Evaluation of Schiff bases of 2,5-dimercapto-1,3,4-thiadiazole as photostabilizer for poly(methyl methacrylate)

The photostabilization of poly(methyl methacrylate) (PMMA) films by Schiff bases of 2,5-dimercapto-1,3,4-thiadiazole compounds was investigated. The PMMA films containing concentration of complexes 0.5% by weight were produced by the casting method from chloroform solvent. The photostabilization activities of these compounds were determined by monitoring the hydroxyl index with irradiation time. The changes in viscosity average molecular weight of PMMA with irradiation time were also tracked (using benzene as a solvent). The quantum yield of the chain scission (Φ_cs) of these complexes in PMMA films was evaluated and found to range between 4.19 × 10^?5 and 8.75 × 10^?5. Results obtained showed that the rate of photostabilization of PMMA in the presence of the additive followed the trend:[1] > [2] > [3] > [4] > [5].According to the experimental results obtained, several mechanisms were suggested depending on the structure of the additive. Among them, UV absorption, peroxide decomposer, and radical scavenger for photostabilizer mechanisms were suggested.     

一种新型的紫外吸收剂——二苯甲酰甲烷的光谱特性及光稳定能力的初步研究

本文研究了一种新型的紫外吸收剂——二苯甲酰甲烷的光谱特性。实验结果表明,在基态,它存在酮式-烯醇式的热化学平衡,且烯醇式形成六元环分子内氢键。在顺-1,4-聚丁二烯溶液光降解的比较实验中,二苯甲酰甲烷的光稳定能力和邻羟基-对正辛氧基二苯甲酮相近,并对光稳定行为的可能机理进行了研究。     

POLYMERIC PHOTOSTABILIZERS CONTAINING TWO KINDS OF PHOTOSTABILIZING GROUPS Ⅱ. SYNTHESIS AND PHOTOSTABILITY OF COPOLYMERS OF 2,2,6,6-TETRAMETHYL-4-PIPERIDINYL METHACRYLATE AND β-HYDROXY-γ-(ORTHO-HYDROXY BENZOXY) PROPYL METHACRYLATE

A new kind of photostabilizers, eopolymer of 2, 2, 6, 6-tetramethyl-4-piperidinyl methacrylate and β-hydroxy-γ-(ortho-hydroxy benzoxy) propyl methacrylate, has been synthesized. The spectral behaviors of these copolymers were studied in detail. In the presence of salicylyl group a strong absorption in the region of 280—330 nm could be observed, and an unusual Stoke's shift appeared in the fluorescence spectrum excited by 310nm. The photostabilization ability of these copolymers in the process of photodegradation of cis-poly (butadiene) was studied. Results indicated that these compounds possess excellent photostabilization ability.