Stable Polymeric Materials Research Articles

Sulfonated poly(ether imide): A versatile route to prepare functionalized polymers by homogenous sulfonation

This work deals with the PEI/ULTHEM sulfonation using acetyl sulfate aiming to obtain chemically and thermally stable polymeric materials employed as membranes. The commercial PEI was chemically modified by homogenous sulfonation reaction, which was conducted with acetyl sulfate prepared by mixing acetic anhydride and sulfuric acid, using N-methyl-2-pyrrolidone (NMP) as polymer solvent. The sulfonated PEI (PEI-SO 3H) films with sulfonation range around 0.02–0.8% were obtained and characterized by Fourier transform infrared spectroscopy, ion exchange capacity, water sorption and glass transition temperature. The PEI-SO 3H films with different sulfonation level were more thermally stable (Tg = 200145 °C) than commercial membranes, Nafion™ 117 (Tg = 110 °C). Dense membrane was prepared with good mechanical properties and showed to be swollen by water. PEI-SO 3H films show that the increase of the sulfonation level led to higher values of water sorption and the IEC properties.

Carbon nanotube-conductive additive-space durable polymer nanocomposite films for electrostatic charge dissipation

Thin film membranes of space environmentally stable polymeric materials possessing low color/solar absorptivity ( α) are of interest for potential applications on Gossamer spacecraft. In addition to these properties, sufficient electrical conductivity is required in order to dissipate electrostatic charge (ESC) build-up brought about by the charged orbital environment. One approach to achieve sufficient electrical conductivity for ESC mitigation is by the incorporation of single-walled carbon nanotubes (SWNTs). However, when SWNTs are dispersed throughout the polymer matrix, the nanocomposite films tend to be significantly darker than the pristine material resulting in a higher α. The incorporation of conductive additives in combination with a decreased SWNT loading level is one approach for improving α while retaining conductivity. Taken individually, the low loading level of conductive additives and SWNTs was insufficient in achieving the percolation level necessary for electrical conductivity. When added concurrently to the film, conductivity was achieved. The chemistry, physical and mechanical properties of the nanocomposite films will be presented.

Aliphatic–aromatic copolyesters derived from 2,2,4,4‐tetramethyl‐1,3‐cyclobutanediol

AbstractWith the massive changes taking place in the world today, the development of new thermally and mechanically stable polymeric materials is of utmost importance. This article focuses on the synthesis and thermal characterization of a new series of copolyesters that incorporate both aromatic as well as aliphatic diols. This is of interest because most polymer materials that exhibit high thermal and/or mechanical properties contain aromatic monomer units only. These aromatic units usually contribute to either the thermal or mechanical properties but typically not both. An example of this is bisphenol A polycarbonate, which has high mechanical properties but only moderate thermal properties when compared, for example, to polyimides. In recent years there has been an interest in copolyesters that contain 2,2,4,4‐tetramethyl‐1,3‐cyclobutanediol (CBDO). This aliphatic monomer imparts some very unique thermal as well as mechanical properties. This article will report the thermal properties of a new series of CBDO‐based copolyesters. These polymers include CBDO, a series of bisphenols, and terephthaloyl chloride. The series of bisphenols discussed here include bisphenol A, AF, F, and HPF. These polymers display glass transition temperatures near 200 °C and decomposition temperatures from 390–420 °C (Argon) and from 385–410 °C (Air). © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3473–3478, 2004

Preparation and optical properties of a poly(N-vinylcarbazole) material

We report on the photorefractive properties of a stable polymeric material based on the host polymer, poly(N-vinylcarbazole). Two-beam coupling and four-wave mixing experiments were used to measure the performance of devices constructed by sandwiching the material, composed of host, plasticizer, photo-sensitizer, and non-linear optical chromophore, between transparent electrodes. A steady-state diffraction efficiency of 60% and a two-beam coupling gain of 22 cm−1 in excess of the absorption of 4 cm−1 were observed at the laser's operating wavelength of 670 nm. The devices are easily prepared and have lifetimes in excess of one year with no indication of degradation when stored at ambient temperatures.

Exchange reactions on solid surface induced by VUV undulator radiation

Quasi-monochromatic undulator radiation was applied to surface modification of poly-tetrafluoroethylene (PTFE), which is one of the most chemically stable polymeric materials. Solid-liquid interface was excited and fluorine atoms on the surface were replaced by oxygen-containing functional groups and hydrogen under VUV undulator light irradiation. The contact angle to water and XPS spectra were measured after the irrradiation. Experimental results show a water layer on PTFE surface promotes the exchange reaction near the absorption edge(165–180nm).

Pyropolycarboranes: The base for self‐lubricating materials with gas lubricant

AbstractThis paper reports the results of an investigation of pyropolycarboranes, nondeformable thermally stable cross‐linked polymeric materials obtained by pyrolysis of carborane‐containing polymers. Carborane‐containing polyamides and polyesters were heated in air under pressure and analyzed by thermomechanical and thermogravimetric methods. Moreover, the friction properties of the filled materials have been investigated. The effect of hydrogen liberation on the friction of filled pyropolycarboranes at elevated temperatures was used in developing self‐lubricating materials with friction coefficients at 300–400°C.

Thermally stable polymeric materials

The object of this article is to discuss some of the factors responsible for high thermal stability in polymers, to review a few of the most important advances that have recently been made in the synthesis of such materials, and to present some of the results of the thermal degradation of an aromatic polyimide under investigation in the author's laboratory.