Polymerization of ethylene by complexes [{((PO)-O-boolean AND)PdMe(L))] ((PO)-O-boolean AND = kappa(2)-(P,O)-2-(2-MeOC6H4)(2)PC6H4SO3)) affords homopolyethylene free of any methyl methacrylate (MMA)-derived units, even in the presence of substantial concentrations of MMA. In stoichiometric studies, reactive {((PO)-O-boolean AND)Pd(Me)L} fragments generated by halide abstraction from [({((PO)-O-boolean AND)Pd(Me)Cl}mu-Na)(2)] insert MMA in a 1,2- as well as 2,1-mode. The 1,2-insertion product forms a stable five-membered chelate by coordination of the carbonyl group. Thermodynamic parameters for MMA insertion are Delta H-not equal = 69.0(3.1) kJ mol(-1) and Delta S-not equal = -103(10) J mol(-1) K-1 (total average for 1,2- and 2,1-insertion), in comparison to Delta H-not equal = 48.5(3.0) kJ mol(-1) and Delta S-not equal = -138(7) J mol(-1) K-1 for methyl acrylate (MA) insertion. These data agree with an observed at least 10(2)-fold preference for MA incorporation vs MMA incorporation (not detected) under polymerization conditions. Copolymerization of ethylene with a bifunctional acrylate-methacrylate monomer yields linear polyethylenes with intact methacrylate substituents. Post-polymerization modification of the latter was exemplified by free-radical thiol addition and by cross-metathesis.