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Urea‐induced conformational changes of chitosan molecules and the shift of break point of Mark–Houwink equation by increasing urea concentration
Author(s) -
Chen Rong Huei,
Tsaih Min Larng
Publication year - 2000
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/(sici)1097-4628(20000118)75:3<452::aid-app16>3.0.co;2-j
Subject(s) - urea , viscometer , intrinsic viscosity , chitosan , chemistry , polymer chemistry , molecular mass , molecule , exponent , viscosity , analytical chemistry (journal) , chromatography , thermodynamics , organic chemistry , polymer , physics , enzyme , linguistics , philosophy
Chitosan solutions of the same 83% degree of deacetylation (DD) but different weight average molecular weights ( M w s) (78–914 kDa) in 0.01 M HCl containing different concentrations of urea (0–6 M ) were prepared. Intrinsic viscosity ([η]) and weight average molecular weight ( M w ) of chitosan were measured with a capillary viscometer and light scattering, respectively. Mark–Houwink exponent a was used as the parameter of conformational index. The Mark–Houwink exponent a increased with increasing concentrations of urea. When solutions contained 0, 2, 3, 4, and 6 M urea, the value of a increased from 0.715 to 0.839, 0.894, 1.000, and 1.060, respectively. This indicates the occurrence of urea‐induced conformational transitions of chitosans. The break point shifted from 223 kDa in solutions containing no urea to 280 kDa in 2 M urea solutions, to 362 kDa in 4 M urea solutions and further to 481 kDa in 6 M urea solutions. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 452–457, 2000