The distribution of reactive groups and micelle formation in amphiphilic macromonomers and the extent of network formation in aqueous solution depend on the segment length of the hydrophobic monomer. The objective of this work was to simulate by dissipative particle dynamics (DPD) the structure of the four-arm star poly(ethylene glycol-co-lactide)-acrylate (SPELA) macromonomer in aqueous solution. The effect of lactide segment length (n) in each arm and macromonomer concentration on the distribution and size of the micelles was investigated. In the absence of lactide, the reactive acrylate groups were uniformly distributed in the aqueous solution. With the addition of lactide segments, micelles formed with a hydrophobic core containing lactide and acrylate beads and a hydrophilic corona of ethylene oxide beads. The size and average number of macromonomers (aggregation number) of the micelles increased with n while the number density of micelles decreased. Furthermore, the fraction of macromonomer arms incorporated in the micelles as either loops or intermicellar bridges increased with increasing n. The macromonomer bridge fraction showed a biphasic behavior with a maximum at n = 4. The accumulation of water beads around acrylates decreased with increasing n. The aggregation of acrylates initially increased with n, and then, it decreased for n > 4 due to the decrease in size and distance between the micelles. The fraction of acrylates in the core surface layer of the micelles decreased from 66 to 19% when n increased from 4 to 16 with a higher fraction of acrylates trapped in the micelles' core. Macromonomer concentration increased the number density of micelles, but it did not have a significant effect on the micelle size or distribution of the acrylates. The simulation results indicate that SPELA macromers with <4 lactide segment length can potentially produce degradable PEG-based hydrogels with the highest network density.