Synthesis and properties of new chiral donor-embedded polybinaphthalenes for nonlinear optical applications

Eight new chiral, chromophore-functionalized donor-embedded polybinaphthalenes were prepared and characterized for their (nonlinear) optical properties. The polymers were prepared by direct polymerization using a Stille coupling reaction between a chiral bis(trimethyltin) binaphthalene derivative and diiodo-functionalized chromophores. The use of diiodo-functionalized instead of dibromo-functionalized chromophores resulted in a significant increase of molecular weight, as demonstrated by end group analysis, GPC, and MALDI-TOF experiments. The reaction conditions allowed the use of a great variety of chromophores with different DpiA structures. The typical treelike macromolecular architecture of the polymers is reflected in the behavior of the glass transition temperature and, more clearly, in the nonlinear optical properties. The nonlinear optical response shows a continuous, linear increase in function of chromophore concentration, indicating that the dipolar interactions between the chromophores are eliminated. Moreover, chiral contributions to the nonlinear optical response were observed and mounted 14% of the highest achiral contribution.