The use of a catalyst is required to synthesize poly(D,L-lactide) (PLA) and tin (II) 2-ethylhexanoate could be highlighted among them. However, this kind of catalysts can produce bio-dangerous compounds limiting the PLA in medical applications, therefore there is a need to investigate novel bio-safe catalysts. Taking into account this problem, this communication reports the use of micro- and nano-ZnO particles as catalysts for the microwave-assisted polymerization of D,L-lactide. By microwave heating a high monomer conversion (higher than 95%) was achieved in a relatively short reaction time (3 hours). Morphology/size and concentration of ZnO particles presented a strong effect on the production of PLA, star-like microparticles leaded to conversion ca. 25%, well below to the values achieved with the nanoparticles. Furthermore, the formation of a ZnO-PLA hybrid was evidenced by spectroscopic and thermal characterization techniques. The methodology herein developed represents a new pathway for the green synthesis of PLA.

An experimental study oriented to gather kinetic modelling data in the ethylene polymerization via metallocenes is reported. Also is illustrated the employment of two methods for determination of kinetic behavior and the instantaneous activity of Ziegler-Natta catalysts in the slurry polymerization of ethylene. The theoretical basis for both methods is described as well as the required instrumentation for its implantation at a laboratory level. An experimental program of polymerization with two different metallocenic systems was executed, showing that the direct (measurement of ethylene flow) as well as the calorimetric method (based on energy balances) give equivalent high quality information on the kinetic performance of the catalyst.

Organic/inorganic (O/I) composite latexes combine the best attributes of inorganic solids with the processability, lightweight and handling advantages of organic polymers. There are common methods to produce polymer nanocomposites: melt compounding, in-situ polymerization and solution mixing. Emulsion polymerization is an unique chemical process widely used to produce waterborne resins with various colloidal and physicochemical properties. This free radical polymerization process involves emulsification of the relatively hydrophobic monomer in water by an oil-in-water emulsifier, followed by the initiation reaction with a water insoluble initiator. This research focuses on the synthesis and reactions kinetics of polyacrylic latex with the incorporation of various nanospheres (SiO2, TiO2, Al2O3 and Fe2O3), and layered silicate (Bentonite nanoclay) nanoparticles via emulsion polymerization. The influence of nanoparticle concentration on reaction kinetics was also investigated. The results showed that the concentration of nanoparticles has significant influence on the monomer conversion, particle size, coagulum content and viscosity of the emulsion. Furthermore, the nanostructured emulsions were shear thinning, exhibiting a power-law behavior, and the viscosity was influenced by the nanoparticle morphology.

Organic films with a thickness of few nanometers are potentially useful components in many practical and commercial applications such as sensors, detectors, displays and electronic circuit components. In this context, the Langmuir-Blodgett (LB) method is one the most promising techniques for preparing these films.

In this work, we report the synthesis and characterization of three new amphiphilic organometallic compounds with ferrocene units, which consist of one ferrocenyl aminocarbene with the general formula FcC=Cr(CO)5NH(CH2)15CH3, and two ferrocenyl amides with the general formula FcC=MNH(CH2)15CH3 where M = S or Se. These new derivatives have been synthesized to study the influence of long alkyl side chain and the hydrophilic head on the film organization behavior at the air-water interface.

The Langmuir-Blodgett (LB) technique was focused for building ordered nanostructures in molecular assemblies of ferrocenyl derivatives, which are apt to form a stable and transferable monolayer film. The π-A isotherm, hysteresis, Brewster angle microscopy (BAM) and film stability were used to characterize the behavior of a monolayer film at the air-water interface. Z- type LB films were prepared from molecular monolayers which were transferred onto glass substrates. These films were characterized by atomic force microscopy (AFM), UV-Visible spectra and X-ray diffraction (DRX) techniques.

Differences on physicochemical properties of poly(pentadecanolide), PPDL, synthesized by enzymatic ring opening polymerization at two different temperatures, 70 C and 90 C, using Novozyme-430 were assessed. PPDL synthesized at 90°C presents lower molecular weight and crystallinity than the one prepared at 70°C. It was detected by FTIR that PPDL synthesized at 90°C presents a large amorphous phase with more terminal OH groups. A difference in the melting and crystallization behavior was detected by differential scanning calorimetry, DSC, where the melting of the PPDL synthesized at 90°C presents multiple melting and crystallization events at lower temperature than those exhibit by PPDL synthesized at 70°C which presents a well defined single melting and crystallization event. The differences in melting behavior are attributed to the presence of a larger amorphous phase in PPDL synthesized at 90°C due to increased number of terminal OH groups that disrupt the crystalline structure. Thermal stability is also higher in PPDL synthesized at 70°C since the onset of decomposition starts 50°C above that observed in PPDL obtained at 70°C.

Poly(acrylamide-co-2-hydroxyethyl methacrylate), hydrogel microparticles were prepared by free radical copolymerization of acrylamide (AAm) and 2-hydroxyethyl methacrylate (2-HEMA) using an inverse emulsion polymerization technique, employing ethylene glycol dimethylacrylate (EGDMA) as crosslinker in the presence of w/o emulsifiers span-80 and span-85 (sorbitol mono-oleate) above the lower critical solution temperature. Water absorption capacity and characteristics of the hydrogel microparticles were analyzed by Optical Microscopy (OM), Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR) and Thermogravimetric Analysis (TGA). Thus, microparticles were submitted to a gravimetric study on their ability to absorb and to retain distilled water at 25°C. One gram of microparticles absorbed at least 15 g of water. By varying the relative ratio between the continuous phase (hexane and emulsifiers) and the dispersed phase (monomers, initiator and crosslinker), non-agglomerated dispersed particles with nearly spherical shape were obtained having a narrow size distribution in the range from 10 to 20 µm. At a constant value of the emulsifier, and as a result of increasing the stirring rate, a particle size reduction was observed from 13 to 7 µm. The PAAm and PHEMA structures of synthesized hydrogel were confirmed using FTIR analysis. Additionally, through thermal analysis the P(AAm-HEMA) hydrogel showed an increase of water retention and thermal stability due to PAAm addition.

The polyaniline (PANI) and regioregular poly(3-hexylthiophene) (P3HTr) are polymers synthesized easily, can be deposited as a film by various techniques, are materials that exhibit a variety of colors to go through oxidation processes and reduction by applying an external potential, both polymers have an immediate response rate of color. The electrochemical behavior of the PANI and P3HTr is complementary, that is, if a positive potential to the device is applied, the PANI film is oxidized while the P3HTr film is reduced, on the other hand, if a negative potential is applied, the PANI film is reduced while the P3HTr film is oxidized. Both films in its redox process are clarified and obscured at the same time, this color change provides a significant difference in optical transmittance on a dual electrochromic device (DED's).

In this research, regioregular poly(3-hexylthiophene) was synthesized and characterized, films were deposited by spin-coating and dip-coating techniques. Polyaniline films were deposited by chemical bath and spin-coating techniques. Dual electrochromic devices based on P3HTr and PANI were prepared. The devices were studied by UV-vis spectroscopy at three different voltages: 1.4 V, 0 V and -1.4 V, optical kinetic tests were also performed at 550 nm applying a positive potential (1.4 V) and negative (-1.4 V). The results indicated the wavelength where both (PANI and P3HT) reach the greatest difference in transmittance. The influence of deposit type of polymer films on electrochromic response was determined.

The chemical synthesis of the copolymers poly(3-HT-co-EDOT-co-fluorene) and poly(3-HT-co-EDOT-co-TDR1) is reported. The first copolymer is derived of 3-hexylthiophene (3-HT), 3,4-ethylenedioxythiophene (EDOT) and 2,2'- (9,9-dioctyl-9H-fluorene-2,7-diyl) bisthiophene (fluorene). The second copolymer is derived of 3-hexylthiophene (3-HT), 3,4-ethylenedioxythiophene (EDOT) and (E)-2-(ethyl(4-((4-nitrophenyl)diazenyl)phenyl)amino)ethyl 2-(thiophen-3-yl)acetate (TDR1). Their physicochemical characterization by 1H NMR, FT-IR, DSC-TGA, GPC, UV-vis, cyclic voltammetry was carried out. These copolymers combine the high electron density and low oxidation potential of EDOT with the high charge mobility and processability of 3-HT. These are candidates for applications as active or barrier layer in electronic devices (bulk heterojuntion organic solar cells) or as functional membranes (e.g., sensors).

Ruthenium-nitrosyl (RuII(NO)) complexes are stable in the dark, but exhibit a unique photoreactivity which can lead either to a solid state isomerization from RuII(NO) to RuII(ON), or to a nitric oxide (NO·) release in solution. From our recent discovery of a high yield of isomerization (> 92%) in [RuII(py)4Cl(NO)](PF6)2, we have developed a computational strategy aimed at designing switchable nonlinear optical (NLO) material with high contrast (large difference in the on / off NLO response) in the solid state. Our synthetic targets are terpyridine based RuII chromophores in which various substituents can be introduced to adjust the NLO response which, at best, should be vanishing in the off state. Alternatively, these complexes can undergo a photo-induced NO· release in solution, a possibility which becomes increasingly appealing in relation to the discovery of the numerous biological roles of NO·, in the context of the emergence of the photodynamic therapy. A promising fluorene-terpyridine RuII(NO) complex was investigated, which could find an additional interest in relation to its capability for releasing NO· by a two-photon absorption process.

Poly(vinyl alcohol) (PVA) is a synthetic polymer which has been used in a wide variety of applications. This polymer has been extensively investigated by a large number of techniques to shed light about its physical and chemical properties. In this work, for fist time, high frequency (1x109-3x109 Hz) relaxation process has been observed in the PVA films in the temperature range of -100C to +1200C. This relaxation exhibits negative activation energy below glass transition temperature Tg and at higher temperature positive activation energy with subsequent saturation. Upon cooling the activation energy was negative again. This high frequency relaxation process and its temperature dependence can be attributed to the interaction of the bounded water and the changes of energy and freedom of movement of OH side molecular chains groups. This conclusion has been supported by in situ FTIR measurements. A possible scenario of this relaxation and dynamics of molecular motion has been proposed.

The addition of nanoparticles into polymeric materials has changed dramatically the properties of the host polymers, promising a novel class of composite materials with different properties and added functionalities. This research focuses on the influence of inorganic nanospheres particles such as SiO2, Al2O3, Fe2O3, TiO2 and nanoplatelets, such as Bentonite nanoclay, on the thermo-mechanical properties of a polyacrylic latex (utilized in commercial coatings). The analysis of the thermal and mechanical properties showed a decrease of Young's modulus and glass transition temperature Tg in the presence of spherical nanoparticles. However, there was an increase of these properties in the presence of nanoplatelets (Bentonite), as demonstrated by the dynamic mechanical analysis and uniaxial tensile analysis. Moreover, water contact angle measurements demonstrated significant increase in hydrophobic behavior when incorporating nanosphere particles as compared to nanoplatelets. These results showed that the metallic oxides nanoparticles greatly influenced the physical and mechanical properties of the neat polyacrylic matrix.

This work presents results on the prediction of the molecular weight distributions (MWD) of chain growth polymerization using conventional software and hardware tools. The investigation focuses on two kinds of polymerization processes: free radical batch and continuous polymerization processes with application to low density polyethylene synthesis (LDPE); and coordination polymerization via metallocenes with application to high density polyethylene synthesis (HDPE). For both processes, kinetic models, consisting of sets of differential equations describing the dynamic behavior of all the chemical species in the reaction media, are presented. From these sets is possible to obtain the molecular weight distribution of the polymer1,2,4

Strategies for the simulation of the polymerization models were developed and results of these simulations are presented. On the free radical polymerization case, the next results are highlighted: i) It was confirmed that the chain transfer to polymer step produces strong asymmetries on the MWD as well as a high polydispersity index; ii) It’s possible to calculate the MWD in the CSTR process through a simulation strategy that permits the decoupling of the live and dead chains populations. On the metallocene polymerization case, it was demonstrated that the coordination standard model represents well the system experimentally studied and it can be employed to directly calculate the molecular weight distribution.

These results confirm the idea that the complete MWD can be directly calculated with conventional hardware and software tools.

An eco-friendly adsorbent was prepared by immobilization of Persimmon Tannin (PT) in cellulose viscopearls to remove caffeine. The immobilization time within a range of 1-42days was performed. Batch adsorption experiments were studied for different Persimmon Tannin on Cellulose Viscopearls (PTIC) gel samples, adsorbent dosage, and initial caffeine concentration. FTIR indicated that PT was successfully immobilized onto viscopearls. SEM images showed differences especially on particle size and shape, between control, day7, and day28 of PTIC gel samples. The adsorption capacity results showed that removal of caffeine as the amount of adsorbed increased, the percentage of caffeine adsorption increased accordingly, but it decreased with the increased in initial caffeine concentration. Results for different PTIC gel samples showed that day 42 PTIC sample exhibits the highest adsorption capacity of caffeine solution of 43.3mg/g. The samples showed water contents in the range of 343-324%.The equilibrium data were analyzed using Freundlich and Langmuir equations. It suggested that viscopearls acted to be a suitable insoluble matrix to immobilized PT, instead of using crosslinkers.

Hyperbranched structures containing pyrrole units were obtained from ortho-, meta- and para-diaminodiphenyldiacetylenes as AB2 type monomers by one-step polymerization.

The para-hyperbranched compound was observed by optical microscopy and scanning electron microscopy.

Microscopy studies identify two phases. The first is the insoluble one which gives origin to flake type structures. The second is acetone soluble phase, which generated crystalline structure manifesting in optic anisotropy and rhomboids and triangles dendrimeric structures.

A potential alternative to achieve smart materials for biomedical applications is the combination of natural and synthetic polymers. In order to understand the structure and properties of two γ-radiation grafted biopolymers, chitosan-g-poly(N-isopropylacrylamide) (CS/PNIPAAm) and cotton-g-2-(dimethylamino) ethyl methacrylate (CG-DMAEMA) were analyzed by solid state nuclear magnetic resonance (SSNMR) 13C-CPMAS at different contact times (tCP). The use of different tCP in this grafted biopolymers showed that chemical shifting, broadening, size and symmetry of the some signals, gives important information for structure elucidation and molecular mobility. SSNMR spectra indicate changes in the local order structure, CG suffered less modifications when it is grafted than CS. CG-g-DMAEMA spectrum is very similar to CG spectrum, in contrast with spectrum of CS-g-NIPAAm, is very different than CS. Spectra of swelling polymers in water showed more structural information about secondary structure.

In recent decades, we have seen an increase in the use of computers. This presents a crossroads in deciding what to do with the units that become "obsolete". As society, we have created a new type of solid waste that must be handled differently because the diversity of materials composition. In addition, at the end of their life cycle also affects the environment when the materials are disposal in landfill; i.e. plastic substrate (polycarbonate), may lead to chronic problems such as hyperactivity, infertility or even cancer.

The recycling of electronic equipment is from whole parts, such as the electronic cables. Recover substances (plastics) and compounds (metals) from electronic cables could it be possible.

We are looking for a solution to this problem and we created a structure of recycling to reduce the waste at the source and allows that which cannot be reduced is recycled, because computers contain 20% of thermoplastics and 6% of plastic mixtures that are the subject of this investigation.

The recycled chemist hired himself since it provides capabilities that address the limitations of the mechanical recycling; you need large quantities of clean, separate, homogeneous plastic waste to be able to guarantee the quality of the final product. Chemical recycling overcomes these drawbacks, since the classification of the different types of plastic resins from of waste is not necessary.

Based on the data obtained from this research, determines that the recycling of computer waste in conjunction with other plans of reduction at source makes this a viable alternative for the management of the same. Benefits that can be derived by establishing a recycling of the computer waste program is donating units or sell these affordable to low-income people who otherwise would not have access to this technology.

The protected agriculture has gained great importance worldwide in the past 10 years. For example in the case of production in greenhouse conditions, that records an annual growth of 20%.

An important aspect greenhouse production is the medium used for growth of the plant, which may be an organic or inorganic substrate.

One of the advantages of the use of regional substrates is the availability and lower cost, and further organic in gives the tendency to manage sustainable production systems.

The organic substrates alone or in mixtures improve conditions for plant growth in terms of physical, chemical and biological as a perspective.

A wide variety of materials that can be used as agricultural substrates, but there are criteria to be considered for its election as: plant requirements, conforming as possible to the ideal characteristics of a substrate and effect on the environment.

Overall, we can summarize that a substrate for growing plants is any material that can provide attachment, oxygen and enough water for optimal development of the same, or in nutrient case requirements can be covered with a single material or combination with others.

In this paper the tomato crop is presented comparing two production systems to determine the yield and fruit quality under plastic cover, high densities of drip irrigation and using the tezontle as substrate, as this provides good drainage, almost no contribution nutrients and slightly neutral PH. And also allows us to transplant to a larger pot without disturbing the root and provides the necessary aeration.

Bioactive materials based on polymer/hydroxyapatite are currently being extensively investigated as materials for promotion of bone tissue regeneration and reconstruction [1]. In this work, a material interpenetrating based on poly 2-hydroxyethyl methacrylate (pHEMA), Chitosan and hydroxyapatite (HA) was prepared following the methodology of the foaming gas Damla Çetin [2], generating an interpenetrated network with the chitosan filled with hydroxyapatite. The materials were evaluated by thermal gravimetric analysis (TGA) and in vitro bioactivity [3] (SBF) and characterized by using scanning electron microscopy (SEM). The TGA studies suggested that there was not existence of possible interactions between polymers and HA but there is a thermal stability increase in the HA content. Meanwhile, SBF and its characterization by SEM, was found that the materials are bioactives as indicated by the formation of a bone-like apatite layer after immersion in simulated body fluid, indicating the potential of this material for use in bone tissue engineering.

Dynamic mechanical properties of polypropylene (PP) and grafted polypropylene (PP-g-MA) composites reinforced with acetylated wheat straw fibers (WSF) is reported in this work. The materials were prepared with different fiber particle sizes (40, 80 and 140 U.S. mesh) and at different fiber contents (5, 10 and 15 wt.%). The PP and PP-g-MA composites, where anhydride maleic (MA) was used as coupling agent, were obtained using a twin-screw extruder; whereas an injection-molding machine molded the composite pellets into testing specimens. To observe the morphology of the composites, micrographs were taken with an optical microscope. The Dynamic mechanical properties were analyzed using a torsional rheometer. The morphological analysis showed a high porous structure somehow similar to foamed materials. The storage modulus (G′) increased by increasing the fiber content, and decreased with fiber particle sizes for the PP composites. Meanwhile, the use of the coupling agent additive promoted a modulus increase due to higher fiber-polymer interaction, from better adhesion and chemical bonds formation between the fibers-coupling agent-PP.

Boron nitride nanotubes (BNNTs), an analogue of carbon nanotube (CNT) is one of the most used non-metallic materials in high technology applications related to thin film fabrications. Taking advantage of their unique properties such as electrically non-conductive, thermally conductive, and high hardness, it has been used in high-temperature electronic devices, multifunctional aerospace materials, and structures and electric and aerospace systems. The main goal of this project was to use BNNTs in the fabrication of nano epoxycomposites to enhance their thermal and mechanical properties to use it for applications in aerospace constituents. In order to accomplish this goal, BNNTs were functionalized with isopherone diisocyante (IPDC). Surface analysis techniques were employed to ensure the modification BNNTs and study the interface of the reinforced composites before and after the modification. Mechanical and thermal conductivity testing was performed in order to understand the quality of the composites. Three different nanocomposites were accomplished with hBN and BNNTs using two different epoxy polymers and three curing agents. The systems EPON 862/Curing Agent W/ (hBN or BNNTs) have Tgs and tan deltas higher compared with those fabricated at the same conditions without nanoparticles. The fabricated BN composites showed improved physical properties due to their particle dispersion and boron nitrite intermolecular interactions with the epoxy polymer.