5430
T. Hagiwara et al. / Polymer 52 (2011) 5426e5430
Table 1
of dimeric byproduct is decreased by lowering the reaction
temperature. The poly[2]catenane had higher solubility in some
solvents than did non-catenated polymer having the same
primary structure. Our final goal of extracting the effect of flexible
[2]catenane units on the macroscopic properties of such polymer
molecules remains to be seen by, for example, measuring thermal
properties.
Composition of polymeric product obtained by poly[2]catenane synthesis.
Product
Total yield (%)
Composition (% in total
product)a
Polymer
Cyclic dimer
3 (r.t.)
88
92
80
80
85
63
18
11
37
3 (0 ꢁC)
Ester-linked poly[2]catenane [6b]
a
Calculated from GPC peak area. Small amount of monomeric [2]catenane was
Acknowledgments
contained.
This research was supported in part by a Nihon University
Individual Research Grant for 2007. We thank Prof. Hiizu Iwamura
at the Graduate School of Nihon University for valuable advice
given during the preparation of this manuscript.
(bent conformer in Scheme 1) of the interlocked ring that allows
both ends to approach for intramolecular 1,3-dipolar reaction.
To evaluate the effect of the catenane structure on polymer
properties, polymer containing 2:2 macrocycle instead of [2]cate-
nane was synthesized. Comparing the 2:2 macrocycle and [2]cate-
nane, it is seen that although the primary structures are the same,
the topological structures differ. Therefore, it is presumed that the
different properties of poly[2]catenane and poly 2:2 macrocycle can
be assigned to characteristic properties of the catenane structure.
The polymer-like product was obtained by Click reaction of
diazido 2:2 macrocycle and 2. The absence of IR absorption due to
the azido group and the ethynyl group shows that the polymeri-
zation reaction proceeded, but the molecular weight could not
be measured by GPC because of the very low solubility of the
product. Since the product was insoluble in any solvent, further
purification processes such as reprecipitation, NMR spectroscopy,
or measurements of mechanical properties could not be performed.
However, the difference in solubility between the poly 2:2 mac-
rocycle and the poly[2]catenane (soluble in DMF or DMSO) is
attributable to the difference in their topological structures. It is
considered that the insolubility of poly 2:2 macrocycle is due to
intermolecular hydrogen bonding of the amide groups in the
macrocycle structure, whereas poly[2]catenane having intra-
molecular hydrogen bonding (between two rings) has fairly high
solubility.
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