Researches On The Preparation, Polymerization Mechanism And Relationships Between Structures, Properties And Performances Of Poly (Dimethyldially Lammonium Chloride)

Poly(dimethyldiallylammonium chloride) (PDMDAAC) is a homopolymer product of dimethyldiallylammonium chloride (DMDAAC) which is a typical cationic polyelectrolyte. It has wide applications in many fields, such as paper making, coal mineral, petroleum beneficiation, dyeing, domestic chemicals, water treatment, biochemical, pharmaceuticals and so on. As a polymer, its properties and performances directly depend on its average molecular weight (i.e. intrinsic viscosity) and distribution. The structure and basic properties of PDMDAAC were introduced. Then, the research progresses about the preparation methods, thermal stability, solution properties, charge neutralization, bridging-netting performance and applications of PDMDAAC were reviewed according to the literatures. The exist problems in the researches were pointed out. Based on these, the research contents and their significations in this dissertation were illuminated. The obtained research progresses in this dissertation are showed as following.The products of PDMDAAC with high and serial molecular weight and their preparation processesAs to the preparation of PDMDAAC products with high molecular weight, three kinds of monomer with different purity were used as raw materials, and APS as initiator. Under the preparation method, that the APS was added in a lump and polymerization temperature was increased stepwise to complete the polymerization gradually, the PDMDAAC product was synthesized. The three monomers were industrial monomer, industrial monomer with high purity and laboratorial monomer. The influences of w(DMDAAC), m(APS):m(DMDAAC),m(Na4EDTA):m(DMDAAC), and polymerization temperature (T1,T2and T3) on the intrinsic viscosity values ([η]) of product and monomer conversion (Conv.) in product were studied, based on the orthogonal optimal experiments. The highest intrinsic viscosity values ([η]max) of PDMDAAC products prepared by using the three monomers at their optimum conditions were 1.59,3.44 and 3.66dL/g with the Conv. of 93.0%,100.0% and 96.7%, respectively. And they could achieve 2.42,4.69 and 4.21dL/g with the 100.0% Conv. in all products, respectively, by prolonging the reaction time from 3h to 102h at maintaining temperature T3. It was worthy to note that the maximum [η] of PDMDAAC in this dissertation was higher than the maximum [η] reported in literatures. Moreover, the effects of preparing conditions and monomer purity on the [η] and Conv. were investigated, respectively. They all could be the foundation for preparation of PDMDAAC products with serial molecular weight.As to the preparation of PDMDAAC products with serial intrinsic viscositie values, two methods, by controlling w(DMDAAC) companying with m(APS):m(DMDAAC), or T3 companying with the maintaining time t were designed effectively to obtain the products with serial [η] ranged from 0.1 dL/g to 3.0dL/g and 3.0 dL/g to 4.5dL/g, and Conv. were higher than 98.0%. They all could be the well fundamental for the further industrial production of PDMDAAC and the researches on structures, properties and performances of the products with serial [η].The studies of several polymerization mechanismsAs to the rationality demonstration for the preparation method mentioned above, the theoretical calculation showed that the adding amount of initiator under the optimum preparation condition was in the optimum range of theoretical estimation, and the chain propagation rate of polymerization was almost constant a short period of time after initiation. Then, the comparison with different preparing methods showed that, the polymerization rate variation of the preparation method, "The initiator was added in a lump and the polymerization temperature increased stepwise", was more close to constant "reaction time-conversion curve" type. Moreover, the comparison of reaction temperatures with different T1, T2 and T3, by using the preparation method showed that, the polymerization rate variation with the temperatures T1, T2 and T3 under the optimal reaction condition was more close to constant "reaction time-conversion curve" type. Therefore, the rationalities of both the preparation method and its optimum reaction condition were demonstrated and explained, by the calculation of the adding amount of initiator, chain propagation rate of polymerization and the comparison of the polymerization rate.As to the effects of impurities contained in monomer on the polymerization activity, a method, using the activity order of impurities and monomer molecule reacting with the initiator radical to represent the influence order of the impurities on the polymerization was designed, on the basis of the radical polymerization theory that the chain initiation was the key step in polymerization, and the impurities contained in monomer solution could react with the initiator radical of APS to produce radical products. The fully optimized structures and thermodynamic properties of different radical products were computed at the B3LYP/6-31G* level. The obtained influence order of the impurities was, dimethyl amine hydrochloride<dimethylallyl amine hydrochloride < allyl alderhyde < allyl chloride <allyl alcohol < dimethyl amine <dimethylallyl amine and Na+ <Cu2+ <Fe3+, based on the comparison of activation energies and the redox potentials. Meanwhile, a simulation experiment method was designed. In the experiments, the effects order of impurities for certain kinds and with different amounts in simulated monomer solutions on the [η] of PDMDAAC products and Conv. in PDMDAAC products could represent the influence order of the impurities on polymerization activity, according to the radical polymerization theory. Each simulated monomer was prepared by quantitatively adding a certain kind of impurities into the raw monomer with high purity synthesized in lab. The polymerization was carried out under the optimum condition. The obtained influence order of the impurities was, NaCl< dimethyl amine hydrochloride< allyl chloride≈dimethyl amine<dimethylallyl amine hydrochloride≈dimethylallyl amine< allyl alderhyde < allyl alcohol <Fe3+ <Cu2+. The results of quantum chemistry calculation and simulation experiments indicated that the impurities in monomer solution had significant influences on the polymerization, so the purity of monomer was a key factor to influence the molecular weight of PDMDAAC products. These researches not only indicated the effects of impurities in monomer solution on the polymerization activity, but also well guided to obtain the products with high molecular weight by using monomer with high purity and helped to set up the quality standard for monomer products.As to the effects of monomer conversion rates on the [η] of PDMDAAC product, a method was designed that the simulation PDMDAAC products with different Conv. was prepared by adding the different amount of monomer to the purified PDMDAAC products with different intrinsic viscosities. The simulation products could be used to study the effects of residual monomer amounts on the [η] of practical PDMDAAC products. The results showed that the influences could be represented as the equation, lg[η’]=lg[η]+lg Conv.’. This law indicated that it was an effective way to obtaining high molecular weight PDMDAAC products by the increase of Conv..The studies of the structures, properties and performances of liner PDMDAAC with serial [η] and crosslink PDMDAACAs to the structure of serial PDMDAAC products, the FTIR and NMR were used to characterization. The spectra showed that higher the molecular weight of linear product was, the less the terminal double bond had in unit weight. The semi-solid NMR spectra showed that the areas ratios of the peaks belonging to the -CH2- of the main chain and to—CH- of branch chain in the crosslink molecular increased significantly when branching and crosslinking side reaction occurred in the products.As to the thermal stabilities of serial PDMDAAC samples, TG-DSC-MS and TG-DTA were used to determinate the kinetics, thermodynamics and mechanisms of thermal decomposition of PDMDAAC samples. The results showed that there were two decomposition stages for PDMDAAC, while there was only one for its monomer DMDAAC. The decomposition activation energy Ea increased with the molecular weight of PDMDAAC. The decomposition characteristics of crosslink products were similar to thant of the linear product. The calculation results by using the Coast-Redfern method indicated that there were two decomposition stages for PDMDAAC, and the reaction order of each stage was one. The Ea of PDMDAAC with [η] 3.83dL/g calculated by Ozawa method was 124.1kJ/mol and 211.1kJ/mol for each decomposition stage. The decomposition gas products were mainly NH2Cl for the first stage and were mainly CH4, C2H2 and C3H8 for the second stage, which verified by the joined analysis results of TG-DSC-MS. The results broke through the limitation of research results in literatures, which used only one PDMDAAC sample with low molecular weight for the studies of kinetics and thermodynamics. Meanwhile, the results demonstrated the mechanisms of thermal decomposition of PDMDAAC, and the effects of intrinsic viscosity of PDMDAAC products on their thermal stabilities.As to the solution properties of serial PDMDAAC samples, GPC-MALLS was used to determinate the molecular conformations and sizes of PDMDAAC in the solvent of c(NaCl)=0.5mol/L at 25℃. The results showed that the higher the intrinsic viscosity value of the sample was, the higher the molecular weight and Rg was, the shorter the eluting time was, and more compliant of the sample molecular chain was. Meanwhile, the constants k and a were calculated by using GPC-MALLS to determine the molecular weights and intrinsic viscosities of serial PDMDAAC samples with narrow distribution. The obtained Mark-Houwink equation was [η]=1.01×10-2M0767([η]<1.57dL/g) and [η]= 0.313 M05044 (1.57dL/g< [η]<4.49dL/g). Moreover, the effects of PDMDAAC mass concentration and testing temperature on the apparent viscosity of PDMDAAC water solution were studied by using circumgyrate viscometer. The results showed that the apparent viscosity increased with the molecular weight of PDMDAAC samples and the mass concentration, while decreased with the temperature increasing. The Mark-Houwink equation could be well applied to calculate the molecular weight of PDMDAAC samples in a much wilder range.As to the flocculation performances of PDMDAAC products, two methods for studying the abilities of charge neutralization to the suspending colloid and for bridging-netting to the suspending coalescence were designed, respectively. In the experiments of the charge neutralization, the water containing Kaolin was used as simulated water, and the changes of turbidity and zeta potential of the supernatant with the adding amount of DMDAAC and PDMDAAC were used as evaluation indexes for the abilities of charge neutralization. When the turbidity of supernatant after treatment was controlled almost unchanged, the results showed that the zeta potentials of suspended particles increased obviously with the adding amount of PDMDAAC, while they increased inconspicuously with the intrinsic viscosity of PDMDAAC. However, zeta potential kept almost unchanged when adding amount of DMDAAC increased. In the experiments of the bridging-netting, the water containing Diatomite was used as simulated water. The changes of the settlement rate, floc size and the transmittance of supernatant with the adding amount of DMDAAC or PDMDAAC were used as evaluation indexes for the abilities of bridging-netting. The results showed that the settlement rate, floc size and the transmittance of supernatant increased with the intrinsic viscosity of PDMDAAC, when the added amount of PDMDAAC was kept the same. However, there was no obvious flocculation happened after the monomer DMDAAC added. Therefore, the performances of PDMDAAC used as the coagulant were both the charge neutralization which mainly depended on the adding amount of PDMDAAC and the bridging-netting which specially depended on the molecular weight of PDMDAAC besides its adding amount. These completed researches offered a possible description for working mechanisms of PDMDAAC in coagulation, which could be a fundamental for the explanation of working mechanism of the composites coagulant containing PDMDAAC in the enhanced coagulation of raw water.The examples for scaled-up of preparing processes of PDMDAAC and application of PDMDAAC products in raw water treatmentAs to the scaled-up of preparation processes of PDMDAAC products with high and serial molecular weight, the products were well manufactured in two scaled-up lines, each with the production ability of 100t per year, by using the industrial monomer with high purity as the raw material, APS as the initiator under the obtained optimal conditions. The highest [η] of PDMDAAC product was 3.36dL/g and its serial intrinsic viscosity values could range from 0.5dL/g to 3.36dL/g.As to the application of PDMDAAC, the serial [η] of PDMDAAC products were composited with poly aluminum chloride (PAC) to form composite coagulants. The examples for the application of the composite coagulants in raw water treatments were showed. The application researches were made by the Jar tests in lab, simulated production line and drinking water production line in factory, step by step. The composite coagulants contained different mass ratios of PAC and PDMDAAC products with serial[η]. The treated raw water in application researches included the water of Yangzi River and Tai Lake, which represented the typical slight polluted river and lake water in China, respectively. The successful results of application in the scaled-up and practical lines showed that the composite coagulant PAC/PDMDAAC had good performances on the removal of turbidity and algae in the process of enhanced treatment of raw water. For adding the same amount of PAC, the higher the [η] or mass ratio of PDMDAAC in composites coagulants, the better the performance of turbidity and algae removal were. For achieving the same treatment efficiency, the higher the [η] or mass ratio of PDMDAAC in composites coagulation was, the less amount of the inorganic coagulants PAC needed. The research results for the application of PDMDAAC in slight polluted raw water treatment could not only be the guarantee for the safety of the drinking water after treatment and the reservation of new technology for raw water treatment for the production of higher quality in the future, but also offer the possibilities of decreasing the adding amount of PAC and the cost for preparing drinking water.The completed researches in this dissertation have enriched the knowledge of processes, mechanisms, and the relationships between structure and properties of PDMDAAC with high and serial intrinsic viscosity values, which could be a well fundamental for the further researches both on theories and on applications of PDMDAAC.