Antiviral polymers are part of a major campaign led by the scientific community in recent years. Facing this most demanding of campaigns, two main approaches have been undertaken by scientists. First, the classic approach involves the development of relatively small molecules having antiviral properties to serve as drugs. The other approach involves searching for polymers with antiviral properties to be used as prescription medications or viral spread prevention measures. This second approach took two distinct directions. The first, using polymers as antiviral drug-delivery systems, taking advantage of their biodegradable properties. The second, using polymers with antiviral properties for on-contact virus elimination, which will be the focus of this review. Anti-viral polymers are obtained by either the addition of small antiviral molecules (such as metal ions) to obtain ion-containing polymers with antiviral properties or the use of polymers composed of an organic backbone and electrically charged moieties like polyanions, such as carboxylate containing polymers, or polycations such as quaternary ammonium containing polymers. Other approaches include moieties hybridized by sulphates, carboxylic acids, or amines and/or combining repeating units with a similar chemical structure to common antiviral drugs. Furthermore, elevated temperatures appear to increase the anti-viral effect of ions and other functional moieties.
The composition-processing-properties relationship of imine containing reversible covalent bonds containing polymers (RCBPs) was studied using an innovative (regarding this type of polymers) combination of characterization methods. This combination led, for...
The development of efficient synthetic strategies for incorporating antibacterial coatings into textiles for pharma and medical applications is of great interest. This paper describes the preparation of functional nonwoven fabrics coated with polyaniline (PANI) via in situ polymerization of aniline in aqueous solution. The effect of three different monomer concentrations on the level of polyaniline coating on the fibers comprising the fabrics, and its electrical resistivities and antibacterial attributes, were studied. Experimental results indicated that weight gains of 0.7 and 3.0 mg/cm2 of PANI were achieved. These levels of coatings led to the reduction of both volume and surface resistivities by several orders of magnitude for PANI-coated polyester-viscose fabrics, i.e., from 108 to 105 (Ω/cm) and from 109 to 105 Ω/square, respectively. Fourier Transform Infrared (FTIR) Spectroscopy and Scanning Electron Microscopy (SEM) confirmed the incorporation of PANI coating with an average thickness of 0.4–1.5 µm, while Thermogravimetric Analysis (TGA) demonstrated the preservation of the thermal stability of the pristine fabrics. The unique molecular structure of PANI, consisting of quaternary ammonium ions under acidic conditions, yielded an antibacterial effect in the modified fabrics. The results revealed that all types of PANI-coated fabrics totally killed S. aureus bacteria, while PANI-coated viscose fabrics also demonstrated 100% elimination of S. epidermidis bacteria. In addition, PANI-coated, PET-viscose and PET fabrics showed 2.5 log and 5.5 log reductions against S. epidermidis, respectively.
The effect of chemical composition on the rheology of a reversible covalent bond containing polyethyleneimine (RCBP) was studied. RCBPs, also known as vitrimers, exhibit thermoplastic‐like processability, but unlike thermoplastic polymers, their behavior is not driven by disentanglement, and all the bonds undergo transformation (almost) simultaneously at constant average crosslink density. Therefore, no lower plateau was observed in a viscosity‐shear rate plot. Transimination, the principal mechanism that imparts flowability, consists of two mechanisms—imine exchange and imine metathesis. Metathesis is only activated by heat, while imine exchange is activated also by stress. Imine metathesis provides low viscosity values at higher crosslink density. A lower viscosity (1092 []Pa0.25emnormals compared to 22,986 []Pa0.25emnormals at 100 Hz) was accomplished by adding 4 wt% triethylenetetramine (TETA). An Arrhenius‐type behavior is shown via relaxation tests with three distinct regions—up to 125°C (only imine exchange), between 125°C and 160°C (imine exchange and imine metathesis) and above 160°C (imine reduction to amine). Imine metathesis seems to promote flow at intermediate temperatures, and at around 150°C, the material behaves as a viscous fluid, otherwise at higher or lower temperatures the dynamic behavior is that of an elastic solid.
Metrics & MoreArticle Recommendations * sı Supporting InformationABSTRACT: [4 + 4] and [2 + 2] cycloadditions are unique reactions since they form and deform cycloadducts under irradiation due to their inherent reversible nature. Whereas promising for the field of recycling, these reactions usually suffer from two major shortcomings: long reaction durations (hours) and the requirement of high-intensity light (∼100 W/cm 2 ), typically at a short wavelength (<330 nm). We demonstrate several tetra-dentate catalysts that can overcome these fundamental limitations. Among them is a tin complex that enables 76% conversion within only 2 min of irradiation at 395 nm, much faster than the known ruthenium-based catalyst, under irradiation with light intensity two orders of magnitude lower than that reported in the literature. Due to the short photopolymerization time, low intensity (27 mW/cm 2 ), and long UV light (395 nm), this unique complex opens new avenues for recycling three-dimensional printing products based on photopolymerization of cycloaddition reactions.
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