Synthesis of poly(thio-1,4-phenylene) by oxidative coupling reaction of diphenyl disulfide with potassium persulfate in strongly acidic solutions

The synthesis of poly(thio- 1,4-phenylene) (PPS) at room temperature by the reaction of diphenyl disulfide with potassium persulfate (K₂S₂O₈) in non-basic solvents, in the presence of trifluoromethanesulfonic acid, is reported. The reaction in chlorinated solvents, such as dichloromethane and tetrachloroethane, resulted in partial oxidation of sulfide to sulfoxide and sulfone. On the other hand, the polymerization proceeded well in nitrobenzene and the PPS formed was free of branches, crosslinks and thianthrene units. The molecular weight of the polymers formed in different solvents were in the range 2000–8000. The reaction proceeded under identical conditions with bis(2,6-dimethylphenyl) disulfide as well, but the polymer yield was lower.     

Cationic polymerization of 1,3-pentadiene I. infrared, 1H-NMR and 13C-NMR investigations on the microstructure of poly(1,3-pentadiene) synthesized with cationic catalysts

This study deals with cationic polymerization of the cis- and trans-isomers of 1,3-pentadiene. The microstructure of the polymer chains is studied by ¹H-NMR, ¹³C-NMR and IR spectroscopies. It is shown that the trans-diene gives strictly trans-1,4 and trans-1,2 residual linear insaturations, whereas the cis-isomer yields also cis-1,4, cis-1,2 and 3,4-units whose overall content can reach 10 mol-%. According to the cyclization degree of the macromolecules, ranging from 30 to 70 mol-%, the number of trans-(1,2+1,4) units varies between 33 to 65 mol-% and that of trans-1,2 units between 4 and 20 mol-%. An analytical method is proposed to evaluate the average number of rings present in the polycyclic sequences. It is found that the cyclic fragments of the polymer chains consist of bi- or tri-cyclohexane fused rings containing α tetrasubstituted double bond.     

New aromatic-aliphatic polyesters based on N-alkyl carbazole groups in the main chain. Synthesis-structure-properties relationships

Polyesters based on N-butyl or N-octylcarbazole units in the main chain were synthesized either by direct polycondensation between the carbazole dicarboxylic acids and ethylene glycol or from alcoholysis of the 2-hydroxyethyl diesters in the presence of different catalytic systems. Depending on the reaction conditions together with the nature and the concentration of the catalyst, diethylene glycol (DEG) is formed as a side-reaction product. DEG is incorporated in the polyester chain concurrently with EG and leads to the formation of ether links in the spacers. The DEG content as well as the length of the alkyl pendant group of the carbazole unit were found to have a drastical effect on the thermal properties. Furthermore, these materials form charge transfer complexes through carbazole nuclei with electron acceptor and electron donor molecules as well.     

Direct and indirect functionalization of polypropylene

Polypropylene is the polymer with the fastest-growing usage rate, owing to its low price combined with properties that have been improved over recent years. However, because it does not carry any functional groups, it has little interaction with useful components of many systems, and it is difficult to paint. Recently, a certain number of attempts have been made to modify this polymer, either through direct copolymerization with reactive monomers, or after chemical modification of the polymer itself or some of its copolymers. The paper is a review of these different approaches, with emphasis on two points: (a) the new possibilities offered by the metallocene family of catalysts and (b), the work carried out in the author's laboratory, based on various functionalizations of copolymers of propylene and dienes.     

A construction of a robust family of exponential attractors

Given a dissipative strongly continuous semigroup depending on some parameters, we construct a family of exponential attractors which is robust, in the sense of the symmetric Hausdorff distance, with respect to (even singular) perturbations.

     

α-(3,7-Dioxa-r-1-azabicyclo[3.3.0]oct-c-5-ylmethoxy)-diazines. Part 1: Synthesis and stereochemistry. Extension to s-triazine series

The general and efficient synthesis of the title compounds, consisting of the (selective) replacement of chlorine in commercial α-chlorodiazines and cyanuryl chloride by the 3,7-dioxa-r-1-azabicyclo[3.3.0]oct-c-5-ylmethoxy group (Williamson method) is described. The stereochemistry of this new series of derivatives is analysed in terms of different conformational chirality exhibited in solution (¹H NMR) versus solid state (X-ray diffractometry), meso against chiral forms, respectively. In solid state, the inclusion capacity of some chiral networks as well as their supramolecular aggregation is pointed out. A good correlation between rotameric behaviour of the c-5-di(s-tri)diazinyloxymethyl group in the two states is found.     

Efficient one pot preparation of variously substituted thieno [2,3‐b] thiophene

An efficient one pot access to variously substituted thieno[2,3‐b]thiophene is described. The title compounds were obtained from 1,3‐dicarbonyl or equivalent compounds, carbon disulfide and halomethyl derivatives in good to high yields and fully characterized.     

Cycloaddition reactions of carbohydrate derivatives. Part V. A hetero Diels-Alder approach to swainsonine analogs

Diastereoselective hetero Diels-Alder reactions of sugar derived azomethines 4a–4g have been used for the construction of chiral piperidones 6 and 7. Configuration of the major products was 6,1′-threo in every case. The enone system of 6 and 7 was reduced diastereoselectively and subsequently swainsonine-analog hydroxyindolizidines 28–32 were prepared by an intramolecular reductive amination.