syndiotactic polymers, the 5-membered ring hydrogen-bonded
polymer 1 makes calcite crystals, whereas the 6-membered ring
hydrogen-bonded polymer, 2iso, and the 7-membered one, 3,
form vaterite crystals. These differences are due to the strength
of the hydrogen bond. Polymer ligand 1 forms weak intra-side-
The formation of weak hydrogen bonds in the polymer ligand
does not affect the CaCO3 crystal growth; however, strong
hydrogen bonds restrict crystal growth. Five-membered-ring
…
O hydrogen-
intra-side-chain and intermolecularly NH
bonded polymer ligand–CaCO3 composites form calcite
…
chain NH O hydrogen bonds just as its model ligand, 4;
crystals due to the formation of the weak hydrogen
…
however, polymer ligands 2iso and 3 form strong hydrogen
bond, while 6- or 7-membered-ring intra-side-chain NH
O
bonds similar to the models, 5 and 6, respectively. Formation
…
hydrogen-bonded polymer ligand–CaCO3 composites form
vaterite crystals because of the formation of the strong
hydrogen bond. In conclusion, various CaCO3 morphologies
can be regulated by slightly changing the strength of the
hydrogen bonds in a polymer ligand.
of weak NH O hydrogen bonds in a polymer ligand results in
the relatively low stabilization of Ca–O bonds and restriction
of CaCO3 crystal growth, and the obtained CaCO3 crystal is
the most stable polymorph, calcite, without any restriction
by the ligands. Actually, poly(acrylate) ligand without the
hydrogen bond forms the most stable polymorph, calcite.5 In
Acknowledgements
…
contrast, strong NH O hydrogen-bonded polymer ligands
We acknowledge the support of this work by a Research
Fellowship of the 21st Century Center Of Excellence Program
‘‘Integrated EcoChemistry’’ for Young Scientists [for
K. Takahashi, 2002–2004] and a Grant-in-Aid for Scientific
Research (A) (No. 12304040) from the Ministry of Education,
Culture, Science, Sports, and Technology, Japan.
stabilize one of the metastable polymorphs, vaterite, which is
rarely found in nature.27,28 Thus, strong intra-side-chain
hydrogen-bonded polymer ligands, such as 2iso
…
O
NH
and 3, restrict CaCO3 crystal growth to obtain vaterite
…
crystals, although a weak intra-side-chain NH O hydrogen-
bonded ligand, such as 1, yields calcite crystals without any
restricting crystal growth.
Kazuyuki Takahashi,a Atsuko Kobayashi,b Mototsugu Doi,a
Seiji Adachi,a Takahisa Taguchi,b Taka-aki Okamura,a
Hitoshi Yamamotoa and Norikazu Ueyama*a
Relationships between polymer tacticities and morphologies of
CaCO3 composites
aDepartment of Macromolecular Science, Graduate School of Science,
Osaka University, Toyonaka, Osaka, 560-0043, Japan.
E-mail: ueyama@chem.sci.osaka-u.ac.jp; Fax: +81-6-6850-5474;
Tel: +81-6-6850-5449
In the present study, the syndiotactic polymer ligand, 2, yields
calcite crystals, although the isotactic-rich polymer ligand, 2iso
forms vaterite crystals. Polymer ligand 2iso forms strong
,
bSpecial Section of Human Life Technology, National Institute of AIST
Kansai, Ikeda, Osaka, 563-8577, Japan
intramolecular hydrogen bonds similar to its model, 5, because
1
the degree of the downfield shift of the amide NH H NMR
signal of 2iso from the COOH to the COO2 forms is similar to
that of 5 in Me2SO-d6. However, 2 does not exhibit a similar
downfield shift. The hydrogen bond in 2 is weak and formed
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Novel poly(methacryloylaminocarboxylate) ligands were
synthesized as model ligands of the acidic peptides in
CaCO3 biominerals. These polymer ligands form 5-, 6-, or
…
7-membered-ring intra-side-chain or intermolecular NH
O
hydrogen bonds between the carboxylate oxyanion and the
…
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2186 | J. Mater. Chem., 2005, 15, 2178–2187
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