Preparation, structure and properties of porous polyimide films via PAA/PU alloy |
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Authors: | Jiugui Liu Lizhong Jiang Jiayu Zhan Dezhen Wu Riguang Jin |
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Institution: | (1) Key Laboratory of Science and Technology of Controllable Chemical Reactions, Ministry of Education, Beijing University of Chemical Technology, Beijing, 100029, China |
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Abstract: | A new route to porous polyimide (PI) films with pore sizes in the nanometer regime was developed. A polyamic acid (PAA)/polyurethane
(PU) blend with PU as the disperse phase was first prepared via in situ polymerization of pyromellitic dianhydride and 4,4-oxydianiline in PU solutions. Porous PI films were obtained from PAA/PU
films by thermolysis of PU at 360°C and imidization of PAA at 300°C, respectively. Fourier transform infrared spectroscopy
and thermal gravimetric analysis were used to detect the imidization and thermolysis processes of PAA/PU blends under thermal
treatment. The microporous structure of the PI films was observed by transmission electron microscopy. It was found that the
size and content of pores increased with an increase in the PU mass fraction in the PAA/PU blend up to 20%. Because of the
existence of nanopores, the dielectric constant of PI films decreased by a wide margin and was less than 2.0 at a PU mass
fraction of 20%. It implies that this is an effective means to reduce the dielectric constant of PI, but it also causes the
decrease of tensile strength and the rise of water absorption.
Translated from Chemistry Journal of Chinese Universities 2006, 27(1): (in Chinese) |
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Keywords: | polyimide polyurethane porosity dielectric constant |
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