Galinski Henning, Ambrosio Antonio, Maddalena Pasqualino, Schenker Iwan, Spolenak Ralph, Capasso Federico
School of Engineering and Applied Science, Harvard University, Cambridge, MA 02138; Laboratory for Nanometallurgy and
School of Engineering and Applied Science, Harvard University, Cambridge, MA 02138; CNR-Institute for Superconductors, Oxides and Other Innovative Materials and Devices (SPIN) and Dipartimento di Fisica, Università degli Studi di Napoli Federico II, 80126 Naples, Italy; and
Proc Natl Acad Sci U S A. 2014 Dec 2;111(48):17017-22. doi: 10.1073/pnas.1409718111. Epub 2014 Nov 17.
Since the pioneering work of Turing on the formation principles of animal coat patterns [Turing AM (1952) Phil Trans R Soc Lond B 237(641):37-72], such as the stripes of a tiger, great effort has been made to understand and explain various phenomena of self-assembly and pattern formation. Prominent examples are the spontaneous demixing in emulsions, such as mixtures of water and oil [Herzig EM, et al. (2007) Nat Mater 6:966-971]; the distribution of matter in the universe [Kibble TWB (1976) J Phys A: Math Gen 9(8):1387]; surface reconstruction in ionic crystals [Clark KW, et al. (2012) Nanotechnol 23(18):185306]; and the pattern formation caused by phase transitions in metal alloys, polymer mixtures and binary Bose-Einstein condensates [Sabbatini J, et al. (2011) Phys Rev Lett 107:230402]. Photoactivated pattern formation in functional polymers has attracted major interest due to its potential applications in molecular electronics and photoresponsive systems. Here we demonstrate that photoactivated pattern formation on azobenzene-containing polymer films can be entirely explained by the physical concept of phase separation. Using experiments and simulations, we show that phase separation is caused by an instability created by the photoactivated transitions between two immiscible states of the polymer. In addition, we have shown in accordance with theory, that polarized light has a striking effect on pattern formation indicated by enhanced phase separation.
自从图灵关于动物皮毛图案形成原理的开创性工作[图灵AM（1952年）《伦敦皇家学会哲学学报B》237(641):37 - 72]，比如老虎的条纹以来，人们付出了巨大努力去理解和解释各种自组装和图案形成现象。突出的例子有乳液中的自发分层，如水和油的混合物[赫尔齐格EM等人（2007年）《自然材料》6:966 - 971]；宇宙中物质的分布[基布尔TWB（1976年）《物理学杂志A：数学与一般物理学》9(8):1387]；离子晶体中的表面重构[克拉克KW等人（2012年）《纳米技术》23(18):185306]；以及金属合金、聚合物混合物和二元玻色 - 爱因斯坦凝聚体中相变引起的图案形成[萨巴蒂尼J等人（2011年）《物理评论快报》107:230402]。功能聚合物中的光激活图案形成因其在分子电子学和光响应系统中的潜在应用而引起了广泛关注。在此，我们证明含偶氮苯聚合物薄膜上的光激活图案形成可以完全用相分离的物理概念来解释。通过实验和模拟，我们表明相分离是由聚合物两种不混溶状态之间的光激活转变所产生的不稳定性引起的。此外，我们已根据理论表明，偏振光对图案形成有显著影响，表现为相分离增强。
