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functionalities and the different network topology, the absolute values of
x
SC
and
x
MC
should not be directly compared.
Each of the samples was cut into two parts. One part was used for the calorimetric
investigations, while the other part was doped with an amount (~8-10%) of
deuterated probe mesogens that was high enough to render the LCEs
2
H-NMR-
sensitive, and at the same time low enough so that it did not alter the intrinsic PN-N
transition behaviour.
a
D
2
-8CB has been used for side-chain LCEs, and a deuterated
variation of the original main-chain mesogen has been used for main-chain LCEs.
After being prepared in the same way as described in Sect.
3.1
, these samples were
used for
2
H-NMR investigations.
The heat-capacity temperature profiles obtained via the ac and relaxation runs
for low-, mid- and high-crosslinking densities of side-chain (V6-crosslinked) and
between the ac and relaxation runs for lower crosslinking densities, which is
evidence of the presence of latent heat along a few-Kelvin-wide coexistence region
of the paranematic and nematic phases. The mismatch of the data obtained by the
two modes gradually decreases for higher concentrations and finally vanishes
within the experimental error for the
x
SC
¼
0.12 samples.
At these high crosslinking densities, a very broad and suppressed
C
p
anomaly and
0.15 and
x
MC
¼
a
b
2.5
x
MC
= 0.120
x
SC
= 0.150
1.0
2.0
x
MC
= 0.060
1.5
x
SC
= 0.105
0.5
1.0
N
PN
PN
N
x
MC
= 0.025
0.5
x
SC
= 0.050
0.0
0.0
-20
-10
0
10
20
-20
-10
0
T
-
T
PN-N
(K)
10
20
T
-
T
PN-N
(K)
Fig. 18 Selected heat-capacity temperature profiles obtained by ac and relaxation runs for (a) side-
chain LCEs (V6-crosslinked) and (b) main-chain LCEs (HD5-crosslinked) with various concen-
trations of V6 crosslinkers. The
solid symbols
stand for the ac and the
open symbols
for the
relaxation runs. The different datasets have been shifted along the
y
-axis (
C
p
) for clarity. Data
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