The formation of colloidal unimolecular polymer (CUP) particles from single polymer strands was investigated as a function of molecular weight. the CUP particle size was correlated with the absolute molecular weight and its distribution. the characteristics of the particles were evaluated with respect to viscosity, acid number, size distribution, and stability. the particle size varied from less than 3 nm to above 8 nm representing polymers with molecular weight in the range of 3000-153,000. Lower molecular weight polymers were found to be unstable. Particle size measurements using dynamic light scattering technique indicated a normal distribution which corresponded to the molecular weight distribution of the copolymer. the statistical distribution of the acid groups in the polymer chains played a significant role in the stability of low molecular weight polymers.