Multi-branched Block Polyether Polymer Surfactant Synthesis, Characterization And Application

We have recently investigated the character and application of amphiphilic polyether copolymers with linear, star and dendrimer structures. These copolymers can self-assemble various aggregation morphologies, which are of interest for potential applications in drug delivery, encapsulation, or in commodity. In particular, these polyether copolymers are very excellent demulsifier for demulsification of crude oil emulsion. Many experiments in our laboratory indicate that the block polyether copolymers with more complex molecular structure perform better demulsification for heavy crude oil emulsion. The main purpose of this present work is to study aggregation behavior and interfacial properties of polyether copolymers in aqueous solutions, so that it can supply a useful illumination for application of these novel dendritic block copolymers.â… , Aggregation Behaviors and Interfacial Properties of Oxyethylated Nonionic SurfactantsFour nonionic surfactants C₁₆E_n with varying EO number were synthesized. The characters of this series of nonionic surfactants including surface tension, critical micelle concentration (CMC), interfacial activity and surface pressure were presented. The surface tension data indicted that γ_cmc increased with hydrophilic PEO chain length while CMC decreased. The area per surfactant molecule at the air/water interface increased as PEO chain length increased. The probe, pyrene, was employed to investigate nonionic micelles of varying EO number in steady-state fluorescence. The CMC, obtained from the I₃/I₁ ratio, agreed well with the results of surface tension experiment. The interfacial properties were studied by using a heptane-toluene/water model system. We found that the interfacial activities increased with the degree of ethoxylation because of their hydrophile-lipophile balance. From the Ï€ -A isotherm, it can be deduced that C₁₆E_n nonionic surfactants had excellent molecular flexibility. The surface pressure data also showed that this kind of surfactants with longer PEO chains occupied larger area per molecule at the interface.II % Characterization and Demulsiflcation of Poly(ethylene oxide)-bIock-Poly (propylene oxide)-block-Poly(ethylene oxide) Linear CopolymersFour poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) copolymers with different molecular weight and PPO/PEO composition ratio were synthesized. The characterization of the PEO-PPO-PEO triblock copolymers was studied by surface tension measurement, UV-vis spectra and Surface pressure method. These results clearly showed that CMC of PEO-PPO-PEO was not a certain value but a concentration range contrast to classical surfactant and two breaks around CMC were reflected on both surface tension isotherm curves and UV-vis absorption spectra. The range of CMC became wider with increasing of PPO/PEO composition ratio. Surface pressure n -A curves revealed that amphiphilic triblock copolymer PEO-PPO-PEO molecule was flexible at air/water interface. We found that the minimum areas per molecule at air/water interface increased with the proportion of PEO chain. The copolymers with the same mass fractions of PEO had similar slopes in the isotherm of n -A curve. From the demulsiflcation experiments a conclusion had been drawn that the dehydrating speed increased with the content of PEO decreasing, but the final dehydrating rate of four demulsifier was approximate. We determined the coalescence of water drops resulted in the breaking of crude oil emulsion from the micrograph.IE, Synthesis and Characterization of Poly(propylene oxide) -block-poly(ethylene oxide) Star CopolymersSix Poly(propylene oxide)-block-poly (ethylene oxide) star copolymers with different molecular weight and PPO/PEO composition ratio were synthesized. The characterization of these star macromolecular surfactants was studied by 'H-HMR, surface tension, UV-vis spectra, surface pressure and interface tension measurement. These results of surface tension isotherm and UV-vis spectra clearly showed that CMCs of star copolymers were concentration range and the range of CMC become wider with increasing of PPO content. We can gain the area of per molecule from surface pressure curves. The n -A curves revealed that amphiphilic diblock copolymer PEO-PPO molecule was flexible on air/water interface. Interface tensionisotherm showed that the interfacial activity of PPO-PEO copolymers were higher with increasing of PPO/PEO composition ratio.IV -. Aggregation Behavior of Polyether Block Copolymers with Dendritic Structure in Aqueous SolutionsIn this study, two dendritic block copolymers with the same contents of PPO and PEO but different branches and blocks were synthesized by anion polymerization. Their aggregation behaviors were investigated by tensiometry, fluorescence, transmission electron microscopy, and dynamic light scattering. The critical aggregation concentration (CAC) of the amphiphilic block copolymers was not a certain value but a concentration range contrast to classical surfactant and two breaks around CAC were reflected on surface tension isotherm curves. We also deduced that the aggregates of dendritic copolymers were different for two copolymers with increasing concentration by fluorescence spectra. For SD64 copolymer with PPO-PEO diblock branch, it can be proved that only intermolecular aggregates are formed, the aggregation number and aggregation diameter are increased with concentration. Whereas for SD343 dendritic copolymer with PPO-PEO-PPO triblock branch, hydrophobic PPO chains located on the edge of SD343 copolymers can associate within the same polymer chain and also between different polymer chains, so the aggregates were inclined to change from intramolecular micelles to intermolecular clusters with concentration increasing.The aggregation numbers of the dendritic copolymers have also been determined by using steady-state fluorescence methods. The concentration dependence aggregation number for copolymer aggregates was observed. The values of aggregation numbers are found to be 1.7 and 7.7 for SD64 concentrations of 500 and 5000 mg L'1, which proves that only intermolecular aggregates are formed. However, the aggregation numbers are found to be 0.8 and 5.5 for SD343 concentrations of 500 and 5000 mg L*1, respectively. It is obviously that intramolecular micelles are formed at 500 mg L'1 and intermolecular micelles are formed at 5000 mg L"1. The hydrodynamic radiis (Rh)of the aggregates of SD64 and SD343, measured by dynamic light scattering, are 7 and 8 nm at 500 mg L'1 together with 38 and 48 nm at 5000 mg L"1, respectively.These dendrimers are well-defined, highly branched, three dimensional molecules with a large number of reactive end groups. So these copolymers can self-assemble various aggregation morphologies, which are of interest for potential applications in drug delivery, encapsulation, or in commodity. In particular, dendritic polyether copolymers are very excellent demulsifier for demulsification of crude oil emulsion. Many experiments in our laboratory indicate that the block polyether copolymers with more complex molecular structure perform better demulsification for heavy crude oil emulsion. The main purpose of this present work is to study aggregation behavior of dendritic polyether copolymers in aqueous solutions, so that it can supply a useful illumination for application of these novel dendritic block copolymers.V -. The Effect of Interfacial Properties of Amphiphilic Block Copolymers with Different Structure on Chemical DemulsificationFive macromolecular surfactants including linear, star and dendrimer polymers were synthesized by anion polymerization using core-first method. From the demulsification experiments a conclusion had been drawn that the demulsifier became more efficient with more complex molecular structure due to increased interfacial activity and penetrability. The interfacial properties of these amphiphilic block copolymers were studied by surface pressure method and interfacial tension measurement. These results clearly showed that dendrimers had high interfacial activity, large interfacial molecule area and excellent molecular flexibility. From the n -A isotherm, it can be deduced that the structure of dendrimers transformed from pancake to brush at the interface with surface pressure increasing. The result of interfacial tension indicated that the block copolymer with high interfacial activity performed better demulsification. The physical model of demulsification and the dehydration micrograph intelligibly explained micromechanism of the flocculation and coalescence of water drops in emulsion because of good adsorption and displacement behaviors of dendrimers.VI % Demulsification of Crude Oil Emulsions with Novel Polyether DemulsifiersA series of novel branching polyether demulsifiers were synthesized through addition reaction with propylene oxide and ethylene oxide by alcohol, amine and phenol-amine resins used as initiator, then were modified by chain extension method using water soluble and oil soluble crosslinking agent. The crude oils of Gudong, Gudao, Caoqiao, Luntai and Daqing were tested using these demulsifiers. The dehydration of crude oil in Linpan oilfield performed very well (over 70%) and the dehydration velocity was rapid even at low temperature 35°C. The dehydration rate reached over 60% at low demulsifier concentration 25 mg-L"1. Other comparison samples were invalid at the same condition. Furthermore, the mechanism of demulsification was studied by surface tension and microscope photo method.