Since most important biological events occur in aqueous solution where biopolymers such as proteins and DNA form a characteristic helical conformation, significant attention has recently been paid to developing artificial polymers and oligomers that adopt a onehanded helical conformation in aqueous solution, particularly in light of emerging applications in the biomedical and materials science fields and also for mimicking protein folding. 1 However, most synthetic helical polymers and oligomers prepared so far are optically active due to their helicity in organic solvents. 2 We recently reported that macromolecular helicity can be induced on a stereoregular, cis-transoidal poly((4-carboxyphenyl)acetylene) (poly-1-H) by an optically active amine, 3 and this helicity can be "memorized" when the amine is replaced by various achiral amines in organic solvents. 4 The poly-1-H was prepared by the polymerization of (4-(triphenylmethoxycarbonyl)phenyl)acetylene with a rhodium (Rh) complex, ([Rh(nbd)-Cl] 2 : nbd ) norbornadiene), in tetrahydrofuran (THF), followed by hydrolysis of the ester groups. 3 We now show that this polymer can be directly prepared by the homogeneous, stereospecific polymerization of (4-carboxyphenyl)acetylene (1-H) in water in the absence of surfactants and any organic solvents, using watersoluble rhodium complexes, such as [Rh(cod) 2 ]BF 4 (cod ) cyclooctadiene), [Rh(nbd) 2 ]ClO 4 , and [Rh(nbd)(tos)-(H 2 O)] (tos ) p-toluenesulfonate) 5 in the presence of bases such as alkaline hydroxides and amines (Scheme 1). Furthermore, the macromolecular helicity can be induced on the polymer in water as a result of noncovalent, electrostatic interactions with natural, free amino acids; the complexes showed a characteristic induced circular dichroism (ICD) in the UV-vis region. Accordingly, the sequence of events including the synthesis of a polymer and the helicity induction on the polymer is entirely possible in water, which is an extremely important medium for organic reactions, polymerizations, and processes, because water is costeffective, safe, and environment-friendly; the use of wetorganic solvents or aqueous biphasic systems is still considered ecologically harmful. 6,7 Table 1 summarizes the polymerization results of 1-H with water-soluble Rh complexes. The Rh-based complexes effectively polymerize phenylacetylenes to afford high molecular weight, cis-transoidal polymers, and well-defined Rh-based initiators can induce living polymerization in organic solvents. 8,9 For these polymerizations, acetic acid is used to remove the active Rh moiety from the propagating polymer end to terminate the polymerization. 8,9 This indicates that acetylenes bearing a carboxy group may not be directly polymerized by the Rh-based complexes. 10,11 However, the use of bases brought about the stereospecific polymerization of 1-H in water. The polymerization was rapid and homogeneous in the presence of bases, producing yelloworange fibrous, high molecular weight polymers in high yields (Table 1), although the molecul...

Rodlike polymers with precisely defined architectures are ideal building blocks for self-assembled structures leading to novel nanometer-scale devices. We found that the living polymerization of a single isocyanide enantiomer bearing an l-alanine pendant with a long n-decyl chain simultaneously produced diastereomeric right- and left-handed helices with different molecular weights and narrow molecular weight distributions. Each single-handed, rodlike helical polymer with a controlled length and handedness isolated by a facile solvent fractionation method with acetone self-assembled to form well-defined two- and three-dimensional smectic ordering on the nanometer scale on a substrate and in a liquid crystalline state as evidenced by direct atomic force microscopic observations and X-ray diffraction measurements, respectively.

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