1 meth acryloyloxy tetrasiloxane undecamethyl 1 meth acryloyloxy pentasiloxane tridecamethyl 1 meth acryloyloxy hexasiloxane examples of organosilylated carboxylate monomers of general formula i wherein r 7 is the ester of the above described formula iii include triisopropylsilyl methyl maleate triisopropylsilyl amyl maleate tri n butylsilyl n butyl maleate t butyldiphenylsilyl methyl maleate t butyldiphenylsilyl n butyl maleate triisopropylsilyl methyl fumarate triisopropylsilyl amyl fumarate tri n butylsilyl n butyl fumarate t butyldiphenylsilyl methyl fumarate and t butyldiphenylsilyl n butyl fumarate the advantage of this invention is that the process uses reactants which can be easily handled another advantage lies in the simplicity and safety of the procedure no filtration of salt neither trapping of corrosive gaseous matter furthermore another advantage is that the reaction may take place without any added catalyst and can be performed under reduced pressure a further advantage is that the formed carboxylic acid may be removed under azeotropic distillation also there is no need to add polymerisation inhibitors and no degradation of the material occurs due to its shortness its easy work up procedure and its high yield the process of the present invention can be considered as a substantial improvement over the existing methods described above still another advantage of the invention is that the organosilylated carboxylate monomers obtained by the process according to the invention have the exactly desired number of dihydrocarbylsilyloxy units said number of dihydrocarbylsilyloxy units being those as defined in the acyloxysilane the organosilylated carboxylate monomers obtained by the process of the invention can be polymerised with various other monomers such as vinyl monomers including acrylic esters methacrylic esters styrene vinyl esters e g vinyl acetate vinyl propionate vinyl butyrate vinyl benzoate vinyltoluene alpha methylstyrene crotonic esters and itaconic esters the polymers and copolymers of said monomers are useful.