Synthesis and Aggregation-enhanced Emission of Poly(3-oligo( ethylene oxide)3-thiophene)
- 材料学院－已发表论文 
通过2-溴-5-碘-3-(三聚氧乙烯)取代噻吩大分子单体的合成、镍催化缩聚等,得到Mn为6000的3-(三聚氧乙烯)取代聚噻吩(P3OET).在非选择性良溶剂四氢呋喃中,P3OET溶液发射橙色荧光.在选择性极性溶剂诱导作用下,P3OET在水中自组装形成稳定的球形自组装体,荧光峰相对红移而发射橙红色光,伴随荧光强度减弱;而在甲醇中,P3OET形成丝状自组装体,荧光峰相对蓝移而发射亮黄色光,但是荧光强度增强,表现出聚集增强发光现象.类似于含有低聚氧乙烯短支链的聚烯烃,P3OET在水溶液中还具有温度响应特性.当水溶液温度升高,荧光峰逐渐蓝移,并且荧光强度增强.P3OET自组装体可进入小鼠黑色素瘤B16F10细胞,并且发光而用于成像.利用控温热台适当加热细胞,或者使用解偶联剂、抗癌药物等化学刺激使细胞活动产生热量时,发光性质随细胞温度升高而发生蓝移、强度增强等规律性变化.This paper reports a polythiophene derivative that contains oligo( ethylene oxide) short side chains,poly( 3-oligo( ethylene oxide)3-thiophene)( P3OET) of Mn≈ 6000,which is synthesized by nickel-catalyzed polymerization of 2-bromo-5-iodine-3-oligo( ethylene oxide)3-thiophene. The presented P3 OET can well dissolve in tetrahydrofuran,a good solvent,and emit orange-colored light under UV illumination at room temperature. In water,a selective polar solvent of P3 OET,P3OET self-assembled into spherical nanostructures that showed a red-colored emission with a red-shifted spectrum and decreased quantum yield,in comparison with that in tetrahydrofuran; in contrast,in methanol,another selective polar solvent of P3 OET,P3OET selfassembled into silk-like nanostructures that showed a yellow-colored emission with a blue-shifted spectrum and enhanced quantum yield,which is a quite unusual phenomenon that is also called "aggregation-enhanced emission". Moreover,the integration of oligo( ethylene oxide) and polythiophenes made the presented P3 OET exhibit temperature responsive behavior in aqueous solutions,similar to that of the temperature responsive polymers of oligo( ethylene glycol) methacrylate reported previously in literatures. This unique property of oligo( ethylene oxide)-contained polymers resulted in reversible temperature-induced twisting of the polythiophene conjugated backbone,allowing the reversible varying on the conjugation length by changing the temperature in milieu,which was accompanied by pronounced spectroscopic changes. At elevated temperatures,the blueshifted spectra with enhanced intensities were recorded in aqueous solutions. These unique features of P3 OET make it possess great potential for chemo-/ bio-detection applications. With mouse melanoma B16F10 cells as the model,the experimental results indicate that the P3 OET assemblies can enter the cells and readily emit strong visible fluorescence for cellular imaging. The temperature responsive behavior of P3 OET also allow manipulate the fluorescence intensity for sensing the cellular temperature change. The cellular temperature change can be induced by both the heat generated by an external heater and the intracellular temperature variations induced by external chemical stimuli,e. g.,adding carbonyl cyanide 4-( trifluoromethoxy)phenylhydrazone,an uncoupler of oxidative phosphorylation in mitochondria that can cause heat production by respiration,or adding 5-fluorouracil,an anticancer drug that can also induce an unveiled temperature variation due to early responses of apoptosis such as DNA cleavage.