Blend Membrane Structure and Properties

2 Pebax 1657-based Blend Membrane Structure and Properties 

PEGEPI appeared to be miscible with the PEG phase of Pebax 1657 in DSC, the PEGEPI- Pebax 1657 blends showed a nniqne glass transition temperature (around 

Car et al. [9,10] reported a two-fold increase in CO2 permeabihty (up to 150 Barrer) without changes in CO2/N2 selectivity when the membrane material changes from pure 

Pebax 1657 to its 50 50 blend with PEG 200. The CO2 penneability increase was attributed to a solubility increase with the increase in ethylene oxide (EO) units, but also to a diffusivity increase due to an increase in free volume (either total fractional free volume or individual free volume space) at high PEG content, there would be an increase of Pebax segment motion, since low molecular weight PEG would act as a plasticizer in inserting its molecules between chain segments to screen out polymer/polymer interactions, and generating additional intermolecular space for small Brownian motion [43]. 

Our sorption and diffusion data indicated an apparently more complex behaviour of the blends. We did not observe a clear increase in CO2 solubihty coefficient in the membrane with increasing PEG content but an increase in the CO2 diffusivity. As no free volume measurements were performed in the present study, we can only suggest a similar mechanism of diffusivity enhancement by PEG additive in Pebax 1657 as that proposed by Yave et al. [43]. 

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