Oligomers, compact structural

Methoxyethanol displays numerous coordination modes (Fig. 2) but is basically a bidentate and assembling ligand [Af(0C2H40Me)n]m alkoxides are thus large oligomers (w = 9, Af = Ca m = 10, Af = Y), sometimes infinite polymers [Af = Bi, Pb(II)]. Despite the large values of the nuclearity, however, they are soluble (with the exception of lead) because of cyclic (Af = Y) or compact structures (Af = Ca) or dissociation of the polymer in solution, as observed for Bi [32]. Aryloxides are, with the exception of barium, either monomers or dimers [30,38]. 

In direct insertion techniques, reproducibility is the main obstacle in developing a reliable analytical technique. One of the many variables to take into account is sample shape. A compact sample with minimal surface area is ideal [64]. Direct mass-spectrometric characterisation in the direct insertion probe is not very quantitative, and, even under optimised conditions, mass discrimination in the analysis of polydisperse polymers and specific oligomer discrimination may occur. For nonvolatile additives that do not evaporate up to 350 °C, direct quantitative analysis by thermal desorption is not possible (e.g. Hostanox 03, MW 794). Good quantitation is also prevented by contamination of the ion source by pyrolysis products of the polymeric matrix. For polymer-based calibration standards, the homogeneity of the samples is of great importance. Hyphenated techniques such as LC-ESI-ToFMS and LC-MALDI-ToFMS have been developed for polymer analyses in which the reliable quantitative features of LC are combined with the identification power and structure analysis of MS. 

Using the phase diagramms the data on the formation of poly(methacrylic acid) (matrix)-poly(ethylene ycol) (oligomer) complexes were interpreted - and it was shown that the prcxluction of compact globular structures of the complexes is possible only for the cxxupkd matrix PMAA and when the critical length of oli mer is reached. 

The formation of PANl-NFs during electrochemical polymerization has been attributed to the combined effect of an electrophilic substitution reaction mainly taking place at the para position of aniline or its oligomers, and aniline oligomers with 1-D structures [290]. It was discovered that the PANl film formed on the electrode exhibited a lamellar structure. Firstly, a thin compact 2-D PANl layer was formed during the initial stage of electrodeposition. Subsequently, microgranular, nanorod-shaped, and nanofibrillar PANl layers were formed from bottom to top, respectively. 

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