| Amphiphilic polymeric surfactants, which show several unique features when compared to low molar mass surfactants, such as a lower critical micelle concentration (cmc), stronger driving force for surface/interface adsorption, and lower molecular mobility, could better improve the micelle stability and reduced the desorption of surfactants from surface/interface. Therefore, amphiphilic copolymers have great application potential as coal water slurry (CWS) additives and oil/water emulsifiers. In this thesis, two kinds of anionic comb-like copolymers were synthesized through grafting of functional groups onto poly(styrene-co-maleic anhydride) (SMA); triblock copolymers were controlled synthesized via step-by-step reversible addition-fragmentation chain transfer (RAFT) polymerizations of N,N-(dimethylamino) ethyl methacrylate (DMA), poly(ethylene glycol) methyl ether methacrylate (PMA) and lauryl methacrylate (LMA). Interfacial activities and dispersing and stabilization effects of copolymers of two categories on CWSs and oil/water emulsions were investigated respectively. Influences of molecular composition and environmental factors on the performances of copolymers were studied, and mechanisms of different copolymers during application were successively determined. Main details for this work are listed as follows:1. Two kinds of anionic comb-like copolymers were synthesized by grafting 1-naphthylamine-6-sulfonic acid alone (SMANS series obtained) or together with methoxypolyethlene glycol (SMANP series obtained) onto SMA copolymers, via esterification and amidation respectively. pH-responsive triblock copolymers PDMA-PPMA-PLMA were synthesized by three-step RAFT polymerizations in a well-controlled manner with pseudo-first-order kinetics, yielding copolymers with tunable molecular compositions and narrow molecular weight distributions. Owing to the pH-sensitivity of tertiary amino groups in PDMA segments, triblock copolymers exhibited remarkable pH-responsive behaviors in water. Through pH-induced self-assembly of triblock copolymers, micelles of various morphologies could be generated.2. The dispersing and stabilization effects of anionic comb-like copolymers on Shenfu coal water slurries were researched in terms of rheological behaviors of slurries, and the mechanisms were investigated and compared by analyses of zeta potential, UV-vis spectrum and contact angle. Results shown that, with the presence of sulfonate groups, anionic copolymers provided electrostatic repulsion among coal particles after adsorption, which was whereas significantly affected by added electrolytes. The mPEG pendants in copolymers offered additional steric hindrance among coal particles, thickened hydrated adsorption layers, and moreover, enabled denser adsorption layer of copolymers on coal surfaces, which consequently further dispersed and stabilized the CWSs. Added in copolymer with optimal composition, coal content of CWS was increased up to 71 wt% from 66 wt%.3. Interfacial activity, adsorption ability and emulsification performances of comb-like copolymers SMAN and triblock copolymers PDMA-PPMA-PLMA in dodecane/water system were researched respectively, and the effects of molecular composition and environmental parameters (ionic strength and pH) on copolymer performances were studied in order to determine the emulsification and stabilization mechanisms. Behaviors of anionic comb-like copolymers in dodecane/water system had a lot in common with those in CWSs. Adsorption layers formed by SMANP copolymers on dodecane droplet surfaces were thick and compact with high strength, due to the presence of mPEG side chains which could also enhance the salt tolerance of copolymers, and thereby better emulsified dodecane and guaranteed the stability of emulsions. Because of the large molecular volume and specific solubility characteristics of each segment of the copolymer, triblock copolymers were driven to adsorb more firmly onto the dodecane/water interface, and would generate much more compact adsorption layers. Thus, they exhibited higher efficiency on dodecane/water interfacial tension reduction and dodecane emulsification, and better stabilized the formed O/W emulsions. Interfacial activity of triblock copolymer was also pH-responsive, and influence of pH was correlated with the proportion of tertiary amino groups in copolymer. Emulsification capabilities of comb-like and triblock copolymers were both further confirmed by application in Shengli crude oil. Stable crude oil emulsions were formed, and the apparent viscosity descended from about 34 Pa-s of crude oil to 247 mPa-s with SMANP (5 mg/mL) and 350 mPa·s with PDMA-PPMA-PLMA (3 mg/mL) after emulsification.4. Polyelectrolyte complexes (PECs) were formed between anionic comb-like copolymers SMANS and cationic triblock copolymers PDMA-PPMA-PLMA in aqueous solution, and their structures were investigated as a function of SMANS concentration, pH of solution and ionic strength. Interfacial activity and emulsification effects of complexes were analyzed, and the configuration of interfacial adsorption layers formed by complexes was also studied under different circumstances. At charge neutralization point, complex micelles were formed with the largest aggregation number and the most compact structures, and the hydrophilic shell consisted of PPMA blocks well stabilized the micelles. The complexes were formed mainly through electrostatic interactions between oppositely charged copolymers, while a too high concentration of SMANS would lead to the transformation of interactions. Compared to either component, complexes exhibited improved interfacial activity and adsorption ability, and therefore more effectively emulsified oil and stabilized the formed O/W emulsions. An increase in pH caused a decrease in charge density of triblock copolymers, and higher salt concentrations led to an increased screening effect on the electrostatic attraction, both resulting in weakened complexation between copolymers and consequently affecting the structure, interfacial activity and emulsification performance of complex. |
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