Linear polyamides from L‐malic acid and alkanediamines

A series of linear polyamides (PnMLM) derived from O‐methyl‐protected L ‐malic acid and 1,n‐alkanediamines with even n values ranging from 4 to 12 were prepared and fully characterized. L ‐Malic acid entered in the chain with a random orientation rendering essentially aregic polymers. PnMLM displayed optical rotation consistent with the content of the polymer in malic units, and they all were crystalline with melting points ranging from 158 to 188 °C and glass‐transition temperatures varying from 37 to 70 °C. PnMLM appeared to be fairly stable to heat with thermal decomposition starting close to 300 °C. Hydrolytic degradation of PnMLM at 37 °C was slow, but the process was significantly faster at 70 °C. Thermal degradation took place with the formation of cyclic malimides in the residual polymer and released the 1,n‐alkanediamine. However, hydrolytic degradation took place in a first stage with the formation of open chains of carboxylic‐ and amine‐ended oligomers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1566–1575, 2004     

Determination of the thermodiffusion coefficient in three binary organic liquid mixtures by the thermogravitational method (contribution of the Universidad del País Vasco,Bilbao, to the benchmark test)

Within the framework of an international benchmark test, the thermodiffusion coefficients D T of the three binary systems formed with dodecane, isobutylbenzene and 1,2,3,4-tetrahydronaphthalene (with a mass fraction of 0.5 for each component at a temperature of 25C) have been measured. Convective coupling in cylindrical thermogravitational columns has been used to determine D T based on the Furry-Jones-Onsager theory. For each system, several columns with different gaps and heights were employed. Our results for these three coefficients are in good agreement with those obtained by other benchmark tests; the maximum deviation from the proposed benchmark values is 8.5%, which is not too bad owing to the difficulties of measuring a thermodiffusion coefficient.     

Law of corresponding states and thermal-diffusion factor of He-Ar mixtures from two-bulb measurements

Experimental data of the thermal diffusion factor for low density He-Ar mixtures are given. The measurement apparatus is a two-bulb operated at T_H = 308 K and T_C = 77.6 K, the mean temperature being T = 148 K. It is concluded that the extended law of corresponding states proposed by Kestin, Ro and Wakeham is able to predict in a correct way the obtained results.     

CP phases in the charged current and Higgs sectors for Majorana neutrinos

The diagonalization of the leptonic mass matrices is performed in the framework of the triplet model to generate Majorana mass terms for neutrinos. This allows the understanding of the role played by the CP-violating phases in the Higgs sector and their relation with those of the charged-current Lagrangian. It is shown that all the leptonic mixings, including those of the Higgs couplings, can be given in terms of a Kobayashi-Maskawa matrix and the relative Majorana phases of the neutrino fields. The characteristic Majorana phases, always appearing together with the neutrino mass, are present in |ΔL|=2 pieces and they show up in processes with a) neutrino-antineutrino propagation, and/or b) at least two different neutrinos as asymptotic states, and/or c) a vertex with a doubly-charged scalar. The phenomenological implications for processes with these characteristics are given.     

Comb-like ionic complexes of cationic surfactants with bacterial poly(gamma-glutamic acid) of racemic composition

Comb-like ionic complexes, nATMA . PG(DL)GA, were prepared from microbial poly(gamma-glutamic acid), with a nearly racemic configuration, and alkyltrimethylammoniun bromides, with linear alkyl chains containing an even number of carbon atoms, n, ranging from 12 to 22. The complexes had a nearly stoichiometric composition, displayed thermal stability up to temperatures above 200 degrees C and were insoluble in water but soluble in organic solvents. In the solid state, they were arranged in a regularly layered structure with the alkyl side chain crystallized for n > or = 18. Heating above melting entailed a contraction in the interlayer distance which varied from 1 to 10% depending on the value of n. Comparison with data reported on similar complexes obtained from nearly enantiomerically pure poly(gamma-glutamic acid) revealed an overall behavior very similar for the two series but with specific significant differences concerning side chain crystallinity and dimensional response to temperature.     

Immobilization of peroxidase glycoprotein on gold electrodes modified with mixed epoxy-boronic Acid monolayers

The development of bioelectronic enzyme applications requires the immobilization of active proteins onto solid or colloidal substrates such as gold. Coverage of the gold surface with alkanethiol self-assembled monolayers (SAMs) reduces nonspecific adsorption of proteins and also allows the incorporation onto the surface of ligands with affinity for complementary binding sites on native proteins. We present in this work a strategy for the covalent immobilization of glycosylated proteins previously adsorbed through weak, reversible interactions, on tailored SAMs. Boronic acids, which form cyclic esters with saccharides, are incorporated into SAMs to weakly adsorb the glycoprotein onto the electrode surface through their carbohydrate moiety. To prevent protein release from the electrode surface, we combine the affinity motif of boronates with the reactivity of epoxy groups to covalently link the protein to heterofunctional boronate-epoxy SAMs. The principle underlying our strategy is the increased immobilization rate achieved by the weak interaction-induced proximity effect between slow reacting oxyrane groups in the SAM and nucleophilic residues from adsorbed proteins, which allows the formation of very stable covalent bonds. This approach is exemplified by the use of phenylboronates-oxyrane mixed monolayers as a reactive support and redox-enzyme horseradish peroxidase as glycoprotein for the preparation of peroxidase electrodes. Quartz crystal microbalance, atomic force microscopy, and electrochemical measurements are used to characterize these enzymatic electrodes. These epoxy-boronate functional monolayers are versatile, stable interfaces, ready to incorporate glycoproteins by incubation under mild conditions.     

Polyesters analogous to PET and PBT based on O‐benzyl ethers of xylitol and L‐arabinitol

The synthesis, characterization, and some properties of new copolyesters of poly(butylene terephthalate) (PBT) and poly(ethylene terephthalate) (PET) based on L ‐arabinitol and xylitol are described. These copolyesters were obtained by polycondensation reaction in the melt of mixtures of 1,4‐butanediol or ethylene glycol and 2,3,4‐tri‐O‐benzyl‐L ‐arabinitol or 2,3,4‐tri‐O‐benzyl‐xylitol with dimethyl terephthalate. Their weight‐average molecular weights ranged between 7000 and 55,000, with polydispersities ranging from 1.4 to 4.7. Copolymers containing 1,4‐butanediol could be analyzed by NMR, and were found to have a statistical microstructure. All these copolyesters were thermally stable, with degradation temperatures well above 300 °C. With increasing amounts of alditol in the copolyester, the melting temperature and crystallinity decreased in both series, and the glass transition temperature increased for the PBT series and decreased for the PET series. Only PBT‐derived copolyesters containing a maximum of 10% alditol units showed discrete scattering characteristic of crystalline material. No substantial differences in either structure or properties were observed between the L ‐arabinitol and xylitol copolyester series. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5167–5179, 2008