Biomedical Engineering Reference
In-Depth Information
Chapter 26
role of Water in dielectric Properties of starch
membranes
Perumal Ramasamy
iNtroduCtioN
There are different kinds of polarization namely electronic, atomic, orientational, and
ionic polarization. These polarizations vary in their frequencies. The behavior of the
orientation polarization in time-dependent fields can, as a good approximation, be
characterized with respect to their relaxation times. This behavior is generally denoted
as
dielectric relaxation.
Dielectric spectroscopy can be used to probe the dynamics of
local motions that are of dimensions less than 1 nm, segmental motions that are of di-
mensions 1-10 nm and dynamics of chain contour that are of dimension ~ 10-100 nm.
Some of the useful properties that can be measured using dielectric measurements are:
(i) Dielectric constant, (ii) Loss factor, (iii) Dissipation factor, (iv) Relaxation time,
(v) Relaxation strength, and (vi) Conductivity. Dielectric spectroscopy can be used to
study a wide variety of materials such as water, glass forming liquids, clusters, ice and
porous materials and colloids. It can be used to study biological materials like lipids,
proteins, cells, DNA, RNA, and tissues.
Biological materials have the advantage of being environmentally friendly materi-
als. Dielectric relaxation spectroscopy (DRS) has been found to be a very useful tool
in studying the polymer dynamics of polysaccharides (Butler and Cameron, 2000;
Einfiled et al., 2001, 2003;.Majumder et al., 2004; Moates et al., 2000; Smits et al.,
2001; Viciosa et al., 2004). In this chapter the usefulness of dielectric spectroscopy
for understanding the dynamics of molecules in starch samples containing varying
water contents will be discussed. Starch is emerging as a useful biomaterial in the
field of energy science. It is an abundantly available biomaterial that is used for energy
storage in plants. Application of starch as membranes for solid state batteries would
greatly help the environment as it is a biodegradable material. Making of membranes
usually involves solvents like water. Water also acts as a plasticizer. The incorpora-
tion of water in membranes can affect the transport of ions in the membranes. It is
therefore essential to learn about the role of water in membranes that contain water.
Also, temperature will affect the transport of charges in the membranes. Hence, in this
chapter, the modifications in the dielectric properties of starch films as a function of
temperature and water content will be discussed.
materials aNd methods
Amioca starch (corn starch) was used for this study. Samples were made by hot press-
ing starch between two brass plates of diameter 30 mm at 1900 bar. The thickness of
Search WWH ::
Custom Search