Fabrication of nano-composite gas barrier films by spin-assisted Layer-by-layer assembly
Date Issued
2011
Date
2011
Author(s)
Chang, Yen-Hsiu
Abstract
This study uses spin-assisted layer-by-layer (SA-LBL) assembly process to deposit nano-composite gas barrier films of sodium montmorillonite (MMT) and branched polyethylenimine (BPEI). The objective is to establish a fast process for fabricating LBL gas barrier films with highly ordered structure and excellent barrier performance, which is evaluated in terms of helium transmission rate (HeTR) and oxygen transmission rate (OTR). By identifying and optimizing the key factors determining the helium barrier performance of the SA-LBL films, including the concentration of MMT and drying time after MMT deposition, we successfully obtained SA-LBL films with excellent barrier performance: 50 bilayers of SA-LBL films (188 nm) deposited on PET substrates reduced the HeTR from 521.1 of the bare substrates to 7.4 (c.c./m2 day), with the OTR reduced from ~10 to 0.13(c.c./m2 day). SEM, TEM and AFM analyses reveal ordered in-plane alignment of the MMT platelets in the SA-LBL films, which accounts for the good barrier performance of the films, as the aligned MMT platelets significantly increase the tortuosity and length of the pathways travelled by permeants. The SA-LBL films also display remarkable optical transparency and flexibility, thanks to the presence of the polymer interlayers. Despite the hydrophilicity of the MMT platelets and the polar BPEI, the barrier performance of the SA-LBL films remains stable in an accelerated aging environment with high humidity (90% RH) and elevated temperature (60 ºC). However, the SA-LBL films are ineffective as moisture barriers, with WVTR reaching 6.507. In our future work, we will examine low-polarity polymers in place of or in addition to BPEI to improve the moisture-barrier performance of the SA-LBL films.
Subjects
gas barrier
clay
nanocomposite films
Layer-by-Layer assembly
Type
thesis
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