Journal of Membrane Science 281 (2006) 700–706 Preparation and characterization of EVOH/PVP membranes via thermally induced phase separation Rui Lv, Jing Zhou, Qiangguo Du ∗ , Haitao Wang, Wei Zhong Department of Macromolecular Science, The Key Laboratory of Molecular Engineering of Polymer, Ministry of Education, Fudan University, Shanghai 200433, People’s Republic of China Received 20 February 2006; received in revised form 15 April 2006; accepted 21 April 2006 Available online 29 April 2006 Abstract Poly(ethylene-co-vinyl alcohol) with ethylene content of 44 mol% (EVOH44)/polyvinylpyrrolidone (PVP) (K30) membranes were prepared via thermally induced phase separation (TIPS). Poly(ethylene glycol) with average number weight of 300 (PEG300) was used as diluent. Differential scanning calorimetry (DSC) and attenuated total reflectance infrared (ATR-FT-IR) spectra were used to investigate the compatibility of EVOH44 and PVP (K30). From disappearance of the melting peak of EVOH, T g of PVP in DSC, the shift of PVP carbonyl and C O bonds of EVOH in ATR, it was indicated that they were compatible. The effects of PVP content on phase diagram, PVP distribution and membrane morphology were studied. It was found that the binodal point shifted to higher temperature and proportion of PVP between polymer matrix to pore surface decreased with PVP content increasing. It was also found that the pore size of the membranes increased as PVP content increased. The hydrophilicity and protein adsorption properties of EVOH/PVP membranes were also measured, the results indicated that they had better hydrophilicity and protein antifouling property compared with pure EVOH membrane. © 2006 Elsevier B.V. All rights reserved. Keywords: Poly(ethylene-co-vinyl alcohol); Polyvinylpyrrolidone; TIPS; Membranes 1. Introduction Poly(ethylene-co-vinyl alcohol) (EVOH) is a crystalline ran- dom copolymer with vinyl alcohol and ethylene segments, and has been widely used as food packaging material due to its excellent gas barrier properties and harmlessness to health. EVOH can crystallize over the whole composition range of ethylene and has good thermal stability and high chemical resistance [1]. Recently, EVOH membranes have attracted plenty of research interest in fields of biomedical sci- ence and water treatment because of its good blood compat- ibility and hydrophilicity [2,3]. Guerra et al. utilized EVOH to research the activation of human plasma prekallikrein as a hemocompatibility test [2]. Cheng and Young [3] inves- tigated hemodialysis with EVOH membranes and proved the excellence of the EVOH membrane application. Porous EVOH membranes can be conveniently prepared by tradi- ∗ Corresponding author. Tel.: +86 21 6564 3891; fax: +86 21 6564 0293. E-mail address: qgdu@fudan.edu.cn (Q. Du). tional wet process, that is, the immersion–precipitation method [4,5] and thermally induced phase separation (TIPS) process [6,7]. TIPS process is one of the most popular methods to make microporous membranes [8,9]. In general, a homogeneous solu- tion of polymer is prepared at an elevated temperature by blending the polymer with a diluent of high boiling point, then the solution is cooled to induce phase separation, and finally a microporous structure is formed after the diluent is extracted by a volatile solvent [10]. Since 1980s, TIPS membrane formation has attracted plenty of research inter- ests because of the advantages of convenient membrane struc- ture control and various polymers applicable. Lloyd et al. made many researches on thermodynamics and kinetics in TIPS [10,11]. Matsuyama and co-workers used a series of alcoholic diluents to prepared EVOH membrane via TIPS [6,7]. Polyvinylpyrrolidone (PVP) is a common additive to enhance the hydrophilicity of polymer membrane [12–16]. The mem- brane porosity can be increased by adding the water-soluble PVP into the polymer solution during membrane formation 0376-7388/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.memsci.2006.04.042