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Keywords Lignin analysis Organosolv lignin Molccular wcight (Mini, Mw and MWD) dctcrminations Hilücbrand's solubility paramctcr Sawdust Pinus caribaea hondurensis SummaryLignin from Pinus caribaea hondurensis sawdust (pre-extracted with bcnzenc/mcthanol 1:1) was obtaincd by pulping using ninc diffcrent organic solvcnts (in 9:1 mixturcs with 2.0 N HC1 aqucous Solutions) in a stainlcss stcel rcactor at 125 °C for six hours.Thc obtaincd lignins wcrc charactcrizcd by chcmical analysis (clcmcntal analysis, mcthoxyl and phcnolic hydroxyl groups) and by infrarcd spcctroscopy. Morcovcr, the avcrage molccular wcights (Mn, Mw and MWD) werc dctcrmincd by vapor phasc osmomctry and high pcrformancc-size exclusion chromatography and shown thrcc diffcrent pattcrns according to thc solvent mixturcs cmploycd. The yields of lignin dcpcnd on the acccssibility and nuclcophilicity of thc solvcnts äs well äs on thc lignin solubility, and are rclatcd to thc Hildcbrand's solubility paramctcrs ( ) of the solvent mixturcs. The plot of lignin yields against 6 show a charactcristic "Bell shapc" curvc wilh maximum at 23 MPa l/2 corrcsponding to thc lignin solubility paramctcr. IntroductionPulping processes can be divided into three main groups, depending on the solvent System employed: -Aqueous processes: These pulping processes use water äs solvent and inorganic reagents to cleave the protolignin to water soluble fragments. The inorganic reagents are generally used in high concentrations and the processes are carried out at high temperatures and pressures. -Organosolv processes: These processes use organic solvents, commonly in association with water and, in the most cases, an acid catalyst. In the acid catalyzed organosolv processes, water acts äs nucleophilic agent and reacts with reactive centers (which have been activated by the catalyst) in the protolignin. Organosolv processes generally use lower temperatures and pressures than the aqueous processes, and differ from in the recovery of the Chemicals, in organosolv processes only the solvent has to be recovered. -Mixed processes: The solubilization power of the organic solvents can be used in association with water and inorganic reagents producing mixed processes. These Systems are also performed at high temperatures and pressures and the inorganic reagents have to be recovered due to economical reasons. Organosolv processes making use of alkaline reagents are included in this group.

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Atomic force microscopy (AFM) and Fourier transform infrared spectroscopy (FTIR) are used to investigate molecular organization in Langmuir-Blodgett (LB) films of two kinds of lignins. The lignins were extracted from sugar cane bagasse using distinct extraction processes and are referred to here as ethanol lignin (EL) and saccharification lignin (SAC). AFM images show that LB films from EL have a flat surface in comparison with those from SAC. For the latter, ellipsoidal aggregates are seen oriented perpendicularly to the substrate. This result is confirmed by a combination of transmission and reflection FTIR measurements, which also point to lignin aggregates preferentially oriented perpendicularly to the substrate. For LB films from EL, on the other hand, aggregates are preferentially oriented parallel to the substrate, again consistent with the flat surface observed in AFM data. The vibrational spectroscopy data for cast films from both lignins show random molecular organization, as one should expect.

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The optical storage capability of mixed Langmuir-Blodgett (LB) films of disperse red-19 isophorone polyurethane (DR19-IPPU) and cadmium stearate has been demonstrated by measuring their optically induced birefringence that originates from the trans-cis isomerization of the azobenzene chromophore. Isomerization was achieved because the azobenzene chromophore could be introduced in the polyurethane main chain in a way that would allow for the free volume necessary for the molecular reorientation inherent in the isomerization process. The amplitude of induced birefringence decreased with the number of layers in the composite LB films, but the film thickness did not affect the time required to achieve maximum birefringence. Stored information could be optically erased by overwriting with a circularly polarized light. The identification of optimized conditions for producing LB films with the required optical properties was based on an extensive characterization process for the monolayers, using surface pressure and surface potential measurements, and for the deposited LB films. The mixed-film approach had to be used because pure monolayers of DR19-IPPU could not be transferred uniformly onto solid substrates. UV-vis and FTIR spectroscopy studies indicated the presence of both cadmium stearate and DR19-IPPU in the films, with a possible J-type aggregation of azobenzene chromophores, whereas X-ray diffraction patterns revealed that the cadmium stearate molecules form separate domains in a DR19-IPPU matrix.

This paper reports the synthesis of Au nanoparticles by 30-fs pulses irradiation of a sample containing HAuCl4 and chitosan, a biopolymer used as reducing agent and stabilizer. We observed that it is a multi-photon induced process, with a threshold irradiance of 3.8 × 10(11) W/cm2 at 790 nm. By transmission electron microscopy we observed nanoparticles from 8 to 50 nm with distinct shapes. Infrared spectroscopy indicated that the reduction of gold and consequent production of nanoparticles is related to the fs-pulse induced oxidation of hydroxyl to carbonyl groups in chitosan.