The Structure and Aggregation of Hydrogen-Bonded Interpolymer Complexes of Poly(acrylic acid) With Poly(N-vinylpyrrolidone) in Dilute Aqueous Solution

Hydrogen‐bonded complexation between high‐molecular‐weight poly(N‐vinylpyrrolidone) (PVP, $\overline{M}_{\rm w}$ = 650 kDa) and poly(acrylic acid) (PAA) with weight‐average molar weights between 0.9 and 50 kDa, is studied in dilute, salt‐free aqueous solution. The onset of complexation, aggregation, and the structure of the formed particles are strongly influenced by PAA molecular weight, solution composition, and the method of sample preparation. With increasing poly(acrylic acid) chain length, IPCs show higher stability against aggregation. IPCs based on high‐molecular‐weight PAA show core‐corona architecture ensuring good sterical stabilization, whereas for those containing the shortest polyacid a loose soft‐sphere structure without distinct borders of different chain densities is found. The molecular structure and colloidal stability of interpolymer complexes formed through hydrogen bonds in aqueous solution are addressed. Particles formed under different solution conditions and molecular weights of the used polymers are characterized to obtain a full picture of a phenomenon that attracts both fundamental and application‐oriented studies.