The effect of high UV radiation exposure environment on the novel PVC polymers.

Although plastic induces environmental damages, almost the consumption of poly(vinyl chloride) never stops increasing. Therefore, this work abstracted by two parts, first, synthesis of Schiff bases 1-4 compounds through the reaction of amino group with appropriate aromatic aldehyde, reaction of PVC with Schiff bases compounds 1-4 in THF to form a new modified PVC-1, PVC-2, PVC-3, and PVC-4. The structures of Schiff bases 1-4 and the modified PVC-1, PVC-2, PVC-3, and PVC-4 have been characterized by different spectroscopic analyses. Second, the influence of introducing 4-amino-1,2,4-triazole as a pendent groups into PVC chain investigated on photostability rules of tests. The modified polymers photostability investigated by observing indices (ICO, Ipo, and IOH), weight loss, UV and morphological studies, and all results obtained indicated that PVC-1, PVC-2, PVC-3 and PVC-4 gave lower growth rate of ICO, IPO, and IOH through UV exposure time. The photostability are given as PVC-4 < PVC-3 < PVC-2 < PVC-1 from different mechanisms which suggested building on existence of 4-amino-1,2,4-triazole moieties in the polymer chain.

SEM analysis of the tunable honeycomb structure of irradiated poly(vinyl chloride) films doped with polyphosphate.

The fabrication of tunable poly(vinyl chloride) porous films containing polyphosphate as an additive was successful. Irradiation of poly(vinyl chloride) films containing polyphosphate at a low concentration (0.5% by weight) with an ultraviolet light (λmax = 313 nm) for 300 h leads to the formation of a honeycomb like structure. The scanning electron microscopy images, at different magnification power, confirmed the production of the PVC honeycomb-like structure. The morphological images of the polymeric film showed a rough surface and a large number of regularly distributed hexagonal pores. The number of pores increased upon irradiation time and it was maximum after 300 h. The honeycomb structure formation could be due to the regular aggregation of polyphosphate among the polymeric chains, the increase in solution intrinsic viscosity and evaluation of hydrogen chloride gas through dehydrochlorination process.

Fabrication of Novel Ball-Like Polystyrene Films Containing Schiff Base Microspheres as Photostabilizers.

Polystyrene films containing a low concentration of three highly aromatic Schiff bases were prepared using the casting method. The polystyrene films were irradiated with ultraviolet light (300 h). The polystyrene infrared spectra, weight loss, molecular weight reduction and the surface morphology were examined upon irradiation. The Schiff bases acted as photostabilizers and reduced the photodegradation of polystyrene films to a significant level in comparison to the blank film. The images recorded of the surface of the miscible polystyrene/Schiff base blends showed novel ball-like microspheres with a diameter of 3.4⁻4.3 µm. The Schiff bases were able to endow excellent protection to polystyrene against ultraviolet irradiation.

Polyphosphates as Inhibitors for Poly(vinyl Chloride) Photodegradation.

Three polyphosphates were used as inhibitors for poly(vinyl chloride) (PVC) photodegradation. The polyphosphates were added to PVC at a concentration of 0.5% by weight. The PVC films (40 µm thickness) were irradiated at room temperature with ultraviolet (UV) light for up to 300 h. The changes in PVC films after irradiation were monitored by Fourier transform infrared spectroscopy, weight loss, viscosity-average molecular weight determination, and atomic force microscopy. These changes were very noticeable in the blank PVC films compared to the ones obtained when additives were used. The polyphosphates can inhibit the PVC photodegradation through direct absorption of UV light, interactions with PVC chains, and acting as radical scavengers.

New Tetra-Schiff Bases as Efficient Photostabilizers for Poly(vinyl chloride).

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.

Efficacy and safety of superficial chemical peeling in treatment of active acne vulgaris.

Acne vulgaris is an extremely common condition affecting the pilosebaceous unit of the skin and characterized by presence of comedones, papules, pustules, nodules, cysts, which might result in permanent scars. Acne vulgaris commonly involve adolescents and young age groups. Active acne vulgaris is usually associated with several complications like hyper or hypopigmentation, scar formation and skin disfigurement. Previous studies have targeted the efficiency and safety of local and systemic agents in the treatment of active acne vulgaris. Superficial chemical peeling is a skin-wounding procedure which might cause some potentially undesirable adverse events. This study was conducted to review the efficacy and safety of superficial chemical peeling in the treatment of active acne vulgaris. It is a structured review of an earlier seven articles meeting the inclusion and exclusion criteria. The clinical assessments were based on pretreatment and post-treatment comparisons and the role of superficial chemical peeling in reduction of papules, pustules and comedones in active acne vulgaris. This study showed that almost all patients tolerated well the chemical peeling procedures despite a mild discomfort, burning, irritation and erythema have been reported; also the incidence of major adverse events was very low and easily manageable. In conclusion, chemical peeling with glycolic acid is a well-tolerated and safe treatment modality in active acne vulgaris while salicylic acid peels is a more convenient for treatment of darker skin patients and it showed significant and earlier improvement than glycolic acid.

Efficacy and safety of superficial chemical peeling in treatment of active acne vulgaris

Abstract: Acne vulgaris is an extremely common condition affecting the pilosebaceous unit of the skin and characterized by presence of comedones, papules, pustules, nodules, cysts, which might result in permanent scars. Acne vulgaris commonly involve adolescents and young age groups. Active acne vulgaris is usually associated with several complications like hyper or hypopigmentation, scar formation and skin disfigurement. Previous studies have targeted the efficiency and safety of local and systemic agents in the treatment of active acne vulgaris. Superficial chemical peeling is a skin-wounding procedure which might cause some potentially undesirable adverse events. This study was conducted to review the efficacy and safety of superficial chemical peeling in the treatment of active acne vulgaris. It is a structured review of an earlier seven articles meeting the inclusion and exclusion criteria. The clinical assessments were based on pretreatment and post-treatment comparisons and the role of superficial chemical peeling in reduction of papules, pustules and comedones in active acne vulgaris. This study showed that almost all patients tolerated well the chemical peeling procedures despite a mild discomfort, burning, irritation and erythema have been reported; also the incidence of major adverse events was very low and easily manageable. In conclusion, chemical peeling with glycolic acid is a well-tolerated and safe treatment modality in active acne vulgaris while salicylic acid peels is a more convenient for treatment of darker skin patients and it showed significant and earlier improvement than glycolic acid

New Eco-Friendly Phosphorus Organic Polymers as Gas Storage Media.

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 (SABET = 24.8⁻30 m²·g⁻1), pore volume (0.03⁻0.05 cm³·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 cm³·g⁻1) and a low hydrogen uptake (up to 7.4 cm³·g⁻1). The adsorption capacity of gasses for polymer 5 was found to be higher than those for polymers 4 and 6.

New photostabilizers for polystyrene based on 2,3-dihydro-(5-mercapto-1,3,4-oxadiazol-2-yl)-phenyl-2-(substituted)-1,3,4-oxazepine- 4,7-dione compounds.

The photostabilization of polystyrene (PS) films by 2,3-dihydro-(5-mercapto-1,3,4-oxadiazol-2-yl)-phenyl-2-(substituted)-1,3,4-oxazepine-4,7-dione compounds was investigated. PS films containing concentration of complexes 0.5% by weight were produced by the casting method from chloroform as a solvent. The photostabilization activities of these compounds were determined by monitoring the carbonyl and hydroxyl indices with irradiation time. The changes in viscosity average molecular weight of PS with irradiation time were also tracked (using benzene as a solvent). The quantum yield of the chain scission (Φcs) of these complexes in PS films was evaluated and found to range between 3.31 × 10(-6) and 7.89 × 10(-6). Results obtained showed that the rate of photostabilization of PS in the presence of the additive follows the trend (I > II > III > IV). According to the experimental results obtained, several mechanisms were suggested depending on the structure of the additive like UV absorption, peroxide decomposer and radical scavenger.

2-(1,3-Dioxoisoindolin-2-yl)acetic acid-N'-[(E)-4-meth-oxy-benzyl-idene]pyridine-4-carbohydrazide (2/1).

In the crystal structure of the title compound, 2C(10)H(7)NO(4)·C(14)H(13)N(3)O(2), the two independent acid mol-ecules are connected through strong O-H⋯N and O-H⋯O hydrogen bonds to the central mol-ecule of the anti-tubercular drug N'-[(E)-4-meth-oxy-benzyl-idene]pyridine-4-carbohydrazide. Two such trimolecular units related by an inversion centre inter-act through a pair of N-H⋯O hydrogen bonds, forming a 3 + 3 mol-ecular aggregate. The dihedral angle between the aromatic rings of the hydrazone mol-ecule is 1.99 (12)°. The crystal packing features weak C-H⋯O and π-π stacking inter-actions, with centroid-centroid distances of 3.8460 (19) and 3.8703 (13) Å.