New organic-inorganic hybrids as multifunctional additives to improve ethylene-norbornene (EN) composite stability (2023)

We present a strategy that leads to the formation of high-performance hybrid pigments made from natural anthraquinone chromophores (alizarin, purpurin) and mineral supports (palygorskite (PAL), sepiolite (SEP), and hydroxyapatite (HAP)). Thanks to the mineral filler form features and the synergy between the organic and inorganic components, the as-prepared hybrid pigments showed excellent thermal and chemical stability. The natural pigments exhibited strong pH-sensing activity, changing their color upon exposure to HCl and/or NH₃ vapors. The PAL-based pigments were found to be the most effective pH indicators, showing pronounced color changes after 10min of exposure to HCl (ΔE for PAL/A was 7.4). ToF-SIMS, ¹³C NMR and XPS techniques revealed interactions between the organic dyes and metal ions present in the minerals. XPS spectroscopy was also used to examine the alterations in the structure of the hybrid colorants following exposure to acid vapors. The proposed pH sensors were successfully applied to elastomer and thermoplastic elastomer matrices. The purpurin-based hybrid pigments exhibited significantly reduced migration from the polymer (about six times lower concentration in ethanol after 14days). The results of this study pave a new way for the design, development, and application of advanced hybrid colorants with pH-sensing activity and improved stability.

In this study, we developed a new organic-inorganic pigment (LP) by precipitation of dye molecules onto aluminum-magnesium hydroxide (LH). The morphology and physico-chemical properties of the pigment were characterized by X-ray diffraction analysis (XRD), secondary ion mass spectrometry (TOF-SIMS), 27-Al solid-state nuclear magnetic resonance (NMR) spectroscopy, scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The incorporation of the azo dye into the LH host caused an increase in the interlayer distances of the LP from 0.751 to 0.758nm. The LP pigment also showed better thermal- and photo-stability than the pristine azo chromophore. The novel organic-inorganic additive was next applied as a filler at different concentrations (2 phr, 5 phr, 10 phr) to obtain colorful ethylene-norbornene (EN) films. The morphological, mechanical and flame-retardant properties of the composites were determined by XRD, SEM, dynamic-mechanical analysis (DMA) and cone calorimetry tests (CCT). The EN films containing the LH/Azo dye demonstrated improved mechanical, barrier and flame-retardant properties. Compared to the neat EN copolymer and EN/LH composite, the EN/LP sample was found to be the most resistant to UV aging, as confirmed by FTIR and mechanical analysis.

Polymer Degradation and Stability, Volume 160, 2019, pp. 210-217

To evaluate the influence of specific parameters, i.e. energy sink concentration and excitons and/or radical migration, on the mechanisms underlying the formation of double bonds in aliphatic polymers, materials with energy sinks in the chain were synthesized. By following the radiation-induced modifications in ethylene/styrene random copolymers, as a function of the styrene content and of the irradiation temperature, we were able to understand the formation mechanisms of trans-vinylenes, trans-trans-dienes, allyl radicals and vinyls. The irradiation temperature allows the discrimination between energy transfers (at 11 K and at room temperature, RT) and of radical migration (at RT). Irradiations were performed using swift heavy ions, and we could show that track overlapping has also an influence on the studied chemical group concentrations. For instance, trans-vinylenes are influenced by excitation transfer and radical migration: their formation decreases in presence of styrene aromatic rings, whatever the dose range and the irradiation temperature. On the opposite, vinyls are formed only at high ionizing density and are not influenced by excitation transfer; however, their concentration is influenced by radical migration.

Polymer Degradation and Stability, Volume 160, 2019, pp. 136-141

β-cyclodextrin (β-CD) cross-linked polymer has been proved to be critical adsorbents for removal of many kinds of environmental pollutants from water resources. This study deals with the fabrication of β-CD cross-linked polymer monolith (CD monolith) through novel phase separation technique and effective removal of the pollutants by using prepared CD monolith columns. CD monoliths were prepared by the reaction of monochloro triazine group modified β-cyclodextrin derivative and polyethyleneimine in water. The obtained CD monoliths showed three dimensional interconnected porous structures, high surface area, and sufficient mechanical properties. The diameter of macroporous structures of CD monoliths was precisely controllable from micro-to nano-meters. This morphological control enables effective water flow based application with low pressure loss. We demonstrated that CD monolith showed high adsorption performance in the adsorption of model pollutants by flow-through experiment.

Polymer Degradation and Stability, Volume 160, 2019, pp. 162-167

Stereochemistry of direct conversion of polyamides to hydroxyesters was investigated using model compounds. Optically active secondary-alkyl amines underwent the conversion to corresponding secondary alcohols in moderate yields by treatment with supercritical methanol in the presence of glycolic acid. The reaction progressed through almost completely stereochemical inversion to give secondary alcohols in high yields. Thus, the substitution reaction of the amino group to hydroxyl group progresses through S_N2 type transition state accompanying with stereoinversion.

Polymer Degradation and Stability, Volume 160, 2019, pp. 264-272

Since the use of biodegradable polymers for food packaging is becoming popular, it is important to investigate the biodegradable-polymer-hydrolyzing potential of microorganisms in fermented foods. Here, we focused on 4 Japanese washed-rind cheeses. Metagenomic analyses revealed that microbiota in the 4 Japanese washed-rind cheeses was composed of bacteria classified into 515 operational taxonomic units (OTUs) and fungi classified into 74 OTUs. Remarkably, a considerable number of marine bacteria were identified in 3 of 4 cheeses. Further, we isolated a poly(3-hydroxybutyrate) (P(3HB))-degrading bacterium, designated as strain MC1, from one of the cheeses—Muchuri. The strain was a gram-negative, rod-shaped bacterium. It grew well and formed a large clear zone on P(3HB)-containing medium at a temperature range of 30–37 °C, while it did not degrade P(3HB) at 4 °C. The phenotypic properties and phylogenetic inference indicated that strain MC1 is related to Alcanivorax dieselolei B-5^T, which is a marine inhabitant. Our study demonstrated that MC1 degrades P(3HB) and that components in cheese promote the degradation of P(3HB) while nutrient-rich conditions suppress it. This suggests that packaging material made of P(3HB) for cheeses could be used under low temperatures and nutrient-rich conditions.

Polymer Degradation and Stability, Volume 160, 2019, pp. 203-209

Fluoropolymer films are frequently used in microfabrication and for producing hydrophobic and low-k dielectric layers in various applications. As the reliability of functional coatings is becoming a more pressing issue in industry, it is necessary to determine the physical stability and degradation properties of this important class of films. To this end, a study has been undertaken to ascertain the aging characteristics of fluoropolymer films under various environmental conditions that such a film may experience during its use. In particular, fluorocarbon films formed by plasma-enhanced chemical vapour deposition (PECVD) using octafluorocyclobutane, or c-C₄F₈, as a precursor gas have been exposed to abrasive wear, elevated temperatures, ultraviolet radiation, as well as oxygen plasma and SF₆ plasma, the latter being commonly used in conjunction with these films in ion etching processes. The results show that sub-micron thick fluoropolymer films exhibit a significant amount of elastic recovery during nanoscratch tests, minimising the impact of wear. The films exhibit stability when exposed to 365 nm UV light in air, but not 254 nm light in air, which generated significant decreases in thickness. Exposure to temperatures up to 175 °C did not generate loss of material, whereas temperatures higher than 175 °C did. Etching rates upon exposure to oxygen and SF₆ plasmas were also measured.

Polymer Degradation and Stability, Volume 160, 2019, pp. 89-95

The surface modification of micro-porous polypropylene membrane is achieved by low-pressure reactive plasma treatments using Ar and He gases. The reactive plasma modified microporous polypropylene membranes which are used as the battery separators were evaluated by the electrochemical performance and static contact angle analysis. It is found that the plasma modified polypropylene separators obtain the superior property for Lithium-ion battery and the variations in surface wettability and surface free energy were examined by static contact angle measurement. The static water contact angle of the plasma-modified polypropylene membrane separator significantly decreased with rising plasma power input at both glow region and remote region in the reactive plasmas. An obvious increase in the surface energy of microporous polypropylenes because of low molecular weight oxidized materials from Ar and He plasma treatment was observed in the rinsing process by static contact angle analysis. The experimental results show the vital part of low molecular weight oxidized materials in the interaction between reactive plasma and polypropylene membrane, which can be controlled by the surface modification to tailor the hydrophilicity of micro-porous polypropylene membrane.