A new class of chiral polyurethanes containing amido linkages in the polymer backbone have been synthesized by reacting toluene diisocyanate with isosorbide (IS) chiral moiety and the chromophores [N,N 0 -ethane-1,2-diyl bis(6-hydroxy hexanamide), N,N 0 -butane-1,4-diyl bis(6-hydroxy hexanamide) and N,N 0 -hexane-1,6-diyl bis (6-hydroxy hexanamide)]. The corresponding chromophores were obtained by the aminolysis of e-caprolactone by using the diamines, diaminoethane, diaminobutane and diaminohexane, respectively. All the polymers were synthesized according to the symmetry conditions so as to obtain the non-centrosymmetric environment. A series of polyurethanes were synthesized by varying the chiralchromophore composition. The polyurethanes developed were characterized by optical and thermal methods.
To understand better the impact of donor-acceptor substitution on the properties of linearly -conjugated compounds, we performed a computational study on a series of variably substituted transpolyacetylenes, polyynes, and polythiophenes. The focus of this work is on how rapidly the impact of a given substituent or a given combination of substituents vanishes along the -conjugated chain. The response of the structural (bond-length alternation, rotational barrier) and molecular properties ((hyper)polarizability, chemical shift) to substitution is analyzed using different protocols, including a superposition model for the evaluation of the cooperative effect of substituents in homo-and heterosubstituted oligomers. With the exception of the (hyper)polarizability, the impact of donor-acceptor substitution is found to vanish following an exponential. The rate of decay of the substituent impact is found to be characteristic for each backbone, whereas the choice of substituent determines the absolute value of the respective property. The combination of substituents is shown to determine whether the substituent cooperative effect on a property is of an enhancing or damping nature. The rate of decay of the cooperative effect on most properties, including the (hyper)polarizability, is also found to follow an exponential law. With the exception of the (hyper-)polarizability, the impact of donor-acceptor substitution is found to vanish following an exponential. The rate of decay of the substituent impact is found to be characteristic for each backbone, whereas the choice of substituent determines the absolute value of the respective property. The combination of substituents is shown to lead whether the substituent cooperative effect on a property is of enhancing or damping nature. The rate of decay of the cooperative effect on most properties, including the (hyper-)polarizability, is also found to follow an exponential law.
The toluene diisocyanate based optically active chiral polyurethanes were synthesized according to the symmetry conditions. The noncentrosymmetric (both charge asymmetry and spatial asymmetry) environment were attained by the incorporation of the chiral units (diethyl-(2R,3R)(þ)-tartrate) and donor-acceptor building blocks in the main chain which induce a helical conformation in the macromolecular chain. A series of optically active polyurethanes containing chiral linkages in the polymer back bone have been synthesized by using DBTDL catalyst by incorporating the amido diols which were obtained by the aminolysis of e-caprolactone by using the diamines, diaminoethane, diaminobutane, and diaminohexane respectively. The effect of incorporation of the chiral molecule diethyl-(2R,3R)(þ)-tartrate on the properties of polyurethanes was studied by changing the chromophores and also by varying the chiral-chromophore composition. Various properties of polyurethanes were investigated by UV, Fluorescence, TG/DTA, XRD, polarimetric techniques, Kurtz-Perry powder techniques, etc.
Extensive theoretical calculation on the effects of spacer length enhancement on the second-order NLO properties of twin donor acceptor molecules having two amide units bridged by the CH 2 spacers was performed. The role of such aliphatic bridges on the Donor-Acceptor groups was computed by ZINDO/CV quantum chemical formalism. The odd-even effects were observed in twin donor acceptor systems (with two aliphatic units) linked by an alkyl spacer of varying length from n = 1 to n = 12. The system considered for the present study was N,N′-alkane-(1, n) diyl bis-4-hydroxy hexanamides. For an odd number of CH 2 spacers, the β value was an order of magnitude higher than that for the even number of CH 2 spacers. The origin for such oscillation is attributed to the similar oscillations in the dipole moment difference between the ground state and the dipole allowed state and to some extent on the variation in the oscillator strength.
The oxidation and subsequent oligo‐ or polymerization of aniline or the N‐C‐para coupled aniline dimer p‐aminodiphenylamine (N‐phenyl‐1,4‐phenylenediamine) with H2O2‐dependent heme peroxidases in aqueous medium at pH = 4.3 is strongly influenced in a positive way by the presence of anionic polymers, micelles or vesicles as soft ‘templates’ (macromolecular or polymolecular additives), to yield products which resemble the emeraldine salt form of polyaniline (PANI‐ES). The positive effect the templates exert on the reaction mainly originates from interactions between the templates and the monomers, reaction intermediates and products, whereby the reaction occurs localized in the vicinity of the templates, suppressing undesired side reactions. As shown in the present work, the templates may even play an additional role, depending on the type of catalyst. Through interactions between the heme protein cytochrome c and anionic vesicles, cytochrome c gains increased peroxidase activity. In this way, the templates not only serve for hosting the oxidation and oligo‐ or polymerization reactions for obtaining PANI‐ES type products, but also simultaneously activate the catalyst in order to trigger the reaction.
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