b**s
发帖数: 589 | 1 Finally, certain rheological measurements can often reveal the presence or
absence of block copolymer structures. For example, the melt viscosity of
block copolymers is usually considerably higher than that of a blend of
homopolymers of similar molecular weight. This is especially true for A-B-A
and -(A-B)n- structures due to the persistence of some degree of physical
network structure even in the melt. This effect is magnified in block
copolymers consisting of segments that are long and tha |
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c*s
发帖数: 2145 | 2 【 以下文字转载自 Chemistry 讨论区,原文如下 】
发信人: ross2000 (ross), 信区: Chemistry
标 题: what kind of polymer has this properties
发信站: The unknown SPACE (Tue Aug 20 10:32:41 2002) WWW-POST
I need a polymer which has high viscosity but low elasticity. u know, it's
something like play-dough. I don't care the chemical structure of the polymer.
so, how can I get it? adding plasticizer to the polymer? I heard that using
plasticizer may increase elasticity. Is that true?
Thanks. |
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b**s
发帖数: 589 | 3 Faint, Why you guys all pick PDMS?
Viscosity and elasticity mostly depend on the crosslinking density of the
target polymers. IF PDMS gets crosslinked, it's a kind of rubber! If
hydrogel-like polymers are not crosslinked, they are gelatinous materials,
just image the agaragar.
|
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a***n
发帖数: 578 | 4 hehe. good arguement.
Since no money, I won't spend more time on it. But I can tell what a general
simulation goes. For example, if you want to simulate this system, you have to
consider what parameters are your input parameters, what data you want from
simulation. Then you set up kinetic equation based on those parameters. Then
you figure out a numerical way to solve this kinetic equation.
For your case, viscosity of polymer molecules in solution, the friction
between solvent and surface, tempe |
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w********h
发帖数: 12367 | 5 you can get some rough answers, but those answers with correct physical
meaning may not be close to the thickness obtained at all...
for such problems involving too many parameters, just forget it or leave
it to fluid people....the major parameters are Temperature, Concentration,
Viscosity, Rotation speed, Evaporation speed of the solvent, Friction
between Solution and the different surface, amount of solution...and some
parameters are correlated with each other...
possible. |
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c*******e
发帖数: 5 | 6 我自己在网上搜了一下，查到了一些参数，可是没有我想要的。
请问，您那儿又没有该材料的viscosity,surface tension,
specific heat,latent heat of fusion?不胜感谢。 |
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w********h
发帖数: 12367 | 7 [eta] is intrinsic viscosity.
you can get criteria for dilute solution from any polymer textbooks..
overlapping concentration C* can be also deduced using a simple fomula.
but this predicted one generally is lower than the real overlapping
concentration.
what's your polymer?
people already have MHS formula for different polymers in different solvents.
you can first use MHS to get [eta], then C*.
what's dilute solution?
just means the regime in which eta-eta(s) is linear with C. |
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w********h
发帖数: 12367 | 8 then you can measure the viscosity to see which is the critical concentration
for the transition from dilute to semi-dilute regimes... |
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w********h
发帖数: 12367 | 9 sure. but that's too complicated for verifying the overlapping concentration.
viscosity's concentration dependence offers all information.
the |
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w********h
发帖数: 12367 | 10 how far?
in fact, semi-dilute regime is really narrow. ~10% to C*.
and the critical concentration (empirical C*) is very clear (if not as sharp
as you expect) from the viscosity increment.
good
of
the
textbooks.. |
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b**s
发帖数: 589 | 11 Poly(vinyl acetate)
Catalog # : 347
CAS : 9003-20-7
Physical Form : Pellets
Approx Mw : 100,000
Density (g/cc) : 1.18
Refractive Index : 1.4665
Inherent viscosity : 0.42
Softening Point (C) : 97
TSCA : TSCA listed
Tg (C) : 30
Soluble in : Acetone, benzene, butyl acetate, carbon tetrachloride,
chloroform, dichloroethylene, ethanol, ethyl acetate, methanol, MIBK, THF,
toluene |
|
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c*******n
发帖数: 1648 | 13 Now I can post:)
Thanks a lot, it seems that tube model predicted a universal power law index,
while based on my experience, in dynamic experiments, different polymers have
different slopes (of cos, my samples are polydisperse). Will this universal
power law index be seen if I use monodisperse samples of different polymers?
If not, tube theory might have missed sth important, regarding to chemistry of
polymers? Comments from you guys are very welcome
viscosities. |
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w********h
发帖数: 12367 | 14 对于多分散的高分子，
在shear thinning region里viscosity和shera rate(or frequency for dynamic
shear)的关系不再是-1次方的关系，而是有一个deviation gamma |
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w********h
发帖数: 12367 | 15 Today I read this paper,
http://pubs.acs.org/cgi-bin/gap.cgi/mamobx/1997/30/i11/pdf/ma961851n.pdf
and found there is one paragraph to mention your problem.
on pp.3310, Nonlinear Viscosity Section.
There are Doi-Edwards prediction,
Curtiss-Bird model,
and Graessley's model.
Probably you want to read that part and the references therein.
PG-NMR as well...;-)
law |
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c*********e
发帖数: 119 | 16 我知道测IV可以得到高分子的分子量。它的单位是dL/g。它的物理意义是什么?怎么用最
精练的语言描述出来?我查了很多书都没有找到。
可别告诉我怎么测它。怎么测它我是知道的。：)
Thanks! |
|
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w********h
发帖数: 12367 | 18 here is one paper for that.
"Equation state for polymer solution"
Polymer, 2002, 43, 3447-3453
or you can check Flory and Fox's original paper in 1951:
JACS, 1951, 73, 1909
最 |
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c*********e
发帖数: 119 | 19 I am reading the paper of "Equation state for polymer solution". It's a little
difficult for me.
用 |
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w********h
发帖数: 12367 | 20 in fact, some terms are just originated from theories.
[eta] is also like that.
eta(sp)/C=[eta]+AC+...
when C--->0, you can get one intrinsic value for one polymer in one solvent at
a certain temperature, that's [eta].
[eta] is closely related to Rg.
I happened to see that paper and think it is rather comprehensive.
little
么 |
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w********h
发帖数: 12367 | 21 I will send you one copy when we submit it.
The experimental results are inconsistent with theoretical prediction.
of course, those scalings are too simple.
Static parameters:
end-to-end distance R, correlation length, and tube diameter.
Dynamic parameters:
relaxation time Tau;
diffusion coefficient D;
modulous G;
viscosity eta.
Scalings:
concentration dependence,
long chain length dependence,
short chain length depedence.
Question:
Excluded volume effect vanishes at which point? Practically... |
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c*******n
发帖数: 1648 | 22 similar to the last one by BF.
Monodisperse
5nm
solid or solidlike (No terminal viscosity)particles in polymer melt
The particle should have enough mobile protons
No aggregation of particles
Easy to synthesize or using physical methods
I think organic chemists here might have seen some of these kinds of well
defined systems. if you have, could you please refer the source? Thanks |
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w********h
发帖数: 12367 | 23 今天看到一篇上次我审的文章在网上贴出来了，还好，照我说得把文章大幅简化，把
他另外一篇文章报道过的一个单体的合成步骤全部删除了。可是我还是弄不懂他如
何能测量intrinsic viscosity一个浓度就搞定(虽然我知道有一点法这种无聊的不
可靠的做法)，DSC图也有问题，反正我是提出疑问了，主编不介意我有什么好说的。
偶的审稿原则就是，让pass是default，除非错\烂\不适合，喜欢make一堆的comments。
偶曾经的一篇文章被审阅人写了四五页纸的comments，从那时起，落下这个变态的毛
病了。。。 |
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w********h
发帖数: 12367 | 24 一个什么咚咚。。。。。。。
（1）einstein-like polymer hydrodynamic contribution;
（2）free volume effect.
（3）entanglement effect..
有谁把第二个因素弄得很清么？那些个solution的Tg比本体低那么多，在同样温度测得的
viscosity的concentration dependence有什么意义么？一团浆糊阿。。。。。
cashine, dashnow, et al....
give me your perspectives. |
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b*****h
发帖数: 29 | 25 Biopolymers. 1979 Dec;18(12):3111-3. Related Articles, Links
On the ionic-strength dependence of the intrinsic viscosity of DNA.
Odijk T.
thank you for your help
b*****[email protected] |
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b*******n
发帖数: 29 | 26 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. |
|
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s****e
发帖数: 2934 | 28 那就是说micelle不受viscosity的影响吗？比方CMC<3％，加了20％的homopolymer这个
溶液的粘度是相对比较大了。 |
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r*******e
发帖数: 83 | 29 要看你加入得homopolymer跟B或C嵌段有没有相互作用得，如果没有作用，聚合物胶束还
是相对比较稳定得
那就是说micelle不受viscosity的影响吗？比方CMC<3％，加了20％的homopolymer这个
溶液的粘度是相对比较大了。 |
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i***y
发帖数: 190 | 30 3mg/ml concentration is high enough...one possibility is that your polymer or
copolymer is a highly aggregated polymer, which means there is no indivadual
marcomolecules in the polymer solution, just big particles. If the
particles are big enough, say >0.45micron, after filtering, no polymers will
be left in the solution, or cut off by guard columns. If so, no signal can
be detected in main columns. The viscosity measurement will tell you how
serious your polymer aggregation is.
PL |
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m*********7
发帖数: 5 | 31 J of Polymer Sci., Part B: Polymer. Phys., 36, 743-753 (1998)
The specific viscosity of partially hydrolyzed polyacrylamide solutions:
Effects of degree of hydrolysis, molecular weight, solvent quality and
temperature by J. Sukpisan 1, J. Kanatharana 1, A. Sirivat 1 , S. Q. Wang 2
Please send to c****[email protected]
Thanks |
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S********e
发帖数: 38 | 32 Is there anyone here know anything about how to get molecular weight
distributions using
the viscosity and RALS individually? Can it be done by GPC sort of comparing
the results for visc and
RALS to get an idea of if forming linear chains or rings... |
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w********h
发帖数: 12367 | 33 你要测啥？稀溶液特性粘数还是melt viscosity?
2000块的预算只有两种解决方案，
（1）买个乌氏粘度计测稀溶液去吧。。
（2）把钱给我，我帮你测melt。。 |
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s**********a
发帖数: 18 | 34 Comparing with small molecules, chain entanglement of polymer chains is a
very important characteristic of polymer. It affects viscosity, orientation,
mechanical properties, et al.
Any techniques to study the entanglement of polymer chains? Any parameters
used to characterize it? |
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j****j
发帖数: 58 | 35 The Society of Polymer Science, Japan (Copyright Holder and Seller)
Title:
Intrinsic Viscosity-Molecular Weight Relationships for Poly(N-
sopropylacrylamide) Solutions
Authors:
Shoei Fujishige
Journal:
Polymer Journal
Volume 19 Number 3 Year 1987 Page 297-300 |
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m********h
发帖数: 405 | 36 yes, my polymer is completely soluble in THF. that is the solvent I used
for GPC. the strange thing is I made the 1mg/ml solution in THF. it is
completely transparent and soluble. also there is no viscosity at all.
but it is so difficult to pass the 0.45 micron PTFE whatman syringe filter.
why is that?
so I wonder because my polymer has high molecular weight, the random coil
is so large than 0.45 micron ? is it possible? I don't know polymer
physics well. |
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w********h
发帖数: 12367 | 37 ATS RheoSystems/REOLOGICA Instruments
Rheology Staff Engineer
ATS RheoSystems/REOLOGICA Instruments are a comprehensive rheological
instrumentation and technical support company specializing in rheometer and
viscometer design, research level rheometers and rheology, capillary
rheometers,
rheological consulting, viscometers, and viscosity measurements, real-time
light
and thermal cure profiling, low and high pressure rheology measurements,
dynamic shear rheometers (DSR) for asphalt testing accord |
|
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h*****1
发帖数: 26 | 39 来自主题: Macromolecules版 - 论文求助 论文求助：
【作者】 Paul Peyser, R. C. Little
【文题】 The drag reduction of dilute polymer solutions as a function of
solvent power, viscosity, and temperature
【期刊名,年份,卷(期),起止页码】 Volume 15 Issue 11, Pages 2623 - 2637 |
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w********h
发帖数: 12367 | 40 the reason is: gap issue.
when a wide range of temperatures are applied in measurements,
it is inevitable to have gap issue, which means gap is not what you can see
from the meter simply because nobody knows how much the sample and the
parallel disks will expand or shrink precisely during the change of
temperature.
consequently, the rheological data such as viscosity and moduli at
temperatures other than the reference temperature can be inaccurate. that's
why the vertical shift factor bT can be |
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f******n
发帖数: 137 | 41 We are looking for a Polymer Material Scientist/Engineer postdoc with
experience in polymer materials development and characterization,
spectroscopy methods (IR, Raman), TGA/DSC, cure viscosity monitoring,
materials and composite performance optimization, resin cure/kinetics, aging
of materials, aging models and lifetime prediction.
Polymer Material Scientist Postdoctoral Appointment Sandia Corporation
Albuquerque, NM
You can view and apply for this job at: http://www.sandia.gov/careers/search-o... 阅读全帖 |
|
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w********h
发帖数: 12367 | 43 open your Polymer Physics book, turn to Page 316.
R^3 changes with T. this also determines if the solvent is theta or good.
of course, in a small range, the difference is not very much. |
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s**********8
发帖数: 25265 | 44 好, 先学习一下. 溶剂是chloroform |
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g****n
发帖数: 7494 | 45 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 |
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D********g
发帖数: 533 | 46 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 |
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O*******o
发帖数: 7091 | 47 【 以下文字转载自 ME 讨论区 】
发信人: OldogZhao (赵小牛), 信区: ME
标 题: help needed with fluid Viscocity measurments, Baozi!
发信站: BBS 未名空间站 (Thu Nov 7 18:11:10 2013, 美东)
does anybody have experience in measuring fluid viscosity? could we do that
on our own (DIY) in the lab without buying specific instruments? any
reference please? |
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B*****n
发帖数: 654 | 48 【 以下文字转载自 Texas 讨论区 】
发信人: Boolean (Soso), 信区: Texas
标 题: 能求个 工作推荐不? polymer chemistry 方向的
发信站: BBS 未名空间站 (Wed Oct 8 18:56:16 2014, 美东)
人在TAMU, 找工作中, 有人能帮帮忙么?
10+ years polymer research scientist/engineer with strong experience in
advanced polymer material synthesis and characterization. Expertise in
polymer coating, extrusion, casting films Rheology analysis of polymeric
systems, polymer additives R&D experience, polymer composites preparation
and nano-material synthesis & characterization. A... 阅读全帖 |
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d*********g
发帖数: 49 | 49 因为我是做viscosity solution, 要求这个scheme, 比如u(t,x)=(Tu)(t-delta,dot)
这个operator T是单调的。好像有限元里面有什么proper还是什么性质的讲法，
有点类似，不好意思，我一知半解地说。 |
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w**a
发帖数: 1024 | 50 i didn't fully understand your problem,
is your problem same to the 'upwind f.d. scheme' in viscosity solution
or 'entropy 'condition? |
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