Low molecular weight siloxane materials having one functional group are provided which have reduced tendency to form phase separated domains after polymerization. Two classes of siloxane materials are included: (1) symmetric siloxane macromonomers containing at least two monomer termini and one polymerizable functional group which is equidistant from the termini, and (2) assymetric siloxane macromonomers having at least one polymerizable functional group terminus and at least one oxygen-containing polar hydrophilic terminus selected from the group consisting of hydroxyl, ether, and polyether. Symmetric siloxane macromonomers having hydroxyl termini are useful for forming biocompatible materials, such as for contact lenses, tissue regeneration scaffold polymers, and coatings to reduce non-specific binding of proteins.