This paper reports the synthesis and characterization of a new rigid diamine monomer, having a spiro carbon moiety and an adamantane bulky group in its structure; namely spiro-(adamantane-2,9′(2',7'-diamino)-fluorene) (SADAF). After its synthesis, using a straightforward methodology, a novel family of aromatic polyimides (PIs) and polyamides (PAs) has been attained by reaction of SADAF with three aromatic dianhydrides and two diacid chlorides, respectively. Two of the polyimides were obtained through the formation of the corresponding polyamic acid and subsequent thermal cycloimidization, whereas the other one, the polyimide from SADAF and 2,2bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA), could be synthesized by chemical imidization from the polyamic precursor. Regarding polyamides, two new ones, made from SADAF and isophthaloyl chloride (IPC) and the diacid chloride of 2,2bis(4-carboxyphenyl)hexafluoropropane (6FC) could be obtained. All the polymers showed high Tg, above 350 ºC, and excellent thermal resistance, with onset degradation temperatures higher than 450 ºC. Polymers formed by the combination of SADAF with 6FDA and 6FC were prepared as dense films with good mechanical properties and their permselectivity properties were measured.

A complete series of aliphatic aromatic copoly(ether-imide)s, based on aromatic dianhydrides (BPDA, BKDA or PMDA) and mixtures of an aromatic diamine (ODA) and an aliphatic diamine terminated poly(ethylene oxide) PEO(2000) (Mw=2000 g/mol) or PEO(6000) (Mw= 6000 g/mol), has been synthesized using different PEO contents. Cast films of these copolymers have been thermally treated to ensure the segregation of the linear PEO chains from the aromatic portion of these copoly(ether-imide)s. Gas permeability (O 2 , N 2, CO 2 and CH 4) of membranes, made from these copolymers with different proportions of PEO, were compared with the predictions of various electrical or thermal conductivity models adapted to gas permeability. Several of these models, from Maxwell-Garnett to percolation theory, proved to be inaccurate. Nevertheless, the model based on the Effective Medium Approximation (EMA) is proved here to succeed in predicting the main features of the experimental results for all mixture proportions, taking as the starting point the sole input of pure homopolymer permeabilities. Specifically, this later method was able to calculate the volume fraction for the maximum increase of permeability, a common feature for all the studied segregated copolymer membranes. The model was even able to predict the permeabilities of a three phase system consisting in the aromatic (BKDA-ODA) phase plus a mixture of amorphous PEO(6000) and crystalline PEO(6000).

The lithium ion is an important type of electrolyte that has technological applications in the manufacture of lithium ion cells; therefore, a better understanding of the nature of its solutions is desirable. When associated to the radical anion of biphenyl in an organic solvent, it forms conducting solutions comparable to strong electrolytes such as lithium perchlorate. We have studied the lithium biphenyl solution in dimethoxyethane using DFT calculations. The nature of these ionic solutions is described in terms of a dynamic equilibrium between different types of ionic associations, the composition of which depends on the solvent and the temperature. The X-ray structure of [Li(+)·4C(5)H(10)O][C(12)H(10)(•-)], a solvent-separated ion pair of lithium biphenyl complexed with tetrahydropyran, is reported. Its main structural characteristics coincide with the calculated one, which we think is the dominant species at room temperature, in agreement with the available physicochemical data.

SummaryIn our previous works, it was observed a clear relationship between the structure and the properties for different copoly(ether-imide)s, besides a good relation was found between SAXS characterization and permeability results. Here, a series of aliphatic aromatic copoly(ether-imide)s, based on an aromatic diamine (ODA), a diamine terminated poly(ethylene oxide) (PEO2000) of a molecular weight of 2000 g/mol and different aromatic dianhydrides (BPDA, BKDA (or BTDA) and PMDA )has been synthesized and characterized.The permeability for O2, N2, CO2 and CH4, increased with the rigidity of the monomers (BKDA < BPDA < PMDA), with the amount of PEO2000 in the copolymers, as well as with the increase in the temperature of treatment of the films. In this case, it was observed that when the proportion of PEO in the copolymer exceeded 50%, the permeability was similar for all samples, and the aromatic portion had no significant influence.Attending to glass transition temperature, Tg, of the aliphatic part, to its melting temperature, Tm, and to its crystallinity, segregation was better for more rigid dianhydrides at lower temperatures of treatment. Higher dianhydride rigidity produced better mechanical properties that were good but decreased a little bit when the percentage of PEO in the samples increased.Good permeselectivity compromises were attained for the CO2/N2 separation .This work gives light to design advanced materials for this separation with the increasing possibilities of controled structure and properties.

Spontaneous disproportionation of lithium biphenyl radical anion into a lithium biphenyl dianion plus neutral biphenyl, according to 2LiBiph ⇄ Li2Biph + Biph, has been evidenced experimentally by UV-vis spectroscopy and backed up theoretically using TDDFT methods.

No abstract

We report an organic photocatalytic system, namely 3,3′,5,5′-tetra-tert-butyl-4,4′-diphenoquinone (DPQ) and air, capable of coupling efficiently with the photocyclization of stilbenes to afford phenacenes. The potential of this new and mild process is shown with the synthesis of [5]-and [7]phenacene, two semiconductors recently implemented into organic electronic devices, with high yields and remarkable purity.