C***S
发帖数: 175 | 1 More specifically, can X-ray or Neutron scattering tell the difference of
polymer in water from water in polymer system. In my case, it is Nafion
ionomer.
Some groups think even in dry state, Nafion still has the polymer in water
structure. I think it is weird. As the Babinet priciple states: due to the
autocorrelation property of scattering, we cannot tell the positive or negtive
image. So A in B case will give the same scattering as B in A.
Am I right? | C***S
发帖数: 175 | 2 this is not good.
I am reading a paper, which cite another paper of themself, which is
in press then. they claimed that in this cited-in-press paper, they
can tell the difference of A in B or B in A. However, when I checked
this cited paper, they concluded they can not tell the difference only
based on the results.
what makes things worse is that their later papers always cited these
two papers as their supporting evidence that the system is polymer in
water not water in polymer even at low leve
【在 C***S 的大作中提到】
: More specifically, can X-ray or Neutron scattering tell the difference of
: polymer in water from water in polymer system. In my case, it is Nafion
: ionomer.
: Some groups think even in dry state, Nafion still has the polymer in water
: structure. I think it is weird. As the Babinet priciple states: due to the
: autocorrelation property of scattering, we cannot tell the positive or negtive
: image. So A in B case will give the same scattering as B in A.
: Am I right?
| b*******n
发帖数: 29 | 3 I think the way polymer dispersing in water is very different
from the way water dispersing in polymer, e.g., water aggregates
then coalesces, which forms very good spherical structure. However,
Non-water soluble polymer in water tends to aggregates, but is hard to
coalesce, which forms a fractal structure.
This is only my GUESS.
negtive
【在 C***S 的大作中提到】
: More specifically, can X-ray or Neutron scattering tell the difference of
: polymer in water from water in polymer system. In my case, it is Nafion
: ionomer.
: Some groups think even in dry state, Nafion still has the polymer in water
: structure. I think it is weird. As the Babinet priciple states: due to the
: autocorrelation property of scattering, we cannot tell the positive or negtive
: image. So A in B case will give the same scattering as B in A.
: Am I right?
| c********x
发帖数: 232 | 4 whoever claims they can tell a in b or b in a through diffraction is
bullshiting. Scattering only tells intensity distribution. That means
all the contrast (A-B) and (B-A) will get squared. Therefore you can
never tell whether it is A-B or B-A.
【在 C***S 的大作中提到】
: this is not good.
: I am reading a paper, which cite another paper of themself, which is
: in press then. they claimed that in this cited-in-press paper, they
: can tell the difference of A in B or B in A. However, when I checked
: this cited paper, they concluded they can not tell the difference only
: based on the results.
: what makes things worse is that their later papers always cited these
: two papers as their supporting evidence that the system is polymer in
: water not water in polymer even at low leve
| b*******n
发帖数: 29 | 5 Contrast is only one of the key factors for SANS or SAXS.
I trust papres from Macromolecule.
By the way, what is the volume fraction of A?
【在 C***S 的大作中提到】
: this is not good.
: I am reading a paper, which cite another paper of themself, which is
: in press then. they claimed that in this cited-in-press paper, they
: can tell the difference of A in B or B in A. However, when I checked
: this cited paper, they concluded they can not tell the difference only
: based on the results.
: what makes things worse is that their later papers always cited these
: two papers as their supporting evidence that the system is polymer in
: water not water in polymer even at low leve
| C***S
发帖数: 175 | 6 about 50%
【在 b*******n 的大作中提到】
: Contrast is only one of the key factors for SANS or SAXS.
: I trust papres from Macromolecule.
: By the way, what is the volume fraction of A?
| b*******n
发帖数: 29 | 7 Oh boy....
A and B are bi-continuously dispersed.
Then what is the point to discuss who is in who?
Are you working with polymeric surfactant?
Bi-continuously dispersed system is too concentrated
to apply simple SANS model without huge modification.
【在 C***S 的大作中提到】
: about 50%
| C***S
发帖数: 175 | 8 No. I am working on Nafion system, the chemical formula is
((CF2)6.5CF(CF2)6.5)n
|
OCF2CF(CF3)OCF2CF2SO3H
I just read the paper, which claims that even at low level hydration level,
Nafion morphology is composed by polymer aggregates dispersed in water. To me,
this is nonsense. So I checked their original paper. In that paper,
they substitute H+ with N(CH3)4+, and do SANS experiments at different H2O/D2O
ratio. After that, they normlized all the SANS profile with 100% H2O, so t
【在 b*******n 的大作中提到】
: Oh boy....
: A and B are bi-continuously dispersed.
: Then what is the point to discuss who is in who?
: Are you working with polymeric surfactant?
: Bi-continuously dispersed system is too concentrated
: to apply simple SANS model without huge modification.
| b*******n
发帖数: 29 | 9 Could you provide the exact paper citation, or tell us more about
the sample composition? Is it one-phase binary system, which is almost
impossible?
By the way, for Nafion ,
((CF2)6.5CF(CF2)6.5)n
|
OCF2CF(CF3)OCF2CF2SO3H
if n is not too large, I believe Nafion can be treated as surfactant.
Then the phase behavior and SANS model have been widely investigated
in the literature.
Good luck.
me,
D2O
they
one
【在 C***S 的大作中提到】
: No. I am working on Nafion system, the chemical formula is
: ((CF2)6.5CF(CF2)6.5)n
: |
: OCF2CF(CF3)OCF2CF2SO3H
: I just read the paper, which claims that even at low level hydration level,
: Nafion morphology is composed by polymer aggregates dispersed in water. To me,
: this is nonsense. So I checked their original paper. In that paper,
: they substitute H+ with N(CH3)4+, and do SANS experiments at different H2O/D2O
: ratio. After that, they normlized all the SANS profile with 100% H2O, so t
| C***S
发帖数: 175 | 10 JPC-B, 106(12), 3033-3036,2002
this is the paper they differentiates these two models.
Nafion is a two phase system once hydrated. Well, the accepted model
is that it is a three-phase system under 15% by weight of hydration,
above this level, it is a two-phase system.
n would be 1000~10000. this is a estimated value since Nafion
can not form true solution.
【在 b*******n 的大作中提到】
: Could you provide the exact paper citation, or tell us more about
: the sample composition? Is it one-phase binary system, which is almost
: impossible?
: By the way, for Nafion ,
: ((CF2)6.5CF(CF2)6.5)n
: |
: OCF2CF(CF3)OCF2CF2SO3H
: if n is not too large, I believe Nafion can be treated as surfactant.
: Then the phase behavior and SANS model have been widely investigated
: in the literature.
| b*******n
发帖数: 29 | 11 The phase separation in a binary system will keep going till
it reaches two layers. SANS of a two phase sample, especially
a low viscosity sample, is very noisy and hard to reproduce.
Nafion cannot be considered as surfactant(n is tooo large) then.
Let me quickly go through the paper first.
【在 C***S 的大作中提到】
: JPC-B, 106(12), 3033-3036,2002
: this is the paper they differentiates these two models.
: Nafion is a two phase system once hydrated. Well, the accepted model
: is that it is a three-phase system under 15% by weight of hydration,
: above this level, it is a two-phase system.
: n would be 1000~10000. this is a estimated value since Nafion
: can not form true solution.
| b*******n
发帖数: 29 | 12 I feel very surprised for this paper because of following reasons,
1.Their model fittings are so poor that they cannot plot the experimental
data and fitting data together. This is my first time to see such an amateur
thing in a decent journal. They cannot say anything basing on the poor fitting
.
2. The q range cannot cover their discussion about the effect of counter-ion.
3. They made a mistake in unit conversion from A-2 to cm-2.
So, you might need to find more papers.
【在 C***S 的大作中提到】
: JPC-B, 106(12), 3033-3036,2002
: this is the paper they differentiates these two models.
: Nafion is a two phase system once hydrated. Well, the accepted model
: is that it is a three-phase system under 15% by weight of hydration,
: above this level, it is a two-phase system.
: n would be 1000~10000. this is a estimated value since Nafion
: can not form true solution.
| C***S
发帖数: 175 | 13 Thanks. this is also my understanding on this paper.
My meaning is, if I did not check this paper and only read their
later papers on Macromolecules, I would think their model is historical.
This is so dissapointed to see such work from a well-known group in this
field.
Thanks.
fitting
.
【在 b*******n 的大作中提到】
: I feel very surprised for this paper because of following reasons,
: 1.Their model fittings are so poor that they cannot plot the experimental
: data and fitting data together. This is my first time to see such an amateur
: thing in a decent journal. They cannot say anything basing on the poor fitting
: .
: 2. The q range cannot cover their discussion about the effect of counter-ion.
: 3. They made a mistake in unit conversion from A-2 to cm-2.
: So, you might need to find more papers.
|
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