Five new thiophenes, namely,N-[(3-bromo-2-methylthiophen-5-yl)methylene]-4-methoxyaniline (4a),N-[(3-bromo-2-methylthiophen-5-yl)methylene]-3,4-dimethoxyaniline (4b),N-[(3-bromo-2-methylthiophen-5-yl)methylene]-3,4-dimethylaniline (4c), 3-[(3-bromo-2-methylthiophen-5-yl)methyleneamino]-2-methylquinazolin-4(3H)-one (4d), and 3-[(3-bromo-2-methylthiophen-5-yl)methyleneamino]-2-isopropylquinazolin-4(3H)-one (4e), have been synthesized. All of these materials brought about a reduction in the level of photodegradation of poly(vinyl chloride) (PVC) films containing the synthesized thiophenes (0.5%; by weight). The results obtained showed that the extent of photostabilization of PVC in the presence of an additive was in the order4e > 4d > 4b > 4a > 4c. For the most favorable additive (4e), the rate of appearance of infrared absorption bands of degradation products was reduced by around two-thirds, while the quantum yield of chain scission was calculated to be reduced by a factor of more than one thousand. It is suggested that the additives may help stabilize PVC by direct absorption of UV radiation and dissipation of the energy as heat or that electrostatic attraction between the additives and PVC may assist transfer of energy from excited state PVC to the additive, from where it can be dissipated.

BackgroundPetroleum polymers contribute to non-degradable waste materials and it would therefore be desirable to produce ecofriendly degradable materials. Biodegradation of polyhydroxybutyrate (PHB) in the presence of oligomer hydrolase and PHB depolymerase gave 3-hydroxybutyric acid which could be oxidized to acetyl acetate. Several bacteria and fungi can degrade PHB in the soil.ResultsBiodegradation of PHB showed a significant decrease in the molecular weight (Mw), number-average molecular weight (Mn) and the dispersity (Mw/Mn) for all the film formulations. Nanofibers of PHB and its composites showed faster degradation compared to other films and displayed complete degradation after 3 weeks. The SEM micrographs showed various surface morphology changes including alterations in appearance of pores, cavity, grooves, incisions, slots and pointers. Such changes were due to the growth of microorganisms that secreted PHB depolymerase enzyme which lead to the biopolymer films degradation. However, PHB nanofibers and its composites films in the presence of TiO2 demonstrated more surface changes with rupture of most nanofibers in which there was a drop in fibres diameter.ConclusionsThe degradation of biopolymers help to overcome some of the pollution problems associated with the use of petroleum polymers. PHB nanofiber and its TiO2 composite were degraded faster compared to other PHB film types due to their three dimensional and high surface area structures. The presence of TiO2 nanoparticles in the composite films slowdown the degradation process compared to PHB films. Additionally, the PHB and its composite films that were prepared from UV treated PHB films led to acceleration of the degradation.Graphical abstractBiodegradation of polyhydroxybutyrate films in soil

Three organotin complexes containing furosemide as a ligand (L), Ph 3 SnL, Me 2 SnL 2 and Bu 2 SnL 2 , were synthesized and characterized. Octahedral geometry was proposed for the Me 2 SnL 2 and Bu 2 SnL 2 , while the Ph 3 SnL complex has trigonal bipyramid geometry. The synthesized organotin complexes (0.5% by weight) were used as additives to improve the photostability of poly(vinyl chloride), PVC, (40 µm thickness) upon irradiation. The changes imposed on functional groups, weight loss and viscosity average molecular weight of PVC films were monitored. The experimental results show that the rate of photodegradation was reduced in the presence of the organotin additives. The quantum yield of the chain scission was found to be low (9.8 × 10 −7 ) when Ph 3 SnL was used as a PVC photostabilizer compared to controlled PVC (5.18 × 10 −6 ). In addition, the atomic force microscope images for the PVC films containing Ph 3 SnL 2 after irradiation shows a smooth surface compared to the controlled films. The rate of PVC photostabilization was found to be highest for Ph 3 SnL followed by Bu 2 SnL 2 and Me 2 SnL 2 . It has been suggested that the organotin complexes could act as hydrogen chloride scavengers, ultraviolet absorbers, peroxide decomposers and/or radical scavengers.

Three new tetra-Schiff bases were synthesized and characterized to be used as photostabilizers for poly(vinyl chloride) (PVC) films. The photostability of PVC films (40 μm thickness) in the presence of Schiff bases (0.5 wt %) upon irradiation (300 h) with a UV light (λmax = 365 nm and light intensity = 6.43 × 10−9 ein∙dm−3∙s−1) was examined using various spectroscopic measurements and surface morphology analysis. The changes in various functional groups’ indices, weight and viscosity average molecular weight of PVC films were monitored against irradiation time. The additives used showed photostability for PVC films, with Schiff base 1 being the most effective additive upon irradiation, followed by 2 and 3. The atomic force microscopy (AFM) images for the PVC surface containing Schiff base 1 after irradiation were found to be smooth, with a roughness factor (Rq) of 36.8, compared to 132.2 for the PVC (blank). Several possible mechanisms that explain PVC photostabilization upon irradiation in the presence of tetra-Schiff bases were proposed.

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Abstract:The photostabilization of poly(vinyl chloride) (PVC) films having five Schiff's bases derived from sulphamethoxazole has been investigated. The casting method was used to produce PVC films containing sulphamethoxazoles (0.5% by weight), in tetrahydrofuran. The photostabilization activities of five additives were determined by monitoring the hydroxyl, polyene and carbonyl indices with irradiation time. In addition, the quantum yield of the chain scission (Φcs) and the changes in viscosity average molecular weight of PVC films containing Schiff's basses were evaluated with irradiation time. The rate of photostabilization for PVC films in the presence of five Schiff's base additives was found to be the highest in the case of 2-hydroxybenzylidene derivative and the lowest in the unsubstituted benzylidene derivative. Several mechanisms have been suggested to explain the photostabilization of PVC in the presence of Schiff's bases that mainly act as UV absorbers and radical scavengers for photostabilizers.

Five Schiff bases derived from melamine have been used as efficient additives to reduce the process of photodegradation of poly(vinyl chloride) films. The performance of Schiff bases has been investigated using various techniques. Poly(vinyl chloride) films containing Schiff bases were irradiated with ultraviolet light and any changes in their infrared spectra, weight, and the viscosity of their average molecular weight were investigated. In addition, the surface morphology of the films was inspected using a light microscope, atomic force microscopy, and a scanning electron micrograph. The additives enhanced the films resistance against irradiation and the polymeric surface was much smoother in the presence of the Schiff bases compared with the blank film. Schiff bases containing an ortho-hydroxyl group on the aryl rings showed the greatest photostabilization effect, which may possibly have been due to the direct absorption of ultraviolet light. This phenomenon seems to involve the transfer of a proton as well as several intersystem crossing processes.

Three phosphate esters 1-3 were successfully synthesized from the reaction of 2-, 3-and 4-hydroxybenzaldehyde with phosphoryl chloride. Reactions of 1-3 with benzidine in the presence of glacial acetic acid gave the corresponding novel phosphorus organic polymers 4-6 containing the azomethane linkage. The structures of the synthesized compounds were confirmed by Fourier transform infrared spectroscopy, nuclear magnetic resonance and elemental analysis. Interesting physiochemical properties for the polymeric materials 4-6 were observed using a combination of several techniques such as gel permeation chromatography, scanning electron microscopy, Brunauer-Emmett-Teller and nitrogen adsorption-desorption isotherm, Barrett-Joyner-Halenda and H-sorb 2600 analyzer. The mesoporous polymers 4-6 exhibit tunable porosity with Brunauer-Emmett-Teller surface area (SA BET = 24.8-30 m 2 ·g -1 ), pore volume (0.03-0.05 cm 3 ·g -1 ) and narrow pore size distribution, in which the average pore size was 2.4-2.8 nm. Polymers 4-6 were found to have high gas storage capacity and physico-chemical stability, particularly at a high pressure. At 323 K and 50 bars, polymers 4-6 have remarkable carbon dioxide uptake (up to 82.1 cm 3 ·g -1 ) and a low hydrogen uptake (up to 7.4 cm 3 ·g -1 ). The adsorption capacity of gasses for polymer 5 was found to be higher than those for polymers 4 and 6.