Polymers ultrapure polymer samples

In ultrapure polymer samples, all chains are terminated in the same way. The MALDI spectrum of an ultrapure polymer resembles a comb and the spacing between the comb s teeths equals the mass, Mrepeat, of the repeat unit. This quantity is often diagnostic and it suggests an almost trivial use of MALDI is the spectral identification of polymers. The reason is that, if one computes the M,.c x.at value for common polymers, most values are different, the number of superpositions being very low [4—6]. The Mrepeat value is not an integer, due to the fact that various isotopes are present. 

In order to facilitate the reader, the chapter is split into various sections. Section 15.2 deals with instrumentation, sample preparation, and matrices, remaining sections deal with the analysis of ultrapure polymers, polymer mixtures in which backbones are identical, and polymer mixtures in which backbones are different, respectively. The final section deals with the determination of average molar masses. 

ICP-MS has been used for the analysis of many materials, including alloys, steels, nuclear materials, ceramics, superconductors, plastics, polymers, and catalysts. Semiquantitative analysis by ICP-MS is often a convenient method to screen samples for trace elements and impurities. Measurement of impurities can be complicated by sample matrix-dependent degradation of sensitivity, particularly if the samples contain high concentrations of heavy elements that create extensive space-charge-induced ion transmission losses. Matrix matching is complicated by the need for ultrapure materials. 

Following immersion in water, the conductivity of the film decreased an order of magnitude over a period of a few hours. The measurements reported below were taken on samples that had been immersed previously in ultrapure water for about 12 hours, after which the electrical behaviour was stable. The time between consecutive measurements in solutions of different pH values was 20 minutes. This was found to be sufficient to allow for stabilisation of the polymer film. 

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