Thermal spectra of liquid crystal, \%p\|n\%\|dodecyloxy benzoic acid were collected at 26\150 ℃ by FTIR microspectroscopy. Conformational apparent enthalpy differences Δ\%H\% in phase transitions have been determine...Thermal spectra of liquid crystal, \%p\|n\%\|dodecyloxy benzoic acid were collected at 26\150 ℃ by FTIR microspectroscopy. Conformational apparent enthalpy differences Δ\%H\% in phase transitions have been determined by vant Hoff equation at constant pressure and plotted with temperature. Compared to DSC, these enthalpies plot with temperature could be divided into three types. The first one was long alkyl chain group which has only one apparent endothermic enthalpy peak at 95 ℃. The second one was partial carbonyl and aromatic ether groups has three endothermic enthalpy peaks in the phase transition. The third type including benzoyl group which has one exothermic enthalpy peak at 95 ℃ and a broad endothermic enthalpy peak in the range of 128\140 ℃. These differences indicated that oxy\|benzoic acid part of dodecyloxy benzoic acid recrystallized to cycle dimer during alkyl chain melting in crystal\|smectic phase transition.展开更多
Harnessing photoresponsive behavior in organic crystals,such as shape and morphology deformation,on multiple scales is intriguing with respect to precise spatiotemporal operation,because dynamic deformations are promi...Harnessing photoresponsive behavior in organic crystals,such as shape and morphology deformation,on multiple scales is intriguing with respect to precise spatiotemporal operation,because dynamic deformations are promising in fabricating future intelligent devices.Here,we synthesized a new photoresponsive molecular crystal composed of dimethyl(E)-2-(3-(naphthalen-1-yl)allylidene)malonate((E)-DNAM)that undergoes E-to-Z photoisomerization accompanied by photoinduced crystal-to-liquid melting phase transition when exposed to visible light.Instead of expanding in bulk polycrystals,single-crystal(E)-DNAM rectangular microplates in an aqueous solution rapidly collapsed into liquid droplets,showing a remarkable drastic reduction in surface area of more than 97%after light illumination.We deduce that the unique microscopic morphology of microplates with high aspect ratios of length-tothickness reaching up to 1000 is mainly responsible for the photoinduced melting leading to drastic collapse.In addition,the cohesive forces of liquid photoproduct facilitate the overall deformations and transformation.We have shown a facile way to achieve the remarkable collapse of molecular crystals into droplets by photochemical reaction and phase transition.展开更多
文摘Thermal spectra of liquid crystal, \%p\|n\%\|dodecyloxy benzoic acid were collected at 26\150 ℃ by FTIR microspectroscopy. Conformational apparent enthalpy differences Δ\%H\% in phase transitions have been determined by vant Hoff equation at constant pressure and plotted with temperature. Compared to DSC, these enthalpies plot with temperature could be divided into three types. The first one was long alkyl chain group which has only one apparent endothermic enthalpy peak at 95 ℃. The second one was partial carbonyl and aromatic ether groups has three endothermic enthalpy peaks in the phase transition. The third type including benzoyl group which has one exothermic enthalpy peak at 95 ℃ and a broad endothermic enthalpy peak in the range of 128\140 ℃. These differences indicated that oxy\|benzoic acid part of dodecyloxy benzoic acid recrystallized to cycle dimer during alkyl chain melting in crystal\|smectic phase transition.
基金supported by the National Natural Science Foundation of China(grant nos.22105071,22220102004,22025503,and 22335004)the Shanghai Municipal Science and Technology Major Project(grant no.2018SHZDZX03)+5 种基金the Innovation Program of Shanghai Municipal Education Commission(2023ZKZD40)the Fundamental Research Funds for the Central Universities,the Programme of Introducing Talents of Discipline to Universities(grant no.B16017)the Science and Technology Commission of Shanghai Municipality(grant nos.21JC1401700 and 22ZR1417100)the Shanghai Sailing Program(21YF1409200)the Starry Night Science Fund of Zhejiang University Shanghai Institute for Advanced Study(grant no.SN-ZJU-SIAS-006)C.Z.gratefully acknowledges the financial support from the China Scholarship Council(202106745008).
文摘Harnessing photoresponsive behavior in organic crystals,such as shape and morphology deformation,on multiple scales is intriguing with respect to precise spatiotemporal operation,because dynamic deformations are promising in fabricating future intelligent devices.Here,we synthesized a new photoresponsive molecular crystal composed of dimethyl(E)-2-(3-(naphthalen-1-yl)allylidene)malonate((E)-DNAM)that undergoes E-to-Z photoisomerization accompanied by photoinduced crystal-to-liquid melting phase transition when exposed to visible light.Instead of expanding in bulk polycrystals,single-crystal(E)-DNAM rectangular microplates in an aqueous solution rapidly collapsed into liquid droplets,showing a remarkable drastic reduction in surface area of more than 97%after light illumination.We deduce that the unique microscopic morphology of microplates with high aspect ratios of length-tothickness reaching up to 1000 is mainly responsible for the photoinduced melting leading to drastic collapse.In addition,the cohesive forces of liquid photoproduct facilitate the overall deformations and transformation.We have shown a facile way to achieve the remarkable collapse of molecular crystals into droplets by photochemical reaction and phase transition.
