Synthesis And Properties Of Hydrophilic/hydrophobic Polystyrene-Based Interpenetrating Polymer Networks

Interpenetrating polymer networks (IPNs) are polymer alloys consisting of two or more crosslinked polymer networks through interlock or permanent entanglement. So far, few hydrophilic -hydrophobic IPNs have been reported due to the intense repulsive interaction between the hydrophilic network and the hydrophobic network. In this dissertation, three series of hydrophilic-hydrophobic IPNs were designed and successfully synthesized via sequential polymerization followed by chemical conversion, the structures were characterized by FTIR and DSC, and the swelling and adsorbing properties of these IPNs were investigated.1. IPNs of poly(methyl acrylate)/polystyrene were prepared by using the sequential polymerization method, and then hydrophilic-hydrophobic IPNs composed of poly(sodium acrylate) and polystyrene (PNaA/PS IPNs) were synthesized by converting the PMA to PNaA under basic environment. The equilibrium swelling experiments showed that PNaA/PS IPN swelled quickly in water, and the swelling ratio changed linearly with the increase of weakly acidic exchange capacity of the IPNs. The results of adsorptive experiments demonstrared that PNaA/PS IPN could adsorb organic compounds such as benzoic acid, o-nitrophenol and p-nitrophenol from aqueous solution, and this implied that resinic adsorbents can be prepared by porogening via swelling of gel-type IPNs. Adsorption properties of one of the PNaA/PS IPNs for various adsorbates were investigated, and the results suggested that adsorption of the above compounds might be mainly based on hydrophobic interaction.2. Another series of hydrophilic-hydrophobic IPNs composed of poly(acrylate acid) and polystyrene (PAA/PS IPNs) were obtained by transforming of PNaA/PS IPN under acidic condition. Differentialscanning calorimetry studies implied that the compatibility between two networks of PAA/PS IPNs was higher than that of PMA/PS IPNs due to the non-classical hydrogen bonding between the carboxyl protons of PAA and the benzene rings of PS. PAA/PS IPNs also displayed high swelling ratios in polar solvent, and the swelling ratios varied with the changes of molar ratio of hydrophilic and hydrophobic groups and crosslinking degree of the IPNs. Adsorption properties of one of the PAA/PS IPNs for pyridine, aniline and Af.Af-dimethylaniline in aqueous solution were investigated, and the results implied an adsorptive mechanism based on the synergism of hydrogen bonding and hydrophobic interactions.3. IPNs of chloromethylated polystyrene/polystyrene (PSCH2C1/PS) were prepared, and hydrophilic-hydrophobic PSCH2N(CH3)3OH/PS IPN-type anion-exchange resins were obtained by amination of the PSCH2CI/PS IPNs. Ion-exchange properties of IPNs with a crosslinking degree of 5% (the first network) for chloride ions in phytic acid aqueous and ethanol solution were measured. It was found that the solvent retention in water and ethanol varied with the variation of crosslinking degree of the second network, and the anion-exchange capacity varied with the change of size of anions. The second network with a crosslinking degree of 20% would not undergo ion-exchange with the large-sized anions such as phytate ions but would undergo ion-exchange with the small-sized anions such as chloride ions from ethanol solution, and thus displayed ion-size selectivity somewhat. These DPNs might be found their use in adsorptive separation of anions with different ion size. Regeneration experiments indicated that the mechanical properties and chemical stability of the EPN-type anion-exchange resins is good enough.