t***m
发帖数: 114 | 1 假设我已经知道数均Mn=10000,由NMR得到PSt－b-PMMA 中mma wt%=7%
我要计算MMA链段数是不是就用10000乘7%
原来一直用mol%,现在发现可能不对，和我们这里另一兄弟争了半天
哪位能给个具体解释。 |
p**y
发帖数: 95 | 2 你不是学高分子的，对吧？
你看看你这里搞混了几个概念？
搞清楚概念了，计算就是小事了。
！在 TGDDM (酸黄瓜) 的大作中提到: 】 |
y****u
发帖数: 50 | 3 it is ok for me since I can understand, hehe
"MMA链段数" means "size of PMMA segment"?
your calculation is right since 7% is based on weight.
【在 p**y 的大作中提到】
: 你不是学高分子的，对吧？
: 你看看你这里搞混了几个概念？
: 搞清楚概念了，计算就是小事了。
: ！在 TGDDM (酸黄瓜) 的大作中提到: 】
|
w********h
发帖数: 12367 | 4 (1) Molecular weight is not repeating unit number.
(2) Mn can be considered as Mw roughly only when DP is close to 1.
(3) There is a slight difference between M(Sty) and M(MMA).
PS unit molecular weight is 104 g/mol
while PMMA is 100 g/mol.
(4) So, how many PMMA segments in a copolymer chain?
(10000 g/mol * 7%) / (100 g/mol) = 7.
【在 y****u 的大作中提到】
: it is ok for me since I can understand, hehe
: "MMA链段数" means "size of PMMA segment"?
: your calculation is right since 7% is based on weight.
|
y****u
发帖数: 50 | 5
if you know Mn, you will get the number of repeating units. and vice versa.
true. but nobody is talking about Mw.
we don't need this for a solution.
it seems to be diblock. so only one PMMA segments in a copolymer chain. but
your calculation is right: 7 MMA repeating units (number average) in a
copolymer chain.
【在 w********h 的大作中提到】
: (1) Molecular weight is not repeating unit number.
: (2) Mn can be considered as Mw roughly only when DP is close to 1.
: (3) There is a slight difference between M(Sty) and M(MMA).
: PS unit molecular weight is 104 g/mol
: while PMMA is 100 g/mol.
: (4) So, how many PMMA segments in a copolymer chain?
: (10000 g/mol * 7%) / (100 g/mol) = 7.
|
w********h
发帖数: 12367 | 6
it doesn't mean they are the same thing.
not that superficial.
if you use Mn,
you can not simply use wt.-% to get the average molecular weight
of MMA segment in a single chain because of the difference in
M(MMA) and M(Sty), though it is slight.
we need that for calculating the different segment
repeating unit number.
yes,
there is one assumption: it is a di-block copolymer.
if tri-block copolymer,
the total number of MMA segment is still 7.
【在 y****u 的大作中提到】
:
: if you know Mn, you will get the number of repeating units. and vice versa.
: true. but nobody is talking about Mw.
: we don't need this for a solution.
: it seems to be diblock. so only one PMMA segments in a copolymer chain. but
: your calculation is right: 7 MMA repeating units (number average) in a
: copolymer chain.
|
y****u
发帖数: 50 | 7 basically the original question was about wt% or mol%. obviously it is wrong
to use mol%.
yes, we can. once we know the Mn of diblock and wt% of MMA, the second monomer
doesn't matter for the answer.
but
My understanding: "segment"="block". |
w********h
发帖数: 12367 | 8 anyway, Mn Mw issue is just for the sake of physics.
block copolymer chain: (Sty)n-----b-----(MMA)m
n Styrene segments and m MMA segments.
monomer
【在 y****u 的大作中提到】
: basically the original question was about wt% or mol%. obviously it is wrong
: to use mol%.
: yes, we can. once we know the Mn of diblock and wt% of MMA, the second monomer
: doesn't matter for the answer.
: but
: My understanding: "segment"="block".
|
t***m
发帖数: 114 | 9 thank you all
我可以这样理解吗
block就是C2H6这样的结构，一个连段是C一个是H
从元素分析得到H含量，C含量，就可以直接用M(C2H6) multipy wt% H
然后得到H的数目
问题是这里的M(C2H6) 到底是高分子的重均还是数均
【在 w********h 的大作中提到】
: anyway, Mn Mw issue is just for the sake of physics.
: block copolymer chain: (Sty)n-----b-----(MMA)m
: n Styrene segments and m MMA segments.
:
: monomer
|
t***m
发帖数: 114 | 10
如果换成PS-b-PB呢
这两个链段区别大些了吧
例如总分子量为50000,PB段有7%wt, 那么就是PB段分子量为3500
PSn-PBm中的 m=3500/54了？
【在 w********h 的大作中提到】
: anyway, Mn Mw issue is just for the sake of physics.
: block copolymer chain: (Sty)n-----b-----(MMA)m
: n Styrene segments and m MMA segments.
:
: monomer
|
y****u
发帖数: 50 | 11 I am a little puzzled. what is your question again?
If your concern is about the (number) average molecular weight of PMMA in
PSt-PMMA diblock copolymer: First get wt% of PMMA (by NMR or whatever), then
get Mn of diblock from GPC.
【在 t***m 的大作中提到】
: thank you all
: 我可以这样理解吗
: block就是C2H6这样的结构，一个连段是C一个是H
: 从元素分析得到H含量，C含量，就可以直接用M(C2H6) multipy wt% H
: 然后得到H的数目
: 问题是这里的M(C2H6) 到底是高分子的重均还是数均
|
w********h
发帖数: 12367 | 12 ffdt...不可以。
你所说的block是一个什么意思？ 为什么是C2H6?
谈到聚合物链段，应该是重复单元吧。
重均或数均，只是对于polydisperse的聚合物来说的，
对于特定单一组成结构的单元或分子，
只有一个分子量。
wrong
chain.
a
【在 t***m 的大作中提到】
: thank you all
: 我可以这样理解吗
: block就是C2H6这样的结构，一个连段是C一个是H
: 从元素分析得到H含量，C含量，就可以直接用M(C2H6) multipy wt% H
: 然后得到H的数目
: 问题是这里的M(C2H6) 到底是高分子的重均还是数均
|
t***m
发帖数: 114 | 13 ft,我知道你的意思，就是模型化而已，便于学生理解
我在带实验课，概念搞混了的说
【在 w********h 的大作中提到】
: ffdt...不可以。
: 你所说的block是一个什么意思？ 为什么是C2H6?
: 谈到聚合物链段，应该是重复单元吧。
: 重均或数均，只是对于polydisperse的聚合物来说的，
: 对于特定单一组成结构的单元或分子，
: 只有一个分子量。
:
: wrong
: chain.
: a
|
t***m
发帖数: 114 | 14 就是你说的这个
Mn from GPC or 膜渗透
wt% from NMR
then wt of PMMA segment
【在 y****u 的大作中提到】
: I am a little puzzled. what is your question again?
: If your concern is about the (number) average molecular weight of PMMA in
: PSt-PMMA diblock copolymer: First get wt% of PMMA (by NMR or whatever), then
: get Mn of diblock from GPC.
|
