Biomass/polyhedral oligomeric silsesquioxane nanocomposites: Advances in preparation strategies and performances

Polyhedral oligomeric silsesquioxane (POSS) as an organic–inorganic hybrid at a molecular level, has excellent mechanical properties, thermodynamic properties, dielectric properties and so on. In recent decades, POSS has been extensively used in modification of various polymers to prepare nanocomposites with enhanced comprehensive performances. Biomass materials such as chitosan, cellulose, silk protein, collagen fibers and gelatin have excellent biocompatibility and biodegradability, which have been widely used in the fields such as biomedical, innovative environmental protection and so on. However, deficiencies including insufficient mechanical properties and rapid rate of biodegradation hampered their application. This paper briefly introduced the principal methods to synthesize POSS nanoparticles, and then focused on technologies for preparing biomass-based composites utilizing diverse functional POSSs. Finally, put forward the prospects of POSS modification technology and its future application direction. This article will have a positive guiding role for the further research and development of biomass/POSS nanocomposites.     

Covalent surface functionalization of nonwoven fabrics with controlled hydrophobicity,water absorption,and pH regulation properties

A modular method for functionalization of nonwoven fabrics was developed using a two-step process. In the first step, the fabrics were grafted with a linker molecule, 10-undecenoyl chloride, via esterification, followed by attachment of a functional material under UV irradiation. Perfluorodecanethiol and 3-mercaptopropionic acid (MPA) were connected to the linker-modified fabrics using thiol-ene click chemistry. Perfluorodecanethiol modified fabrics exhibited hydrophobicity with water contact angle of about 140° while MPA-modified fabrics were able to lower the pH of a solution by about 1.6. We additionally demonstrated the possibility to connect functional polymers to the linker-modified fabrics by radical graft polymerization of acrylic acid; this produced a thin layer of the polymer on the surface of the fabric. Fabrics modified with poly(acrylic acid) exhibited increased hydrophilicity with water contact angle of 0° for both cotton and viscose-polyester fabrics, while the water absorption capability for polypropylene fabrics increased from about 50 to 1200%.     

Low surface energy self-polishing polymer grafted MWNTs for antibacterial coating and controlled-release property of Cu2O

Marine biofouling had been a headache when engaging in marine activities. The most effective and convenient method for dealing with this problem was to apply antifouling coatings. But now a single anti-fouling system was hard to satisfy the requirement of anti-fouling simultaneously. Therefore, it was particularly important to develop novel multi-system anti-fouling technology. In the work, a novel polymer coatings with polydimethylsiloxane (PDMS) segments in the main chain and hydrolysable side chain was designed and synthesized which showed low surface energy and self-polishing performance, and then we creatively covalently immobilized the polyurethane on the surface of multi-carbon nanotubes (MWNTs) to form multisystem antifouling coating. The results showed that the polymer coating would produce hydrolysable regions in the hydrophobic PDMS segment to endure the polymer coating hydrophobic and hydrolysis properties when contacted with water. In addition, the self-polishing rate and the surface energy could be regulated by varying its copolymerization, and the addition of MWNTs could kill the microorganisms and endowed the polymer coating itself enhanced antibacterial effect. Furthermore, considering the high specific surface area and physicochemical characteristics of MWNTs, it could be combined with antifoulant Cu₂O through a polar or non-polar combination as a carrier to control the release rate of Cu₂O in coatings.     

Effect of particle size on flame retardancy and mechanical properties of hydroxyethyl diphosphate modified aluminum hydroxide intrinsic polyethylene terephthalate

Organic–inorganic hybrid flame retardant was obtained by modifying aluminum hydroxide with different particle size with 1-hydroxyethylidene-1,1-diphosphonic acid. The structure of the organic–inorganic hybrid flame retardant is characterized by Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy, while ¹H-NMR spectroscopy only characterizes specific samples. The thermal stability and flame retardancy of the samples were analyzed by thermogravimetric analysis, limiting oxygen index (LOI), vertical combustion of UL-94 and cone calorimeter. The results show that the modified 10 μm aluminum hydroxide has a better effect than the 25 μm aluminum hydroxide and 100 nm aluminum hydroxide. Compared with pure polyethylene terephthalate (PET), the LOI value of the best sample is increased by 24.4%, and UL-94 V reaches V-0 level. Heat release rate, total heat release rate, and carbon monoxide production rate decreased by 45.8%, 33.2%, and 41.5%, respectively, compared to pure PET. The results showed that the aluminum hydroxide with a particle size of 10 μm exhibited the best flame retardant effect, which could be attributed to the decomposition of organic phosphoric acid and the dehydration of aluminum hydroxide, yielding a higher amount of residual carbon.     

Antibacterial self-healing anticorrosion coatings from single capsule system

It is highly desirable to develop self-healing anticorrosion coatings with enhanced antibacterial function to prevent the scratched area to be fouled or corroded in harsh environments. Herein, we report antibacterial self-healing anticorrosion coatings via the simple incorporation of the easily synthesized single polymer microcapsule system. Well-defined polymer microcapsules containing isophorone diisocyanate (IPDI) as a healing agent and 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one (DCOIT) as antibacterial molecules were synthesized by one-pot polymerization. The diameter and core fraction were around 30 μm and 90%, respectively. The active DCOIT content in the core material could be precisely controlled by adjusting the DCOIT/IPDI feeding ratio. The DCOIT/IPDI microcapsules-embedded protective coating exhibits an adaptive self-healing anticorrosion property, as shown by electrochemical test under the condition of the salt-water immersion. Furthermore, the self-healing coating showed efficient antibacterial function against Escherichia coli and Pseudomonas aeruginosa, which is due to the released active biocide molecules on the damaged surfaces. In contrast to other systems, this single capsule system without any catalyst is perspective for extending the service time of the antibacterial self-healing materials in harsh environment.     

Progress and challenges in sustainability,compatibility, and production of eco-composites: A state-of-art review

Owing to economic and environmental benefits, new generations of materials/commodities follow “from waste to wealth” strategy. Recently, there has been a huge upsurge in research on the development of eco-composites using recycled plastic polymers and agro-residues because the eco-composites satisfy the stringent environment regulations and are cost-effective. Herein, we present a detailed review on the potential use of several types of natural fillers as an efficient reinforcement for recycled plastic polymers. In particular, the characterization of different categories of eco-composites according to their morphological, physical, thermal, and mechanical properties is extensively reviewed and their results are analyzed, compared, and highlighted. Furthermore, a framework to produce functional eco-composites, which includes functionalization of ingredients, critical issues on microstructural parameters, processing, and fabrication methods, is outlined and supported with sufficient data from the literature. Finally, the review outlines the emerging challenges and future prospects of eco-composites to be addressed by interested researchers to bridge the gap between research and commercialization of such a class of material. Overall, the acquired knowledge will guide researchers, scientists, and manufacturers to plan, select, and develop various forms of eco-composites with enhanced properties and optimized production processes.     

Antibacterial properties of polyaniline derivatives

This work presents a detailed study on the effect of various functional groups both at the ortho position of the aromatic ring and in the amino group of PANI on the antibacterial properties of polymers against gram-positive (Bacillus subtilis) and gram-negative (Pseudomonas aureofaciens) microorganisms. It was found that incorporation of methyl, methoxy, or pentyl groups into the ortho-position of PANI did not increase the antibacterial activity but in most cases causes a significant decrease in the antibacterial properties of functionally substituted polyanilines. At the same time, PANI derivatives modified by incorporation of pentyl groups into the amino group were found to be more efficient antibacterial compounds against both gram-positive and gram-negative microorganisms than the original polymer. It was also found that N-substituted PANI derivatives manifest not only bactericidal but also bacteriostatic properties toward the test microorganisms. Varying the nature and position of the substituent allowed us to conclude that the synthesis of various N-substituted PANI derivatives with a high degree of doping is the most promising approach to PANI modification for application in bacterial growth inhibition.     

Polyester functionalization for mycobacterial capture

Tuberculosis (TB) is one of the deadliest diseases known to man and ranks among the top ten global causes of fatalities. Children often develop a paucibacillary form of this disease which makes diagnosis arduous even with the aid of sophisticated techniques. In these cases, the concentration of bacteria in their sputum falls below the lowest limit of detection for sputum smear microscopy, the technique predominantly used in developing countries. In this study we aim to test the hypothesis that modifying a polymer, often used in buccal swabs, could assist in creating a capturing and concentrating oral swab for Mycobacterium tuberculosis (Mtb), the pathogenic bacterial species responsible for TB. Such a device will assist in meeting the detection limit and allow for rapid detection of the disease. The polymer used was a micro fibrous form of poly(ethylene terephthalate) (PET) which was surface functionalized with Concanavalin A (Con A), a lectin based adhesin with an affinity for the mannose groups on the Mtb cell wall. The functionalization was mediated with glutaraldehyde as bioconjugate molecule and found to produce a surface uniformly covered with Con A. Affinity studies between the modified fibers and the Mycobacterium bovis bacillus Calmette-Guérin (BCG), as Mtb mimic, were conducted to evaluate the capturing abilities of the substrate. The results indicate that the fibers avidly captured BCG and that the fibrous matrix aided in its function. Dilution studies showed successful capturing of the bacterial species at concentrations characteristic of paucibacillary cases. In this study a commercial polymeric material was successfully surface modified with a biological entity to create a substrate to which Mtb could adhere and accordingly be captured.     

Study on polyurethane-acrylate/cerium dioxide modified by 3-(Methylacryloxyl)propyltrimethoxy silane and its UV absorption property

Firstly, cerium dioxide(CeO₂) was modified by 3-(Methylacryloxyl)propyltrimethoxy silane (KH-570), and modified CeO₂ (mCeO₂) was prepared. Then poly (urethane-acrylate) was modified by mCeO₂, and poly (urethane-acrylate)/modified CeO₂ (PUA/mCeO₂) composites with ultraviolet absorption property were prepared. The morphology, thermal hydrophobicity, mechanical properties, optical properties, and UV-absorption properties of PUA/mCeO₂ composites were studied. XRD and SEM analysis showed that the modified CeO₂ had better dispersion in the matrix than that of pure CeO₂. Ultraviolet–visible spectrum and thermogravimetric analysis were used to characterize the optical properties and thermal stability of PUA/mCeO₂ composites. The results showed that with the increasing of the mCeO₂ content, the UV-absorption property of PUA/mCeO₂ composites was improved gradually. When the content of mCeO₂ is 3%, the absorption of ultraviolet of PUA/mCeO2 composites is about 5 times of pure PUA film, and the absorption band is mainly in the UVA section. The thermal stability of PUA/mCeO₂ composites was improved with the adding of mCeO₂. With the increasing of mCeO₂ content, the contact angle of PUA/mCeO₂ composites increased significantly. And the UV-absorption mechanism of PUA/mCeO₂ Composites was studied. UV-curable PUA/mCeO₂ composites have good UV absorption property and water resistance. They will be used in the sun screen and protect people's skin.     

Chemiresistor sensor using elastomer-functionalized carbon nanotube nanocomposites for the detection of gasoline spills

Two types of multi-walled carbon nanotube (MWNT)-based elastomer nanocomposites are used as a sensor material for the detection of gasoline spills by applying the interdigitated electrode (IDE) device. MWNT-g-polyisoprene (PI) and Si-MWNT/natural rubber (NR) are prepared by applying “grafting-from” and “grafting-to” process, respectively. When compared based on the identical condition of gasoline sensing test, the maximum response value to the exposure of gasoline is 17.5 for MWNT-g-PI sensor and 12.9 for Si-MWNT/NR sensor, which reach the maximum in less than 3 min. The MWNT-g-PI sensor selectively detects gasoline, and its response is completely reversible. It shows that the longer chain length of PI brings about the larger response of MWNT-g-PI sensor to gasoline. The sensitivity of MWNT-g-PI sensor highly depends on both how much gasoline is exposed to the sensor and what bias voltage is applied to the IDE device. The IDE sensor using MWNT-g-PI nanocomposites effectively detects gasoline spills.