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苯乙烯阴离子本体聚合引发剂缔合及其机理的研究 总被引:1,自引:0,他引:1
分别以正丁基锂和叔丁基锂为引发剂,采用自制管式流动反应装置,对较高温度下苯乙烯阴离子本体聚合动力学进行了研究.证实了正丁基锂主要以六元缔合结构形式引发聚合,并导致超分子团聚体的形成,从而使进一步的聚合因单体扩散受阻而受到限制,并伴随聚合转化率停滞平台(SCP)的产生.随后由于前期聚合累积的能量,使超分子结构完全解离.聚合温度越高,SCP持续时间越短.结果还表明,在正丁基锂引发剂中,存在一个以六元缔合结构为基础形成的更大的缔合体结构.原子力显微镜照片显示,超分子结构的直径分别为20~30nm和50~60nm.此外,在阴离子聚合过程中活性种的缔合结构只决定于初始引发剂的分子结构,而不同活性种缔合结构对阴离子聚合的链增长存在很大影响,从而解释了采用不同结构的锂系引发剂引发苯乙烯单体聚合时聚合速率存在巨大差异的原因. 相似文献
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乙酰丙酮铁催化丙交酯开环聚合的研究 总被引:7,自引:0,他引:7
以乙酰丙酮铁 [Fe(acac) 3]为催化剂进行D ,L 丙交酯的开环聚合及在聚乙二醇 (PEG)存在下的开环共聚 ,研究了催化剂用量、反应温度和反应时间对聚合反应的影响以及PEG用量对共聚反应的影响 ,并探讨了丙交酯开环聚合机理 .结果表明 ,Fe(acac) 3是按配位 插入机理催化丙交酯开环聚合的 ;在本文的聚合条件下 ,大部分聚合的单体转化率都达 90 %以上 ,聚合产物的粘均分子量最高可达 6 6 0 0 0 ,均显示出较好的催化性能 .在PEG存在下 ,PEG作为引发剂参入了丙交酯的开环聚合 ,D ,L 丙交酯是沿着PEG分子两端开环聚合的 ,分子链的链端结构是以羟基为端基的乳酰基结构单元 ,Fe(acac) 3有促进PEG参与聚合成酯的作用 . 相似文献
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本文研究并比较了不同条件下新引发剂体系AlCl_3/SbCl_3/D(电子给体)的α-蒎烯聚合产物。结果表明,该新引发体系可获得迄今分子量最高、分子量分布较窄的树脂;聚合物分子链结构单元与常用引发剂的不同。据此本文提出了正离子开环聚合作用机理的假设。 相似文献
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本文以粘度法研究在苯溶剂中,ε-己内酯负离子开环聚合过程,增长链活性种烷氧基锂(—O~-Li~+)的缔合,发现己内酯活性种的缔合和一般非极性单体不同,前者在聚合过程中(单体消耗完以前)并不发生缔合。在单体消耗完以后,聚己内酯活性种才确实以缔合体的形式存在。这是由于内酯本身贡献了强的溶剂化作用。 相似文献
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醇铁化合物引发丙交酯开环聚合的研究 总被引:1,自引:0,他引:1
分别以乙醇铁、正丙醇铁、异丙醇铁、正丁醇铁为引发剂进行D,L-丙交酯和L-丙交酯的本体开环聚合,研究了在130℃的聚合温度下引发剂用量和聚合时间对聚合反应的影响.结果表明这些醇铁化合物对丙交酯开环聚合都有较好的引发作用;聚合36h,单体转化率可达90%以上.单体转化率在引发剂/单体摩尔比为1/1000时最高,然后随引发剂用量增加和聚合时间延长而降低.乙醇铁表现出最高的引发活性,聚合产物的相对粘均分子量最高可达7·28×104[聚(D,L-丙交酯)]和19·00×104[聚(L-丙交酯)].醇盐配体对聚合产物的分子量和分子量分布影响显著,随醇铁配体体积增大,聚合产物的分子量逐渐降低,分子量分布也逐渐加宽.1H和13C-NMR分析表明醇铁对L-丙交酯的开环聚合没有发生消旋化,对D,L-丙交酯的开环聚合有一定的等规加成选择性.MALDI-TOF MS分析指出D,L-丙交酯在开环聚合过程中发生了分子间的酯交换反应,用13C-NMR评价了各醇铁引发体系在聚合过程中的酯交换程度.但基于谱峰分辨原因,醇铁配体对立构加成选择性和酯交换的影响的规律性不明显. 相似文献
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本文研究了以正丁基锂为引发剂,四氢呋喃为添加剂,环己烷为溶剂中的α-甲基苯乙烯阴离子平衡聚合动力学。讨论了体系中的反应活性种;提出了聚合机理;得到了聚合温度为20℃时的平衡单体浓度与活性种速率常数及添加剂浓度之间的关系式。 相似文献
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三氟甲磺酸稀土催化ε-己内酯开环聚合 总被引:1,自引:0,他引:1
采用三氟甲磺酸稀土(镧、钕、铒)作为单组分催化剂催化了ε-己内酯的本体开环聚合反应. 考察了稀土元素种类、催化剂浓度、聚合时间及温度对单体转化率和聚合产物分子量的影响. 该类催化剂在催化聚合过程中具有单一活性中心, 且催化活性较高. 此聚合反应可能是通过阳离子活性末端链聚合机理进行的. 相似文献
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Cline Farcet Julien Nicolas Bernadette Charleux 《Journal of polymer science. Part A, Polymer chemistry》2002,40(24):4410-4420
The controlled free‐radical homopolymerization of n‐butyl acrylate was studied in aqueous miniemulsions at 112 and 125 °C with a low molar mass alkoxyamine unimolecular initiator and an acyclic β‐phosphonylated nitroxide mediator, N‐tert‐butyl‐N‐(1‐diethylphosphono‐2,2‐dimethylpropyl) nitroxide, also called SG1. The polymerizations led to stable latices with 20 wt % solids and were obtained with neither coagulation during synthesis nor destabilization over time. However, in contrast to latices obtained via classical free‐radical polymerization, the average particle size of the final latices was large, with broad particle size distributions. The initial [SG1]0/[alkoxyamine]0 molar ratio was shown to control the rate of polymerization. The fraction of SG1 released upon macroradical self‐termination was small with respect to the initial alkoxyamine concentration, indicating a very low fraction of dead chains. Average molar masses were controlled by the initial concentration of alkoxyamine and increased linearly with monomer conversion. The molar mass distribution was narrow, depending on the initial concentration of free nitroxide in the system. The initiator efficiency was lower than 1 at 112 °C but was very significantly improved when either a macroinitiator was used at 112 °C or the polymerization temperature was raised to 125 °C. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4410–4420, 2002 相似文献
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Kevin M. Burridge Nethmi De Alwis Watuthanthrige Camryn Payne Richard C. Page Dominik Konkolewicz 《Journal of polymer science. Part A, Polymer chemistry》2021,59(21):2530-2536
An enduring question is: what is the simplest and easiest way to obtain tailored polymers? This communication explores a robust photoiniferter polymerization with only two active ingredients that requires no prior deoxygenation and can be performed on the milliliter scale or sub-milliliter scale. Rather than leaving headspace in the polymerization vessel or scaling reactions up to fill the vessel, this approach fills the headspace of the reaction vessel with mineral oil or inert solvents. This approach can also be applied to polar monomers in aqueous media, using oil as the inert solvent, or to hydrophobic monomers with water as the inert solvent. This method removes enough ambient oxygen that the photoiniferter reaction proceeds with no deoxygenation step, and achieves high conversion and good molecular weight control in 10–20 h in both aqueous and organic solvents. Complex polymer architectures such as multiblock copolymers and gradient polymers were successfully synthesized by this approach. 相似文献
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原子转移自由基聚合(ATRP)应用于乳液聚合体系的主要挑战在于如何同时保证乳液的稳定性和聚合反应的可控性。本文主要对乳液ATRP体系中影响聚合反应可控性和乳液稳定性的各种因素、乳液ATRP的机理和乳液ATRP的应用等方面进行了综述。表面活性剂亲水亲油性及其亲水亲油基团的化学性质、催化剂/配体在油/水两相之间的分配行为、引发剂的溶解性、反应温度以及各组分的浓度是影响反应可控性和乳液稳定性的主要因素。各组分在油/水两相中的分配行为使得乳液ATRP的机理比传统乳液聚合更加复杂。乳液原子转移自由基聚合结合了活性自由基聚合和乳液聚合的优点,在理论研究和工业生产上具有很大的应用前景。 相似文献
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Reverse iodine transfer polymerization (RITP) is a new controlled radical polymerization technique based on the use of molecular iodine I2 as control agent. This paper aims at presenting the basics of RITP and the strategy that we have followed for the development of this process in the past three years, from the validation in homogeneous solution polymerization up to recent results in heterogeneous aqueous polymerization processes. Typical examples of RITP of butyl acrylate in emulsion and RITP of styrene in miniemulsion are discussed. 相似文献