| Summary: | 碩士 === 元智大學 === 化學工程研究所 === 86 === Dynamic light scattering (DLS) was used to study the solution property of poly(vinyl alcohol)-borax
(PVA-borax) semidilute solutions with a PVA concentration of 40g/L and borax concentrations varied from 0.0 M to 0.2 M.
The DLS experiments were carried out at 25℃ with various scattering angles
(i.e Θ=30o,45o,60o,90o and 120o). Four relaxation modes (tsol,tf,tm, and ts) were observed from the DLS correlation functions .
The mode (tsol ) with the relaxation time tsol shorter than 1 ms was attributed the solvent diffusive mode ;
the mode (tf ) with a relaxation time around 10-4 sec was attributed to the relaxation of molecular chain between two entanglements ;
the mode (tm) with a relaxation time around 10-1 sec was attributed to the relaxation of small PVA cluster bound through H-bond;
and the mode which had the longest relaxation time (ts ) with ts longer than 1 sec was attributed to the motion of large PVA
cluster bound through H-bond and borate ion. The ts , tm and tf are all angular dependent indicating they are diffusive modes.
As the borax concentration was higher than 0.14 M, the slow mode (ts) was not observed on the DLS
correlation functions suggesting that PVA-borax system may form a gel as the borax concentration was higher than 0.14 M.
|
|---|
