Facile Polycyclotrimerization of Simple Arylene Bipropiolates: A Metal-Free, Regioselective Route to Functional Hyperbranched Polymers with High Optical Transparency, Tunable Refractive Index, Low Chromatic Aberration, and Photoresponsive Patternability

A facile synthetic route to functional hyperbranched polymers is developed. Arylene bipropiolates (HC C-CO2-Ar-O2C-C CH; 1-4) are readily prepared from a one-step esterification reaction between commercially available propiolic acid and arylene diols. Polycyclotrimerizations of 1-4 proceed regioselectively in reflux dimethylformamide (DMF), giving hyperbranched poly[1,3,5-tri(aroxy-carbonyl)phenylene]s (hb-P1-hb-P4) of high molecular weights (M-w up to similar to 8.3 x 10(5)) in high yields (up to 82%). The polymers possess perfect 1,3,5-regiostructures and high degrees of branching (DB similar to 88%). Little weights are lost when the polymers are heated to 390 degrees C under nitrogen or 380 degrees C in air. The polymers are highly transparent, allowing almost all light in the entire visible spectral region to transmit through. Thin solid film of hb-P1 shows high refractive indices (RI = 1.6255-1.681) in the wavelength region of 400-1700 nm, extremely high modified Abbe number (nu(D)' = 1030.7), and very low optical dispersion (D' = 0.00097). Its RI values can be modulated and its thin films can be cross-linked by UV irradiation, enabling ready generation of negative photoresist patterns.