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Attachment of Train Segments to Active Sites

To determine the conformation of adsorbed polymers the fraction of adsorbed polymer segments (p) and the fraction of the occupied surface sites (6) are often measured. Fontana and Thomas2 were the first to measure p and 6 by IR spectroscopy. At present, the application of IR spectroscopy is limited to finely divided substrates, e.g. nonporous silica, and requires that the surface area and the number of surface sites (e.g. the silanol groups) per unit area are accurately known in advance. The adsorbed amount T of polymer per surface site can be determined from adsorbance A(g/cm2) and the total area of the adsorbent. However, it can also be evaluated from the ratio 6/p. [Pg.47]

Fontana and Thomas2 determined p, 6, and T for poly (lauryl methacrylate) of molecular weights of 33 X 103 to 1190 X 103 adsorbed from n-dodecane and cis-decalin onto silica particles by observing IR shifts of the C = O bands in the polymer and the surface silanol group. They found that 6 increased whereas p remained nearly constant with rising T. [Pg.47]

Linden and Leemput10 measured p, 0, and T for polystyrene adsorbed on the Aerosil 130 silica from cyclohexane and carbon tetrachloride solutions at 35 °C as a function of molecular weight. To minimize the complexity due to molecular weight [Pg.47]

Very recently, Kawaguchi et al.103 have studied the same system and compared the experimental data of p, 8, and T with the theory of Scheutjens and Fleer48 and that of Silberberg47. The adsorption isotherms obtained were of the high affinity type. The molecular weight dependence of adsorbance in the plateau region displayed a behavior [Pg.50]


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