The Relatively Research On Hyperbranched Poly (Amine-ester)-Based Separation Membranes

In the past decade, dendritic polymers have drawn increasing attention due to their unique structures and properties. According to the structure, dendrimers and hyperbranched polymers (HBP) constitute the two types of dendritic polymers. However, practical application of dendrimers are limited owning to the difiBculty of large-scale synthesis and purification. On the other hand, HBPs are polymers having the most similar structure and properties to dendrimers'. At the same time, HBPs could be synthesized efficiently in large-scale through one-step polycondensation process. Polymer membranes act as the most important roles in membrane separation development. Exploring new membrane material is needed in order to improve the hydrophilicity, anti-fouling, and biocompatibility. The design and preparation about HBP-based membrane rarely has been taken into account. According to the structure and properties of HBP, the HBP-based separation membrane was prepared and characterized. The synthesized hyperbranched poly(amine-ester) (HPAE) used as new pervaporation membrane material and modifying agent of porous poly(vinylidene fluoride) (PVDF) membranes were introduced in this paper. Also, the poly(aimdo-amine) (PAMAM) and HPAE were used as template to prepared copper nanoparticles, which might be useful in design of membrane catalysis process.First, amine ended poly(aimdo-amine) (PAMAM) dendrimers were synthesized by divergent procedure and hydroxyl ended HPAEs were synthesized by pseudo-one-step respectively. PAMAM and HPAE have narrower molecular weight distribution as indicated by GPC. The intrinsic viscosity of HPAE and PAMAM was decreased with the temperature increasing.The dense films were prepared by crosslinking the ended hydroxyl group of HPAE using Glutaraldehyde(GA) and succine anhydride (SA). Different membranes were prepared by changing the hydroxyl/aldehyde group and the HPAE generation. The surface structures of the crosslinked HPAE films were imaged using AFM and SEM, and their properties were characterized by hydrophilicity, solvent swelling,mechanics, and protein adsorption measurements. It was found that the water static contact angle on the upper surface of the crosslinked HPAE films were smaller than 45°, the tensile strength was higher than 0.35 Mpa, the elongation at break was higher than 9.2 percent, the swelling degree was higher than 63 percent in water. The BSA adsorption on the films surface was relatively low. These results indicated that those crosslinked films having promising application in biological materials, structural material, etc.The crosslinked HPAE membranes were used as pervaporation membrane to separation the mixture of water and isopropanol. The flux was increased accompanied with the decrease of a when the water concentration in the feed solution was increased. The pervaporation separation factor could reach 27.6 and the penetrate flux reach 2014.8g/m2h when 200um thickness membrane (hydroxyl/aldehyde group molar ratio= 2) was used to separated isopropanol mixture containg 10.5wt% water. Due to the swollen degree of G5-HPAE-GA crosslinked film was higher than that of G4- HPAE-GA film, the latter exhibiting higher a and lower flux.To investigate the influences of HPAE molecules on the thermodynamic stability and dynamic phase separation behaviors of ordinary polymer, the thermodynamic properties and precipitation kinetics of HPAE/PVDF/DMAc systems was characterized by light scattering instrument and light transmission instrument respectively. The coagulation value of the HPAE/PVDF/DMAc system decreased from 5.99g to 3.17g and the phase separation delay time changed from 11.4s to 5.2s with the HPAE concentration increasing from 2wt% to 12wt%. However, if the HPAE generation changed from the third to the sixth, the coagulation value of the HPAE/PVDF/DMAc system decreased from 5.66g to 4.38g and the phase separation delay time increased from 3.1s to 10.8s.By blending HPAE into PVDF casting solution, HPAE modified porous PVDF membranes (B-HPAE-PVDF) were prepared by solution phase inversion method. Some hydrophilic HPAE molecules were encapsulated in the B-HPAE-PVDF membrane as detected by ATR/FTIR, XPS, and element analysis. When theconcentration of HPAE in casting solution was increased, water contact angle on the upper surface of the membrane and the BSA adsorbed on the membrane surface decreased, the anti-fouling properties improved, the water flux recovery by chemical cleaning was higher. The results indicated the B-HPAE-PVDF membranes had relatively high hydrophilicity and good anti-fouling properties. With the HPAE concentration changing from 2wt% to 12wt%, the water contact angle on the membrane upper surface changed from 82.7° to 73.9°. If HPAE generation in the casting solution was raised, the water contact angle decreased and the anti-fouling properties were further improved. The BSA absorbed on the membrane surface could be cleaned more easily.The stability of HPAE in B-HPAE-PVDF membrane was characterized by the water contact angle change after the membrane was immersed different time in water. The water contact angle of the membrane prepared from the casting solution containing 12wt% G2-HPAE increased from 73.9° to 90° after immersion 10 days in water. It was indicated the hydrophilic HPAE molecules move to the water phase slowly in the period of immersion.In order to improve the stability of HPAE in the membranes, some of the terminal hydroxyl groups were crosslinked with GA and PVDF membranes with crosslinked HPAE (C-HPAE-PVDF) were prepared by solution phase inversion method. The chemical and morphological changes of the membranes were confirmed by FTIR, XPS, SEM and element analysis. The effects of reaction time and hydroxyl/aldehyede group ratio on the structure and properties of C-HPAE-PVDF membranes were studied. The water contact angle of C-HPAE-PVDF membranes decreased with the immersion time prolonged. When hydroxyl/aldehyde group ratio was 2, the water contact angle of the membrane decrease from 95° to 75° after immersion 10 days in water. As indicated by XPS, the amount of nitrogen and oxygen on the membrane surface increased from 0.69% and 3.08% to 2.69% and 9.99% respectively. The results suggested that the hydrophilic hydroxyl group in HPAE would move to the surface of the membrane and enrichment on the membranessurface. Compared with the B-HPAE-PVDF, the hydrophilicity of C-HPAE-PVDF membrane was improved and stabilized due to the forming of interpenetrating HPAE-PVDF network by crosslinking the end hydroxyl group of HPAE.Copper nanoparticles were prepared with G7-NH2-PAMAM and G6-0H-HPAE molecules template. Ultra-violet spectra and transmission electron microscope were adopted to characterize the absorption properties of the solution and the morphology of the formed composite particles respectively. 4nm G7-NH2(Cu)n nanoparticles was prepared and it could stay stable in homogenous state for at least a week at oxygen-free conditions. lOnm G6-0H(Cu)n nanoparticles could exist stable in oxygen-free solution longer than 11 h. The copper particles size, as well as the aggregation of the particles increased with the increasing of the Cu2+/G7-NH2, Cu2+/G6-OH molar ratio. The size of particles was smaller and size distribution was narrower than mat of HPAE template prepared, due to the perfect structure compared to HPAE molecules.