 Marguerite Rinaudo

Marguerite Rinaudo investigated polysaccharides and the interactions governing their behavior in solution and assembled materials. Her 2006 paper discusses how ionic interactions, hydrogen bonds and other non-covalent interactions affect chain conformation, solubility and gel formation. Its primary byline identifies her CERMAV-CNRS affiliation.^[ref]

This connects chemical composition to behavior without requiring a new covalent bond for every structural change. Changing pH can change the charge state of an ionizable chain, and changing ionic strength can alter interactions between charged segments. Measuring only the polymer repeat unit therefore need not predict the chain's shape or interactions in a particular solution.

For an original independent-site model of protonatable amine groups, suppose the conjugate acid has $\mathrm{p}{K}_a=6.5$. The protonated fraction isAt pH 5.5 it is $10/11\approx 0.909$; at pH 7.5 it is $1/11\approx 0.091$. A chain with 100 equivalent sites would therefore have mean charges about $+91$ and $+9$ in this stipulated model. The backbone need not be cleaved for its electrostatic behavior to change.

Real chains can couple neighboring sites and change their effective acid-base behavior with salt concentration and conformation. The simple calculation is not a fitted result from Rinaudo's paper. It illustrates why controlled solution conditions and measurements of charge, size or viscosity complement a structural formula.