【作者】 冷杰；

【导师】 黎华明；

【作者基本信息】 湘潭大学 ， 高分子化学与物理， 2010， 硕士

【摘要】 近年来,纳/微米材料的合成及其性质研究引起了研究者们的广泛兴趣。与无机和高分子纳/微米材料不同,有机小分子的结构多样性、功能性以及易裁剪性,使得有机功能小分子纳/微米材料的研究越来越受到重视。在文献报道的有机纳/微米材料的合成方法中,再沉淀法因其简易的特点得到了广泛的应用。本论文采用嵌段共聚物PDMA-b-PNIPAM辅助再沉淀法制备了有机1-(2-吡啶偶氮)-2-萘酚(PAN)纳/微米材料,系统研究了共聚物浓度、PAN浓度等因素对材料形貌以及尺寸的影响,并对其生长过程进行了探讨。(1)嵌段共聚物的合成。以S-乙基-S’-(2-甲基-2-丙酸丙炔酯基)三硫代碳酸酯(PEMP)为链转移剂,偶氮二异丁腈(AIBN)为引发剂,采用可逆加成断裂链转移(RAFT)聚合反应合成了一系列不同分子量的聚N,N-二甲基丙烯酰胺均聚物(PDMA)及聚N,N-二甲基丙烯酰胺聚N-异丙基丙烯酰胺嵌段共聚物(PDMA-b-PNIPAM)。采用GPC对所合成聚合物的分子量及分子量分布进行了分析,GPC分析结果显示链转移剂PEMP对RAFT聚合过程的可控性较好。同时采用动态光散射(DLS)对嵌段共聚物的胶束化行为进行了研究,DLS测试结果表明随着聚合物溶液浓度的增加,其临界胶束温度(CMT)降低且胶束粒径减小。(2)有机PAN纳/微米材料的制备。利用温敏型嵌段共聚物PDMA-b- PNIPAM辅助再沉淀法制备了有机PAN纳/微米材料,系统研究共聚物浓度、PAN浓度等因素对纳/微米材料形貌以及尺寸的影响。采用扫描电子显微镜(SEM)对产物的形貌进行了表征,结果表明通过调控聚合物浓度或者PAN浓度,可以得到不同形貌(纤维状、棒状、束状)的纳/微米材料;红外光谱(FTIR)结果证明所得到的纳/微米材料为纯PAN而没有夹杂聚合物分子。利用紫外-可见光光谱(UV-Vis)及荧光光谱对PAN纳/微米材料的光物理性能及其生长过程进行了跟踪研究。UV-Vis测试结果表明,相对于PAN溶液的吸收峰,PAN纳/微米材料的吸收峰发生了红移现象,为J-聚集体;并且随着时间的延长,其吸收峰的强度逐渐减弱,长波拖尾现象加剧。荧光光谱则表明,PAN纳/微米材料的发射强度要比其原料稀溶液的发射强度有明显的增强,即聚集诱导的荧光增强现象(AIEE),并且在长波方向出现了新的发射峰;同时还发现,其荧光发射强度随着时间的延长而逐渐增强。更多还原

【Abstract】 During the past few years, nano/microstructures represent attractive building blocks for the fabrication of functional nano/microscale devices. However, most of the reported nano/microstructures have been focused on inorganic materials or polymers. Recently, nano/microstructures based on small organic functional molecule have been attracting considerable and increasing attention due to their unique optoelectronic properties and applications compared to those of their inorganic counterparts. Among the few synthesis methods, the so-called“reprecipitation method”has been one of the most popular methods for organic nano/microstructures formation due to its easy and versatile operation. In this paper, 1-(2-pyridylazo)-2- naphthol (PAN) was employed as a model compound to fabricate its corresponding organic nano/microstructures by reprecipitation with the assistance of poly(N,N- dimethylacrylamide)-poly(N-isopropylacrylamide) copolymer (PDMA-b-PNIPAM). The effects of copolymer concentration and PAN concentration on the size and shape have been investigated. Furthermore, the growth process of the products was discussed.(1) The preparation of block copolymers. A series of thermoresponsive diblock copolymers, PDMA-b-PNIPAM were synthesized by RAFT polymerization using 2-propynyloxy-2-(ethylthiocarbonothioylthio)-2-methyl propanoate (PEMP) and 2,2’- azobisisobutyronitrile (AIBN) as the RAFT agent and initiator, respectively. The molecular weight and the polydispersity (PDI) were determined by gel permeation chromatography (GPC). The results indicated that all polymerizations proceeded with good control, as evidenced by low polydispersity. The thermally aggregation behavior of the copolymers were investigated by dynamic light scattering (DLS) and the results indicated that critical micelle temperature (CMT) decreased with the increasing of polymer aqueous concentration.(2) Fabrication of organic PAN nano/microtructures. Nano/microstructures of a small organic functional molecule, 1-(2-pyridylazo)-2-naphthol (PAN), were successfully prepared via the reprecipitation method with the assistance of thermoresponsive diblock copolymer PDMA-b-PNIPAM. The effects of concentrations of copolymer and PAN on the size and shape have been investigated. Scanning electron microscopy (SEM) indicated that the morphology of the nano/microstructures prepared as either nano/microfibres, nano/microrods, or bundle- like nano/microstructures can be readily controlled by varying the experimental conditions such as the concentration of the polymer or PAN. Fourier transform infrared spectra (FTIR) were used to demonstrate that the as-prepared nano/micro- structures were essentially pure PAN without a noticeable incorporation of PDMA-b-PNIPAM molecules inside the nano/micromaterials. The optical absorption and fluorescence emission properties of the PAN nano/microtructures were also investigated, and the time-dependent spectra of the precipitating solution for nano/microstructures formation were measured to monitor the self-assembly process of PAN molecules. The nano/microstructures present a red shifts absorption spectrum to that of the monomers, suggesting that these as-obtained nano/microstructures were J-aggregates. Meanwhile, these absorption bands of the molecules decreased gradually and the baseline of the absorption at longer wavelength gets higher with the aging time increasing. Furthermore, the fluorescence emission demonstrated aggregation-induced emission enhancement (AIEE) phenomenon, which were caused by the restriction of the intramolecular vibrational and rotational motions in an indirect manner. Besides, new emission bands were observed at longer wavelength. With increasing aging time, intensities of the emission increase gradually whereas the peak positions are consistent.更多还原