C2‐Symmetric Zirconocenes in the Polymerization of Conjugated Diolefins

C₂‐symmetric zirconocenes activated by methylaluminoxane were utilized as catalysts in the polymerization of 1,3‐diolefins. The results indicate that the most crowded catalytic precursor rac[CH₂(3‐tert‐butyl‐1‐indenyl)₂]ZrCl₂ ( 1 ) is also the most active one, giving 1,4‐polymerization of 1,3‐butadiene and (Z)‐1,3‐pentadiene and 1,2‐polymerization of (E)‐1,3‐pentadiene and 4‐methyl‐1,3‐pentadiene. Probably, the different behavior of 1 with respect to other C₂‐symmetric zirconocenes utilized is due to the different stability of the bond between the last inserted monomer unit and the metal, as well as to the coordination of incoming monomer.     

New Ni(II) based catalysts active in the polymerization of olefins

Polymerization of ethylene in the presence of Cp₂Ni (Cp: cyclopentadienyl) and methylaluminoxane affords polyethylene of high molecular weight and with high melting point. The same catalyst is active in the polymerization of styrene and 1,3-butadiene to give partially isotactic polystyrene and 1,4-cis-polybutadiene, respectively.     

Industrial cutting waste granite dust reinforced cardanol benzoxazine/epoxy resin hybrid composites for high-voltage electrical insulation applications

An attempt has been made to develop hybrid composites from benzoxazine monomer (C-ddm) hybridized with DGEBA epoxy resin (EP) and reinforced with varying weight percentages (20 wt%, 40 wt%, 60 wt%, 80 wt% and 100 wt%) of glycidoxypropyltrimethoxy- silane (GPTMS) functionalized granite dust (GD) obtained from industrial granite cutting and polishing process in order to utilize them for electrical insulation applications. The thermal stability of granite dust reinforced poly(EP-co-C-ddm) composites was studied by TGA analysis. Among the composites samples studied, 100 wt% GD reinforced poly(EP-co-C-ddm) composites possess better thermal stability than that of other neat matrices and composites. Among the composites prepared using varying weight percentages of functionalized GD reinforcement, it was observed that 80 wt% GD reinforced poly(EP-co-C-ddm) composites possesses better hydrophobic character than that of other neat matrices and composites. The value of LOI calculated for neat matrix (poly[EP-co-C-ddm]) and 20 wt%, 40 wt%, 60 wt%, 80 wt% and 100 wt% GD reinforced composites was found to be 22, 28, 34, 40, 43 and 45 respectively. The 80 wt% GD reinforced poly(EP-co-C-ddm) composites possess the higher values of tensile strength and flexural strength of 47 MPa and 140 MPa, respectively than those of their samples. The values of electrical surface resistivity and electrical volume resistivity of all the neat matrices and GD reinforced polybenzoxazine composites were found to be in the order of 10¹² and 10¹³ respectively. The values of dielectric strength obtained from break down voltage (BDV) for neat matrix [poly(EP-co-C-ddm)] and 20 wt%, 40 wt%, 60 wt%, 80 wt% and 100 wt% of GD reinforced poly(EP-co-C-ddm) composites are 15.0, 15.5, 16.5, 17.0, 17.0 and 17.0 kV/mm, respectively. Data obtained from thermal stability, hydrophobic behavior and dielectric studies it was inferred that the hybrid polymer composites developed in the present work can be conveniently used in the form insulators, sealants, adhesives and matrices where application demands at high-performance industrial and engineering applications.     

Field Effect Devices Based on SrTiO3 Gate Dielectrics for the Investigation of Charge Carrier Mobility in Macromolecular Films

Field effect devices (FET) allow an exhaustive investigation of the electronic transport properties of innovative semiconductors of interest for new applications in modern electronics. In this contribution, we report on the fabrication and characterization of FET devices where SrTiO₃ (STO) single crystals and organic macromolecular compounds, such as doped and undoped polythiophenes, or poly(N-vinylcarbazole) (PVK), are used as insulating and semiconducting layers, respectively. STO, with ε_r of about 300, offers the possibility to strongly modulate the charge carrier density in the organic films, thus overcoming the limitations related to the use of more conventional oxides.