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超级小笨瓜

银虫 (小有名气)

[求助] RAFT试剂对强酸的稳定性问题

有做RAFT试剂的大神没,RAFT试剂(二硫酯)对有机强酸如三氟乙酸的稳定如何,能否在RAFT聚合的过程中加入强酸同时实现可控/"活性"聚合。
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shakete

金虫 (正式写手)

【答案】应助回帖

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感谢参与,应助指数 +1
超级小笨瓜: 金币+3, ★有帮助 2013-06-24 20:13:28
Meteorの泪: 金币+2, 感谢交流 2013-06-24 20:57:13
Chaleux好像一篇文章中提到过RAFT试剂在酸性条件下会水解
具体数值不太清楚,应该是70℃下几个小时内就有相当量的RAFT试剂水解
所以加入强酸之后可能会有一定的影响
2楼2013-06-24 18:16:53
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超级小笨瓜

银虫 (小有名气)

引用回帖:
2楼: Originally posted by shakete at 2013-06-24 18:16:53
Chaleux好像一篇文章中提到过RAFT试剂在酸性条件下会水解
具体数值不太清楚,应该是70℃下几个小时内就有相当量的RAFT试剂水解
所以加入强酸之后可能会有一定的影响

能给下文章的题目么
3楼2013-06-24 20:13:49
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love-study

至尊木虫 (职业作家)

【答案】应助回帖

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感谢参与,应助指数 +1
Meteorの泪: 金币+1, 感谢交流 2013-06-24 20:57:57
超级小笨瓜: 金币+3, ★★★很有帮助 2013-06-24 21:45:35
双硫脂在强酸体系里的稳定性不是很好,能发生酸解反应
学海无涯
4楼2013-06-24 20:25:30
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shakete

金虫 (正式写手)

【答案】应助回帖

★ ★ ★ ★
超级小笨瓜: 金币+4, ★★★很有帮助 2013-06-25 15:50:41
Trithiocarbonates are known to be less subjected to hydrolysis than dithiobenzoate.(47, 48) However, a UV study performed at pH = 8.0 revealed that after only 30 min at 80 °C the absorbance of the PMAA macroRAFT agent at λ = 310 nm (corresponding to the maximum absorbance of the thiocarbonylthio function) decreased by 36% meaning that one-third of the chains had lost their RAFT chain end. After 5 h, only 14% of the chains still carried an active chain end. These results clearly explain the high amount of unreacted PMAA-CTPPA observed at this pH and the consequent poor control of the polymerization. By comparison, the hydrolytic stability of PMAA-CTPPA was significantly better at pH = 3.4 since a decay of only 4% was observed after 30 min at 80 °C and the proportion of living chains was still of 75% after 5 h (see Figure S2 in Supporting Information). In the emulsion polymerization performed at pH = 3.4, PMAA-CTPPA chains do not spend more than 45 min in the aqueous phase (Figure 1) and chain end hydrolysis can thus be neglected.


不知道怎么发图片,就把原句截下来了
http://pubs.acs.org/doi/full/10.1021/ma300875y这是文献的出处
atch Emulsion Polymerization Mediated by Poly(methacrylic acid) MacroRAFT Agents: One-Pot Synthesis of Self-Stabilized Particles
5楼2013-06-25 09:48:19
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lanye6209

铁杆木虫 (正式写手)

一般pH在2以上不会有太大的影响,当然时间不能太长
在路上走走看看
6楼2013-06-26 10:35:38
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