I. Introduction 4013 II. Helical Polymers 4015 A. Polyolefins 4015 B. Polymethacrylate and Related Polymers 4016 1. Poly(triphenylmethyl methacrylate) 4016 2. Poly(triphenylmethyl methacrylate) Analogues: Anionic Polymerization 4017 3. Poly(triphenylmethyl methacrylate) Analogues: Free-Radical Polymerization 4018 4. Polymers of Other Acrylic Monomers 4022 C. Miscellaneous Vinyl Polymers 4023 D. Polyaldehydes 4023 1. Polychloral and Related Polymers 4023 2. Other Polyaldehydes 4024 E. Polyisocyanides 4024 1. Polymers of Monoisocyanides 4024 2. Polymers of Diisocyanides 4025 F. Polyisocyanates and Related Polymers 4025 1. Polyisocyanates 4025 2. Polycarbodiimides 4027 G. Polyacetylene Derivatives and Related Polymers 4027 1. Polyacetylene Derivatives 4027 2. Polyphosphazene 4029 H. Poly(aryleneethynylene)s 4029 I. Polyarylenes 4030 J. Si-Containing Polymers 4031 1. Polysilanes 4031 2. Polysiloxane 4032 K. Other Types of Polymers 4032 1. Miscellaneous Examples 4032 2. Mimics and Analogues of Biopolymers 4033 III. Helical Polymeric Complexes and Aggregates 4033 A. Helicates 4033 B. Helical Aggregates 4033 IV. Summary and Outlook 4034 V. Acknowledgments 4034 VI. References 4034

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Dibenzofulvene (DBF) was polymerized using anionic initiators to afford a vinyl polymer. Oligo(DBF)s having from two to eight side-chain fluorene moieties bearing different chain-terminal groups were isolated by preparative size-exclusion chromatography. The structures of the isolated oligomers were revealed by single-crystal X-ray and (1)H NMR analyses. Both in solution and in crystal, the in-chain fluorene moieties stacked on top of each other, while the terminal conformation varied depending on the terminal group. These conformational characteristics were supported by molecular mechanics and dynamics calculations. The oligomers and polymers indicated hypochromism and red shift in UV absorption spectra and exclusive excimer emission in fluorescence spectra. In addition, reduced oxidation potentials were observed for the oligomers in electrochemical analyses, which suggests charge delocalization over the pi-stacked electron systems. The photophysical and electrochemical effects increased with the chain length of the oligomers and leveled off around the chain length of an oligomer consisting of five fluorene units.

Asymmetric oligomerization of triphenylmethyl methacrylate (TrMA) was carried out with complexes of 9-fluorenyllithium and chiral ligands in toluene at -78 "C, and the oligomers obtained were converted into methyl esters. The resulting oligo(methy1 methacry1ate)s were first fractionated by gel permeation chromatography in terms of degree of polymerization and further separated into diastereomers and optical isomers by high-performance liquid chromatography. The distribution of oligomers and the ratio of isomers in each oligomer gave important information on the mechanism of the asymmetric (helix sense selective) polymerization of TrMA. The reactivity of each oligomer anion depended greatly on its degree of polymerization and stereostructure. The oligomer anions whose asymmetric centers have R configuration in the system with the complex of 9-fluorenyllithium and (-)-sparteine and those of S configuration in the systems with (+)-(2S,3S)-2,3-dimethoxy-1,4-bis(dimethy1amino)butane and (+)-(S)-1-(2-pyrrolidinyImethyl)pyrrolidine as chiral ligands predominantly propagated to a one-handed helical polymer. A stable helix starts at degree of polymerization 9 in the former system and at degree of polymerization 7 in the latter two systems. One helix turn seems to consist of three or four monomeric units. The main chain of the resulting polymer in the former system possessed RRR---absolute configuration and that in the latter systems SSS---, though both polymers are considered to be of the same helicity, P or M . These results indicate that the helicity of the polymer is not governed by the configuration of the main chain but by the chirality of the ligands.