Mediation of Photochemical Reactions of 1-Naphthyl Phenylacylates by Polyolefin Films. A ‘Radical Clock’ to Measure Rates of Radical-Pair Cage Recombinations in ‘Viscous Space’
作者:Weiqiang Gu、Richard G. Weiss
DOI:10.1016/s0040-4020(00)00512-3
日期:2000.9
generated upon irradiation of 1-naphthyl phenylacetate (1a) and 1-naphthyl 2-phenylpropanoate (1b) in three unstretched and stretched polyethylene films and isotactic and syndiotactic polypropylene films have been investigated. From dynamic fluorescence measurements, the primary locus of reactions by 1 is within amorphous regions of the films. The reaction cages afforded by these media inhibit escape of the
研究了在三个未拉伸和拉伸的聚乙烯薄膜以及等规和间同规聚丙烯薄膜中,辐射1-萘基苯基乙酸酯(1a)和1-萘基2-苯基丙酸酯(1b)时产生的苯基酰基/ 1-萘氧基单线态自由基对的命运。从动态荧光测量中,主要反应位点为1在膜的无定形区域内。这些介质提供的反应笼抑制了自由基对的逸出,并介导了它们的重新定向运动,从而导致了光炸和相关产物的生成。从本质上讲,这些笼子起着坚固壁模板的作用。另外,描述了一种测量单线态自由基对的速率常数的方法。因此,来自基团对1(> 10 8 s -1)的2-苯基酰基-1-萘酚的速率常数(导致酮前体))是4异构体速率常数的> 6倍。膜拉伸增加了这种选择性,但是笼内自由基对的重组速率与宏观聚合物,诸如结晶度和支链频率等性质之间没有明显的相关性。相比之下,2-苄基-1-萘酚的(酮前体)的形成(由苯酰基脱羰基化后的笼内重组)比4-苄基-1-萘酚的形成要慢。