Study Of Hydrophobically Modified Cationic Polyacrylamides P(DMBAC-AM)

Cationic polyacrylamide is an important organic polymer flocculant, and the hydrophobically modified cationic polyacrylamides, based on the hydrophobic association bridging action, could enhance the interaction between polymer and small organic molecules, which promotes the performance of phase transition and the flocculant window dosage. So the hydrophobically modified cationic polyacrylamides have much more practical values in applications. In this thesis, the aggregation behaviors of cationic monomer (N,N-Dimethyl-N-methacryloyl oxyethyl-N-benzyl)ammonium chloride (DMBAC ) were studied, the results indicated that DMBAC has self-association ability in aqueous solution. Based on this amphiphilic monomer DMBAC, several kinds of cationic hydrophobically modified polyacrylamides P(DMBAC-AM) were constructed by microheterogeneous copolymerization system. The solution properties and flocculation behaviors were studied in detail.1. Kinetic behaviors of DMBAC homopolymerization and DMBAC-AM copolymerization were studied by photopolymerization process, and the monomer reactivity ratios of the copolymerization were evaluated. The experiment results indicated that the polymerization rate (Rp) is proportional to the concentration of photoinitiator and monomer with exponents of 0.29 and 0.89, respectively, the apparent activation energy (Ea) is about 13.74 kJ·mo1-1 in homopolymerization process, while in copolymerization process Rp is proportional to the concentration of photoinitiator and monomers with exponents of 0.82 and 0.83, respectively, Ea is about 10.97 kJ·mo1-1. The reactivity ratios of rl 0.27 for AM and r2 2.00 for DMBAC were also obtained, which suggested that AM prefers to form copolymers whereas DMBAC produces homopolymers, thereby increases the probability of forming microblock-like structure of DMBAC unites in copolymers.2. Series of cationic hydrophobically modified polyacrylamides P (DMBAC-AM) with different content of DMBAC and molecular weights, were synthesized using microhetergeneous copolymerization process, and the solution properties of P (DMBAC-AM) were studied. The results indicated P (DMBAC-AM) has strong thickening properties in aqueous solution. As the copolymer concentration above the critical association concentration (CAC), P (DMBAC-AM) forms network structures based on intermolecular association which results in the enhancement of hydrodynamic volume and a rapid increase of appearant viscosity. With the increase of DMBAC content and the molecular weight, the CAC of P (DMBAC-AM) decreases.3. The hydrophobically modified cationic polyacrylamides P (DMBAC-AM), based on the hydrophobic association bridging action and the charge patch mechanism, exhibited good flocculation and separation performance in the Kaolin suspension flocculation process. The decolorization of sulphur blue suspension demonstrated that P (DMBAC-AM) has higher COD removal efficiency than that of P (DMC-AM) because of the hydrophobe characteristics of DMBAC.