Molecular self-assembly is the spontaneous association of molecules under equilibrium conditions into stable, structurally well-defined aggregates joined by noncovalent bonds. Molecular self-assembly is ubiquitous in biological systems and underlies the formation of a wide variety of complex biological structures. Understanding self-assembly and the associated noncovalent interactions that connect complementary interacting molecular surfaces in biological aggregates is a central concern in structural biochemistry. Self-assembly is also emerging as a new strategy in chemical synthesis, with the potential of generating nonbiological structures with dimensions of 1 to 10(2) nanometers (with molecular weights of 10(4) to 10(10) daltons). Structures in the upper part of this range of sizes are presently inaccessible through chemical synthesis, and the ability to prepare them would open a route to structures comparable in size (and perhaps complementary in function) to those that can be prepared by microlithography and other techniques of microfabrication.

Molecular self-assembly and nanochemistry: A chemical strategy for the synthesis of nanostructures

Renewable resources are used increasingly in the production of polymers. In particular, monomers such as carbon dioxide, terpenes, vegetable oils and carbohydrates can be used as feedstocks for the manufacture of a variety of sustainable materials and products, including elastomers, plastics, hydrogels, flexible electronics, resins, engineering polymers and composites. Efficient catalysis is required to produce monomers, to facilitate selective polymerizations and to enable recycling or upcycling of waste materials. There are opportunities to use such sustainable polymers in both high-value areas and in basic applications such as packaging. Life-cycle assessment can be used to quantify the environmental benefits of sustainable polymers.

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Sustainable polymers from renewable resources

Chemical modification of lignins: Towards biobased polymers

Synthesis, properties, and applications of magnetic iron oxide nanoparticles

A review on pyrolysis of plastic wastes

INTRODUCTION Lignin, a valuable resource for chemicals and energy, is a main component of wood, together with cellulose and hemicellulose. It is the second large source of organic raw material, constituting about 4-35 wt% of most biomass, 16-25 wt% of hardwoods and 23-35 wt% of softwoods. As the most abundant natural aromatic polymer, lignin has a highly branched three-dimensional phenolic structure including three main phenylpropane units, namely p-coumaril, coniferyl and sinapyl (Fig. 1). Softwood lignin contains relatively fewer sinapyl units and consists mainly of guaiacyl structures, while hardwood lignin contains guaiacylsyringyl structures. As a by-product of the paper industry, lignin is most often used by paper mills as a fuel for the recovery of its energy content. However, due to the very large generated quantities, lignin is increasingly considered as a potential source of chemicals, and studies on its thermal degradation receive much interest. “Pyrolytic lignin”, the organic phase obtained from the pyrolysis of wood or of other biomass resources, consists of a brown tar containing high molecular weight compounds derived from lignin, while the water-soluble fraction, accounting for 60-70 wt% of the whole oil, contains lower molecular weight substances.

Thermal degradation of lignin - a review

Co-pyrolysis of pine cone with synthetic polymers

The main difficulties in wood and pulp analyses arise principally from their numerous components with different chemical structures. Therefore, the basic problem in a specific analytical procedure may be the selective separation of the main carbohydrate-derived components from lignin due to their chemical association and structural coexistence. The processing of the wood determines some structural modification in its components depending on the type of wood and the applied procedure. Fourier transform infrared (FT-IR) spectrometry and X-ray diffraction have been applied to analyze Eucalyptus g. wood chips and unbleached and chlorite-bleached pulp. The differences between samples have been established by examination of the spectra of the fractions obtained by successive extraction (acetone extractives, acetone free extractive samples, hemicelluloses, and lignins) by evaluating the derivative spectra, band deconvolution, etc. The energy and the hydrogen bonding distance have been evaluated. The relationship between spectral characteristics and sample composition has been established, as well as the variation of the degree of crystallinity after pulping and bleaching. The integral absorption and lignin/carbohydrate ratios calculated from FT-IR spectra of the IR bands assigned to different bending or stretching in lignin groups are stronger in the spectrum of eucalyptus chips than those from brown stock (BS) pulp spectra because of the smaller total amount of lignin in the latter. FT-IR spectra clearly show that after chlorite bleaching the structure of the wood components is partially modified or removed. Along with FT-IR data, the X-ray results confirmed the low content of lignin in the pulp samples by increasing the calculated values of the crystalline parameters. It was concluded that FT-IR spectroscopy can be used as a quick method to differentiate Eucalyptus globulus samples.

Cornelia Vasile

Papers

Thermal degradation of lignin - a review

Co-pyrolysis of pine cone with synthetic polymers

Spectral Characterization of Eucalyptus Wood

Vibrational spectroscopy and X-ray diffraction methods to establish the differences between hardwood and softwood

Vacuum pyrolysis of PVC I. Kinetic study