Soluble, high molecular weight polysilsesquioxanes with carboxylate functionalities

High molecular weight polysilsesquioxanes with carboxylate functionalities were prepared by sol-gel polymerization of organotrialkoxysilanes beating tert-butyl ester groups. Trialkoxysilyl-containing monomers of the type (RO)₃Si(CH₂)₃C(O)OtBu (R = Me, Et) were prepared by hydrosilation of the corresponding vinylic tert-butyt esters CH₃CHCH₂ C(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.