No abstract

No abstract

This manuscript consists of two parts which focus on enhancing control over the polymerization of conjugated polymers. In the first part, the controlled chain-growth character of the polymerization of poly(selenophene) using Pd(Ruphos) as a catalyst system is demonstrated. Next, all-conjugated thiophene−fluorene−selenophene triblock-copolymers are synthesized in all possible orders using this catalyst. Subsequent, the properties of these advanced structures are assessed using GPC chromatography and 1 H NMR, UV−vis, and fluorescence measurements. DFT calculations were performed to explain the unusual independence of the monomer sequence during the polymerization, traditionally observed in other chain-growth protocols for conjugated polymers. ■ INTRODUCTIONπ-Conjugated polymers are well-studied materials during the last decades because of their optoelectronic properties and their potential in low-cost electronics resulting from their conductivity and easy processing. 1−10 The quest toward complex and tailored polymeric structures to improve the performance and usability was the topic of research in the recent past and continues nowadays. 11 This quest starts with obtaining as much control as possible over the polymerization mechanism, hereby turning it into a controlled chain-growth mechanism with control on end-group functionalization and molar masses. 12−15 Moreover, this enables block-copolymerization by successive monomer addition, in which the next monomer is added after the previous monomer is completely consumed. The research groups of McCullough and Yokozawa simultaneously discovered the chain-growth character of poly(3-hexylthiophene) with Ni(dppp)Cl 2 (dppp = diphenylphosphinopropane) as a catalyst. 16−19 Further research resulted also in control over other conjugated polymers that were formed in a chain-growth fashion using the same or other Ni-and Pd-based catalysts. 20−34 The controlled nature of the polymerization relies on the association of the catalyst with the π-system of the propagating polymer chain after the reductive elimination (catalyst-transfer polycondensation, CTP). 35 As a consequence, termination and transfer reactions are avoided and a controlled chain-growth polymerization mechanism is obtained. In principle, if the controlled polymerization of two different monomers is obtained under the same conditions, allconjugated block-copolymers (π-BCPs) are accessible by sequential monomer addition. Nevertheless, since the mechanism relies on the association of the catalyst with the propagating polymer, the synthetic direction is fixed from the monomer with the lowest catalyst affinity to the one with the highest catalyst affinity, as reported by the groups of Yokozawa and Wang. 30,32 As a consequence, the number of all-conjugated block-copolymers composed of electronically different blocks prepared by successive monomer addition remains scarce, e.g.

The effects of bleaching using high power ultrasound (20 kHz) on the quality of olive oil were considered in this study, in order to verify the modifications that can occur in fatty acid composition and minor compounds. During the treatment of olive oil under ultrasonic waves, a rancid odour has been detected. Treated olive oils show no significant changes in their chemical composition but the presence of some volatile compounds, due to ultrasonic treatment. Some off-flavour compounds (hexanal, hept-2-enal and 2(E),4(E)-decadienal) resulting from the sonodegradation of olive oil have been identified. A wide variety of analytical techniques (GLC, HPLC and GC/MS) were used to follow the quality of bleached olive oils with ultrasonic waves by the determination of the amounts of certain minor compounds such as sterols and tocopherols. Steradienes, resulting from the dehydration of sterols, were detected with small quantities especially in severe conditions of sonication. Solid phase micro-extraction (SPME) coupled to gas chromatography was known to be a sensitive technique to follow changes in the oxidative state of vegetable oils by measuring the amount of volatile materials produced during the refining process.

Production of fatty acid esters from stearic, oleic, and palmitic acids and short-chain alcohols (methanol, ethanol, propanol, and butanol) for the production of biodiesel was investigated in this work. A series of montmorillonite-based clays catalysts (KSF, KSF/0, KP10, and K10) were used as acidic catalysts. The influence of the specific surface area and the acidity of the catalysts on the esterification rate were investigated. The best catalytic activities were obtained with KSF/0 catalyst. The esterification reaction has been carried out efficiently in a semi-continuous reactor at 150°C temperature higher than the boiling points of water and alcohol. The reactor used enabled the continuous removal of water and esterification with hydrated alcohol (ethanol 95%) without affecting the original activity of the clay.