Wearable strain sensors have been attracting special attention in the detection of human posture and activity, as well as for the assessment of physical rehabilitation and kinematics. However, it is a challenge to fabricate stretchable and comfortable‐to‐wear permeable strain sensors that can provide highly accurate and continuous motion recording while exerting minimal constraints and maintaining low interference with the body. Herein, covalently grafting nanofibrous polyaniline (PANI) onto stretchable elastomer nanomeshes is reported to obtain a freestanding ultrathin (varying from 300 to 10 000 nm) strain sensor that has high gas permeability (10–33 mg h–1). The sensor demonstrates a low weight and can be directly laminated onto the dynamic human skin for long periods of time. The sensor, which produces an intimate connection with solid or living objects, has a stable performance with excellent sustainability, linearity, durability, and low hysteresis. It exibits excellent performance for continuous interrogation of complex movements, mimicking muscle activities, and resembling brain activity. This includes a very precise discrimination of bending and twisting stimuli at different angles (1–180°) and speeds (3–18 rpm) and very low exertion of counter‐interference. These results imply the utility of this appraoch for advanced developments of robotic e‐skins or e‐muscles.
This article describes an ultrasonically assisted in situ interfacial dynamic inverse emulsion polymerization process of aniline in the presence of multiwalled carbon nanotubes (MWNT) in chloroform. During polymerization, MWNT are coated with polyaniline (PANI) forming a core-shell structure of nanowires, as evidenced by cryogenic transmission electron microscopy. Thermogravimetric analysis curves and conversion measurements provided important knowledge regarding the unique polymerization method. Scanning electron microscopy images and surface resistivity imply that PANI/ MWNTs are characterized by a structural synergistic effect. The PANI coating of MWNT leads to a remarkable improvement in separation and dispersion of MWNT in chloroform, which otherwise would rapidly coagulate and settle. The presented interfacial dynamic polymerization process is very fast, reaching 82% conversion within 5 min of sonication and produces stable clear dispersions of doped PANI in chloroform. V C 2010 Wiley Periodicals, Inc. J Appl Polym Sci 120: [676][677][678][679][680][681][682] 2011
This communication describes an ultrasonically assisted in‐situ dynamic inverse emulsion polymerization process of aniline in the presence of multi‐walled carbon nanotubes (MWNT) in toluene. During polymerization, MWNT are coated with polyaniline (PANI), forming a core‐shell structure of nano‐wires observed by high‐resolution scanning electron microscopy (HRSEM). The PANI coating of MWNT leads to a remarkable improvement in separation and dispersion of MWNT in toluene, which otherwise would have rapidly coagulated and settled. The presented dynamic polymerization process is very fast and produces stable clear dispersions. CNT enhances both the mechanical properties and electrical conductivity of PANI. Copyright © 2009 John Wiley & Sons, Ltd.
This paper summarizes a study of controlled migration of an antifog (AF) additive; sorbitan monooleate (SMO), from linear low density polyethylene (LLDPE) films containing a compatibilizer, LLDPE grafted maleic anhydride (LLDPE-g-MA). LLDPE/LLDPE-g-MA/SMO blends were prepared by melt compounding. Bulk and surface properties of compression molded LLDPE films containing SMO and LLDPE-g-MA were characterized using Fourier transform infrared spectroscopy and contact angle measurements. Thermal properties were investigated using a thermal gravimetric analyzer. Diffusion coefficient (D) was calculated, and AF properties were characterized using a "hot fog" test. Compression molded films were characterized for their morphology using high-resolution scanning electron microscopy, and rheological properties were measured using a parallel-plate rotational rheometer. It was found that the LLDPE/LLDPE-g-MA/SMO systems are characterized by a slower SMO migration rate, a lower diffusion coefficient, and lower contact angle values compared with LLDPE/SMO blends. These results are well correlated with results of a hot fog test. Morphological studies revealed a very fine dispersion of SMO in the LLDPE films, when 3 phr LLDPE-g-MA was combined with 1 phr SMO. Thermal analysis results show that the incorporation of 3 phr LLDPE-g-MA and 1 phr SMO significantly increases the decomposition temperature of the blend at T > 400°C. At high shear rates, the LLDPE blends show that the AF and the compatibilizer have a lubrication effect on LLDPE.
This research presents a new fabrication method for tailoring polymer/carbon nanotube (CNT) nanostructures with controlled architecture and composition. The CNTs are finely dispersed in polymeric latex, that is, polyacrylate, via ultrasonication, followed by a microfiltration process. The latter step allows preserving the homogeneous dispersion structure in the resulting solid nanocomposite. The combination of microfiltration and proper choice of the polymer latex, particle size, and composition allows the design of complex nanostructures with tunable properties, for example, porosity and mechanical properties. An important attribute of this methodology is the ability to tailor any desired composition of polymer–CNT systems, that is, nanotube content can practically vary anywhere between 0 to 100 wt %. Thus, for the first time, a given polymer/CNT system is studied over the entire CNTs composition, resembling two-phase polymer blends. The polyacrylate in these systems exhibits a structural transition from a continuous matrix (nanocomposite) to segregated domains dispersed within a porous CNTs network. An analogy of this structural transition to phase inversion phenomena in two-phase polymer blends is suggested. The resulting polyacrylate/CNT layers exhibit a percolation threshold as low as 0.04 wt %. Additionally, these nanomaterials show low total reflectance values throughout the visible, NIR and SWIR spectrum at a CNT content as low as 1 wt %, demonstrating their potential applicability for optical devices.
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