The critical gelation concentration (cgc) was estimated by an inverse
fluid method which was carried out using a ꢀ 14 mm sample tube. The
gel-to-sol transition temperature was also estimated by an inverse fluid
method to be 53, 37, 32, 30, 41 and 39 ЊC in G12-vinyl, copoly-G12 (n/m =
2), copoly-G12 (n/m = 4), copoly-G12 (n/m = 12), t-G12 (n = 10) and t-G12
(n = 25), respectively.
Transmission and scanning electron microscopic (TEM and SEM)
observations were carried out with JEOL JEM-2000FX and JSM-
8310LV, respectively. Circular dichloism (CD) spectroscopy was carried
out with JASCO J-725.
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Fig. 2 CD spectra of a cyclohexane–ethanol (9 : 1) gels with G12-vinyl
(5 mM) and copoly-G12 (5 unit-mM) at 15 ЊC. Copoly-G12 (n/m = 12) gel
provides a similar CD specrum to that of copoly-G12 (n/m = 4).
panied by disappearance of the cotton effect around 260 nm
indicating disappearance of the vinyl group.
When a cyclohexane–ethanol (9 : 1) gel with copoly-G12 was
heated from 15 to 60 ЊC, the gel state collapsed into a sol state
similarly observed in G12-vinyl.‡ However, the CD pattern was
maintained even at 60 ЊC while the strength reduced to about
70%. These results indicate that highly-oriented aggregates with
chiral order exist even in a sol state, but the aggregates are not
well-developed to maintain a gel-formation network.
In conclusion, we have prepared a new class of -glutamide-
derived organogelators with polymeric groups and a molecular
design which facilitates the addition of specific functionality.
The copolymerization of a key unit with MA disturbs their
gelation ability slightly, but the resultant gels include unique
multi-cellular structures and the molecular orientation in the
aggregates is more stabilized than the original organogelators.
We expect this new class to expand possible applications of
organogelators.
Acknowledgements
This research was supported in part by a Grant-in-Aid for
Scientific Research from the Ministry of Education, Science,
Sports, and Culture of Japan.
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Notes and references
‡ G12-H, G12-a and G12-b were obtained by previously reported
methods.8,11,22 G12-H: mp 118 ЊC. Anal. calc. for C29H59N3O2: C, 72.3; H,
12.3; N, 8.7. Found: C, 72.3; H, 12.4; N, 8.7%. G12-a: mp 178 ЊC. Anal.
calc. for C40H70N4O6: C, 69.9; H, 10.3; N, 8.2. Found: C, 69.6; H, 10.2;
N, 7.9%. G12-b: mp 144 ЊC. Anal. calc. for C32H64N4O3: C, 69.5; H, 11.7;
N, 10.1. Found: C, 68.4; H, 11.4; N, 9.5%. G12-SH was derived from
G12-b by coupling with γ-thiobutyrolactone: mp 218 ЊC. Anal. calc. for
C36H70N4O4S: C, 60.0; H, 10.8; N, 8.6. Found: C, 64.3; H, 10.5; N, 8.2%.
G12-vinyl was derived from G12-b by coupling with vinyl benzoyl chlor-
ide: mp 199 ЊC. Anal. calc. for C39H70N4O4: C, 72.0; H, 10.5; N, 8.2.
Found: C, 72.0; H, 10.3; N, 8.0%.
The telomerization and polymerization were carried out in tetra-
hydrofuran, initiated with AIBN. The resultant telomers (t-G12) and
copolymers (copoly-G12) were obtained from addition of methanol. 1H-
NMR did not show any proton signal belonging to a vinyl group. The
average degree of polymerisation was determined by 1H-NMR spectro-
scopy (400 MHz, CDCl3) with the proton ratios at the chiral center of
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Jpn., 1984, 57, 3253.
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Biopolym., 1973, 12, 2423; (b) H. Yamamoto, A. Nakazawa and
T. Hayakawa, J. Polym. Sci., Polym. Lett. Ed., 1983, 21, 131.
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(b) M. Shibata, H. Ihara and C. Hirayama, Polymer, 1993, 34, 1103.
G
12 (δ 4.35, s, CH) and the methoxy group of MA (δ 3.65, s, OCH3).
O r g . B i o m o l . C h e m . , 2 0 0 3 , 1, 3 0 0 4 – 3 0 0 6
3006