J. R. Dios

Bio: J. R. Dios is an academic researcher. The author has contributed to research in topics: Glass transition & Thermal analysis. The author has an hindex of 3, co-authored 3 publications receiving 28 citations.

Improving the Processability of Conductive Polymers: The Case of Polyaniline

Abstract: Polyaniline (PANI) is one of the most widely used conductive polymers because of its ease of synthesis in addition to its good electrical properties. However, the difficulty in its processability limits its potential applications. In this work, conductive emeraldine salt (i.e., one of the different oxidation states of PANI) was synthesized by oxidative chemical polymerization. Different techniques such as Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, differential scanning calorimetry, and dynamical mechanical thermal analysis were used to characterize the synthesized PANI. The processability of PANI has been improved by processing it, both by compression and extrusion methods, with different thermoplastic matrices such as polycaprolactone and polybutylene terephthalate. The obtained compounds have not only better processability but also improved thermal and mechanical properties. However, their conductivity decreases with respect to PANI, to a greater extent, for the compounds synthesized by the extrusion method. © 2012 Wiley Periodicals, Inc. Adv Polym Techn 32: E180–E188, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/adv.21261

Dielectric Properties of Piezoelectric Polyimides

Abstract: Polyimides are the most promising amorphous piezoelectric polymers not only because of their excellent thermal, mechanical and dielectric properties, but also and, mainly due to their high glass transition temperatures. Here we report on the synthesis of polyimides with one CN (poly2-6) and two CN groups (poly2CN) in the repetition unit, the latter being synthesised for the first time. The dielectric measurements show that remnant polarisation and piezoelectric coefficients values depend strongly on the number of pendant nitrile dipoles in the repetition unit, on the orientation of the backbone anhydride dipole as well as on the imidisation and the poling processes.

Polyalkene-based shape-memory polymers

Abstract: A series of polymers showing shape memory properties were developed based on polyalkenes derived from cyclooctene and related structures. These polymeric systems were synthesized via ring-opening metathesis polymerization (ROMP) using a well-defined ruthenium catalyst (Grubbs' type) by varying reaction conditions and proportions. Control over molecular weight was achieved by the inclusion of a chain transfer agent (CTA) and its influence on the behaviour of the obtained materials was evaluated. In order to provide them with shape memory behaviour the compounds were subjected to suitable chemical-thermal treatments and its characterization was accomplished by means of several techniques: differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), etc. Thus polymers developed herein could become a different alternative to the most studied and commercially available polyurethane based systems.

Synthesis, characterization, and thermal properties of piezoelectric polyimides

Abstract: Three amorphous piezoelectric polyimides have been synthesized and characterized to analyze their utility for high-temperature applications. The studied polyimides have been prepared from 4,4'-oxydiphthalic anhydride and the diamines 2,4-di(3-aminophenoxy)benzonitrile (poly2-4), 2,6-bis(3-aminophenoxy)benzonitrile (poly2-6), and 1,3-bis-2-cyano-3-(3-aminophenoxy)phenoxybenzene (poly2CN). These polyimides differ in the position of the dipolar groups -CN in the aromatic ring (poly2-4 and poly2-6) and in the number of these groups in the repetitive unit (poly2-6 and poly2CN). The imidization degree has been studied by Fourier transform infrared (FTIR) and thermogravimetry-mass spectrometry (TG-MS) and thermal properties by differential scanning calorimetry (DSC) and thermogravimetry (TG). The piezoelectric behavior has been analyzed from remnant polarization measurements.

Magneto-active shape memory composites by incorporating ferromagnetic microparticles in a thermo-responsive polyalkenamer

Abstract: Covalently crosslinked semi-crystalline polyalkenamer-based shape memory polymers (SMPs) were prepared and characterized. Thermal and thermo-mechanical properties of thermo-sensitive polymers manufactured by melt compounding were investigated, and shape memory features demonstrated. For remote activation of shape recovery properties, electromagnetic inductive heating of a series of iron-based ferromagnetic microparticles was evaluated for subsequent incorporation into a shape memory polymeric matrix. The inductive heating capacity of micro-sized iron-filled polyalkenamers with different volume fraction contents was optimized and a comparison of thermo-mechanical properties of filled and unfilled shape memory polymeric networks was performed. Electromagnetically triggered shape memory properties of easily formed composites were documented and shape memory recovery rates comparable to those obtained by conventional heating methods were demonstrated for further research and design of new types of applications.

Preparation of Electrospun Nanocomposite Nanofibers of Polyaniline/Poly(methyl methacrylate) with Amino-Functionalized Graphene

Abstract: In this paper we report upon the preparation and characterization of electrospun nanofibers of doped polyaniline (PANI)/poly(methyl methacrylate) (PMMA)/amino-functionalized graphene (Am-rGO) by electrospinning technique. The successful functionalization of rGO with amino groups is examined by Fourier transforms infrared (FTIR), X-ray photoelectron spectroscopy (XPS) and Raman microspectrometer. The strong electric field enables the liquid jet to be ejected faster and also contributes to the improved thermal and morphological homogeneity of PANI/PMMA/Am-rGO. This results in a decrease in the average diameter of the produced fibers and shows that these fibers can find promising uses in many applications such as sensors, flexible electronics, etc.