Non-diffusing melts of 3-dimensional architectured polymers: giant molecules and soft-nanoparticles, and the boundary of the liquid-solid transition*

The extreme architecture deviating from the 1-dimensional chain would be a 3-dimensional soft-cluster. Two experimental cases, giant molecules and soft-nanoparticles, as well as coarse-grained soft-clusters by molecular dynamics simulation. Giant molecules have been precisely synthesized, having 16 or 24 POSS building blocks chemically linked by short, flexible chains. Of 25 and 38 kg/mol respectively, they show different dynamics above Tg: one is liquid while the other is solid-like. We also use microemulsion polymerization to synthesize series of nanogels to act as soft-nanoparticles. We propose an equation to describe their relaxation time as a function of diameter and crosslinking degree. It can describe the critical diameter, ranging from 5 to 21 nm, as a function of crosslinking degree. Soft-nanoparticles smaller than this critical diameter can relax in melt, while larger than it cannot relax. The critical diameters may serve as the boundary between thermal molecular or macromolecular domains and athermal colloidal domain, and can be unified as the number of basic moving units in the 3-dimensional architectured polymers. Recent molecular dynamics study further confirms this and suggests its connection to the concept of cooperation during glass transition.