1. Introduction
A very fundamental principle in nature is close-packed solid state structures that minimize the ‘‘empty space’’ between atoms. Accordingly, porous structures form only under special conditions that are able to overcome the tendency of close packing. In most cases, porosity is created either by templating strategies or by the use of directional bonding effect (Kadib et al., 2011).
Chitosan is available in large quantity in nature, non-toxic and biocompatible. Its source, chitin, is the second most abundant organic resources next to cellulose. Chitosan have been mixed with several materials in order to obtain the porous surface membrane by varying the weight ratio of chitosan to the poly (acrylic acid) (De Lima et al., 2009) and poly (vinyl alcohol) (Jia et al., 2007) for examples. The surface morphology of the porous membranes normally has been investigated using scanning electron microscopy (SEM).
In this progress report field emission scanning electron microscopy (FESEM) was used to validate the porous surface of chitosan-acetate (CA) membranes.
2. Experimental (CANNOT BE SHARED: P & C matter)
The surface morphology CA membranes were analyzed using FESEM (Zeiss Supra 35VP).
3. Results and discussions
Figure 1 depicts the surface morphology images of CA at various weight (X-Z g) drying at room temperature. All CA show clear membranes without existing of any significant differences in Figure 1 (a-c). This show all CA membranes mixed homogenously with N under vigorously stirred using mixer. However, the presence of porosity membranes was not observed.
Meanwhile, the surface morphology images of CA at various weight (X-Z g) drying at M °C are shown in Figure 2. There is existence of irregular circular pores on CA membrane surface (Figure 2b) compared to dense CA membrane surface (Figure 2a). The average of pores sizes were in a range between 230-473 μm. Figure 2c reveals the surface morphology images of CA with non-porous and more wrinkled pattern surface compared to Figure 2b.
There is existence of significant differences between CA membranes with Y g of chitosan powder surface morphology dried at room temperature and elevated temperature (M °C). For CA with Y g chitosan powder dried at room temperature, the pore did not exist because the membrane hard to swell without temperature assistance. On the other hand, an elevated temperature (M °C) can increase the swelling of the CA hollow membrane matrix resulted in an increase in the free volume, frequency, and amplitude of the polymer chain motions (Tsai et al., 2008).
Besides that, another factor that contributed to the porous surface morphology of CA membranes is weight of chitosan powder. There is no existence of pores on CA membranes surface for sample with X and Z g of chitosan powder even treated at elevated temperature (M °C). When the amount of chitosan powder was X g, the CA membrane did not show any difference due to low content of chitosan powder. The low content of chitosan would complicate the construction of pores on CA membrane surface even treated at M °C (Jia et al., 2007). Nonetheless, for CA membrane with Z g, the pores cannot be existed attributed to the highly content of chitosan powder. In fact physically of membrane was very rigid membrane.
4. Conclusion
The surface morphology of CA membrane have been investigated by varied amount of chitosan weight from X to Z g and varied temperature of drying process at room temperature and M °C. CA membrane with X g chitosan powder and dried at M °C had an optimum surface morphology with porous surface and size of pores were in a range between 230-473 μm.
5. Next Progress Report
The surface morphology of chitosan-acetate membranes by different techniques approaches.
References
De Lima, M. S. P., Freire, M. S., Fonseca, J. L. C., Pereira, M. R. Chitosan membranes modified by contact with poly(acrylic acid). Carbohydrate Research 344 (2009) 1709-1715.
Jia, Y.-T., Gong, J., Gu, X.-H., Kim, H.-Y., Dong, J., Shen, X.-Y. Fabrication and characterization of poly (vinyl alcohol)/chitosan blend nanofibers produced by electrospinning method. Carbohydrate Polymers 67 (2007) 403-409.
Kadib, A. E., Molvinger, K., Cacciaguerra, T., Bousmina, M., Brunel, D. Chitosan templated synthesis of porous metal oxide microspheres with filamentary nanostructures. Microporous and Mesoporous Materials 142 (2011) 301-307.
Tsai, H.-A., Chen, W.-H., Kuo, C.-Y., Lee, K.-R., Lai, J.-Y. Study on the pervaporation performance and long-term stability of aqueous iso-propanol solution through chitosan/polyacrylonitrile hollow fiber membrane. Journal of Membrane Science 309 (2008) 146-155.
Figure 1: FESEM image of chitosan-acetate membranes at various weights of (a) X g, (b) Y g and (c) Z g drying at room temperature.
Figure 2: FESEM image of chitosan-acetate membranes at various weights of (a) X g, (b) Y g and (c) Z g drying at M °C.
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