Study of the porosity in cellulose acetate membranes by 3γ annihilation of positrons

抄録

A series of cellulose acetate membranes with different porosities were prepared. The porosity of the membrane was adjusted by adding different molecular weights and contents of polyethylene glycol (PEG), which acts as pore-forming agent in the preparation process. Positron annihilation lifetime measurement and γ-ray energy spectroscopy were employed to evaluate the porosities of the membranes. The lifetime results indicate the size of the free-volume holes in all the membranes are nearly the same. The 3γ annihilation results suggest that, with the increase of porogen content: if the molecular weight of the porogen is low (PEG200, PEG400), pore combination is dominant in the preparation process; while if the molecular weight of the porogen is higher (PEG1000, PEG2000), new pores are formed and/or pores are enlarged.