【作者】 黄剑莹；

【导师】 戴李宗； 邹友思；

【作者基本信息】 厦门大学 ， 高分子化学与物理， 2007， 博士

【摘要】 TEMPO调控下的活性自由基聚合由于具有自由基聚合和活性聚合的诸多优点,反应条件温和,可以得到分子量和聚合物结构可控,分散性窄的聚合物,但其较高的反应温度和冗长的反应时间限制了其工业应用前景。因此,优化聚合条件已成为近年来研究的热点。本文通过寻找有效的加速剂的方法缩短了聚合时间,研究了NMRP共聚体系的竞聚率;实现了TEMPO调控下UV光引发活性聚合,制备了ABA型三嵌段聚合物。具体工作如下:1、在TEMPO调节的苯乙烯本体聚合体系中,发现了8种新型的加速剂,分别为丙二酸二酯类衍生物(DMM,DEMM,DEBM,DEDEM)、乙酰丙酮类衍生物(MPD,HFA)和丙二腈类衍生物(Ac-MN,DM-MN)。研究了各自的最佳投料量及加速效果。这些加速剂的使用均可明显提高聚合速率。其中以丙二腈类添加剂的加速效果最为明显。乙酰基丙二腈的加入可使聚合体系在125℃下仅反应1.5小时即可达到99%的转化率,为目前已有报道中加速效果最好的加速剂;丙二腈的加入可使聚合体系在125℃下反应1.5小时即可达到96%的转化率。而且丙二腈同样可用于TEMPO调控下St/MMA共聚体系的加速。并以丙二腈为代表,对其加速机理进行了探讨。发现这些加速剂在结构上都存在亚甲基上被吸电子基团取代的共同点,且随着吸电子基团吸电子能力的提高,其衍生物的加速效果也随之提高;随着衍生物位阻的增大,其对聚合体系的加速效果也随着提高。2、对TEMPO调控下的苯乙烯与极性单体的活性自由基共聚体系进行研究,通过核磁或红外方法确定共聚物中的组成比,并通过Kelen-Tud(?)s公式计算出各共聚体系中各单体对的竞聚率,首次报道了苯乙烯和这些单体在TEMPO存在下的活性自由基聚合竞聚率。在苯乙烯和甲基丙烯酸甲酯的共聚体系中,加入丙二腈或三氟乙酸酐作为加速剂,可以明显提高共聚速度,但竞聚率基本不变。比较发现苯乙烯的竞聚率均比第二单体的竞聚率大,表现出较强的共聚能力。测定了共聚体系的分子量及其分布,发现在TEMPO调控下的苯乙烯与极性单体的活性自由基共聚体系中,单体对中苯乙烯含量增加时,共聚物中苯乙烯的含量和聚合速率随之增大,多分散性系数随之降低,且所得聚合物的分子量控制效果越好。3、首次研究了苯乙烯的TEMPO调控的自由基可控光聚合,发现在较低温度下,聚合体系表现出活性聚合的特征,获得了良好的转化率与时间、转化率与数均分子量之间的线性动力学关系,且多分散性系数小于1.5。且与TEMPO调控下的热聚合相比,苯乙烯的光聚合反应条件温和,且聚合速率快。并讨论了光活性聚合的引发剂浓度、光强等条件对苯乙烯UV光聚合体系的影响;通过GPC、IR和NMR表征技术,表征了苯乙烯在TEMPO调控下的光聚合的动力学行为。4、利用反向原子转移自由基聚合,采用廉价的引发剂合成得到了窄分布的末端含氯的聚丙烯酸丁酯(PBA-Cl)。以PBA-Cl作为原子转移自由基聚合的大分子引发剂,引发苯乙烯单体合成两嵌段共聚物(PBA-b-PSt-Cl)。两嵌段共聚物在强还原剂和一价铜盐的催化下发生高分子偶合反应,得到结构可控的ABA型(PBA-PSt-PBA)三嵌段聚合物。实现了极性差别较大的苯乙烯和丙烯酸丁酯的共聚,得到了分子量分布窄,分子量可控的聚合物。更多还原

【Abstract】 The control of macromolecular structure has become an important facet of polymer science from both an academic and industrial viewpoint. Combining the advantages of free-radical polymerization and living polymerization, a range of new polymerization techniques based on living free radical procedures have been developed.Of the living free radical techniques developed, the procedures mediated by stable nitroxide free radicals, such as 2,2,6,6-tetramethylpiperidinyl-1-oxy （TEMPO）, have attracted considerable interest. In the nitroxide mediate radical polymerization （NMRP）, the polymerization can be considered as pseudo-living in nature and the condition of NMRP is mild. Meanwhile, the procedure does not suffer from the gel effect, which may be beneficial for industrial-scale production. One of the major drawbacks of NMRP is the long reaction time and elevated temperatures that are required for these reactions to reach completion. A definite need for the development of simple rate accelerating additives therefore exits.The main purpose of this work is to optimize the condition of NMRP, study the monomer reactivity ratio in NMRP, achieve the UV-irradiated NMRP and prepare the ABA type block copolymer. The main results and progresses of this dissertation are underlined as following:1、The bulk polymerizations of styrene were completed in the presence of TEMPO using the derivates of dimethyl malonate, acetoacetic ester and malononitrile （DMM, DEMM, DEBM, DEDEM, MPD, HFA, Ac-MN, DM-MN） as new rate-accelerating additives respectively. Varying amounts of these additives were added to the polymerization. Significantly, all of these additives were found to have a great rate-accelerating effect on the polymerization. Among them, the polymerization rate of styrene is so quick that the conversion reaches 99% using Ac-MN as additive and 96% using MN as additives within 1.5 hours at 125℃. The derivates of malononitrile had more dramatic rate enhancement effect and resulted in more than 20 times higher rate of polymerization of styrene. There is a common ground that the methylene was substituted by electron-withdrawing groups in all the additives. A possible explanation for these effects is that because of the electron-withdrawing effect, the C atom of methylene had an acidic property and could aggregate around TEMPO due to the electron effect. It was found that the rate enhancement effect is greater with the stronger electron-withdrawing and greater steric hindrance groups substituted.2、Monomer reactivity ratios are important quantitative values to predict the copolymer composition for any starting feed and to understand the kinetic and mechanistic aspects of copolymerization. They are considered as a possible mechanistic probe, as they express the effects of rate constants. Usually, monomer reactivity ratios are obtained by establishing the relationship of the composition between the monomer. Therefore, this work is devoted to studying the monomer reactivity ratios of the living free-radical copolymerization of St with methacrylate （MMA,EMA, BMA）, acrylate （MA, EA, BA）, vinyl acetate （VAc）, 2-hydroxyethyl acrylate （HEA）, N,N- dimethylacrylamide （DMAA）, and 2-（dimethylamino）ethyl acrylate （DMAEA）. The living free-radical copolymerizations had been analyzed by GPC. The data from GPC showed that the polydispersities of the most resulted copolymers were below 1.5, and the rate of polymerization increased, while the polydispersity declined with increase in St molar fraction in the feed. Monomer reactivity ratios had been determined by expanded Kelen-Tudos method by ¹H-NMR and FT-IR. In the copolymerization of St with acrylates the monomer reactivity ratio r1 （St） decreases and in the copolymerization of St with methacrylates the monomer reactivity ratio r1 （St） increases while the length of the substituted group increases.3、Living free radical polymerizations are employed to synthesize polystyrene in the presence of TEMPO irradiated with UV light at 50℃. In the polymerizations, the conversion increased linearly with time, the molecular weight increased linearly with the conversion, and polymers exhibited narrow molecular weight distribution as the value of PDI below 1.5 characterized by GPC, which is characteristic of a controlled/living free radical polymerization. Compare to the thermal-initiated polymerization, the condition of UV-irradiated polymerization is milder and the rate is faster. The polymers were analyzed by ¹H-NMR and FT-IR.4、Atom transfer radical polymerization （ATRP） and Reverse ATRP （RATRP） are useful methods for realization of living polymerization and syntheses of block copolymers. First, polybutylacrylate caped with chlorine, PBA-Cl, was synthesized by RATRP method using AIBN as initiator and FeCl₃/PPh₃ as catalyst at 80℃. Then using the PBA-Cl as macroinitiator, ATRP of styrene was realized and the copolymer, PBA-b-PSt-Cl was obtained. Finally, using the nano Cu power as catalyst, atom transfer radical coupling （ATRC） of the copolymer PBA-b-PSt-Cl was realized and the ABA type copolymer, PBA-b-PSt-b-PBA, was prepared.更多还原