We have developed a metal free synthetic pathway to homopolypeptide rod-coil block copolymers. The concept was proven for the synthesis of poly(benzyl-Lglutamate-b-styrene). A dual initiator containing a primary amine and a nitroxide group was used in a macroinitiation approach with high initiation efficiency. Good control over the molecular weight in the ring opening polymerization of benzyl-L-glutamate N-carboxyanhydride was obtained in DMF at 0 8C yielding poly(benzyl-L-glutamates) with low polydispersities around 1.1. The almost quantitative incorporation of the dual initiator was confirmed by MALDI-ToF analysis. Macroinitiation of styrene by nitroxide-mediated controlled radical polymerization yielded the block copolymer with high structural control. The diblock structure was confirmed by molecular weight increase upon macroinitiation by size exclusion chromatography and retention time comparison with homopolymers using gradient polymer elution chromatography. Both polymerizations were also successfully conducted in one pot without intermediate isolation owing to the high compatibility of both polymerization techniques.

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Phase diagrams of blends of poly(methylphenylsiloxane) in short PMPS and two low molecular weight liquid crystals (4-cyano-4Ј-n-pentyl-biphenyl and an eutectic mixture of paraphenylenes) are reported. Two polymers with very different weight-average molar masses are considered in an evaluation of the loss of miscibility resulting from a known increase in the weight-average molar mass. The experimental diagrams have been constructed via polarized optical microscopy and are rationalized in terms of the Flory-Huggins theory of isotropic mixtures and the Maier-Saupe theory of nematic order. The results show a good agreement between the theory and experiments and reveal a remarkable enhancement of miscibility with respect to similar systems involving poly(dimethylsiloxane). Variations of the interaction parameter with the temperature are compared for different systems of polysiloxanes. The effects of the nature of the liquid crystal and the polymer molar mass on the parameter are evaluated.