【作者】 王剑；

【导师】 武志刚；

【作者基本信息】 中北大学 ， 化学， 2018， 硕士

【摘要】 稳定自由基如2,2,6,6-四甲基哌啶氮氧自由基（TEMPO）具有独特的稳定性和顺磁特征,特别是其顺磁特征对溶剂的极性、温度、粘度、空间位阻、构象和构型等环境具有很强的依赖性,因而TEMPO可以作为自旋探针被广泛用于生物医学领域。研究者通常需要将TEMPO标记到特定聚合物或基体的特定位置,方能解析特定体系的环境信息。梳形聚合物是侧链密集接枝在聚合物主链上的一类大分子,与相同分子量的线性聚合物相比,梳形聚合物具有较小的分子尺寸,显著的末端效应以及侧链相互排斥导致的伸展链构像,进而使其具有广阔的应用前景。本论文利用原子转移自由基聚合（ATRP）设计并成功合成了系列外围接枝不同柔顺性链的含TEMPO自由基的梳形聚合物,并探究了梳形聚合物的顺磁性质。所取得的主要结果如下:（1）侧链为聚丙烯酸甲酯（PMA）的含TEMPO梳形聚合物的合成与表征首先,以2-溴异丁酸乙酯（EBiB）为引发剂,甲基丙烯酸羟乙酯（HEMA）为单体,通过ATRP聚合制备得到聚甲基丙烯酸羟乙酯（PHEMA）,将侧基的羟基进一步溴化之后得到大分子引发剂PBiBEMA,继而引发丙烯酸叔丁酯（tBA）单体聚合得到梳形聚合物PHEMA-g-PtBA。然后,利用ATRP继续使丙烯酸甲酯（MA）单体进行聚合制备得到梳形聚合物PHEMA-g-（PtBA-b-PMA）。随后,在三氟乙酸（CF₃COOH）的存在下将梳形聚合物中侧链的t BA单体单元水解得到羧基,并利用羧基和4-缩水甘油基-2,2,6,6-四甲基哌啶氮氧自由基（GTEMPO）之间的反应将TEMPO引入到聚合物中,分别得到含TEMPO的梳形聚合物PHEMA-g-（PAA-g-TEMPO）和PHEMA-g-[（PAA-g-TEMPO）-b-PMA]。利用凝胶渗透色谱仪（GPC）、核磁共振波谱仪（¹H NMR）、差示扫描量热仪（DSC）和元素分析等手段对聚合物进行了详细表征。利用电子顺磁共振（EPR）技术研究了含TEMPO梳形聚合物在不同温度和不同浓度下的EPR谱图。结果表明,聚合物溶液的浓度主要对EPR谱图的信号强弱产生影响,而温度则对EPR谱图的形状起控制作用,原因可归属于TEMPO自由基运动能力的改变。明显的是,外围的PMA链段对内部的TEMPO自由基有屏蔽作用,很大程度上削弱了自由基之间的自旋-自旋交换作用,在EPR谱图中体现为含精细结构的裂分峰。（2）侧链为聚苯乙烯（PS）的含TEMPO梳形聚合物的合成与表征首先,以梳形聚合物PHEMA-g-PtBA为大分子引发剂,利用ATRP使苯乙烯（St）单体进行聚合制备得到梳形聚合物PHEMA-g-（PtBA-b-PS）。同样,在CF₃COOH的存在下将聚合物侧链中的t BA单体单元水解得到羧基,进一步利用羧基和GTEMPO之间的反应将TEMPO引入到聚合物中,得到外围侧链为PS的PHEMA-g-[（PAA-g-TEMPO）-b-PS]的含TEMPO梳形聚合物。利用GPC、¹H NMR、DSC和元素分析等手段对聚合物进行了详细表征。利用EPR技术分别研究了聚合物在不同温度和浓度下的EPR谱图。结果表明,随着聚合物浓度的增加,EPR谱图的信号增强,谱图形状却几乎没有变化。随着温度的改变,EPR谱图的形状也发生了系列转变。同样,由于外围PS链段对内部TEMPO自由基的屏蔽作用,EPR谱图也不同程度地呈现了一些精细结构。总体上,通过本论文的研究工作,我们合成了系列新型含TEMPO的梳形聚合物,并系统研究了聚合物结构和顺磁性质之间的关系。论文工作的研究有望为含TEMPO聚合物在生物医学方面的应用以及新型功能材料的制备提供理论基础。更多还原

【Abstract】 Stable free radicals such as 2,2,6,6-tetramethylpiperidine nitroxyl radical（TEMPO）have unique stability and paramagnetic characteristics,and can be used as spin probes in biomedical applications.The paramagnetic property has much dependence on environmental information,such as the viscosity,polarity,temperature,configuration,and so on.Researchers usually need to immobilize TEMPO on a specific position of a polymer or matrix in order to analyze the environmental information of a specific system.Combshaped polymers are a class of macromolecules with densely grafted side chains on the polymer backbone.Compared to linear analogues with the same molecular weight,comb-shaped polymers have a smaller molecule size,more significant end effects,and stronger side chain exclusion effects,resulting in an extended chain conformation.In this work,a series of comb-shaped polymers containing TEMPO radicals were designed and synthesized by atom transfer radical polymerization（ATRP）,and the side chains with different softness were further grafted.The paramagnetic properties of comb-shaped polymers were also explored.The main results are as follows:（1）Synthesis and characterization of TEMPO-containing comb-shaped polymers with poly（methyl acrylate）（PMA）side chainFirst,using ethyl 2-bromoisobutyrate（EBiB）as initiator,and hydroxyethyl methacrylate（HEMA）as monomer,linear poly（hydroxyethyl methacrylate）（PHEMA）was prepared by ATRP.After further modification of hydroxyl groups on PHEMA,the macroinitiator PBiBEMA was obtained.Then,tert-butyl acrylate（t BA）monomer was polymerized to give comb-shaped polymer PHEMA-g-PtBA.The comb-shaped polymer PHEMA-g-（Pt BA-b-PMA）was further prepared by ATRP of methyl acrylate（MA）monomer.Subsequently,the tBA units in the comb-shaped polymer are hydrolyzed in the presence of trifluoroacetic acid（CF₃COOH）to give carboxyl groups.The TEMPO was finally introduced into the polymers by reaction between carboxyl group and4-glycidyl-2,2,6,6-tetramethylpiperidine nitroxyl radical（GTEMPO）,to gave comb-shaped polymerscontainingTEMPO,PHEMA-g-（PAA-g-TEMPO）and PHEMA-g-[（PAA-g-TEMPO）-b-PMA].The polymerswere comprehensively characterized by gel permeation chromatography（GPC）,nuclear magnetic resonance spectroscopy（NMR）,and differential scanning calorimetry（DSC）and elemental analysis.The electron paramagnetic resonance（EPR）technology was used to study the paramagnetic property of TEMPOcontainingcomb-shapedpolymersatdifferenttemperaturesand concentrations.The results show that the concentration of the polymers mainly affects the signal intensity of EPR spectra,while the temperature modulate the shape of EPR spectra.Obviously,the peripheral PMA segments shielded the internal TEMPO radicals,and greatly reduced the intermolecular spin-spin exchange effect,The EPR spectra were showed with superfine information of the structure.（2）Synthesis and characterization of TEMPO-containing comb-shaped polymers with polystyrene（PS）side chainsFirst,the comb-shaped polymer PHEMA-g-（PtBA-b-PS）was prepared by ATRP of styrene（St）using comb-shaped PHEMA-g-PtBA asmacroinitiator.Similarly,the tBA units in the polymer side chain were hydrolyzed by CF₃COOH to give carboxyl group,and the TEMPO groups were further introduced into by using the reaction between the carboxyl groupandGTEMPO,TheTEMPO-containingcomb-shapedpolymer PHEMA-g-[（PAA-g-TEMPO）-b-PS]with a peripheral side chain PS was obtained.The polymers weresystematically characterized by GPC,NMR,DSC and elemental analysis.The EPRtechnologywasusedtostudytheparamagneticpropertyof TEMPO-containingcomb-shaped polymers at different temperatures and concentrations.The results showed that,the signal intensity of the EPR spectrum becames stronger with the concentration increasing.With the temperature lowering,the EPR spectrum also underwent a series of change.Due to the shielding effect of the peripheral PS segments,the EPR spectra with superfine information can also be discriminated.In general,a series of novel comb-shaped polymers containing TEMPO,were synthesized in this work.The relationship between polymer structure and paramagnetic properties was systematically studied.The result is expected to provide a theoretical basis for the application of TEMPO-containing polymers in biomedical applications and the preparation of new functional materials.更多还原