Cyclosiloxanes, mixed

We also used HPLC in connection with MALDI-MS. Our aim was to separate cyclic siloxanes, even larger ones not distinguishable by SFC, from linear ones quantitatively. Hexane and ethyl acetate were mixed in a ratio of 90 to 10 by volume and used as mobile phase in HPLC separations of mixtures of the cyclic siloxane sample with the diol sample. Cyclosiloxanes elute first, followed by the diols. Under these conditions only a small overlapping area is to be seen (Fig. 4a). The sample was fractionated and MALDI-MS spectra were taken from the fractions. 

A relatively new process for siloxane manufacture is aqueous phase emulsion polymerization. Cyclosiloxanes such as D4 when mixed with water and alkylbenzenesulfonates as a surfactant, along with some free sulfonic acid, form an emulsion. When the mixture is heated to > 60 °C, ring opening of the cyclosiloxane takes place to give a, ty-dihydroxy oligosiloxanes, which undergo acid-catalyzed condensation to form long-chain siloxanes. 

Selective and Stepwise Synthesis of Cyclosiloxanes with Mixed and "Inorganic" Substituents... 

The copolymerization of a functional cyclotrisiloxane with D3 leads to a copolymer of dimethylsilojane units and sUoxane-containing functional group units which-in similar manner to the copolymer obtained by ROP of cyclosiloxane with mixed units-contains macromolecules of uniform structures with regards to the size, monomer unit composition and sequencing [117]. However, the distribution of units along the chain is different The more reactive comonomer enters the chain... 

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