N****g
发帖数: 5172 | 1 ☆─────────────────────────────────────☆
copolymer (copolymer) 于 (Wed Jul 29 12:08:56 2009, 美东) 提到:
谢谢
☆─────────────────────────────────────☆
mir (rebates) 于 (Wed Jul 29 12:09:12 2009, 美东) 提到:
不行
☆─────────────────────────────────────☆
ampicillinct (未名牛) 于 (Wed Jul 29 12:11:27 2009, 美东) 提到:
for clearance item, you can only do it in the same store
☆─────────────────────────────────────☆
copolymer (copolymer) 于 (Wed Jul 29 12:12:23 2009, 美东) 提到:
····
不行 |
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H**********y
发帖数: 7928 | 2 ☆─────────────────────────────────────☆
SavageSG (自费留学-->自费海归->美分党) 于 (Sun Sep 5 00:28:08 2010, 美东) 提到:
我手动查到了我case number前后一共16个pp case。
A. 大概是10%的case直接file 140 + PP；
B. TSC每个月大概收到375份140；
C. 如果直接PP和追加PP一半一半的话，TSC在给定时间内其实也就30个案子待处理。
规律如下
1. 收到PP的第二天有LUD。
2. 一般来说PP后4-5天会有第二个LUD，时间一般在下午1点之后。 表明案子已经
assign给了移民官。几乎所有案子在第二个LUD的那天都会有结果。如果被批的话，当
天晚上（第二天凌晨）网上状态就会更新为案子已批，notice寄出。如果被rfe的话，
相应时间会显示变成了request for evidence。如果第二次LUD后第二天网上还是现实
initial review，基本上是被NOID了。
3. 如果你运气不好的话，直到第11，12天才会有第二个LUD... 阅读全帖 |
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J**********7
发帖数: 2619 | 3 我觉得：wulai跟probass都是对的。
但是probass可能太急着回复了，没看明白我想讨论的问题。
我的第一篇是想讨论牛顿第一定律在光速下还适应不。
probass回了个牛顿第一定律对汽车的运动是对的。
wulai还是明白我想讨论啥的，就是不论牌子和价钱，只论材料的话，FC线宣称的那些
特性，真的影响上鱼吗？
1. 反光率跟水相近，能得出结论鱼就看不不到线？ tackletour的结论是不能确定，但
是线越细，鱼越看不见，就是说fc和mono的区别，还不如降低一磅的线径对鱼的影响大
。我观察到1寸小鱼群围着碳线咬，他们可能把碳线的反光看成更小的鱼。
2. fc比重比水大，下沉快。 我保守的同意fc适用沉底钓。 但是为啥保守的同意呢？
因为fc太沉，在水底是有一段贴底的，鱼线并不是直的， 我觉得mono与水的比重基本
是1:1， 说直的话，mono在水里应该更直。 pro们说fc线是直的，pro们都用fc。pro是
渔具的代理。
3.比起mono和fc来，我更倾向于copolymer。 copolyer的材料是啥？呵呵，这个水太深
了，还要从copolymer的定义讲起： 任何2... 阅读全帖 |
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c****n
发帖数: 134 | 4 I am preparing amphiphilic block copolymers: polyisobutylene-b-poly(vinyl
alcohol).
It is expected that the block copolymers is water soluble when the PIB segment
is short enough, so I can get water soluble surfactants.
however when DPn of the PIB segment is 50 or even 15, and the DPn of PVA is
200-260,
the block copolymers are not soluble in water.
when I use DMSO (a good solvent for PVA), the block copolymers are dissolved.
Any comments on this? Thanks a lot. |
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f******n
发帖数: 640 | 5 （GONE）（GONE）（GONE）（GONE）
小杂志 适合攒文章
有兴趣的朋友请站内邮件我你的邮箱和一小段介绍（用来回复invitation和推荐）
谢谢了
Abstract: PET is one of the most important commercial polymers and much
effort is being made to modify PET by melt copolymerization with a second
glycol or diacid comonomer in a way that yields an amorphous material with a
high Tg. In this study, various amounts (0-100 %) of
tricyclodecanedimethanol (TCDDM) were used to copolymerize ethylene glycol
and terephthalic acid to form a series of copolyesters (PETD). The
... 阅读全帖 |
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b**s
发帖数: 589 | 7 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****n
发帖数: 134 | 8 This criterion was listed in Quirk's book "Anionic polymerization",
but personally I don't think it is a good criterion.
Block copolymer may not be formed if you add propylene to living anionic
polystyrene...
block copolymer will be formed only when two monomer are similar in reactivity
in a specific polymerization (such as styrene and butadiene in anionic
polymerization). when the two monomers are quite different in reactivity, the
block copolymer may not be formed or there may be contaminatio |
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c****n
发帖数: 134 | 9 来自主题: Macromolecules版 - 问个傻问题 1. if homopolymers and copolymer have different solubilities, you may try
separation by extraction.
2. if it is copolymer instead of homopolymer mixture, MW should be higher
3. new NMR peak could arise for copolymer, attributable to groups connecting
two monomer units. |
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w********h
发帖数: 12367 | 10 哦，你说这个意思啊。
我觉得诡异的地方是同样ABA，有的就是单平台。
另外，我所说的random copolymer，
其实也是block copolymer,
不过是multi-block copolymer,
like this: AAAAABBBBBAAAAAAAABBBBBAAABBBBB... |
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p******4
发帖数: 38 | 11 I am using AFM to demonstrate self assembly of well-defined diblock
copolymers, but so far haven't got any good images. The block copolymer has
one polar and one nonpolar segments, so it is supposed to show morphology
not so difficult. The copolymer was spin coated on glass slides (which have
been cleaned in Piranha solution). My questions are
1. Do the glass substrates need to be coated with some polymers? In some
references it mentioned that the glass slides were coated with pure
polystyrene t |
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c********r
发帖数: 2227 | 12 Thanks for your post.
My understanding is it can not even give you an estimation.
for statistical copolymer you do not have to consider the dependence of Tg
on
molecular weight, since you will use the Tg for the high molecular
homopolmer.
Same for the Gorden-Taylor equation.
Or an equal question is for two miscible polymers, Will the statistical
copolymer and block copolymers with same weight fractions show same Tg?
If yes, we can get nothing about the block length from the fox equation.
I might... 阅读全帖 |
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x****a
发帖数: 1041 | 13 MODI mass spectrum 行不行？ 以前组里好像有人用这个测block copolymer的。你去
看看block copolymer的文献，怎么表征的。你用相同方法表征不出来就是random
copolymer了。 |
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a*i
发帖数: 1652 | 14 I just saw a journal paper titled "Posterior chamber collagen copolymer
phakic intraocular lenses to correct myopia: Five-year follow-up" ( Journal
of Cataract & Refractive Surgery Volume 37, Issue 5, May 2011, Pages 873-880
).
At present, the Visian Implantable Collamer Lens pIOL (Staar Surgical Co.)
is the only posterior chamber pIOL approved by the United States Food and
Drug Administration (FDA) for the treatment of moderate to severe myopia.
This pIOL is of a foldable collagen copolymer mat... 阅读全帖 |
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i******4
发帖数: 20643 | 15 ☆─────────────────────────────────────☆
NewEgg (驻驴观花|落英缤纷 落雪缤纷 尘缤纷土缤纷) 于 (Mon Jan 23 00:00:05 2012, 美东) 提到:
看了春晚开始的2012龙舟logo，我突然明白，原来2012，华人都fine，
因为在龙身上稳着呢，大家从出生的那一天，都已经拿到了2012的船票:)
2012，祝愿龙的传人都平安幸福，心想事成
2012，祝愿mitbbs这个海外华人的绿洲欣欣向荣
2012，祝愿ebiz这个众JS腾云驾雾大展身手的地方，也宝光祥瑞，和气生财
2012，让我们从龙年新春大吉包开始，1/id，截止时间1/23/2012 23:59:59 (以bbs系
统时间为准)
__
http://mitbbs.com/article1/WBCenter/12532167_3_0.html
☆─────────────────────────────────────☆
FIBA (飞吧) 于 (Mon Jan 23 00:00:23 2012, 美东) 提到:
沙发
☆────────... 阅读全帖 |
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l**********0
发帖数: 665 | 16 产品介绍里有，全是化学溶剂，虽是毒性小的，还是不敢用，做化学的妈妈伤不起!
Important Information
Safety Information
For external use only. Not for children under 3 years old.
Indications
Apply one coat of MAVALA Stop on the entire nail and allow it to dry for one
minute. Repeat the application every two days until you have broken the
habit of biting your nails. After 10 days, your nail should have grown
normally but may require strengthening! We would then recommend our nail
hardener MAVALA Scientifique and Nail Cream to complete t... 阅读全帖 |
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r******s
发帖数: 925 | 17 ☆─────────────────────────────────────☆
fluting (fluting @ night) 于 (Thu Mar 10 03:35:11 2011, 美东) 提到:
申请的这段时间在网上得到许多网友的帮助，衷心感谢！也把自己在等485期间做过的
一些乱七八糟的事，罗列一下， ：）
RD9/2. 曾经一直安静地等着的。。。到了1月下旬，终于淡定不能了，开始要求做SR，
CSR却不给。2月份的时候，联系了3个议员，只有1个转复了USCIS的信息，说是还在
normal processing time。
2/11时总算找到一个 level 2 CSR给做了SR。2/17去了INFOPASS，得到些消息，说是
name check cleared了，让我回来 等。但2/22却收到followup SR的一封信，说是我的CASE需要additional review，让我接着等；并说如果过了9-12个月还没有进一步消息的话，再
跟TSC联系。
收到信时，我石化了。。。把485提交的资料找出来，发现我把485表上的H1B
expiration da... 阅读全帖 |
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d******6
发帖数: 276 | 18 HI blehum
I'd like review MS for JAPS.
pls see the following information. Many thanks
Ⅰ: PERSONAL INFORMATION
Name: Xiaoyi XU
Telephone Number: +1-(650)391-5991
E-mail Address: d******[email protected];
x**[email protected]
Address: Stanford University, School of Medicine
3801 Miranda Ave, Palo Alto, CA, 94304, US
Ⅱ: EDUCATION EXPERIENCE
YEAR INSTITUTION DEGREES /
2003.09-2006.06 Changchun Institute of Applie... 阅读全帖 |
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d******6
发帖数: 276 | 19 我是做高分子化学药物控释，包括前药这个方向的，求审稿推荐。多谢
Ⅰ: PERSONAL INFORMATION
Name: Xiaoyi XU
Telephone Number: +1-(650)391-5991
E-mail Address: x**[email protected]
Address: Jilin University
Stanford University, School of
Medicine
3801 Miranda Ave, Palo Alto, CA, 94304, US
Ⅱ: EDUCATION EXPERIENCE
YEAR INSTITUTION DEGREES /
2003.09-2006.06 Changchun Institute of Applied Chemistry, Ph... 阅读全帖 |
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G****e
发帖数: 11198 | 20 introduction:
http://chem.berkeley.edu/people/faculty/xu/xu.html
group page:
http://www.mse.berkeley.edu/groups/xu/index.htm
Research Interests: Polymers, Biomaterials, Materials Chemistry
The key to future technology is the design and fabrication of functional materials having structures ordered down to the molecular level. This goal can't be reached by conventional "top-down" approaches and remains as the "holy grail" using synthetic materials such as block copolymers. In addition, there have ... 阅读全帖 |
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s******s
发帖数: 1159 | 21 【 以下文字转载自 Chemistry 讨论区 】
发信人: silverks (pig), 信区: Chemistry
标 题: 工作机会 (转载)
发信站: BBS 未名空间站 (Sat Feb 11 21:13:18 2012, 美东)
发信人: silverks (pig), 信区: Postdoc
标 题: 工作机会
发信站: BBS 未名空间站 (Sat Feb 11 21:12:46 2012, 美东)
Hope all is well. I am an Executive Recruiter with Towerhill and was pointed
in your direction by a colleague who thought your background looked like a
great match for a client of mine. I'm working directly with the founders of
a rapidly growing startup (both PhD’s from CalTech). They'v... 阅读全帖 |
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r******0
发帖数: 2753 | 22 这么粗浅的问题还想难倒我们？切！
这个高分子应该是一个copolymer，结构比较复杂，我们测量了它在各种溶剂中的溶解度，发现都不太好（换了好几种溶剂都没把瓶子洗干净），估计有一定程度的交联，所以表征比较困难。最后我们把工作的重点转移到monomers的官能团活性上，希望能从这方面的研究来推测和验证形成的高分子的结构，我们做了......（哈，回到小分子反应了吧）。我们还发现另一个结构相似的monomer也能生成类似的copolymer......（NND，又做砸了一锅）。
刚才忘了说性质，我们认为这种高分子在粘接剂应用上会有很大的潜力，它不但在极性表面上有很好的粘性（粘在玻璃瓶上洗不下来），而且对非极性表面如塑料（洗瓶子的时候，试管刷上也粘了不少），金属表面如不锈钢（小药铲上也粘了不少）都表现了很好的粘性。对于它能在各种不同的表面都产生很好的粘着性的机理，我们还在进一步的研究中。 |
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p*******8
发帖数: 158 | 23 Ideal copolymers and the second-order transitions of synthetic rubbers. i.
non-crystalline copolymers.
Journal of Applied Chemistry
Volume 2, Issue 9, pages 493–500, September 1952 |
|
q****i
发帖数: 6923 | 24 Synthesis and gas permeability of cyclotetrasiloxane-containing methacrylate
copolymers.
Journal of Macromolecular Science, Pure and Applied Chemistry (1992), A29, (
6), 415-40. CODEN:JSPCE6 ISSN:1060-1325.
Title: CROSS-LINKABLE POLAR SILOXANE COPOLYMERS FOR ION DETECTION DEVICES
Author(s): GANKEMA H; LUGTENBERG RJW; ENGBERSEN JFJ; et al.
Source: ADVANCED MATERIALS Volume: 6 Issue: 12 Pages: 944-947 DOI: 10
.1002/adma.19940061209 Published: DEC 1994
Chemically modified field effect tran... 阅读全帖 |
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s******s
发帖数: 1159 | 25 【 以下文字转载自 Postdoc 讨论区 】
发信人: silverks (pig), 信区: Postdoc
标 题: 工作机会
发信站: BBS 未名空间站 (Sat Feb 11 21:12:46 2012, 美东)
Hope all is well. I am an Executive Recruiter with Towerhill and was pointed
in your direction by a colleague who thought your background looked like a
great match for a client of mine. I'm working directly with the founders of
a rapidly growing startup (both PhD’s from CalTech). They've received solid
backing from one of the top Venture Capital firms in the US - Khosla
Ventures and ... 阅读全帖 |
|
x****a
发帖数: 1041 | 26 一定要用RAFT吗？ 用最基本的自由基聚合不就是random了嘛 |
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S***k
发帖数: 158 | 27 是这样的么？我只用过各种living radical polymerization，所以不太敢做普通的自
由基聚合。
普通的自由基聚合不是不容易控制polydispersity和molecular weight么？ |
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r**x
发帖数: 408 | 28 对啊，不放RAFT AGENT，直接自由基聚合不就是RANDOM么。或者试试乳液聚合。 |
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m*****e
发帖数: 1506 | 29 这个应该水相聚合吧，查查看两个单体的竞速率怎样，r1*r2=1是差不多最理想的条件
。不过水相RAFT有点复杂，还要调pH什么的，单体有可能和RAFT agent反应。可以查查
McCormick的文献，他是水相RAFT专家。
random |
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S***k
发帖数: 158 | 30 怎么直接自由基聚合啊？直接加单体和引发剂然后就除氧就好了么？
乳液我知道，但是我们实验室没有相关的设备，超声和强力的搅拌都没有，估计是不能
做乳液聚合了。
说来惭愧，我只做过living radical polymerizaiton，关于不加ATRP、RAFT的
conventional radical polymerization还从来没做过…… |
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L**i
发帖数: 22365 | 31 polymer handbook上的都是conventional radical polymerization的数据吧 |
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q****i
发帖数: 6923 | 32 Synthesis and characterization of novel polycarbonate-polydimethylsiloxane
block copolymers with controlled block lengths and an alternating block
architecture
Annual Technical Conference of the Society of Plastics Engineers (2011),
69th, (Vol. 2), 1141-1145
Fluorine-containing poly(carbonate-block-siloxane) copolymers
Polymer Science, Series B (2012), 54, (1-2), 94-98
Research progress of hyperbranched polysiloxane (II)
Quick View Full Text
By Huang, Yan
From Xiandai Tuliao Yu Tuzhuang (2007), ... 阅读全帖 |
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b**s
发帖数: 589 | 34 Film clarity is another method frequently used to distinguish between block
copolymers and homopolymer blends. The gross incompatibility characteristic of
most homopolymer blends results in opaque films due to a high degree of light
scattering at the interface between the two phases. An exception occurs in the
relatively rare case in which the two homopolymers have similar refractive
indices. On the other hand, block copolymers produce transparent alms, since
they usually exist in microphase- |
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b**s
发帖数: 589 | 35 The clarity of high-concentration polymer solutions (e.g., > 10 wt.%
polymer) can distinguish between block copolymer structures and incompatible
polymer blends. Since block copolymers constitute a single chemical species,
they produce clear single-phase solutions. On the other hand, incompatible
homopolymer blends result in cloudy solutions that eventually separate into
two liquid layers due to well-known thermodynamic immiscibility phenomena. |
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w********h
发帖数: 12367 | 36 Discher DE, Eisenberg A
Polymer vesicles
SCIENCE 297: (5583) 967-973 AUG 9 2002
Zhang LF, Yu K, Eisenberg A
Ion-induced morphological changes in ''crew-cut'' aggregates of amphiphilic
block copolymers
SCIENCE 272: (5269) 1777-1779 JUN 21 1996
ZHANG LF, EISENBERG A
MULTIPLE MORPHOLOGIES OF CREW-CUT AGGREGATES OF POLYSTYRENE-B-POLY(ACRYLIC
ACID) BLOCK-COPOLYMERS
SCIENCE 268: (5218) 1728-1731 JUN 23 1995
Let's |
|
y****u
发帖数: 50 | 37
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. |
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w********h
发帖数: 12367 | 38
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. |
|
c*****e
发帖数: 238 | 39 For asymmetric diblock copolymer melts, the phase transition point from
mean field approximation is not \chi*N>10.495, but is higher.
The 10.495 limit is only at the critical point which is for symmetric diblock
copolymers. |
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c****n
发帖数: 134 | 40 For synthesis of ABA triblock copolymers,
a guy published three macromolecules...
However, I can write only one for my triblock copolymer...
because I have a very simple method to circumvent his problems...
This is very unfair: for similar results, less work means higher efficiency. |
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c****n
发帖数: 134 | 41 There is an amphiphilic triblock copolymer.
The center is hydrophobic, and the end blocks hydrophilic.
The hydrophilicity of the end blocks can be controlled
as the content of the -OH group can be controlled during polymn.
when the block copolymer with high -OH content is dissolved in THF,
it looks clear and homogeneous.
but the solution can't pass through a membrane for GPC sample preparation.
I believe it is because of the physical association of the end blocks...
but a group member said it co |
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c****n
发帖数: 134 | 42 来自主题: Macromolecules版 - 问个傻问题 3. It is not about end group. If the copolymer is random to some degree, there
will be a lot of AB or BA sequences, which are not available in respective
homopolymers and could have new peaks in NMR. (It is true for my random
copolymer. but it is only supporting information and can't rule out the
presence of homopolymers.)
connecting |
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c****n
发帖数: 134 | 43 random copolymer? very little information from Sci-finder
but you can try anionic copolymerization of st with butadiene
then hydrogenate the copolymer... |
|
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c****n
发帖数: 134 | 45 "it" is a random copolymer I mentioned as an example,
the surface energy may be tuned in a wider range.
it seems to me from the paper that they are the first to use crosslinked
random copolymer to tune the surface energy.
just curious why people didn't do it earlier...
http://www.sciencemag.org/cgi/content/full/308/5719/236?maxtoshow=&HITS=10&hit
s=10&RESULTFORMAT=&author1=craig+hawker&searchid=1113597928104_10041&stored_se
and
and |
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c*******n
发帖数: 1648 | 46 I am sure that tuning properties (not limited to surface tension) by using
copolymers has been regular practice in adhesive industry. Do you use "post
it" by 3M? That's a crosslinked acrylic copolymer, and dated back to 1970s.
http://www.sciencemag.org/cgi/content/full/308/5719/236?maxtoshow=&HITS=10&hit
s=10&RESULTFORMAT=&author1=craig+hawker&searchid=1113597928104_10041&stored_se
random |
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r******0
发帖数: 2753 | 47 Does anyone know any vendors I can buy polymers from, except Aldrich and Scien
tific Polymers? Thanks. I need buy some polyacrylates copolymer with cations on side chains but the copolymer cannot be water-soluble. :) |
|
c*****e
发帖数: 238 | 48 Microphase transition or microphase separation are indistinguishable to me,
the only possible difference is, for block copolymer, there is only one
component, thus is better termed microphase transition, for block copolymer
blended with hompolymers, they can phase separate in a microscopic length
scale, thus better termed microphase separation, in general, the physics is
the same to me. Both refer to incompatible phases.
Your second question is not clear to me. What kind of length scale are you |
|
s****e
发帖数: 2934 | 49 多谢了，nanoletter的文章我读了，很喜欢，但还没有看所有cite的文章。 cite20做的
东西和我的idea很相似。你说的有人做硅球表面修饰后交连的工作,他们预测define的程
度和表面官能团的密度有关，这篇文章在nanoletter的cite的文献里？还没看见。
大概在95年左右就有人用block copolymer合成nanoparticle了，size control应该是不
成问题的。具体资料可见Judy Riffle 在NSF的funding和用block copolymer和
nanoparticle做关键词找的文章。
“
<1 |
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s****e
发帖数: 2934 | 50 我想对amphiphilic block copolymer在良溶剂中，应该没有什么临界胶束浓度吧？任何
浓度都可以使amphiphilic block copolymer呈花朵状分散在良溶剂里吧？不溶的blcok是
花心，溶的block是花瓣。那么只要可溶的block的末端可以反应，那把两种中间含有
nanoparticleA，B的amphiphilic block copolymerA，B混合均匀，那么他们末端的a，b
官能团发生反应不是可以使他们ordered吗？
这个想法怎么样，大家给我挑挑刺，多谢了！ |
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