Photoacid-catalysed pigmentation of dyestuff precursors enhanced by acid amplifiers in polymer films
作者:Kunihiro Ichimura、Koji Arimitsu、Masaru Tahara
DOI:10.1039/b314112h
日期:——
The pigmentation of BOC-protected pigment precursors catalysed by photogenerated acidic species in films of polystyrene (pSt) and poly(α-methylsytrene) according to the latent pigment technology was investigated to reveal that the process consists of three steps: the deprotection to give free indigo molecules, the subsequent diffusion of the molecules, and their aggregation to give the hydrogen-bonded pigment. The photoacid-catalysed regeneration of indigo protected with tert-butoxycarbonyl (BOC) residues is comprised of two processes: a fast process at the early stage, followed by a very slow one. The former likely corresponds to the reaction within reactive spheres in polymer films, whereas the subsequent slow process displays a suppressive effect of polymer matrices on the migration of the molecules from the reactive spheres so that the completion of the pigmentation requires prolonged heating. On the other hand, the addition of an acid amplifier, which decomposes autocatalytically to liberate new sulfonic acid molecules, results in the marked enhancement of the deprotection and consequently the pigmentation. Particle size analysis of solutions dissolving pigmented films showed that smaller particles of indigo of about 20 nm in diameter are formed under heating below the glass transition temperature (Tg) of pSt whereas larger ones of a few hundred nm become predominant when films are heated above the Tg, reflecting both the fast and slow processes.
研究人员根据潜伏颜料技术,在聚苯乙烯(pSt)和聚(α-甲基苯乙烯)薄膜中通过光生酸性物质催化受 BOC 保护的颜料前体着色,结果发现该过程包括三个步骤:脱保护以产生游离靛蓝分子、分子的后续扩散和聚集以产生氢键颜料。受叔丁氧羰基(BOC)残基保护的靛蓝在光酸催化下的再生包括两个过程:早期的快速过程和随后的非常缓慢的过程。前一个过程可能与聚合物薄膜中反应球内的反应相对应,而随后的缓慢过程则显示了聚合物基质对分子从反应球迁移的抑制作用,因此色素沉淀的完成需要长时间的加热。另一方面,加入酸放大器后,酸放大器会自动催化分解,释放出新的磺酸分子,从而显著提高脱保护作用,进而提高色素沉积效果。对溶解颜料薄膜的溶液进行的粒度分析表明,在低于 pSt 玻璃转化温度(Tg)的加热条件下,会形成直径约为 20 纳米的较小靛蓝颗粒,而当薄膜加热到高于 Tg 时,则主要形成几百纳米的较大靛蓝颗粒,这同时反映了快速和慢速过程。