Fig. 5 Swelling property of poly-HEMA-CF.
Fig. 3 Compressive stress–strain curves from samples B, C, D and
G–T. Inset is Young’s modulus values obtained from the initial slope
of the stress–strain curves in relation to HEMA content.
Self polymerisation to produce a novel ion-conducting gel
has been demonstrated. Radical polymerisation is dominant in
the polymerisation mechanism. The HEMA was miscible with
CF for all ratios studied and no phase-separation was
observed after polymerisation. Different ratios of poly-HEMA
to CF contribute to different combinations of properties i.e.
conductivity, physical form, hardness, and swelling property.
High ionic conductivity gel (3 mS cmÀ1 at 25 1C) was achieved
with 80% (v/v) CF. These tuneable properties will allow
versatile use of the gels in biomedical applications and sensors.
The authors would like to acknowledge Mr George Lane for
viscosity measurement.
Notes and references
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Fig. 4 Conductivity of CF and poly-HEMA-CF samples C–G.
content is about 42%. Addition of crosslinker (sample G–T)
facilitates softer gel-formation at lower HEMA contents,
thus the Young’s modulus of this sample has deviated from
linearity (the break in the stress–strain curve for this sample
indicates internal rupture with increasing force).
3 P. Vidinha, N. M. T. Lourenc¸ o, C. Pinheiro, A. R. Bras,
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Conductivity of the materials was investigated using
impedance spectroscopy (Fig. 4). The conductivity of the pure
CF IL is around 0.01 S cmÀ1 at 25 1C. The conductivity
decreased with increasing HEMA content. Sample B was a
very hard gel and it was difficult to measure temperature-
dependent conductivity. However, the RT conductivity of this
material is around 3 Â 10À6 S cmÀ1
.
The sample G–T has slightly lower conductivity than
the corresponding polymer in liquid form (sample G).
Coincidentally, the conductivity of G–T was very similar to
the conductivity of sample F in Fig. 4. The aqueous swelling
property of the gels was studied (Fig. 5). The highest swelling
ratio (up to 288%) was observed for the sample D. Generally
the higher the CF content the higher the swelling percentage.
However, the CF dissolves slowly out of the gel over time and
thereby a decrease in weight is observed after a maximum
degree of swelling which is reached at about one week.
Various biomolecules such as cytochrome C, DNA, glucose
oxidase and horseradish peroxidase can be entrapped in the gel.
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biomolecules provide a promising alternative to conventional
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area are in progress and will be reported separately.
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ꢀc
This journal is The Royal Society of Chemistry 2009
Chem. Commun., 2009, 3041–3043 | 3043