Elastomeric composites based on Ethylene-Propylene-Diene-Monomer (EPDM) filled with multi-wall carbon nanotubes (MWNTs) have been prepared, showing improved mechanical properties as compared to the pure EPDM matrix. The results have been discussed using the Guth model. The main focus of the study was on the electrical behavior of the nanocomposites, in view of possible sensor applications. A linear relation has been found between conductivity and deformations up to 10% strain, which means that such materials could be used for applications such as strain or pressure sensors. Cyclic experiments were conducted to establish whether the linear relation was reversible, which is an important requirement for sensor materials.

Electrically Conductive Polymer nanocomposites have attracted lots of attention in the last years, especially for their sensitivities to external solicitations, like temperature or pressure variation. This work concerns the modelling of toluene diffusion behaviour in poly(ethylene-co-ethyl acrylate) (EEA)-carbon nanoparticles (CNP) CPC. One of the main objective of our work was to control and model the physical mechanisms involved in this type of material during sorption and desorption phases in the presence of solvent vapour. Two approaches was explore, thin layer to study quick electrical response and thick layer to look after swelling effect induces by toluene. The thick layer mass measurement was compare with our diffusion model.

The unique properties of carbon-nanotube (CNT)-doped polymers have generated several promising applications including gas sensors, high-strength/light-weight materials, and electromagnetic interference shielding. The ability to process CNT-doped materials into complex architectures may enable further advancement of these devices. We have developed a direct-write technique for processing CNT-doped poly(methyl methacrylate) (PMMA) into 3D arrays of precisely-positioned fibers with micro- and sub-microscale diameters. In this method, a programmable micromanipulator-controlled syringe was loaded with solvated CNT/PMMA and utilized to draw an array of freely-suspended solution filaments on a substrate in a “connect-the-dots” fashion. As the filaments are drawn, they are thinned by surface tension-driven necking as they dry and form solid fibers. The degree of thinning can be controlled by varying the viscosity of the solution, which acts to resist the necking while the volatile solvent evaporates and solidification occurs. Multiple fibers were drawn to investigate the effects of several factors on fiber diameter and process yield. These variables included fiber length (4, 8, and 18 mm), fiber drawing velocity (5 and 20 mm/s), polymer concentration in solution (22 and 24% by wt.), and CNT concentration in solution (0, 0.5, 1, and 1.5% by wt.), with the latter two of these variables strongly influencing solution viscosity. Measurement of the fibers via scanning electron microscopy (SEM) revealed several trends: Fiber diameter was not influenced by CNT concentration, but increased with increasing PMMA concentration (P<0.001), increasing drawing rate (P<0.01), and decreasing fiber length (P<0.001), with fiber diameter ranging from 538 nm to >100 μm. Furthermore, fiber yield exceeded 75% for all tested solutions except for the lowest viscosity CNT-doped solution (24% PMMA/0.5% CNT, η=50.1 Pa*s), which experienced capillary breakup prior to solidification. The conductivities of direct-write PMMA/CNT fibers ranged from <10-7to 0.15 S/m, with shorter fibers having higher conductivities (P<10.005). Also, fibers drawn from solutions with 1.0% CNTs had higher conductivities that those drawn from solutions with 0.5% or 1.5% CNTs (P<0.01). This nonlinear trend was further investigated by cleaving fibers in liquid nitrogen and imaging their cross-sections with an SEM. This analysis illustrated that the CNTs, which were functionalized to remain dispersed in the solvent, tended to randomly aggregate within the polymer-fiber matrix, particularly for fibers drawn from solutions containing 1.5% CNTs. In conclusion, CNT/PMMA fibers were successfully drawn with the direct-write technique and CNT doping had no significant influence on fiber diameter or yield compared with fibers drawn from PMMA homopolymer. However, the CNTs were found to strongly aggregate when drawn from solutions loaded at high concentrations (1.5%), thereby hindering electrical transport.

The conductive polymer nanocomposite (CPC) of multiwall carbon nanotubes (MWNT) filled Polycaprolactone (PCL) was formulated by melt mixing method. PCL based conductive phase served as disperse phase, blended with polypropylene (PP) and polyamide 12 (PA12) respectively. The thermo- and chemo-electrical properties of mono- and bi-component CPC have been investigated independently. Results show that PP/PCL-CNT CPC is a good temperature sensor whereas no significant response was observed while exposing to toluene vapor. In contrast, PA12/PCL-CNT exhibits good vapor sensing capability instead of temperature sensor. It is assumed that PP phase prevents the diffusion of vapor molecules within PCL conductive phase. The vapor sensing results indicated that PP external matrix provides the CPC with higher barrier effects than PA12.

Solution electrospinning was used to prepare fibers of both the stable – trigonal α and “metastable” – orthorhombic β complexes between poly(ethylene oxide) (PEO) and urea. The 300-800 nm fibers were highly crystalline and both types presented a relatively large level of molecular orientation. Characterization of the poorly-studied β complex was performed using wide-angle X-ray diffraction, infrared spectroscopy, optical microscopy and differential scanning calorimetry. It was shown that β complex possesses a 3:2 PEO:urea stoichiometry, in contrast with a previously suggested 1:1 molar ratio, and that the α inclusion complex keeps the 4:9 molar ratio as when prepared by the conventional co-crystallization method. A new structural model was suggested for the β complex, in which the unit cell would contain 12 PEO repeat units (4 chains in the ab plane with 3 repeat units along the c axis) and 8 urea molecules arranged in a ribbon-like structure and intercalated between the two PEO layers. This layer-structured β complex is quite different from the usual channel-like α inclusion complex and results in different phase transitional properties.

Organic vapour sensors based on poly (methylmethacrylate)-multi-wall carbon nanotubes (PMMA-CNT) conductive polymer nanocomposite (CPC) were developed via layer by layer technique by spray deposition. CPC Sensors were exposed to three different classes of solvents (chloroform, methanol and water) and their chemo-electrical properties were followed as a function of CNTcontent in dynamic mode. Detection time was found to be shorter than that necessary for full recovery of initial state. CNT real three dimensional network has been visualized by Atomic force microscopy in a field assisted intermittent contact mode. More interestingly real conductive network system and electrical ability of CPC have been explored by current-sensing atomic force microscopy (CS-AFM). Realistic effect of voltage on electrical conductivity has been found linear.

New unique abilities towards solvents' vapor of electrically Conductive Polymer nanoComposites (CPCs) have made it a subject, holding the attention of research groups. The direct conversion from chemical information into an electrical signal can take advantage of existing low power microelectronics and sensing technology such as detection of toxic vapor; environmental monitoring in chemical industry and quality control in food processing, beverage and perfume industry. Conductive Polymer nanoComposite (CPC) is a heterogeneous system consisting of insulated polymer matrices and conductive nanofillers. In this paper we have investigated a new route for CNT grafting via ring opening polymerization of e-caprolactone. The influence of this treatment on chemo-electrical properties of the so-called CPC based sensor was investigated in this work.

Carbon nanotubes (CNT) / conjugated polymer composites have been used for the preparation of thin film-modified electrodes. Thin, short, multi-walled CNT (MWNT) (purity higher than 95%) was completely coated by regioregular poly(3-hexylthiophene) (P3HT) through precipitation of a mixture of both in the non-solvent methanol. This work reports the electrochemical and optical characterization of P3HT and composites after dissolution in xylene and spin casting of films with thickness <1 micrometer. Cyclic voltammetry showed that all samples were characterized by a semi-reversible behavior. The samples with 0% and 2% of MWNT, for instance, present anodic peak potential at +0.67 and +0.68V respectively when cycling at 100 mV/s. Optical properties, such as optical absorption and photoluminescence (PL), have been investigated. The samples showed maximum of absorption at ˜530 nm and intense PL in the orange. PL spectra of nanocomposites exhibited a new band at lower energy characteristic of a structure with higher conjugation length when compared to P3HT.