Crosslinked acrylate polymers with coumarin crosslinker displayed a light (UV) only triggered self-healing property.

A simple nanostructured, photoresponsive film made from a coumarin-modified tetrafunctional monomer, which is both photodegradable and photoreproducible, was prepared using a simple spin-coating process and UV irradiation. The film produced from this system self-healed scratches using only UV light, with no need for catalyst, heat, or other stimuli. The photoreversible mechanism was investigated, and a range of techniques were used to characterize the resultant photoproducts after the polymerization and depolymerization processes. Infrared spectroscopy was used to determine the optimal energy for a complete reversible polymerization reaction, and the mechanism was further confirmed by UV−vis spectroscopy which was able to monitor key structural changes. GPC analysis was used to track the molecular weight changes after the depolymerization reaction, which showed that the polymer was able to be converted back to monomers and oligomers, demonstrating the highly reversible polymerization and suggesting a potential for recyclability. Microhardness measurements of neat and irradiated samples were also used to determine the changes in mechanical properties before and after cleavage of the polymer network, and following the recovery of its structure, the latter showed a recovery of up to 91% of its mechanical properties.

The photooxidative degradation process of plastics caused by ultraviolet irradiation leads to bond breaking, crosslinking, the elimination of volatiles, formation of free radicals, and decreases in weight and molecular weight. Photodegradation deteriorates both the mechanical and physical properties of plastics and affects their predicted life use, in particular for applications in harsh environments. Plastics have many benefits, while on the other hand, they have numerous disadvantages, such as photodegradation and photooxidation in harsh environments and the release of toxic substances due to the leaching of some components, which have a negative effect on living organisms. Therefore, attention is paid to the design and use of safe, plastic, ultraviolet stabilizers that do not pose a danger to the environment if released. Plastic ultraviolet photostabilizers act as efficient light screeners (absorbers or pigments), excited-state deactivators (quenchers), hydroperoxide decomposers, and radical scavengers. Ultraviolet absorbers are cheap to produce, can be used in low concentrations, mix well with polymers to produce a homogenous matrix, and do not alter the color of polymers. Recently, polyphosphates, Schiff bases, and organometallic complexes were synthesized and used as potential ultraviolet absorbers for polymeric materials. They reduced the damage caused by accelerated and natural ultraviolet aging, which was confirmed by inspecting the surface morphology of irradiated polymeric films. For example, atomic force microscopy revealed that the roughness factor of polymers’ irradiated surfaces was improved significantly in the presence of ultraviolet absorbers. In addition, the investigation of the surface of irradiated polymers using scanning electron microscopy showed a high degree of homogeneity and the appearance of pores that were different in size and shape. The current work surveys for the first time the use of newly synthesized, ultraviolet absorbers as additives to enhance the photostability of polymeric materials and, in particular, polyvinyl chloride and polystyrene, based mainly on our own recent work in the field.

A catalyst-free and environmentally friendly process was employed for the production of biodiesel from sea mango seed oil. This oil is non-edible and contains several fatty acids such as palmitic acid (C16), trans-9-elaidic acid (C18:1t), oleic acid (C18:1), linoleic acid (C18:2), and linolelaidic acid (C18:2n6t). The in situ extraction and transesterification of the oil were carried at the subcritical methanol-water condition. The effect of reaction temperature and time on the yield of biodiesel was studied. The maximum yield of biodiesel was 98.58% and achieved at 200 °C, 40 bar and reaction time of 6 h. The ratio among sea mango seed, methanol, and water was 2:10:1.

The reactions of poly vinyl chloride (PVC) with different aliphatic amines in Tetra Hydro Furan, THF, have been studied. These reactions led to the formation of new polymers (PVC-L) which were characterized by spectroscopic methods (Infra Red, IR and Uv-Visible spectrophotometry). Composite of the new polymers were prepared and their optical activities in the region (200-400 nm) were studied. The optical data analyzed and interpreted using the theory of phonon assisted direct electronic transition.

Modification of poly(vinyl chloride) surface was achieved via introducing a new Schiff base containing 1,2,4‐triazole ring system to the polymer backbone. The new Schiff base containing 1,2,4‐triazole ring and the resulted homogenous polymer (PVC‐L) was characterized using Fourier‐transform infrared spectroscopy. Copper chloride was then added to coordinate with homogenous polymer to form PVC‐L‐CuII. The UV stability of the modified polymer was tested under long periods (300 h) of UV‐irradiation. The morphology of the modified surface was investigated by scanning electron microscopy. J. VINYL ADDIT. TECHNOL., 26:475–480, 2020. © 2020 Society of Plastics Engineers

A dynamic linear polymer was formed by the [2π + 2π] reversible cycloaddition reaction of a thymine-based monomer under topochemical conditions and was used in self-healing applications. The reversible polymerisation of the thymine monomer was confirmed by UV and GPC analysis. Irradiation at 302 nm resulted in polymerisation of the monomer, and irradiation with wavelengths lower than 240 nm resulted in depolymerisation and the production of oligomeric units. This leads to a reduction in the glass transition temperature, and promoted healing of surface scratches due to the increased chain mobility. The self-healing ability of scratched samples was assessed based on the visual disappearance of the damage. In addition, the mechanical properties of the polymer before and after healing were found to be similar. [a] Dr. M. Abdallh, Mr. P. He, Prof. M. T.

The change in the optical band gap and optical activation energy have been investigated for pure and doped Poly (vinyl alcohol) films with different cupper chloride concentrations. The optical properties were measured in the wave length range from (200-800) nm at room temperature. The optical band gap (E g) for allowed direct transition decrease with increase the concentration of cupper chloride. The optical activation energy for allowed direct transition band gap was evaluated using Urbach-edges method.