Interpolymer complexation of poly(acrylic acid) and poly(acrylamide): Structural and dynamic studies by solution- and solid-state NMR
- Univ. of San Diego, CA (United States). Dept. of Chemistry
- Columbia Univ., New York, NY (United States). Henry Krumb School of Mines
- Columbia Univ., New York, NY (United States). Dept. of Chemistry
Understanding the structure and dynamics of intermacromolecular complexes is of interest because of the occurrence of such structures in many systems of biological importance. Interpolymeric complexes of poly(acrylic acid) PAA and poly(acrylamide) (PAAm) at 60, 20, 5, and 0% ionization ([alpha]) were studied by [sup 1]H/[sup 13]C solution-state and [sup 13]C solid-state cross-polarization magic angle spinning (CPMAS) NMR experiments. The solid-state NMR results support a model in which ionization ([alpha] or pD) alteration leads to conformation and segment changes along the PAA-PAAm polymeric backbone. Solid-state relaxation measurements show short T[sub 1] values at high ionization ([alpha] = 60%) but long T[sub 1] values toward low ionization ([alpha] [<=] 20%). This is consistent with a model in which the PAA and PAAm polymers take on a stretched but mobile conformation at high ionization but become immobile and restricted at low ionization. Dynamic restriction of the polymer is attributed to symbiotic hydrogen bonding of the carboxyl group of PAA and the amide residue of PAAm to form interpolymer complexes. Other relaxation parameters such as [sup 1]H-[sup 13]C cross-polarization times T[sub CH](SL), proton spin-lattice relaxation times in the rotating frame T[sub 1p](H), and [sup 13]C dipolar-dephasing results are also consistent with this model.
- OSTI ID:
- 5437112
- Journal Information:
- Macromolecules; (United States), Vol. 27:1; ISSN 0024-9297
- Country of Publication:
- United States
- Language:
- English
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