【作者】 刘斌；

【导师】 张兴宏； 徐君庭；

【作者基本信息】 浙江大学 ， 高分子化学与物理， 2019， 博士

【摘要】 环氧化物与CO2在催化剂作用下制备五元环碳酸酯是一种“绿色”固定CO2的方法。五元环碳酸酯由于其优异的化学稳定性,被广泛应用到锂离子电池以及聚氨酯等领域。本论文针对五元环碳酸酯在发光领域的局限性,创建了多种基于环碳酸酯的新型发光聚合物荧光材料,并将其应用到多色发光二极管(Light-Emitting Diodes,LEDs)领域。主要工作包括以下四部分:(1)通过双环碳酸酯与二胺开环加聚,制备了固态和溶液中均具有蓝色荧光性质的聚羟氨酯,报道了聚羟氨酯的非传统发光性质。这一体系克服了大部分传统共轭聚合物存在聚集诱导猝灭或者溶液不发光的难题。通过调控聚羟氨酯的分子结构,证实了羟基诱导氢键作用是实现荧光发射的关键结构因素。结合UV-vis光谱特点,提出了聚羟氨酯荧光来源于 HO…C=O{n(HO)→π*(C=O)}和 C=O…C=O {n(C=O)→π*(C=O)}产生的 n→π*跃迁。研究了影响聚羟氨酯荧光性质的因素,如分子链柔顺性、分子量、温度、浓度、光照时间以及不良溶剂等,结果表明:分子链柔顺性和分子量是影响荧光性质的关键因素。含硅氧烷的柔性聚羟氨酯,荧光最强,荧光量子产率可达23.6%,且随着Tg的升高,荧光强度明显降低;荧光强度随分子量升高呈指数形式上升。基于固态发光以及激发依赖荧光特性,将其与紫外芯片结合实现了冷白光LEDs的制备。(2)利用含三官能度环碳酸酯与己二胺反应,氯仿作为溶剂,一锅法制备得到氯掺杂聚羟氨酯微球,开发了一种新型白光高分子材料。基于荧光聚羟氨酯发射蓝光特点,以双官能环碳酸酯作为模型单体,利用NMR、XPS以及EDX等手段定量分析氯掺杂量以及掺杂位点。通过控制反应温度调控微球中氯掺杂含量,获得系列由蓝光到白光微球材料。由于重原子效应,微球的荧光量子产率随氯掺杂量的升高而降低。此外,考察了单体浓度以及搅拌速度对微球形貌的影响。并将白光微球结合紫外芯片成功制备显色指数高达95的白光LEDs,开辟了白光微球在LEDs领域的新应用。(3)利用三官能度环碳酸酯与乙二胺反应,水为溶剂,通过水热法首次制得了高荧光量子产率的超支化分形聚合物纳米碳材料,在溶液中和固体中均发光,荧光量子产率分别达36.6%和11.7%。研究结果表明,超支化分形纳米碳表面未碳化的聚合物是其固态高荧光量子产率的主要原因。通过调控水热反应的温度和时间,证实了超支化分形纳米碳是由碳化聚合物点的自组装形成。结合DLVO理论及表面电位测定结果证明组装驱动力源于低(或逐渐变小并趋近于零)的表面电位。将该超支化分形纳米碳作为单一荧光粉分别与紫外和蓝光芯片结合可得到橘黄光和暖白光LEDs。(4)以侧基为五元环碳酸酯的甲基丙烯酸酯为单体,以化学修饰的荧光黄为引发剂,采用原子转移自由基聚合方法,获得了中心基元为荧光黄、侧基为环碳酸酯的丙烯酸酯聚合物,以其为单一荧光粉,结合蓝光芯片制备了纯白光LEDs,其色坐标为(0.33,0.33),显色指数可达82。由此发展了调控聚合物侧基种类来调控黄光的色坐标位置以获得纯白光LEDs的方法。该聚合物基LEDs的发光颜色可通过调节电压和聚合物荧光粉用量,当聚合物荧光粉足够过量时,白光LEDs将转化为黄光LEDs。更多还原

【Abstract】 The preparation of five-membered cyclic carbonate from epoxides and carbon dioxide(CO2)in the presence of catalysts is a green method for the fixation of CO2.Because of its excellent stability,five-membered cyclic carbonate has been widely used in lithium ion batteries and polyurethane fields.In this work,aiming at the narrow application fields of five-membered cyclic carbonate and its limitations in the field of light-emitting,we successfully prepared various fluorescent materials using five-membered cyclic carbonate as raw materials,and applied them in the field of multicolor light-emitting diodes(LEDs).This work includes the following four parts:(1)Poly(hydroxyurethane)s(PHUs)with blue fluorescence both in solid and solution were prepared using bi-cyclic carbonate and diamine as raw materials.By regulating the molecular structure of PHUs,hydroxyl-induced hydrogen bonding interaction is confirmed to be the key factor to achieve fluorescence emission.UV-vis absorption spectra showed that the fluorescence of PHUs originates from the n→π*transition produced by HO…C=O {n(HO)→π*(C=O)} and C=O…C=O {n(C=O)→π*(C=O)}.In addition,the influence factors of the fluorescence properties of PHUs,such as the flexibility of molecular chain,molecular weight,temperature,concentration,radiation time and poor solvents,were explored.The results showed that the flexibility of molecular chain and molecular weight were the key factors for luminescent properties.The fluorescence intensity of PHUs containing siloxane with flexible structure was the strongest,and the quantum yield(QY)could reach up to 23.6%.The fluorescence intensity decreased obviously with the increase of Tg,and increased exponentially with the increase of molecular weight.Based on the solid-state luminescence and excitation-dependent feature,cool white LEDs were fabricated by combining with UV chip.(2)Chlorine-doped PHUs microspheres were successfully prepared by one-pot reaction of tri-cyclic carbonate with hexamethylenediamine and chloroform as solvent based on the precondition of the blue light-emitting PHUs.By selecting the bi-cyclic carbonate as the model monomer,the doping amount of chlorine and reaction sites were quantitatively analyzed by NMR,XPS and EDX.The transformation from blue-light to white-light microspheres was realized by controlling the reaction temperature and the doping content of chlorine.The QY of microspheres decreases with the increase of chlorine doping because of the heavy atom effect.In addition,we explored the effect of concentration and stirring speed on the morphology of the microspheres.Finally,white LEDs with color rendering index up to 95 were achieved by combining with UV chip,which opened up new applications of white-light microspheres in the field of LEDs.(3)Fractal nanocarbons with hyperbranched morphology under the hydrothermal carbonization of tri-cyclic carbonate and ethylenediamine at high temperature were prepared.It was the first time to prepare nanocarbons with hyperbranched morphology,named hyperbranched fractal nanocarbons(HFNs).The QYs of nanocarbons are 36.6%in solution and 11.7%in solid,respectively.Uncarbonized polymers on the surface of HFNs are responsible for the high solid state QY.By adjusting the carbonization temperature and time,it was confirmed that the HFNs were formed by self-assembly of carbonized polymer dots rather than direct access.Low surface potential was the fundamental reason for the formation of HFNs according to the DLVO theory.Based on solid-state fluorescence,orange and warm white LEDs were obtained by combining the single HFNs with UV and blue chips,respectively.(4)Fluorescein with yellow fluorescence was dispersed different polymers by ATRP to obtain pure white LEDs,and the CIE coordinates of yellow light were adjusted by changing the kinds of side groups of polymers.When DOMA with five-membered cyclic carbonate was selected as monomer,the CIE coordinates of the polymer were successfully located on the extension line of 460 nm blue chip and pure white light CIE coordinates(0.33,0.33).Pure white LEDs with CRI up to 82 were fabricated by combining with 460 nm blue chip.The color of LEDs can be controlled by voltage and the amount of polymer phosphor.When the polymer phosphor is overdosed,white LEDs will be converted into yellow LEDs.更多还原