Transcription and Translation of Plasmid Inserts by their Hosts

The anionic and cationic emulsion polymerization of dimethylcyclosiloxanes in aqueous phase, has received little study to date. The acid-catalysed emulsion polymerization of a series of cyclic dimethylsiloxane monomers, with varying emulsifiers, has recently been studied. Whilst qualitatively the mechanism appears consistent with the Harkins model, quantitatively the system, as might be expected, shows wide deviations from Smith-Ewart predicted behaviour. This emulsion polymerization system is interesting in that initiation, propagation, and termination proceed by ionic pathways. 

The difficult process of substituting Si—H side-groups in a preformed polymer of poly(methylhydrogensiloxane), without causing extensive crosslinking of the polymer, has been reported. Methanolysis of the side-chain Si—H, catalysed by alkali carbonates and EtjN, has proved possible. 

It has been postulated that intramolecular rather than intermolecular chain-transfer contributes the predominant reaction in a solution of living poly(methyl-phenylsiloxane), and poly(dimethylsiloxane) with trimethylsilyl end-blocked groups. Occurrence of the intramolecular reaction, leading to formation of cyclic compounds of various sizes, was ascribed to the flexibility of siloxane chains. 

Molecular Structure.—Studies of the unperturbed dimensions of poly(diethyl- 

Flory s equation of state satisfactorily represented the pressure-volume-temperature behaviour for all seven siloxanes.  

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