“Three-arm star” poly[11-(4′-cyanophenyl-4′′-phenoxy)undecyl acrylate]s were synthesized by atom transfer radical polymerization (ATRP) of 11-(4′-cyanophenyl-4′′-phenoxy)undecyl acrylate using two new trifunctional initiators: 1,3,5-tri- (methyl 2-bromopropionate)benzene and 2,4,6-tri[4′-methyl(2′′-bromopropionate)phenoxymethyl]mesitylene. The polymers synthesized with 1,3,5-tri(methyl 2-bromopropionate)benzene (series II) contained 14–127 repeat units according to gel permeation chromatography relative to linear polystyrene (GPCPSt) and 13–271 repeat units according to GPC with a light scattering detector (GPCLS). Those synthesized with 2,4,6-tri[4′-methyl(2′′-bromopropionate)phenoxymethyl]mesitylene (series III) contained 14–87 repeat units according to GPCPSt and 10–120 repeat units according to GPCLS. The absolute molecular weight, size, and shape of both series of polymers were characterized by light scattering in CH2Cl2, and their thermotropic behavior was analyzed using differential scanning calorimetry; both types of properties were compared to those of the other architectures, especially the corresponding three-arm star poly[11-(4′-cyanophenyl-4′′-phenoxy)undecyl acrylate]s synthesized previously using 1,3,5-trisbromomethylmesitylene as the initiator. The size and shape of the three-arm star polymers in CH2Cl2 are similar, although the isotropization temperature in the solid state decreases and the breadth of the isotropization transition increases with increasing size and flexibility of the trifunctional core.