【作者】 王琦；

【导师】 庞新厂；

【作者基本信息】 郑州大学 ， 材料科学与工程， 2021， 硕士

【摘要】 光诱导“活性”/可控自由基聚合,将光化学（环保、反应条件温和以及优异的时空控制）与“活性”/可控自由基聚合（能够合成具有精确分子量和明确定义结构聚合物）的优点集于一身,为制备功能性材料提供新的路径与方法。广泛应用于生物材料、嵌段和接枝共聚物的制备、纳米复合材料以及表面改性等领域。目前,已经开发了种类众多的光催化剂,如金属配合物、有机非金属、金属氧化物、量子点等。然而,传统金属催化剂易残存、毒性高,多数有机催化剂合成困难,因此开发无金属且无毒无害的光催化剂成为研究热点。硅量子点（SiQDs）作为一种半导体纳米晶体,含量丰富、制备简单、具有低细胞毒性和良好的生物相容性,使其成为极具竞争力的低成本催化剂。此外,光诱导表面引发的活性自由基聚合技术对表面进行改性已经成为制备功能性表面和合成特定功能的复合材料的重要手段。然而多数聚合体系中,除催化剂之外,还需要额外的连接剂将引发剂修饰到基材上。由于SiQDs表面氨基的功能性,SiQDs可以起到聚合物与基材之间的连接剂和光催化剂的双重作用,从而为基材的表面引发聚合提供了简便方法。本文以表面氨基封端的SiQDs作为光催化剂,在可见光下分别对光致电子或能量转移可逆加成-断裂链转移（PET-RAFT）聚合以及光诱导原子转移自由基聚合（ATRP）体系进行了研究,然后考虑到SiQDs表面氨基的功能性,将其作为RAFT试剂与基材之间的连接剂以及PET-RAFT聚合的光催化剂,进行了基材表面接枝的研究。（1）以水热法合成的表面氨基封端的SiQDs作为光催化剂,在可见光下进行了一系列PET-RAFT聚合,探究了不同溶剂、光源和单体对聚合的影响。实验结果表明在可见光照射下,聚合表现出良好的可控制性,并且获得了具有明确分子量和窄分子量分布的聚合物。另外,电子给体的引入可以提高聚合速率。（2）利用上述制备的氨基封端的SiQDs作为光催化剂在可见光下进行了一系列光诱导ATRP实验。并通过改变光源和单体探究不同因素对聚合的影响。结果表明,基于SiQDs催化的ATRP反应,表现出良好的“活性”特征,所得聚合物结构定义明确,分子量分布较窄。证明SiQDs可以作为PET-RAFT聚合以及光诱导ATRP的通用催化剂,并在多种单体和溶剂中表现出良好的普适性。（3）基于SiQDs表面氨基的功能性,将其作为基材与RAFT试剂的连接剂以及PET-RAFT聚合的催化剂,进行SiQDs原位催化基材表面引发的PET-RAFT聚合。结果表明,该方法可在硅片和Si O₂表面成功接枝聚合物刷。动力学研究表明,可以通过控制光聚时间影响表面接枝聚合物的分子量,从而实现对Si O₂表面聚合物壳层厚度的调控。更多还原

【Abstract】 Photo-induced"living"/controlled radical polymerization combines the advantages of photochemistry,such as environmentally friendly,mild reaction conditions,and excellent time and space contrability,with"living"/controlled radical polymerization,which can synthesize polymers with precise molecular weights and well-defined structures.It provides a new method for preparing functional materials which has a wide range of applications in the fields of biomaterials,block and graft copolymer preparation,nanocomposites,and surface modification.At present,many types of photocatalysts had been developed,such as metal complexes,organic non-metals,metal oxides,quantum dots and so on.However,traditional metal-based catalysts were easy to remain and had high toxicity,and most organic catalysts were difficult to synthesize.Therefore,the development of metal-free,non-toxic and harmless photocatalysts has become a research hotspot.Silicon quantum dots（SiQDs）,as a kind of semiconductor nanocrystals,are rich in content,simple to prepare,and have low cytotoxicity and good biocompatibility,which makes SiQDs a very competitive low-cost catalyst.In addition,surface-initiated living radical polymerization technology had become an important means for preparing functional surfaces and synthesizing composite materials with specific functions.However,in most polymerization systems,apart from the catalysts,an additional linking agent was required to combined initiators with substrates.Due to the functionality of the amino groups on the surface of SiQDs,SiQDs can play dual roles for photocatalysts and linking agents between polymers and substrates,thereby providing a simple method for surface-initiated polymerization.In this paper,amino-terminated SiQDs were used as photocatalysts to perform photo-induced electron or energy transfer reversible addition-fragmentation chain transfer（PET-RAFT）polymerization and photo-induced atom transfer radical polymerization（ATRP）under visible light.And then considering the functionality of the amino groups on the surface of SiQDs,it was used as the linking agent between the RAFT reagents and the substrates and the photocatalyst for surface-initiated PET-RAFT polymerization.（1）A series of PET-RAFT polymerizations were carried out under visible light irradiation by using amino-terminated SiQDs synthesized by hydrothermal method as photocatalysts,and the influences of different solvents,light resources and monomers on the polymerization were explored.The experimental results showed that the polymerizations exhibited good controllability,and polymer with precise molecular weight and narrow molecular weight distribution was obtained.In addition,the introduction of electron donors could increase the polymerization rate.（2）A series of light-induced ATRP experiments were carried out under visible light using the amino-terminated SiQDs prepared above as the photocatalysts.And we studied the impact of different solvents and monomers on the polymerization by changing the experimental conditions.The results showed that the ATRP catalyzed by SiQDs exhibited good"living"characteristics,and the resulting polymer had well-defined structure and narrow molecular weight distribution.It was proved that SiQDs could be used as general catalysts for PET-RAFT polymerization and light-induced ATRP,and the versatility of SiQDs in different monomers and solvents had also been proved.（3）Considering the functionality of the amino groups on the surface of SiQDs,it provided a possible facile way for the surface-initiated PET-RAFT polymerization.SiQDs can play as a bridge between substrates and carboxyl group ended chain transfer agents（CTAs）and catalysts for PET-RAFT polymerization as well.The results showed that the polymer brushed were successfully grafted on the surface of silicon wafer and Si O₂particles.Kinetic studies had shown that the molecular weight of the surface grafted polymers could be controlled by controlling the photopolymerization time,so that the regulation of the thickness of the polymer shell layer on the Si O₂ surface realized.更多还原