第 39 回日本バイオレオロジー学会年会

プログラム・抄録集Solution Properties of Acetylated Dextran Studied by Light Scattering andOptical Beam Deflection MethodIsala Dueramae1, Masaru Yoneyama2, Naoki Shinyashiki3, Shin Yagihara3, Rio Kita3
Micro/Nano Technology Center, Tokai University, Kitakaname, Hiratsuka, Kanagawa 259-1292
2
Faculty of Science and Technology, Gunma University, Tenjin-cho 1-5-1, Kiryu, Gunma 376-8515,
3
Department of Physics, Tokai University, Kitakaname, Hiratsuka, Kanagawa 259-1292.
1

3. Results and Discussion
The Mw and Rg of dextran increased dueto the acetylation process as showed in Table
1. When dissolved in water, Ac-DEXs canself-aggregate due to intra- and/orintermolecular hydrophobic interactions. The
positive second virial coefficient (A2) ofmodified samples implied that water is a good
solvent for the modified dextran.
The Soret coefficient, ST, of all samples
significantly increase with increasing oftemperature. Moreover, the increase of ST,
were observed with increase of acetylation
degrees. This indicates that the hydrogenbonding between polysaccharide molecules
and water are broken by heating andsubstitution of acetylated functional groups.

%Acetylation
04.62
9.62
17.11
20.85
26.43

Mw(kg/mol)
41.8
58.6
43.8
42.0
45.2
44.4

Rg(nm)
14.3
84.0
82.2
76.3
62.6
44.7

A2(molL/g2)
0.000640.00087
0.00106
0.000790.001800.00034

0.06
0.04
0.02
-1

T

2. Experimental Method
Ac-DEXs were synthesized by the reaction ofdextran (Mw of 40 kg/mol) with various amountsof acetic anhydride to change the acetylation
degree (0 to 26.42%) in the present of pyridine at
50 oC for 24 hour. Ac-DEXs were dissolved inwater to study the solution properties.
Light scattering experiment was performed at
25oC with sample concentration of 2-10 gL-1
Thermal diffusion property was studied attemperature range of 20-50 oC with10 gL-1
by an optical beam-deflection method.

Table 1. Mw, Rg, and A2 of Ac-DEX solutions
with different degree of acetylation

S (K )

1. Introduction
Dextran, a soluble water polysaccharide
consisting predominantly of -1,6-glucosidic
linkages has a long history in biomedical usage．
Modified of polysaccharides are an interesting fordesigning new materials with applications inbiomedicine. Hydroxyl groups in glucose
repeating units have been replaced withacetylated groups to trigger theirs properties.
Altering of thermal and mechanical properties
have already shown in the acetylated
polysaccharides [1-2]. Initially, the influence ofacetylation degree on solution properties haveinvestigated in this study.

0-0.02

o25 C
o30 C-0.04

o35 Co-0.06

40 Co45 C-0.08-5051015202530

Acetylation Degree (%)

Figure 1. ST of Ac-DEX solutions withdifferent degree of acetylation
4. ConclusionAcetylation process can induce theformation of self-aggregate, rendering theincreasing of molecular weight and radius ofgyration.
Hydrogenbonding
betweenpolysaccharide molecules and water can bedestroyed by substitution of acetylated groups onhydroxyl groups in dextran molecular chains.
Acknowledgement
Micro/Nano Technology Center, TokaiUniversity,
Kitakaname,
Hiratsuka,
Kanagawa 259-1292
References
1) N. Teramoto, and M. Shibata, Carbohydr.
Polym, 63 (2006) 476–481.
2) B.H. Zimm, J. Chem. Phys, 16 (1948)
1093-1099.