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End functionalized polylactides are prepared by ring opening polymerization of L-lactide in the presence of stannous octoate (Sn(Oct)2). Three chromophores, 9H-carbazol-ethanol (CA), 9-fluorenyl-methanol (FM), and 2-(4-(2-chloro-4-nitrophenylazo)-N-ethylphenylamino)ethanol (Disperse Red 13, DR), are for the first time used as co-initiators in the polymerization process. The polymerization reaction is initiated by conventional thermal treatment, but in the case of FM, microwave-assisted polymerization is also carried out. CA and FM absorb and emit in the UV portion of the electromagnetic spectrum, whereas DR absorbs in the visible part. The obtained end-capped polylactides derivatives show the same photophysical properties as the initiator, so they are &ldquo, macromolecular dyes&rdquo, (MDs) that can be used &ldquo, as synthesized&rdquo, or can be blended with commercial poly(lactic acid) (PLA). The blends of PLA with MDs have ultraviolet-visible (UV-Vis) absorption and fluorescence emission features similar to that of MDs and thermal properties typical of PLA. Finally, migration tests, carried out onto the blends of PLA with MDs and PLA with free chromophores, show that MDs are less released than free chromophores both in solution and in the solid phase.

Few decades ago, the expertise gained from well-established extraction, processing and degradation techniques, paved the way for the use of ultrasounds as an alternative energy source in chemistry. Among other peculiar features, the locally extreme temperatures and pressures resulting from cavitation, proved to efficiently trigger reactions while maintaining mild average conditions, enhancing rates and yields and, hence, contributing to increase the popularity of sonochemistry up to the present level. The physical properties of the irradiated mixture are crucial for the effectiveness of cavitation, as well as for the proper transfer of acoustic energy to reactants. Therefore, the choice of a solvent that meets these requirements, while minimizing the environmental impact of the process is a fundamental one. Studies that combine sonochemistry with green, non-conventional solvents or with no solvents are surveyed in this review, evidencing how the most frequently investigated options are water phase, ionic liquids, followed by ethylene glycol and its oligomers, glycerol and few other biomass-based solvents. Numerous solvent-free, ultrasound-promoted procedures are also reported in the literature and are included in this contribution. The vast majority of the examples gathered here describe organic reactions, syntheses of nanosystems and polymerizations.

A lot of research is focusing on improving physico-chemical and mechanical features of PLA, but less efforts are made to study and expand its optical activity in the UV-visible region. Since its general characteristics make PLA particularly useful for fibers, packaging and similar applications, UV-barrier capabilities and aesthetic appearance are topic issues with a strong influence on the performances of products and appeal. Considering the difficulties in dying PLA-fibers and the possible loss by evaporation or leaching of low molecular weight dyes mixed with the polymer matrix, the immobilization of the chromophores onto the polymer matrix can be a valuable alternative to produce a stable and homogeneously dyed PLA films or fibers. In this paper the use of chromophores as initiators in the ring opening polymerization (ROP) of L-lactide catalyzed by stannous octoate was proposed. The so obtained end-functionalized polylactides may be considered "macromolecular dyes" that can be used "as synthesized" or can be blended with other polymers. In this study, the ROP of L-lactide catalyzed by stannous octoate was carried out in bulk in the presence of three chromophores: 9-fluorenyl-methanol (FM), 9H-carbazol-ethanol (CA) and 2-[4-(2-chloro-4-nitrophenylazo)-N-ethylphenylamino]ethanol (Disperse Red 13, DR). FM and CA absorb in the UVa and UVb region and emit by fluorescence in the range between 300 and 400 nm, whereas DR is a commercially available dye with absorption maximum at about 480 nm in the visible portion of the electromagnetic spectrum. Different initiator/lactide ratios were used for each chromophore in order to keep low the MWs of the products, to facilitate their characterization and to emphasize the relation between initiator and polymer properties. The obtained materials were structurally characterized by FT-IR, 1H-NMR and SEC; their thermal properties were studied by DSC and their photophysical features were determined by UV-Vis spectroscopy and fluorescence emission and compared to those of the free chromophores. Some selected macromolecular dyes were mixed to high molecular weight PLA with the aim to obtain "dyed PLA" films. For comparison high molecular weight PLA was melt mixed also with the free chromophores. The films were analyzed by UV-Vis spectroscopy and florescence emission and it was demonstrated that the photophysical properties of the macromolecular dyes were transferred to the PLA films. Moreover, by migration tests carried out suspending the PLA films containing the macromolecular dyes or the free chromophores in aqueous/ethanol solution, it was observed that the low molecular weight chromophores are lost by migration whereas macromolecular dyes are not released.

Bipyridine-functionalized poly(lactic acid) (PLA)-based stereocomplexes were employed to stabilize Pd-nanoparticles (NPs). The well defined heterogeneous catalysts were suitable to catalyze the partial hydrogenation reaction (i.e. p(H 2 ) = 3 bar, 25 and 60 °C) of phenylacetylene and diphenylacetylene in THF to give styrene and cis -stilbene with a chemoselectivity of 96% and 91%, respectively. Since the polymer support revealed stable under real catalytic conditions, stabilizing also efficiently the Pd-NPs in the course of the catalytic reaction, the heterogeneous catalytic system was easily recyclable. The catalytic activity as well as the chemoselectivity of the supported catalyst proved to be comparable in four consecutive catalytic cycles even by recovering the catalyst in air atmosphere after each cycle.

Pyridine-end-functionalized poly(ethyleneglycol) was used to stabilize Pd-NPs, which were obtained by the reduction of defined Pd-macrocomplexes with hydrogen. The obtained Pd catalysts were employed to catalyze the areobic oxidation of alpha,beta unsaturated alcohols in water to the corresponding carbonyl compounds. The type of Pd-macrocomplex used (i.e. molar ratio between macroligand and Pd(II)) determined the final NPs' size and the stability of the latter against agglomeration in the course of the catalytic reaction.

In temperate regions, latewood is produced when cambial activity declines with the approach of autumnal dormancy. The understanding of the temporal (cambium activity vs dormancy) and spatial (phloem, cambial region, maturing xylem) regulation of key genes involved in the phenylpropanoid pathway during latewood formation represents a crucial step towards providing new insights into the molecular basis of xylogenesis. In this study, the temporal pattern of transcript accumulation of 12 phenylpropanoid genes (PAL1, C4H3/5, C4H4, 4CL3, 4CL4, HCT1, C3H3, CCoAOMT1, COMT2, COMT5, CCR2) was analyzed in maturing xylem and phloem of Picea abies during latewood formation. Quantitative reverse transcription-polymerase chain reaction analyses revealed a well-defined RNA accumulation pattern of genes involved in the phenylpropanoid pathway during latewood formation. Differences in the RNA accumulation patterns were detected between the different tissue types analyzed. The results obtained here demonstrated that the molecular processes involved in monolignol biosynthesis are not restricted to the cambial activity timeframe but continued after the end of cambium cell proliferation. Furthermore, since it has been shown that lignification of maturing xylem takes place in late autumn, we argue on the basis of our data that phloem could play a key role in the monolignol biosynthesis process.

Melted poly(ethylene glycols) (PEGs) were used for the first time as solvent for the sonochemically promoted cyanation of aryl halides employing inexpensive and safe K4[Fe(CN)6] and a relatively low amount of Cu-based catalyst. The Mw (weight-average polymer molecular weight) of PEG proved to notably influence the substrate conversion, which is indicative of a strong dependence of the sonication efficacy on solvent properties. Gel permeation chromatography (GPC), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) contributed to the characterization of the polymer and the elucidation of the catalytic system.

International audience; Melted poly(ethylene glycols) (PEGs) were used for the first time as solvent for the sonochemically promoted cyanation of aryl halides employing inexpensive and safe K4[Fe(CN)6] and a relatively low amount of Cu-based catalyst. The Mw (weight-average polymer molecular weight) of PEG proved to notably influence the substrate conversion, which is indicative of a strong dependence of the sonication efficacy on solvent properties. Gel permeation chromatography (GPC), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) contributed to the characterization of the polymer and the elucidation of the catalytic system.

The formation of a fibrin network following fibrinogen enzymatic activation is the central event in blood coagulation and has important biomedical and biotechnological implications. A non-covalent polymerization reaction between macromolecular monomers, it consists basically of two complementary processes: elongation/branching generates an interconnected 3D scaffold of relatively thin fibrils, and cooperative lateral aggregation thickens them more than 10-fold. We have studied the early stages up to the gel point by fast fibrinogen:enzyme mixing experiments using simultaneous small-angle X-ray scattering and wide-angle, multi-angle light scattering detection. The coupled evolutions of the average molecular weight, size, and cross section of the solutes during the fibrils growth phase were thus recovered. They reveal that extended structures, thinner than those predicted by the classic half-staggered, double-stranded mechanism, must quickly form. Following extensive modeling, an initial phase is proposed in which single-bonded "Y-ladder" polymers rapidly elongate before undergoing a delayed transition to the double-stranded fibrils. Consistent with the data, this alternative mechanism can intrinsically generate frequent, random branching points in each growing fibril. The model predicts that, as a consequence, some branches in these expanding "lumps" eventually interconnect, forming the pervasive 3D network. While still growing, other branches will then undergo a Ca(2+)/length-dependent cooperative collapse on the resulting network scaffolding filaments, explaining their sudden thickening, low final density, and basic mechanical properties.

Poly(lactic acid) and poly(caprolactone)-based macroligands bearing a pyridine end-group were employed to coordinate to Pd(II). The resulting macrocomplexes were used to catalyze the aerobic oxidation of alcohols to carbonyl compounds in toluene. The poly(lactic acid) based catalyst showed high stability in the course of the catalytic reactions, while its poly(caprolactone) counterpart degrades due to transesterification reaction occuring between the substrate and the polymer chain.

Biodegradable polymers, as well as polymers produced from renewable feedstocks, are attracting increasing interests as possible substitutes for conventional plastics: a higher energy efficiency in synthesis and processing steps must be continuously pursued in order to maximize the intrinsic environmental benefits brought by this class of materials. Microwave assisted organic synthesis (MAOS) is nowadays a major topic in green chemistry and a great (yet rising) number of papers can already be found that report striking advantages over conventional thermal heating. Nonetheless microwave (MW) energy sources are recently being chosen also for several polymerization reactions. Indeed, reduced heating times and superior homogeneity provided by MW reactors may play a central role in optimizing production processes, with a dramatic improvement in the environmental performance. In the introduction of this chapter we’re briefly recalling some theoretical principles of microwave-matter interaction; several experimental setups are then examined and, eventually, thermal and non-thermal specific microwave effects are described and commented. The following paragraph is dedicated to a comprehensive survey of synthesis examples found in scientific literature and categorized by polymerization technique, in which particular relevance is given to products of increasing commercial importance like poly(e-caprolactone) (PCL) and poly(lactic acid) (PLA). A third part of the chapter deals with the employment of microwave heating for chemical modification and processing of polymers; the last paragraph summarizes advantages and drawbacks of microwave assisted polymer chemistry, stressing the energy efficiency topic and drawing conclusions.

Pd(II)-macrocomplexes of diffferent coordination geometries and bearing pyridine-end-functionalized poly(lactic acid) were synthesized and characterized.

The suitability of L-poly(lactic acid) (L-PLA) as a transparent matrix, alternative to poly(methylmetacrilate) (PMMA), for use in luminescent solar concentrators is herein demonstrated. Low molecular weight L-PLA-based films, both chemically modified or blended with an oligothiophene luminescent dye (T(5)OH), showed excellent processability, photostability, and exhibited fluorescence quantum yields (of about 35%) even higher than T(5)OH-doped PMMA.

Since the first contributions by Gedye and Giguere in 1986, growing attention has been registered on the use of microwave heating in organic synthesis. However still many aspects need to be clarified especially about the so called “microwave effect” and the possible degradation phenomena that may be recognized during polymer synthesis. In this work the complex cone-25,27- dipropyloxy-26,28-dioxo-calix[4]arene titanium (IV) dichloride (1) has been tested for the ring opening polymerization of L-lactide, comparing the effect of conventional heating with a possible microwave assisted strategy. The polymers obtained were fully characterized (NMR, IR, HPLC-SEC, DSC, MALDI-TOF and WAXD analysis). As expected the use of microwave irradiation induced an increase of the polymerization rate. On the other side the use of microwaves resulted in a slight loss of the control over molecular weight and molecular weight distribution if compared with a conventional thermal treatment.