Combined polymers with lateral

Polymerizations catalyzed with coordination compounds are becoming more important for obtaining polymers with special properties (linear and stereospecific). The first linear polyethylene polymer was prepared from a mixture of triethylaluminum and titanium tetrachloride (Ziegler catalyst) in the early 1950s. Later, Natta synthesized a stereoregular polypropylene with a Ziegler-type catalyst. These catalyst combinations are now called Zieglar-Natta catalysts. 

The steric frustrations have also been detected in LC polymers [66-68]. For example, the smectic A phase with a local two-dimensional lattice was found by Endres et al. [67] for combined main chain/side chain polymers containing no terminal dipoles, but with repeating units of laterally branched mesogens. A frustrated bilayer smectic phase was observed by Watanabe et al. [68] in main-chain polymers with two odd numbered spacers sufficiently differing in their length (Fig. 7). 

The first chiral combined lc polymers prepared for this purpose showed the desired cholesteric and chiral smectic C phases only at high temperatures (8) (the melting point was always above 100°C). By using lateral substituents (see Figure 3) it is possible however to suppress the melting temperature and to obtain polymers with a glass transition temperature of about room temperature, without losing the cholesteric and chiral smectic C phases (9). 

Raman-NSOM has been demonstrated for a variety of samples, including adsorbed dye molecules [358-361] and polymers [357]. By combining NSOM with SERS molecular spectroscopy and imaging with a lateral resolution of 70 nm is possible [337], Also IR-NSOM can be used for chemical imaging [338], Thin him analysis benefits from NSOM. The technique has been used to probe the excitonic transitions in J-aggregates of l,l -diethyl-2,2-cyanineiodide grown in poly(vinyl sulfate) thin films [290]. 

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