This Account describes how stereochemical ideas focused on chirality have been directed widely across polymer science allowing experiments that could not be conducted on small molecules and leading to new insights and new kinds of materials. In one approach, a helical polymer was studied, and it was discovered how the chiral information necessary to choose helical sense is greatly amplified. In another approach, the racemization kinetics of atropisomers were used to characterize the restrictions to motion associated with a polyelectrolyte that forms clusters around hydrophobic groups in water and in an entirely different system, the glassy state formed by polymers.

A series of 6-substituted indolinobenzospiropyrans were resolved by chiral stationary phase HPLC and rate constants k rac for their thermal racemization were measured by circular dichroism spectropolarimetry at 60 °C in three different solvents: cyclohexane, 90:10 hexanes/2-propanol, and acetonitrile. Results show that the spiropyrans undergo thermal racemization most rapidly in acetonitrile, with k rac values ranging from 9.3 × 10 -5 to >5.0 × 10 -3 s -1 , and least rapidly in cyclohexane, with k rac values ranging from 6.8 × 10 -6 to 4.6 × 10 -4 s -1 . V-shaped plots of log k rac vs Hammett σ p constants in 90:10 hexanes/2-propanol and acetonitrile suggest that thermal racemization of the 6-substituted spiropyrans proceed via two competing mechanisms: a polar mechanism involving heterolytic C(sp 3 )-O bond cleavage with anchimeric assistance from the indoline nitrogen and a nonpolar electrocyclic ring opening mechanism with no anchimeric assistance from the indoline nitrogen. The outcome of this competition appears to be strongly influenced by solvent polarity: plots of log k rac vs σ p and σin cyclohexane show a near-linear correlation with negative slope, which is consistent with the nonpolar mechanism. However, an increase in solvent polarity results in a shift toward a linear correlation with positive slope, which is consistent with the polar mechanism.

The synthesis of Ru2(μ-O2CR)4(μ´-O2CR) (1), R = -CH2(CH2)6CH=CH(CH2)5CH3, has been achieved and characterization using elemental analysis and FTIR and UV-Vis spectroscopies undertaken. Strong evidence for a hexagonal discotic mesophase has been found using differential scanning calorimetry, variable-temperature polarizing optical microscopy, and X-ray powder diffraction. A solid to liquid crystal transition was found upon heating at 128°C and the mesophase is found to persist to room temperature upon cooling from 150°C. This is the first report of room temperature mesomorphism in a mixed-valent metallomesogen. Key words: ruthenium carboxylate, liquid crystal, metallomesogen, mixed valence, polymer.

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The diphenylmethylenecyclohexane, 2, and the substituted 2-methyleneadamantanes, 3-7, have been prepared. The radical cation of each was generated by photochemical oxidation using 1,4-dicyanobenzene as the sensitizer, and their reactivity was examined in methanol-acetonitrile mixtures with added tetraethylammonium cyanide. Although compound 2 reacted only by tautomerization, the other compounds all gave addition products. For the monoaryl alkenes 3, 4, and 5, comparable yields of both methanol and HCN addition products were obtained, resulting from nucleophilic attack at either end of the alkene radical cation. For the diphenylalkenes 6 and 7, the regioselectivity favored nucleophilic attack at the adamantyl carbon, and the addition products were predominantly those of HCN addition. For the 5-methoxy compound 7, HCN addition was facially selective with a syn:anti ratio of 58:42.Key words: methyleneadamantanes, facial selectivity, radical cations.

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