM study of temperature-induced chain conformational changes. 

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