Soluble, High Molecular Weight Polysilsesquioxanes with Carboxylate Functionalities

摘要

High molecular weight polysilsesquioxanes with carboxylate functionalities were prepared by sol-gel polymerization of organotrialkoxysilanes bearing tert-butyl ester groups. Trialkoxysilyl-containing monomers of the type (RO)_3Si(CH_2)_3C(O)OtBu (R = Me, Et) were prepared by hydrosilation of the corresponding vinylic tert-butyl esters CH_3CHCH_2C(O)OtBu. Acid- or base-catalyzed polymerization of the monomers leads to very high molecular weight polymers with relatively narrow polydispersities. The polymerization results in complete condensation of the alkoxy groups while the tert-butyl ester functionality remains fully intact, Partial or full deprotection of the tert-butyl group can easily be achieved to yield the corresponding carboxylic acid polymers. The ester and carboxylic acid functionalities of these new materials allow for their potential use in a variety of applications such as scavenging of heavy metals.