| Summary: | 博士 === 國立成功大學 === 化學工程學系 === 87 === 英文摘要
The homopolymer or copolymer of dimethylaminoethyl methacrylate- methyl chloride(DMAEM-MC) is very useful in industry. Generally, aqueous polymerization with redox initiators is the most widely used method for producing this type of polymer. However, there are some disadvandges existing in this method which is difficult to modify or overcome. In this dissertation , the problems were solved by using new initiator and new technique of polymerization. Four subjects were probed as follow. 1st, the Sn+2 and EDTA were added to the monomer solution and initiated the polymerization by the electrolysis and chemical methods. Simultaneously, the comparison of the two different methods were also discussed. 2nd, the polymerization was carried out by the sacrifical Sn anode which generated Sn+2 in-situ and the affecting factors of this system were also determined. 3rd, The system was further simplified by using Sn electrodes without any coinitiators, EDTA, i.e. bare anode and the Sn+2 was also generated in-situ. Last, the postpolymerization of the product was examined by the investigation of conversion and polymer molecular weight.
The electropolymerization of DMAEM-MC was carried out in aqueous solution by using Sn+2-EDTA as initiator and graphite as electrodes and the results compared with that of chemical method. The results showed that both the polymerization rates of electrolysis and chemical methods increased with monomer and initiator concentrations. However, at the same operating condition, the polymerization rate of electrolysis method was higher than that of the chemical method. It showed that the Sn+2 ion was generated by the electrode during the electropoly-merization which induced the concentration of Sn+2 to be a constant and resulted the higher polymerization rate comparing to the chemical method. The results indicated that the major factors affecting the molecular weight of the polymer were the pHi value and the [Sn+2]i /[EDTA]i ratio. On the other hand, in the range of 35 to 55℃, the molecular weight increasing rate was 1.14x105 g/mole-h and was independent to temperature. i.e. temperature was the minor factor of the electropolymerization,which was quite different from chemical method. Increasing the pHi values of the electrolyte decreases the polymer molecular weight at fixed operating conditions. The optimum [Sn+2]i /[EDTA]i ratio to obtain the highest polymer molecular weight mainly depended on the pHi value. In the range of higher pHi values, pHi=3.25 or higher , the optimum ratio of [Sn+2]i/[EDTA]i is about 5.00. However,in the range of lower pHi values, pHi=2.50 or lower , the optimum ratio is 1.00. In the electropolymerization, the polymer molecular weight could be controlled easily by current density and the highest molecular weight obtained by the electrolysis method was 1.69x106compared to the 2.97x105 of chemical method. The free radical generation mechanisms were shown in Eqs. (1) and (2)：
where is -OOC2H4N(CH3)3Cl
The sacrifical Sn anode method was used to make breakthrough of some problems of previous electropolymerization and to simplify the
polymerization system. The results showed that the sacrificial anode
could be used to initiate the monomer system and the major affecting factors were agitation rate, pHi, current density and geometry of electrodes.
On the other hand, temperature was also a minor factor in the range from 25 to 45℃ and the effect of monomer concentration was similar to the
chemical method. The optimum agitation rate, pHi, temperature and monomer concentration were 0 rpm, 1.75, 45℃ and 0.98M, respectively.
The optimum [EDTA]i increased with reaction time, it may be maintained by continous addition of EDTA to the electrolysis during the reaction
time. The reaction rate increased with current density. However, the current efficiency decreased with the increase of current density. The kinetic equation was obtained as shown in Eq. (3)：
Rp1=K1 [current density]0.46 [DMAEM-MC]1.85 (3)
The polymerization was further simplified by only using Sn+2 cation as initiator which was generated in-situ by the bare sacrificial anode method without EDTA. The major factors which affected both the conversion and polymer molecular weight were pHi, current density and assembly of electrodes. On the other hand, temperature was also a minor factor in the range from 25 to 45℃ and the effect of monomer concentration was similar to the chemical method.
The optimum agitation rate, pHi ,temperature and monomer concentration were 0 rpm, 5.50, 25℃ and 0.73M, respectively. The effect of current density was same as that of sacrificial anode. The kinetic equation was obtained as shown in Eq. (4)
Rp2=K2 [current density]0.98[DMAEM-MC]0.76 (4)
The last subject of this dissertation was the study of postpolymeriz-ation. The results showed that all the synthesis methods had showed the postpolymerization apparently. The conversion of postpolymerization
increased with shelf time. However, the molecular weight of postpolymerization might reach a maximum and slowed down
to a stable value. It indicated that the degradation of polymer might
happen during the shelf- time in some runs, especially, in the presence of
much more EDTA. The pHi ,[Sn+2]i/[EDTA]i ratio and [DMAEM-MC]i were the major factors which affected the rate of postpolymerization.
When the pHi was smaller,or equal to ,2.50 and the [Sn+2]i/[EDTA]i ratio was 1.00 or2.00, the postpolymerization was obvious. However, when the pHi was larger,or equal to, 3.25 and the [Sn+2]i/[EDTA]i ratio is 5.00 or 10.0, the postpolymerization was obvious. The results also revealed that the rate of postpolymerization increased with the increase of [DMAEM-MC]i. The stable molecular weight by chemical, electropolymerization and sacrifical anode methods could be as high as 1.20x107 and the stable molecular weight obtained by the sacrificial anode without coinitiator was 5.00x106.
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