Preparation And Characterization Of Superabsorbent Polymers Based On Polymetizable Polyurethane Macromolecular Surfactants

High concentrations of small molecular surfactant and/or NaCl are needed to solubilize the hydrophobic comonomers in traditional micellar crosslinking copolymerization technique. When such a hydrogel is immersed in a large amount of pure water, it becomes fragile and does not exhibit the initial mechanical performance due to the removal of surfactants from the gel. In our previous work, a modified micellar crosslinking copolymerization approach, where small molecular surfactant and NaCl were replaced by polymerizable macromolecular surfactants (PMSs), was employed to make hydrogels with excellent mechanical properties. After drying, however, none of these hydrogels could be used as superabsorbents, due to the low water absorbency. The objective of this work is to make superabsorbent polymers (SAPs) using this modified micellar crosslinking copolymerization method.The main contents and conclusions of this thesis are as follows:1. Three nonionic polymerizable polyurethane macromolecular surfactants PMS-600, PMS-1000 and PMS-2000 were prepared from polyethylene glycol (PEG), isophorone diisocyanate (IPDI) and 2-isocyanatoethyl acrylate (AOI). The critical micelle concentrations (CMC) of the obtained PMSs are about 0.001 g mL-1. SAPs were prepared through photo initiated copolymerization of partially neutralized acrylic acid (AA) and acrylamide (AM) in the presence of PMSs which can self-assemble into micelles acting as multifunctional cross-linkers. The influence of the chain length of PEG in PMS, the concentrations of PMS and initiators, the molar ratio of AA/AM, the neutralization degree of AA, etc., on the saline water absorbency (Qs) of the obtained SAPs under atmospheric pressure and under load (P? 2000 Pa) as well as the mechanical strength of the hydrogels which are in-situ synthesized and not dried were studied in detail. It has been found that the Qs and AUL of the SAPs prepared at optimal conditions are 36.5 g/g and 24.6 g/g, respectively. For a given SAP under different PMS or initiator concentrations, there is a linear relationship between the AUL of SAPs and the Young's modulus (E) of the in-situ synthesized hydrogels.2. Fast-swelling superabsorbent polymers were prepared by micellar cross-linking copolymerization of acrylic acid and acrylamide using PMSs as multifunctional cross-linkers with foaming technique. Sodium bicarbonate (NaHCO3)/acetone and Pluronic(?) F127 were used as foam (or porosity) generators and stabilizer, respectively. The influence of different components, including porosity generator, foam stabilizer, monomer concentration, PMS concentration and the PEG chain length of the PMSs on the swelling behavior of the hydrogels were investigated in detail. The equilibrium Qs and AUL of the prepared SAPs under optimal conditions are 34.3 g/g and 18.4 g/g, respectively, and the resin could reach its half equilibrium water absorbency within 30 seconds.