Synthesis of star-shaped polydimethylsiloxanes containing SiO2 core units

Star-shaped polysiloxanes consisting of SiO2 cores and polydimethylsiloxane (PDMS) branches were successfully prepared by three methods using functionalized solvent-soluble silicates as a starting material. The first method involved the lithiation of a SiOH functional silicate with butyllithium, followed by reaction with hexamethylcyclotrisiloxane (D3) and termination with a chlorosilane to afford a star polymer. In this case, the chain ends were substituted with vinyl or SiOH functional groups. In the second method, a SiCl functional silicate was used as the source of the SiO2 core. A PDMS chain with a lithium silanolate terminal group was reacted with the SiCl functional silicate to provide a star polymer. In the third method, a PDMS chain with a diethylamino group at one chain end was reacted with the SiOH functional silicate to form a star polymer. The Mark-Houwink constant a of the star polymer was 0,74, which is very close to that of a linear PDMS.