Ring opening polymerization hexamethylcyclotrisiloxane, anionic

Poly (dimethyl siloxane) obtained by anionic ring-opening polymerization of hexamethylcyclotrisiloxane (D3) can also be end-capped with vinylbenzyl bromide or other electrophiles, such as p. (chlorodimethylsilyl)styrene80). 

Cyclic siloxanes can undergo a ring-opening polymerization that is a chain-growth process. Free radicals are not useful as initiator species, because of the nature of the siloxane bond, but anionic and cationic initiators are very effective. The reaction is illustrated using the most common cyclic oligomers, the trimer hexamethylcyclotrisiloxane... 

The syntheses of siloxanes with vinyl groups at the silicon atoms of the chain was performed by anionic ring-opening polymerization of vinyl group-containing cyclotri- or cyclotetrasiloxanes (03, 04 ) with alkyl lithium compounds as initiators. The polymerizations were terminated by chlorosilanes with additional silico- or carbofunctional groups or octyl groups. In the block copolymerizations we used 03 or 04 and hexamethylcyclotrisiloxane (D3) (Scheme 1 and 2). 

The living polysiloxanes having various densities of vinyl groups were obtained by anionic living ring-opening polymerization of 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane (V3) or by copolymerization of this monomer with hexamethylcyclotrisiloxane (D3) or with 2-vinyl-2,4,4,6,6-... 

The end-functionalized PEO block was prepared via an etherification reaction between an HO-terminated poly(ethylene oxide) of a defined block length and allyl bromide. The SiH-functionalized polysiloxane was prepared by anionic ring-opening polymerization (ROP) of hexamethylcyclotrisiloxane (D3) and quenching of the chain end with chlorodimethylsilane (Scheme 1) [3]. 

The tethered diphenyldimethylsiloxane oil was prepared by a kinetically controlled anionic ring opening polymerization of hexamethylcyclotrisiloxane (D3) and hexaphenylcyclotrisiloxane (Dj ) in the presence of n-BuLi (Figure 5) (7). Once the lithium salt of D3 and 03 6 was formed in a two step process, it was then quenched with water to give a silanol terminated diphenyldimethylsiloxane product (2). 

MALDI-tof-ms has been used to study the preparation of linear polysilox-anes with hydride end-capped and cyclic polysiloxanes from the ring-opening anionic polymerization reaction with hexamethylcyclotrisiloxane and octamethylcy-clotrisiloxane (99). The PDMS reaction was followed by MALDI and the incorporation of the hydride end cap and the creation of the cyclics was studied as a function of time. Further studies (100) employed MALDI and sims it was found that MALDI provides more reproducible relative intensities of the n-mers than does SIMS. 

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