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Investigation on surface molecular conformations and pervaporation performance of the poly(vinyl alcohol) (PVA) membrane

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Abstract.
A simple method of changing pre-treatment temperature in the course of film formation was used
to tune the surface structures of PVA membranes. Surface structure and property of the resulting
membranes were characterized by X-ray photoelectron spectroscopy (XPS), sum frequency generation
(SFG) vibrational spectroscopy, and contact angle measurements. The results show that PVA have different
molecular conformations at the membrane surface while those membranes were prepared at different
pre-treatment temperature. At higher pre-treatment temperatures, polar acetoxyl residues and hydroxyl
groups of the PVA chains oriented in a more orderly fashion, as induced by the faster evaporation of
water. When the membranes were in air, CH3 groups adjacent to the acetoxyl groups covered the surface
in order to minimize the surface free energy, while backbones of the PVA were rarely observed. These
surfaces exhibited a hydrophilic nature upon contact with water due to rapid surface reconstruction.
Conversely, at lower pre-treatment temperatures, the backbone CH2 groups dominated the surface,
forming a less hydrophilic surface. When the PVA membranes were employed to separate ethanol/water
mixtures, it was found that the PVA membranes with more hydrophilic surface exhibited higher water
selectivity. Our investigation indicates that molecular conformations on the membrane surface have
considerable influence on pervaporation performance.

Keywords:
Surface molecular conformation
PVA membrane
Pervaporation
SFG
Ethanol/water mixture

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Ketersediaan

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Informasi Detail

Judul Seri

Journal of Colloid and Interface Science

No. Panggil

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Penerbit

London : Elsevier Inc.., 2009

Deskripsi Fisik

Journal of Colloid and Interface Science 333 (2009) 346–353

Bahasa

English

ISBN/ISSN

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Klasifikasi

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Tipe Isi

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Tipe Media

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Tipe Pembawa

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Edisi

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Subjek

KIMIA

Info Detail Spesifik

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Pernyataan Tanggungjawab

agus

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