Determination of the Molar-Mass Averages of Random Poly(aspartate-co-lactide) Copolymers by Tuning the Ionic Strength of the Solvent

作者：Gricar Maja; Zigon Majda; Ljubic Tina Smigovec; Zagar Ema^*

来源：Chromatographia, 2012, 75(5-6): 205-212.

DOI：10.1007/s10337-012-2180-1

• Size-exclusion chromatography
• Light scattering
• Poly(aspartate-co-lactide)
• Amphiphilic copolymer

Water-soluble sodium poly(aspartate-co-lactide) (PALNa) copolymers with a molar ratio of aspartate-to-lactide units equal to 1:0.6, 1:1.0 and 1:1.5 were studied using NMR spectroscopy to determine the composition as well as SEC-MALS and static light-scattering measurements to determine the molar-mass characteristics of the copolymers. In the copolymer aqueous solutions, high-molar-mass species were detected, most probably due to the incomplete dissolution of the samples. The molar-mass averages determined in water with added simple electrolyte, i.e., NaCl, were much lower than the values determined in pure water. The concentration of the salt, which allows dissolution on a molecular level, and the separation predominantly according to a size-exclusion mechanism depend on the chemical composition of the PALNa copolymers. The optimal mobile phase for the PALNa-1/0.6 and the PALNa-1/1.0 copolymers was 0.1 M NaCl at pH 9, and for the PALNa-1/1.5 copolymer with a higher content of lactide units it was 0.05 M NaCl at pH 9. The molar-mass averages of the PALNa-1/1.0 copolymer, determined by SEC-MALS and static light-scattering measurements, were comparable.

• 出版日期2012-3