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kl5top

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[交流] 请问有人做过聚氯甲基苯乙烯的后交联反应吗

大家好，之前通过悬浮聚合制备了一些聚氯甲基苯乙烯微球，其中加入20%二乙烯基苯作为交联剂（P-VBC-DVB）。粒径大概0.3mm~1mm

现在打算以FeCl3作为催化剂进行后交联（postcrosslinking）,使氯甲基反应掉，从而合成出具有高比表面积的超高交联聚合物小球（hypercrosslinked polymer bead）。

现在采用的方式是：高分子小球在氮气保护下在2氯乙烷中溶胀2小时，然后把无水氯化铁和另一部分2氯甲烷加入反应器，然后继续搅拌一小时以充分分散。接着升温80度反应8小时。

补充：
1.反应原料均充分除水，反应在氮气保护下进行；
2.催化剂无水FeCl3的含量有所调整，最少是小球质量的五分之一，最多是小球质量的1.2倍
3.电热套加热，油浴加热，机械搅拌，磁子搅拌都尝试过
4.尝试过室温下直接加无水氯化铁，也尝试过冰浴下加入。

但现在的问题是所以实验结果就两种：
1.小球完全破碎
2.小球形态保存良好，但测试IR发现氯甲基峰明显还存在（尽管小球颜色已经明显变化）

请问有没有做过相同或者相似反应的同仁可以给我一些帮助或者建议呢，谢谢了！

另外悬浮聚合通常需要用到索氏提取，那么应该是开始制备小球之后就进行还是后交联之后再做？或者需要做两次？

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1楼2012-04-16 14:13:50

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5楼: Originally posted by quintion at 2012-04-19 09:38:42:
试下ALCL3.FECL3多用于小分子的付克反应催化,而其作为高分子中的付克反应的催化剂强度是不够的.但ALCL3的催化作用太强,它能使二氯乙烷的氯脱掉变正离子,从而使二氯乙烷兼备交联剂的性质(脱氯后剩下的-C2H4-连在主 ...

Friedel–Crafts  reaction  can  proceed  in  a  rather  limited number of  inert solvents,  such  as  aliphatic  hydrocarbons,  benzene, nitrobenzene,  CS2,and chlorinated  or  fluorinated  hydrocarbons. Among  these  solvents,  however, only  chlorinated hydrocarbons,  particularly  EDC,  nitrobenzene,  as  well  as cyclohexane  at  an  elevated  temperature,  are  suited  for  the synthesis  of hypercrosslinked  polystyrene,  since  they  are thermodynamically  good  solvents  for  both  the  initial polystyrene  and  the  final  products  of  crosslinking. The  choice of  a  catalyst  is  dictated  by  two  main  requirements:  it  should dissolve  in  the  selected  solvent  and  provide  a  sufficiently high  rate  of chemical  reaction  between  polystyrene  and  a  crosslinking  agent.  The activity  of  anhydrous  Friedel–Crafts  catalysts  is  well  known  to  decrease  in the  following  sequence:
AlBr3≈AlCl3> FeCl3> SnCl4> TiCl4> ZnCl2>>  BF3> HCl> H2SO4 > P2O5

AlCl3 and  AlBr3 are  the  most  active  catalysts  but  they  cause degradation  of polystyrene  chains.  FeCl3 represents  a  rather  strong  oxidative  agent,  and  so there  always  exists  an  anxiety  for  introducing  some  functional  groups  into the  final products.  Both  AlCl3 and  FeCl3 possess  low  solubility  in  the solvents suitable  for  the  reaction.  Still,  FeCl3 and  AlCl3 are  often  used  to catalyze  the  post-crosslinking  of  preliminary  chloromethylated
styrene–DVB  copolymers.  The  salts,  though  scarcely  soluble in  EDC, readily  migrate  into  the  swollen  copolymer  beads  due to  a  fairly  fast formation  of  a  reaction  complex  with  an  aromatic  species  [92,  93].  A substantial  shortcoming  of  both  AlCl3 and  FeCl3 is  that  they  also  catalyze the  reaction  of  the  solvent, EDC,  with  polystyrene  [94].  SnCl4 and  TiCl4 may  be considered  as  most  suitable  catalysts  for  the  post-crosslinking reaction,  at  least  for  laboratory-scale  studies.  Finally, hydrochloric  and  sulfuric acids,  though  catalyzing  the crosslinking  of  polystyrene  with  the  most reactive  1,4-dichloromethyl-2,5-dimethylbenzene  [95],  are  too  weak  to provide  a  sufficiently  high  rate  of  the  reaction. It  must  be  emphasized  here  that  all  Friedel–Crafts  catalysts  are  strongly hygroscopic  and  decompose  in  improperly  dried  solvents, although  indications  can  be  found  in  the  literature  that  small  traces  of  water  or  alcohols  act as  activating  co-catalysts.  In any  case  attention  must  be  paid  to  the  purity  of the  solvent  selected  for  the  post-crosslinking  reaction. In  laboratory  experiments  we  opted,  for  convenience  reasons, for  the use  of  stannic  tetrachloride,  which  dissolves  in  EDC,  cyclohexane,  and nitrobenzene,  possesses  sufficiently  high  activity  at  elevated  temperatures, and  at  the  same  time  initiates  a  rather  smooth  beginning  of  the  reaction.