Scheme 129

the length of the aminoalkanes, the apparent stiffness of the polymers on the surface could be influenced.

Polyisocyanide 50 with a stable induced helix in water (see Section 12.3, Chapter 11 and Fig. 11.16) [62, 63], was found to be able to induce helicity in another oppositely charged polyelectrolyte based on a polyacetylene [105]. The inter polymer complexation proved to be dependent on both the pH and the salt concentration. This helix replication strategy opens numerous possibilities for the growth of ordered helical assemblies.

Much research has been focused on the use of polyisocyanides as scaffolds for the creation of well defined molecular wires with special magnetic, optical or electronic properties.

Polyisocyanides 51 functionalized with crown ethers of different sizes were reported to yield architectures containing 4 arrays of cofacially stacked rings connected to the polymer backbone (Scheme 12.10) [56, 106]. The polymers appeared to be able to function as ion channels when incorporated within bilayer membranes.

Persoons and coworkers studied polyisocyanide 52 and related compounds, which are functionalized with non-linear optically active (NLO) side groups [107-111]. In solution a first hyperpolarizability exceeding 5000 x 10"30 electrostatic units was measured. Electric field-induced second-harmonic generation measurements revealed a larger non-linear response for the polymer than for the monomer. The second order non-linear response might be further optimized in structures with a smaller angle (60° for this structure) between the polymer backbone and the chromophores [107]. Langmuir-Blodgett films of polymer 52, showed stable second harmonic generation without the need of poling [110]. This observed NLO effect is thought to originate from the highly defined orientation of the side chains obtained at the air-water interface.

Polyisocyanides 53 and 54 were designed as macromolecular ferromagnets [112], however, no evidence for ferromagnetism or any other short-range ordering among the unpaired spins was observed.

A chiral redox responsive polyisocyanide bearing ferrocenyl groups (55) has been reported by Takahashi and coworkers (Scheme 12.10) [113]. Redox cycles of this polymer proved to be completely reversible. CD measurements revealed that

55 56

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