Abstract
A microscopic theoretical study of glassy dynamics in dense fluids of soft many-arm-star polymers is performed which elucidates the connection between local packing, shear elasticity and activated relaxation. A soft-jamming crossover is identified, below which particle-softness–dependent apparent power law concentration scaling of the shear modulus and supra-exponential relaxation occur. Dynamic fragility varies over a remarkably wide range, increasing logarithmically with star functionality. Beyond the soft-jamming threshold, the shear modulus increases linearly with volume fraction.