g****n
发帖数: 7494 | 1 我在做用超声波讲解多糖
分别用Huggins和Kraemer来估算intrinsic viscosity[n]
Huggins：
nsp/C=[n]+K'[n]^2C
Kraemer:
ln(nrel)/C=[n}+K"[n]^2C
结果发现根据讲解时间的长短，Kraemer constant(K")一直是负值，Hugginsconstant(
K')开始时正值，后期变成负值
K'-K"的差值从0.5左右随着降解时间延长逐渐减小
搜了很多文献，都是讨论Huggins constant大于小于1的讨论，没有见过有讨论过正负的
所以，希望达人能帮忙解答一下 |
C*******b
发帖数: 174 | 2 我也在做这个，我没出现负值，但是我的Huggins曲线不是一条直线。
Hugginsconstant(
负的
【在 g****n 的大作中提到】
: 我在做用超声波讲解多糖
: 分别用Huggins和Kraemer来估算intrinsic viscosity[n]
: Huggins：
: nsp/C=[n]+K'[n]^2C
: Kraemer:
: ln(nrel)/C=[n}+K"[n]^2C
: 结果发现根据讲解时间的长短，Kraemer constant(K")一直是负值，Hugginsconstant(
: K')开始时正值，后期变成负值
: K'-K"的差值从0.5左右随着降解时间延长逐渐减小
: 搜了很多文献，都是讨论Huggins constant大于小于1的讨论，没有见过有讨论过正负的
|
D********g
发帖数: 533 | 3 sugar is one kind of polyelectrolyte. Did you add screening salt (like NaCl)
in your viscosity measurement? if not, at lower concentration, high
dissociation leads to larger swell of your polymer coil which causes
increase of solution reduced viscosity.
Typically inherent viscosity is quite robust to this. I don't know why, but
most of time if you don't add salt (even 0.1 M may be enough), you can see a
huge deviation from linear curve for reduced viscosity.However, the
inherent viscosity looks fine.
Hugginsconstant(
负的
【在 g****n 的大作中提到】
: 我在做用超声波讲解多糖
: 分别用Huggins和Kraemer来估算intrinsic viscosity[n]
: Huggins：
: nsp/C=[n]+K'[n]^2C
: Kraemer:
: ln(nrel)/C=[n}+K"[n]^2C
: 结果发现根据讲解时间的长短，Kraemer constant(K")一直是负值，Hugginsconstant(
: K')开始时正值，后期变成负值
: K'-K"的差值从0.5左右随着降解时间延长逐渐减小
: 搜了很多文献，都是讨论Huggins constant大于小于1的讨论，没有见过有讨论过正负的
|
D********g
发帖数: 533 | 4 BTW. If you have He Manjun's Polymer physics book. Check the molecular
weight measurements -> Viscosity part. I remember they have more discussion
on the shape of curve and Huggins constant.
Hugginsconstant(
负的
【在 g****n 的大作中提到】
: 我在做用超声波讲解多糖
: 分别用Huggins和Kraemer来估算intrinsic viscosity[n]
: Huggins：
: nsp/C=[n]+K'[n]^2C
: Kraemer:
: ln(nrel)/C=[n}+K"[n]^2C
: 结果发现根据讲解时间的长短，Kraemer constant(K")一直是负值，Hugginsconstant(
: K')开始时正值，后期变成负值
: K'-K"的差值从0.5左右随着降解时间延长逐渐减小
: 搜了很多文献，都是讨论Huggins constant大于小于1的讨论，没有见过有讨论过正负的
|
g****n
发帖数: 7494 | 5 忘记说了，所有的样品，为了保证在相同的离子浓度下对比，最后都调整到0.1M NaCl
NaCl)
but
a
【在 D********g 的大作中提到】
: sugar is one kind of polyelectrolyte. Did you add screening salt (like NaCl)
: in your viscosity measurement? if not, at lower concentration, high
: dissociation leads to larger swell of your polymer coil which causes
: increase of solution reduced viscosity.
: Typically inherent viscosity is quite robust to this. I don't know why, but
: most of time if you don't add salt (even 0.1 M may be enough), you can see a
: huge deviation from linear curve for reduced viscosity.However, the
: inherent viscosity looks fine.
:
: Hugginsconstant(
|
w********h
发帖数: 12367 | 6 how did you measure [eta]?
if you manually do that, the error bar is too large to be discussed.
Hugginsconstant(
负的
【在 g****n 的大作中提到】
: 我在做用超声波讲解多糖
: 分别用Huggins和Kraemer来估算intrinsic viscosity[n]
: Huggins：
: nsp/C=[n]+K'[n]^2C
: Kraemer:
: ln(nrel)/C=[n}+K"[n]^2C
: 结果发现根据讲解时间的长短，Kraemer constant(K")一直是负值，Hugginsconstant(
: K')开始时正值，后期变成负值
: K'-K"的差值从0.5左右随着降解时间延长逐渐减小
: 搜了很多文献，都是讨论Huggins constant大于小于1的讨论，没有见过有讨论过正负的
|
D********g
发帖数: 533 | 7 1)try to increase to 1M NaCl.
2)try non-polar solvent instead of water
And don't forget you can try other method too for molecular weight: like
osmotic pressure, which is not dependent on the hydrodynamic radius.
NaCl
【在 g****n 的大作中提到】
: 忘记说了，所有的样品，为了保证在相同的离子浓度下对比，最后都调整到0.1M NaCl
:
: NaCl)
: but
: a
|
