A grafted and/or functionalized macromolecule comprises entanglement-inhibited architecture wherein the polymer exhibits reduced melt viscosity. In one embodiment, the macromolecule comprises a polymer of an isoolefin having about 4 to about 7 carbon atom and a para-alkylstyrene, wherein a grafted macromonomer such as a terminally functionalized polystyryl chain of very narrow molecular weight distribution is attached to the para-alkyl group of the para-alkylstyrene such that entanglement of adjacent chains in the melt are inhibited. In addition to distributed macromonomer grafts, other functionality may be attached to the para-alkyl group of the para-alkylstyrene to introduce other desirable properties such as radiation curability. In another embodiment the macromolecule comprises a polymer of one or more simple olefinic monomers wherein a macromolecule is attached to pendent functionality and/or copolymerized into the polymer backbone. A particularly preferred macromonomer comprises a terminal norbornene functional group.