Preparation of permeability-controlled track membranes on the basis of ‘smart’ polymers

doi:10.1016/S0376-7388(00)00494-4

Journal of Membrane Science

Volume 179, Issues 1–2, 15 November 2000, Pages 155-161

https://doi.org/10.1016/S0376-7388(00)00494-4 Get rights and content

The modification of polymer track membranes from polyethylene terephtalate (PET) and polypropylene (PP) was performed by radiation-induced graft polymerization of thermosensitive poly-N-isopropylacrylamide (poly-NIPAAM). The opening and closing of the pores was controlled by temperature and studied by the electric conductivity and water flow methods. The structure of the grafted membranes was investigated by scanning electron and atomic force microscopy.

Introduction

The ability of ‘smart’ polymers to respond to small changes in the environmental conditions can be used in the production of permeability-controlled track membranes. ‘Smart’ or ‘intelligent’ polymers are the nick-names of the water soluble polymers and hydrogels. They are able to change drastically their some properties (volume of macromolecules) in water solution even at small changes in the environment conditions (temperature, pH, magnetic field strength, etc.) [1], [2], [3]. Among ‘smart’ polymers, the greatest number of papers has been devoted to poly-N-isopropylacrylamide (poly-NIPAAM), a thermoresponsive polymer [3], [4], [5]. This polymer has a lower critical solution temperature (LCST) of about 32°C in water. Recently it was proposed to manufacture composite membranes by grafting stimulus-responsive polymers onto porous cast membranes [6], [7] and track membranes [8], [9], [10]. The thermosensitive membranes were used to separate a feed solution containing hydrophobic and hydrophilic solutes [11]. Following this principle, we prepared thermosensitive membranes by the radiation-induced graft polymerization of N-isopropylacrylamide (NIPAAM) onto polyethylene terephalate (PET) and polypropylene (PP) track membranes.

Section snippets

Materials

Biaxially oriented PET films (10 and 20 μm thick) manufactured in Russia and Melinex films (12 μm thick) of ICI (USA) were used. Polypropylene Torayfan films (10 μm thick) of Toray (Japan) were also used. In this work, the monomer to be grafted was NIPAAM obtained from Across Organics. It contained 0.1% of stabilizer and was used as received. Reagent grade acetone and distilled water were used to prepare the monomer solutions. As homopolymerization inhibitors, we used reagent grade CuCl₂·2H₂O. To

Results and discussion

The grafted polymer can be located both on the membrane external surface and inside the pores, depending on the grafting conditions. On its surface and on the walls of the pores, such a membrane has immobilized polymer molecules which are transformed from one conformation state to another as the environment conditions change even slightly. This transformation leads to an increase or a decrease in the pore size. The electric conductivity of the initial PET membrane is linearly dependent on the

Conclusions

Poly-NIPAAM-grafted polymer track membranes can be prepared by radiation-induced graft polymerization. The polymer is located on both sides of the external surface and inside the pores. Using conductivity method in combination with the scanning electron and atomic force microscopy, the properties of track membranes grafted by responsive hydrogel were analyzed. Poly-NIPAAM inside the pores of track membranes exhibit a change in thickness as the solution temperature changes, and the membrane

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View full text

Preparation of permeability-controlled track membranes on the basis of ‘smart’ polymers

Introduction

Section snippets

Materials

Results and discussion

Conclusions

Radiat. Phys. Chem.

‘Smart’ polymers in biotechnology and medicine

Russian Chem. Rev.

Radiation-induced graft polymerization as a method for surface modification of polymers

J. Polym. Sci. B

Temperature-responsive characteristics of N-isopropylacrylamide-grafted polymer films prepared by photografting

J. Appl. Polym. Sci.