Properties of Polysiloxane Cyclics

The conformational dynamics of PDMS cyclics of various sizes have been studied by ultrasound. The magnitudes of the dispersions obtained were used to estimate energy differences between stable and less-stable conformations. Analogous information has been obtained using excimer emission from small probes placed into a cyclic PDMS. Chemical shifts and relaxation times in the Si NMR spectra of cyclic PDMS have also been used for this purpose. There has been work with regard to the structure and dynamics of cyclics in general, including percolation of linear polymers in melts of cyclic polymers.  

In some cases, cyclic and linear PDMS have been combined to form conetworks, and unsaturated cyclic side-chain fragments have been placed into polysiloxanes to make them thermoreactive. Interactions between ring polymers have also been analyzed and related to loops in chromatin. Also, some cyclic oligosiloxanes having polar end groups show liquid-crystal-line behavior, specifically smectic A and E phases. Finally, several PDMS cyclics have been exposed to vacuum pyrolysis and the products analyzed by matrix-isolation spectroscopy. The pyrolysis products obtained under a variety of conditions identified the radical reactions that were involved. 

With regard to simulations, improved Monte Carlo methods have been developed for characterizing cyclic polymers in the melt. A simple 

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