The synthesis and the microstructural characterization of isotactic poly (N‐pentenyl‐carbazole) (i‐PPK) are reported. The achieved polymer is semicrystalline, the melting temperature is 138°C. i‐PPK Fourier transform infrared spectroscopy (FTIR) spectrum and X‐ray diffraction pattern are compared with those of polyvinylcarbazole. The observed differences are tentatively associated to higher flexibility of the i‐PPK chains due to the alkylene group connecting the carbazole group to the main chain. The presence of intrachain and interchain interactions between carbazole units, which bring these groups to stack each other, is assumed. i‐PPK optical properties are investigated and an electroluminescent behaviour of polymer is observed. Organic light emitting diodes based on i‐PPK layers are founded to emit white light. POLYM. COMPOS., 36:1110–1117, 2015. © 2015 Society of Plastics Engineers

We describe alkoxo‐aluminum catalysts of chiral bipyrrolidine‐based salan ligands that follow the dual‐stereocontrol mechanism wherein a given combination of stereogeneities at the metal site and the proximal center of the last inserted lactidyl (“match”) is active towards lactide having a proximal stereogenic center of the opposite configuration, while the diastereomeric combination of stereogeneities (“mismatch”) is inactive towards any lactide. Polymerization of rac‐LA by the enantiomerically pure catalysts was sluggish and gave stereoirregular poly(lactic acid) (PLA) because selective insertion to a match diastereomer gives a mismatch diastereomer. The racemic catalysts showed higher activity and led to highly heterotactic PLA following polymeryl exchange between two mismatched catalyst enantiomers. A succession of match diastereomers in selective meso‐LA insertions led to syndiotactic PLAs reaching a syndiotacticity degree of α=0.96. This polymer featured a Tm of 153 °C matching the highest reported value, and the highest crystallinity (ΔHm=56 J g−1) ever reported for syndiotactic PLA.

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The electroluminescence (EL) of isotactic and syndiotactic poly(N-pentenyl-carbazole) (PPK), achieved by coordination polymerization, is studied in order to investigate the interrelation between thepolymer tacticity and theirphysical-chemical properties. The use of these polymers in organic light-emitting diode (OLED) fabrication is also explored. Thermal and x-ray diffraction analyses of PPKs show that the isotactic stereoisomer is semicrystalline, whereas the syndiotactic one is amorphous. Optical analysis of both stereoisomers, carried out on film samples, reveals the presence of two different excimers:'sandwich-like' and 'partially overlapping'. Nevertheless, the emission intensity ratio between 'sandwich-like' and 'partially overlapping' excimers is higher in the isotactic than in the syndiotactic stereoisomer. Using the synthesized polymers as OLED emitting layers, the influence of the polymer tacticity on theEL properties of the device is highlighted. In detail, while blue OLEDs are obtained by using the syndiotactic stereoisomer, OLEDs witha multilayer structure fabricated with the isotactic stereoisomer emit white light. The contribution of three different emissions (fluorescence, phosphorescence and electromer emissions) with comparable intensities to the detected white light is discussed.