w********h
发帖数: 12367 | 1 （1）高分子本体的密度和单个分子链的密度、一个重复单元的密度相同么？
（2）Kuhn length究竟有什么意义？
（3）高分子本体里面的分子链周围全是其他分子链，充满整个空间体积，
没有一点间隙么？ | M*******n
发帖数: 508 | 2 do you mean apparent density by bulk density?
for (1) and (3), I don't think so. At least, you have steric effects.
and that's why we have LDPE and HDPE, right?
【在 w********h 的大作中提到】
: （1）高分子本体的密度和单个分子链的密度、一个重复单元的密度相同么？
: （2）Kuhn length究竟有什么意义？
: （3）高分子本体里面的分子链周围全是其他分子链，充满整个空间体积，
: 没有一点间隙么？
| w********h
发帖数: 12367 | 3 good point. we indeed calculate the density of polymers using the parameters
of packing.
I thought of that density problem when I met Lodge-McLeish model.
apparently they use the same density value for all of them.
approximately it is RIGHT, anyway.
The second question is because I have a question:
why polymer dynamics has various length scales?
from backbone bond to repeat unit length to Kuhn length to screening length to
Rg to whatsoever...
for others, I am clear,
but for that Kuhn length,
I a
【在 M*******n 的大作中提到】
: do you mean apparent density by bulk density?
: for (1) and (3), I don't think so. At least, you have steric effects.
: and that's why we have LDPE and HDPE, right?
| b**s
发帖数: 589 | 4
关于3，如果不全是其他分子链，那会是什么，空气，电子云，真空？
【在 w********h 的大作中提到】
: （1）高分子本体的密度和单个分子链的密度、一个重复单元的密度相同么？
: （2）Kuhn length究竟有什么意义？
: （3）高分子本体里面的分子链周围全是其他分子链，充满整个空间体积，
: 没有一点间隙么？
| b*o
发帖数: 47 | 5
This is an interesting question. Anybody would like to give an update on the
free volume concept?
【在 b**s 的大作中提到】
:
: 关于3，如果不全是其他分子链，那会是什么，空气，电子云，真空？
| c****n
发帖数: 134 | 6
肯定不是电子云，电子云应该还是属于分子链的
如果空隙体积够大，而且某些气体分子可以渗透入高分子的话，这个空间应该包含气体分
子；如果体积太小，里面只能是真空了。
【在 b**s 的大作中提到】
:
: 关于3，如果不全是其他分子链，那会是什么，空气，电子云，真空？
| U******n
发帖数: 75 | 7
分
or solvent molecules if it is big enough
if it is small enough, there still have probability of having charge cloud
just thinking if it will be vacuum, then the time must be short. it other way,
back to electron cloud probability function to describe the space between
electron and proton, or between two molecules
【在 c****n 的大作中提到】
:
: 肯定不是电子云，电子云应该还是属于分子链的
: 如果空隙体积够大，而且某些气体分子可以渗透入高分子的话，这个空间应该包含气体分
: 子；如果体积太小，里面只能是真空了。
| b*******n
发帖数: 29 | 8 （1）对于半晶高分子，相同温度下，其本体的晶区、非晶区密度都不同，因此高分子本
体密度与单个分子链的密度、一个重复单元的密度没有多大联系；对于非晶高分子，其自
由体积与热历史有关，所以在同一温度下，密度严格的说也不是定值，因此与常数的单个
分子链的密度、一个重复单元的密度没有等同关系。
（3）高分子的非晶区不是紧密，因此可以做气体的分离膜，从而断定常见高分子非晶区
里应该有一定气体成分；高分子晶区结构致密，晶胞内除了排好的原子（或分子）之外还
有啥，我就不知道了。
【在 w********h 的大作中提到】
: （1）高分子本体的密度和单个分子链的密度、一个重复单元的密度相同么？
: （2）Kuhn length究竟有什么意义？
: （3）高分子本体里面的分子链周围全是其他分子链，充满整个空间体积，
: 没有一点间隙么？
| c*s
发帖数: 2145 | 9 as I think, Wonderlich is asking about the current opinion toward the packing
of atom in polymer of his interest. As i think, in inorganic crystals, the
atoms are closed packed in some ways, and can not be further densified at
normal conditions. However, the packing efficiency of polymer chains are not
as high as crystal, only near range order exists, they have some "void" in the
body, I incline to take the void as vacumn.
The definition of 重复单元的密度 will be blurred and so that the 单个分子链的
密度, I t
【在 b*******n 的大作中提到】
: （1）对于半晶高分子，相同温度下，其本体的晶区、非晶区密度都不同，因此高分子本
: 体密度与单个分子链的密度、一个重复单元的密度没有多大联系；对于非晶高分子，其自
: 由体积与热历史有关，所以在同一温度下，密度严格的说也不是定值，因此与常数的单个
: 分子链的密度、一个重复单元的密度没有等同关系。
: （3）高分子的非晶区不是紧密，因此可以做气体的分离膜，从而断定常见高分子非晶区
: 里应该有一定气体成分；高分子晶区结构致密，晶胞内除了排好的原子（或分子）之外还
: 有啥，我就不知道了。
| c*******n
发帖数: 1648 | 10 Free volume concept is still in debate. Hard-core quantum mechanics people
tend to consider substances as a continuous electron cloud landscape and
refuse every arguement of free volume. This can explain the measurements of
free volume heavily depend on probes. However, free volume concept was so
sucessful (partially because of WLF, Wisconsin school used to dominate polymer
dynamics), sometimes you have to say they are sth real, but not vaccum:)
packing
the
的
子
其
单
晶
外
【在 c*s 的大作中提到】
: as I think, Wonderlich is asking about the current opinion toward the packing
: of atom in polymer of his interest. As i think, in inorganic crystals, the
: atoms are closed packed in some ways, and can not be further densified at
: normal conditions. However, the packing efficiency of polymer chains are not
: as high as crystal, only near range order exists, they have some "void" in the
: body, I incline to take the void as vacumn.
: The definition of 重复单元的密度 will be blurred and so that the 单个分子链的
: 密度, I t
| w********h
发帖数: 12367 | 11 today I saw one paper online..
from the title, it should be related to our question here.
I didn't read it yet.
http://pubs.acs.org/cgi-bin/asap.cgi/mamobx/asap/pdf/ma0499021.pdf
polymer
the
not
链
分
，
的
非
之
【在 c*******n 的大作中提到】
: Free volume concept is still in debate. Hard-core quantum mechanics people
: tend to consider substances as a continuous electron cloud landscape and
: refuse every arguement of free volume. This can explain the measurements of
: free volume heavily depend on probes. However, free volume concept was so
: sucessful (partially because of WLF, Wisconsin school used to dominate polymer
: dynamics), sometimes you have to say they are sth real, but not vaccum:)
:
: packing
: the
: 的
| c*s
发帖数: 2145 | 12 hehe, a continuous electron cloud landscape
polymer
the
not
链
分
，
的
非
之
【在 c*******n 的大作中提到】
: Free volume concept is still in debate. Hard-core quantum mechanics people
: tend to consider substances as a continuous electron cloud landscape and
: refuse every arguement of free volume. This can explain the measurements of
: free volume heavily depend on probes. However, free volume concept was so
: sucessful (partially because of WLF, Wisconsin school used to dominate polymer
: dynamics), sometimes you have to say they are sth real, but not vaccum:)
:
: packing
: the
: 的
|
|
