• Viscosity and intrinsic viscosity emerged as the core quantitative descriptors of polymer behavior, linking molecular weight, temperature, solvent, and shear. Across polyisobutylene and polystyrene, researchers established MW–viscosity relationships, temperature coefficients, and even relaxation under stress, demonstrating coherent rheological paradigms [2], [4], [5], [6], [7], [1].

• Second-order transition temperatures (glassy transitions) were probed by dilatometry and refractometry, revealing strong molecular weight dependence and rapid approach to asymptotic limits. These studies defined MW-influenced T_g-like properties for polystyrene and related polymers, spanning papers in 1948–1950 [3], [13], [20].

• Molecular architecture and viscometric dimensions were tied to branching and end-group chemistry: artificially branched polystyrene, intrinsic viscosity–molecular weight relations, and branching size effects shaped how viscosity reflected size and topology [14], [9], [5].

• Polymer–solvent interactions and swelling were treated as thermodynamic probes, linking swelling, μ, and M_c to solvent quality and cross-linking. The swelling determination framework and gel thermodynamics show early, parallel routes to quantify solution behavior and network properties [16], [11].

• Polymerization kinetics and copolymerization theory formed a unifying framework for polymer architecture, via kinetic rate expressions, general theories, and polymerization in suspension/emulsion. These microfoundations connected to Oligomerization and copolymerization works shaping macromolecular structure [10], [15], [12].