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Studies on Chloromethylation of Polystyrene by Micellar Catalysis and New Technology to Prepare Microsphere of Crosslinking Chloromethylated Polystyrene by Past Crosslinking Method

Author: LiuQiFa
Tutor: GaoBaoJiao
School: University of North
Course: Applied Chemistry
Keywords: Polystyrene Chloromethylation Micellar catalysis Surfactant Phase reversion emulsification Drying in liquid Chloromethylated polystyrene microsphere Past-crosslinking
CLC: TQ325.2
Type: Master's thesis
Year: 2006
Downloads: 190
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Abstract

The solubilization properties of surfactants for polystyrene which was dissolved incarbon tetrachloride were determined by using UV method. The chloromethylation reaction ofpolystyrene was carried out in micellar catalysis system, and the structure of chloromethylatedpolystyrene (CMPS) was characterized with FTIR and its composition was measured withVolhard method. The catalysis effects of anionic , cationic and non-ionic surfactants werecompared and the effects of the chemical structure of surfactants and adding of organicelectrolyte tetrabutyl ammonium bromide ((Bu)4NBr, TBAB) on miceller catalysis wereexamined.The mechanism of micellar catalysis for chloromethylation reaction of polystyrenewas explored, and the effects of surfactant structures on micellar catalysis were examined.The phase reversion emulsification-drying method in liquid was adopted to preparechloromethyl polystyrene (PCMS) microspheres which diameter could be controlled in therange of 2-40μm and which dispersion degrees were better were prepared successfully. Theeffects of the agitating rate, the ratio of oil phase to water phase, the composition and theadded amount of emulsification and dispersion system were examined on the particlediameter and dispersion degree. Two-step method of lightly hydrolyzing-crosslinking andpast-crosslinking was adopted to successfully prepare crosslinking chloromethylatedpolystyrene microspheres. with controlled degree of crosslinking. the effects of differentcrosslinking condition were investigated and the structure of the linear chloromethylatedmicrospheres and the crosslinked chloromethylated microspheres was characterized by meansof FTIR, the change of chemical constitution of the microballoons was measured.Themorphology of the microspheres was observed with the scanning electron microscope.The experiment results show that micellar solution of surfactant can solubilizepolystyrene dissolved in CCl4, namely, polystyrene can transfer into micellar solution ofsurfactant along with solubilization of CCl4 in the micellar solution of surfactant. micellarcatalysis is a effective way to realize chloromethylation for polystyrene, The mechanism ofthe reaction between polystyrene, formaldehyde and hydrochloric acid consists of two typesof reactions which are electrophilic substitution and nucleophilic substitution steps. Cationicsurfactant is more effective than anionic surfactant, and it displays that the nucleophilicsubstitution step is the controlling step.The experiment results also show that the adding ofTBAB speeds up obviously the chloromethylation reaction of polystyrene in the micellarcatalytic systems in which nonionic surfactant nonyl phenol polyethyleneoxide ether (NP-10)or anionic surfactant lauryl sodium sulfate (SDS) are used, especially in the system in whichnon-ionic surfactant NP-10 is used the acceleration is more distinct. On the contrary, in themicellar catalytic systems in which cationic surfactant CTAB is used, TBAB hardlyinfluences the reaction rate. On one hand the reason for this may attribute to the decrease ofcritical micelle concentration of SDS or NP-10 and the increase of solubilization ofpolystyrene in the micellar solution because of adding electrolyte TBAB, on the other hand, amore primary reason is that organic cation (Bu)4N+ of TBAB may be embedded into micellesdue to the synergistic effect of electrostatic attraction and hydrophobic interaction betweenbutyl groups and the hydrocarbon chains of SDS , so that the inhibiting effect of anionic headgroups of SDS towards the nucleophilicsubstitution reaction that is a controlling step isweakened. Under hydrophobic interaction, organic cation (Bu)4N+ of TBAB may also becombined on the surface of NP-10 micelles, so that the surface of NP-10 micelles arechargedpositively, and the nucleophilic substitution reaction is accelerated distinctly. ForCTAB system, the cation (Bu)4N+ can not be closed to the micelles of CTAB owing toelectrostatic repellence, so the adding of TBAB can not speed up chloromethylation reactionof polystyrene.The experiment results show that PCMS microspheres with better dispersion degree andexcellent sphericity can be prepared by phase reversion emulsification-drying method inliquid. The agitating rate, the composition and the added amount of emulsification /dispersionsystem effect on the particle diameter greatly, whereas the main factors which effect on thedispersion degree of particle diameters are the agitating rate and the ratio of oil phase to waterphase. As the added amount of emulsifier is fixed, the added amount of dispersant also hasgreat influence on the dispersion degree. By controlling various factors, PCMS microsphereswith different diameter and better uniformity can be obtained and even monodispersemicrospheres can be prepared. After the Linear chloromethylated polystyrene was hydrolyzedand lightly crosslinked,The swelling the beads in an organic solvent can be further crosslinkedto prepare the crosslinking chloromethylated polystyrene microsphere. By controlling someconditions,such as the reaction temperature, the reaction time, the catalyst type and the usedamount of catalyst and so on, the microsphere with different crosslinking degree can beobtained.After past crosslinking,the microsphere sphericity still remains excellently.

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CLC: > Industrial Technology > Chemical Industry > Synthetic resins and plastics industry > Polymer resin and plastic > Polystyrene and its copolymers
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