 Karl-Heinz Hellwich

Karl-Heinz Hellwich contributed to IUPAC polymer nomenclature and terminology. IUPAC's author index lists his coauthorship of A brief guide to polymer nomenclature and the recommendations on biorelated polymers.^[ref]

A central scientific use of nomenclature is to distinguish molecular structure from a material's origin or intended use. Saying that a polymer is used in a medical device does not specify its polymer repeat unit, copolymer sequence, end groups or molecular-size distribution. Those distinctions can matter when comparing chemical reactions or measured properties.

For an original atom-counting example, a repeat unit written $-\mathrm{C}{\mathrm{H}}_2-\mathrm{C}{\mathrm{H}}_2-\mathrm{O}-$ has composition ${\mathrm{C}}_2{\mathrm{H}}_4\mathrm{O}$. A sequence of 100 such repeat units contributes ${\mathrm{C}}_{200}{\mathrm{H}}_{400}{\mathrm{O}}_{100}$ before the end groups are counted. Its repeat-unit contribution to molar mass is approximately $100\times 44.05=4405\mathrm{g}\mathrm{mo}{\mathrm{l}}^{-1}$; the complete chain requires the additional end-group composition. The structural repeat is not by itself a complete molecular formula for a finite molecule.

Likewise, two copolymers can have the same overall monomer proportions and different sequences. A block copolymer and a statistical copolymer therefore cannot generally be identified solely by elemental composition. Precise structural descriptions make such comparisons reproducible without implying that a naming convention predicts every material property.