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Mesoporous silica nanoparticles are among the most promising nanovectors for controlled release of active compounds. In this work we design a mesoporous silica-based delivery system in which the release of the active compound is controlled by specific pore/wall interactions and can also be triggered by an external stimulus, such as the simple addition of water into the surrounding releasing medium. Due to its reversibility in presence of water, imine bond formation between amino groups and aldehydes has been proposed as a valuable approach to reach this scope. The amino-group is provided by the amino-functionalized mesoporous silica which has been obtained through the functionalization of Santa Barbara Amorphous (SBA)-15 with aminopropyltrietoxysilane. Whereas the aldehyde is represented by the active compound itself: the natural antimicrobial vanillin. The obtained particles have been embedded into PCL-based films. The amino-functionalization of mesoporous silica has been confirmed through NMR analysis and X-ray diffraction. Imine bond formation and evolution has been followed by 13C NMR before and after the contact of mesoporous silicas with water. Release kinetics of vanillin show that the diffusion of vanillin from films containing the functionalized mesoporous silica is delayed by about 20% and 75% with respect to films containing free vanillin, in water and in ethanol respectively. The most significant feature of the system is the stepwise behavior which shows that the release of the amount of vanillin bound to the NH2 groups of functionalized SBA is triggered only after the addition of water to the surrounding ethanolic solution. These findings give an important insight into the use of pristine and functionalized mesoporous silicas for the development of polymer films for active responsive packaging materials.

Corrosion inhibitors are largely exploited for the development of highly performing polymeric active coatings. One of the major drawbacks, however, relies in their UV sensitivity, which may compromise their ability to effectively prevent corrosion processes. This issue is particularly relevant in the field of cultural heritage preservation, in which polymeric active coating which are able to ensure a reliable and long-lasting protection against corrosion are highly needed. Besides proving that UV-induced photodegradation impressively lowers the corrosion inhibition ability of benzotriazole (BTA), in the present work we show that this phenomenon can be largely prevented by exploiting inorganic nanocarriers. More specifically, BTA molecules loaded into functionalized mesoporous silica nanoparticles are preserved from photodegradation and released in the host coating only in the presence of acid-related external stimuli. Accelerated corrosion tests carried out on a commercial acrylic-based coating containing engineered mesoporous silica nanoparticles loaded with BTA demonstrated that the developed system possesses an excellent anticorrosion ability.

In the present paper, we report results about the preparation and the morphological, thermal, mechanical and electrical characterization of new materials for the impregnation of rotor and stator windings of medium power traction motors. These new materials are obtained by the addition of nano-sized alumina (Al 2O 3) fillers to commercially available silicone resin. Their measured physical properties are compared with those of the unfilled matrix, used as a reference, and the influence of the weight concentrations, ranging between 1 wt % and 7 wt % is fully discussed.

Formation of micro-cracks is a critical problem in polymers and polymer composites during their service in structural applications. In this context, materials endowed with self-healing features would lead to the next polymers generation. In the present paper, an epoxy system integrating Diels-Alder epoxy adducts is investigated by thermal and spectroscopic analysis. The direct and retro D-A reaction have been studied by FTIR and specific absorption bands have been identified. Finally, mechanical tests have been performed on the system. The polymer is able to heal fracture and micro-cracks recovering its stiffness after a thermal treatment.

Rigid-rod vinyl ester resins represent an interesting family of materials. They can be synthesized starting from the corresponding epoxy resin. Due to their composition, they exhibit outstanding properties, such as heat and chemical resistance, high impact, and corrosion resistance. These features, combined with the ease of curing, make vinyl ester resins good candidates for several industrial applications, such as glass fiber composites, adhesives, corrosion-resistant coatings, electrical encapsulation, and radiation-curable inks. In the first part of this study, a new liquid crystalline methacrylated monomer was prepared and tested as an adhesive. The synthesis was carried out by reacting methacrylic acid with a rigid-rod epoxy monomer derived from the reaction between p-(2,3-epoxypropoxy)-α-methylstilbene (DOMS, diglycidyloxy α-methylstilbene) and aniline in a molar ratio of 3 to 2. The monomer was named md3a2 (methacrylated derivative of DOMS-aniline epoxy compound). Md3a2 is liquid crystalline in a w...

Diglycidyl terminated 4,4′-oxydiphenyl cured with an aromatic diamine exhibits liquid crystalline properties, even if the amount of hardener is used in defect with respect to the stoichiometric amount. Physical properties of the resin, hardened with different quantities of amine are presented and discussed. In particular the high values of fracture toughness of this class of thermoset has been explained on the basis of the biphasic nature of the crosslinked resin.The differences in mechanical properties are analyzed taking into account the different crosslink densities.

Objective The effect of a novel light curing process, namely soft light energy release ( SLER ® ), on shrinkage, mechanical strength and residual stress of four dental restorative materials (DEI experience, Gradia Direct, Enamel Plus HFO and Venus) was investigated. Methods Composite specimens were fast cured through high level of power density and soft light energy release. Temperature, linear shrinkage and light power measurements were acquired in parallel in order to assess the effect of light modulation on temperature and shrinkage profiles during the light curing process and the following dark reaction phase. The small punch test and Raman spectroscopy were adopted to investigate the effect of SLER ® on mechanical strength and on internal stress, respectively. Results The soft light energy release photo-polymerization allows to reduce of about 20% the shrinkage rate and to increase the strength of fast light cured specimens. In addition, a more relaxed and homogeneous internal stress distribution was observed. Significance Properties of fast cured restorative materials can be improved by adopting the soft light energy release process.

he study reports on the synthesis of poly arylene vinylenes by use of a cascade Suzuki-Heck reaction polymn. The reaction between suitable aryldibromides with potassium vinyltrifluoroborate in the presence of a Pd(0) catalyst permits the access to a series of poly(fluorenylenevinylene)s. The protocol is characterized by a great versatility, deriving from the use of easily attainable substrates, and yields polymers with low percentages of structural 1,1-diarylenevinylene defects. Exploiting this procedure, a series of random poly(9,9-dioctyl-2,7-fluorenylenevinylene-co-N-octyl-3,6-carbazolylenevinylene) copolymers at 20+80% mol/mol of carbazole (PFV2-6) was achieved. Their properties have been investigated by 1H-NMR, IR, TGA, DSC, cyclic voltammetry, UV-Vis and photoluminescence, and compared to those of poly(9,9-dioctyl-2,7-fluorenylenevinylene) (PFV1) obtained by the same method. The electroluminescence properties of the materials were tested by constructing OLED devices of ITO/PEDOT-PSS/PFV1-6/Ca/Al configuration. (c) 2008 American Institute of Physics.

Thermotropic liq.-cryst. ethylene glycol-p-hydroxybenzoic acid-terephthalic acid polyester, when spun into fibers, sorbs very little CO2, thus making these polymers highly qualified for application requiring very high barrier properties.

Because of their superior mechanical and thermal properties, light weight, andfavorable cost/performance ratio, nanocomposite materials appear to be suitablereplacements for metals and alloys in many industrial applications in fields such asautomotive, structural plastics, electronics, packaging, and so on (1). The technolog-ical relevance of this large-scale market for polymers is evidenced by the numerouspatents issued over the last few years, even though only few applications have en-tered the market. Polymer-clay nanocomposite systems were successfully preparedby melt compounding using several thermoplastic matrices (polyamides, polyolefins,etc.), but few data are reported in the scientific literature on polyester-based nano-composites (2). Because of the high commercial relevance of polyesters, we have in-vestigated the effect of organoclay inclusion on the structure and properties of thesehybrid systems. In particular, we have studied the relationships between process-ing conditions, hybrid composition (organoclay type and content), nanoscale mor-phology and properties of poly(butylene terephthalate) (PBT) nanocomposites basedupon several commercial organo-modified montmorillonites at different weight per-centages. The melt compounding was performed using a twin-screw extruder, at extru-sion rates of 90 or 150 rpm. Polym. Eng. Sci. 44:1012–1018, 2004.

The presence of hydrogen bonds in the chemical structure of polymers promotes and stabilises the crystalline phase. For liquid crystalline (LC) polymers, the side insertion of aliphatic units to the mesogenic unit is a suitable artifice to decrease the crystalline stability, without significantly affecting the stability of the LC phases. Here, we report on the synthesis of a LC homo-polyurethane with high hydrogen bond concentration along the chain and bearing an n-pentyl side-chain. Rheological behaviour, thermal analysis, and X-ray diffraction show that the stable LC phase is the nematic.

The use of the same thermoplastic polymer for both the matrix and the filler in the preparation of composites is very attractive, because such composites are in principle fully recyclable. Recently it has been reported the preparation of a mono-material composite (MMC) made of polypropylene to be used in automobile parts. In this work we report on the preparation and characterization of matrices for quasi MMC made of poly(ethylene terephthalate) (PET). Particularly we found PET copolymers containing isophthalate (IPA) units adequate to be used as matrix.

The modification of the interface between polycarbonate (PC) and liquid crystalline 40/60 poly(ethylene terephtalate-co-p-hydroxybenzoate) (PetPhb60) was studied. The ester interchange reaction between the components of the 50% w/w mixture, responsible for the formation of molecular segments of intermediate affinity toward the parent polymers, has greatly affected the morphology of extrudate samples. The reacted compound was used in the ratio of 5% as compatibilizer in the formulation of the in situ composite between PC and PetPhb60, containing 10% of the reinforcing thermotropic liquid crystal polymer (TLCP). The effects of the adhesion promoter has been evaluated comparing the morphological features of melt-drawn fibers with the previous result concerning the fibers without the compatibilizer

Thermal treatment of amorphous poly(aryl-ether-ether ketone) below the glass transition temperature has been studied. The extent of aging was measured by differential scanning calorimetry. X-ray and Fourier transform infrared spectra were used to study both melt-cast and annealed samples. The effect of the thermal treatment of viscoelastic response was evaluated using creep tests. Aging has been shown to be accompanied by a marked change in the transport properties of the material.