Coloration properties and chemo-rheological characterization of a dioxazine pigment-based monodispersed masterbatch

The effect of masterbatch pigments on the crystallisation, morphology, and shrinkage behaviour of Isotactic Polypropylene

Variations in mould shrinkage when using organic and inorganic pigments in semicrystalline polymers is a well-known phenomenon within industry. These differences in mould shrinkage are thought to be caused by the presence of the pigments acting as nucleating agents, altering the crystallisation of semicrystalline polymers. These shrinkage variations can give rise to problems in obtaining the correct interference fit between parts and can cause issues in automated equipment such as filling lines. It has been previously reported that the onset temperature of crystallisation measured via DSC (differential scanning calorimetry) can be used to predict shrinkage when a variety of neat pigments are added to un-nucleated PP (polypropylene). However, the shrinkage and crystallisation behaviour of masterbatch pigments, which are widely used industrially is poorly understood. To better understand the influence of masterbatch pigments on crystallisation and shrinkage behaviour, injection moulded samples were prepared using variety of reds, whites, and purple commercial-masterbatch pigments with PP. The crystallisation kinetics and crystallinity were studied using DSC, LPOM (Linkam hot stage polarising optical microscopy), XRD (X-ray diffraction), and FTIR (Fourier transform infrared spectroscopy). The morphology was investigated via LPOM and SEM (scanning electron microscopy). A clear correlation was observed between the crystallisation onset temperature measured using DSC and the recorded shrinkage. A strong relationship was also observed between the percentage crystallinity measured using FTIR and shrinkage. Quinacridone and pyrrole based red and purple pigments were found to act as strong nucleating agents, with the pyrrole based red pigment also acting as β nucleator in PP. The white pigments were found to have less influence on the nucleation behaviour. For the pigments which induced the largest variation in shrinkage, a higher rate of nucleation and proportionally smaller spherulitic diameter was observed by DSC, SEM, and LPOM.

Linear-type carbazoledioxazine-based organic semiconductors: the effect of backbone planarity on the molecular orientation and charge transport properties

We report the synthesis of a linear-type dibromocarbazoledioxazine (CZ) derivative as a new precursor for semiconducting polymers. The chemical structures of the CZ unit and its polymers with thiophene or thienothiophene spacers (namely, PCZT and PCZTT) were fully characterized. PCZT and PCZTT possessed similar medium optical band gap (E^opt_g) and electrochemical band gap (E^cv_g) of around 1.70 eV estimated from the onset absorption and electrochemical redox potentials of the thin films, respectively. Computational density functional theory (DFT) calculations suggested that the backbone of the PCZT might be highly twisted, while that of PCZTT could be very planar. The effect of different backbone geometries on the charge–transport properties was studied by using thin film transistors (TFTs). The TFT device based on PCZTT showed a four times higher hole mobility as compared to that based on PCZT. The superior TFT performances of PCZTT were reasonably attributed to its edge-on backbone packing orientations toward the Si substrate revealed by the grazing-incidence wide-angle X-ray scattering (GIWAXS), which was favorable for in-plane charge transport in the TFT devices.

A linear-type dibromocarbazoledioxazine (CZ) derivative and its two polymers are newly designed and synthesized. Structure–property relationship studies reveal that PCZTT shows a four times higher hole mobility than PCZT.