highmolecularmass

High molecular mass refers to substances with very large molecular weights. In polymer science, high molecular mass typically denotes polymers with molar masses in the range of 10^5 to 10^6 g/mol, although the exact threshold varies by material and context. The concept is closely tied to molecular weight distribution and the degree of chain entanglement in the material.

Molecular weight is not a single value but a distribution. The most common measures are the number-average molecular weight (Mn) and the weight-average molecular weight (Mw); the ratio Mw/Mn is the polydispersity index (PDI). Techniques such as gel permeation chromatography (GPC/SEC), light-scattering, viscometry, and mass spectrometry are used to estimate Mw, Mn, and PDI, with calibration affecting accuracy.

High molecular mass influences physical properties. Higher Mw generally increases solution and melt viscosity, improves melt strength, and enhances mechanical properties such as tensile strength and toughness due to chain entanglements. It can also reduce diffusion and crystallinity and complicate processing.

Control of molecular mass is a central goal in polymer synthesis. Living or controlled polymerization methods can produce high Mw with relatively narrow dispersities, while conventional step-growth or chain-growth processes may yield broader distributions. The choice of initiators, catalysts, and reaction conditions determines maximum achievable Mw and PDI.

Applications of high molecular mass polymers include fibers, films, coatings, and impact-resistant plastics. In biology, very large biomolecules such as proteins and nucleic acids exemplify high molecular mass systems, illustrating that the concept spans synthetic and natural materials.