【作者】 时钢印；

【导师】 潘才元；

【作者基本信息】 中国科学技术大学 ， 高分子化学与物理， 2009， 博士

【摘要】 环状聚合物包括单环和多环聚合物,是一类具有特殊拓扑结构的聚合物,具有不同于支化聚合物的特殊性质,引起了人们广泛的关注。由于合成困难,目前只有少数关于环状聚合物的报道,且这些报道大部分是关于单环聚合物的合成与表征,关于复杂环聚合物的研究非常少。在已经报道的环状聚合物的研究中,最常用的方法是在特定位置上带有可以反应的基团的线形前驱体,在极稀浓度下,进行分子内的关环反应,这些前驱体的合成都是基于阴离子或者阳离子聚合技术,往往需要苛刻的实验条件,可选择的单体种类有限。活性自由基聚合技术和点击反应为合成各种特殊结构的聚合物,如嵌段、接枝、星形、环形、超支化聚合物提供了有效的手段。在前人工作的基础上,本论文在环状拓扑结构聚合物的合成上进行了有意义的拓展:首先制备了一系列多官能团引发剂,通过可控活性自由基聚合和开环聚合制备了一系列在特定位置上带有炔基（叠氮）的线形或者星形聚合物,在极稀浓度下,进行分子内的关环反应,制备了蝌蚪形,数字8形,杂化数字8形和θ形等环状聚合物,并对其性质进行了初步的研究。具体研究结果简述如下:1.采用RAFT聚合和点击化学相结合,成功制备了两亲性蝌蚪形聚合物,即线形PNIPAAM-b-环状聚苯乙烯。首先,采用RAFT聚合制备了在聚苯乙烯链段带有端炔基、在两嵌段中间带有叠氮基团的两嵌段聚合物;然后,该嵌段聚合物在极稀浓度下,发生分子内关环反应,制备了两亲性蝌蚪形聚合物。研究了蝌蚪形聚合物和线形前驱体的表面性质的差别,发现水滴在蝌蚪形聚合物表面的接触角大于其在相应的线形两嵌段聚合物表面的接触角。2.发展了一种制备分子量可控、分子量分布窄的数字8形聚合物的方法。合成过程为:1.通过原子转移自由基聚合和端基转化制备了在聚合物链两端带有两个叠氮基团、在聚合物中间带有两个炔基的四官能团聚苯乙烯;2.通过在极稀浓度下,进行分子内点击反应,制备了一系列不同分子量的数字8形聚苯乙烯。用DSC对其玻璃化转变温度进行了测试,发现数字8形的聚苯乙烯的玻璃化转变温度大于和其同等分子量的线形前驱体的玻璃化转变温度。3.成功制备了由聚苯乙烯和聚己内酯组成的杂化数字8形共聚物。首先,通过原子转移自由基聚合和开环聚合制备了在聚苯乙烯链段带有端溴、在聚己内酯链段带有端羟基的四臂星形聚合物;然后,分别把羟基转换成炔基,把溴转化成叠氮;最后,通过四臂星形聚合物在极稀浓度下,进行分子内的两步点击反应,得到了杂化数字8形共聚物。对其热性质和结晶行为分别用DSC和偏光显微镜进行了研究。发现环状结构导致数字8形聚合物中PCL链段的链段运动受阻,其结晶度和结晶速度都小于星形聚合物中PCL链段。4.成功制备了环状聚苯乙烯-b-环状聚己内酯。合成过程为:1.制备带有两个炔基、一个溴、一个羟基的四官能团引发剂;2.以其为引发剂进行原子转移自由基聚合苯乙烯、开环聚合己内酯和端基转化制备了在两个聚合物链段各带有一个端叠氮基团、在聚合物链段中间带有两个炔基的两嵌段聚合物,N₃-PCL-（CH≡C）₂-PS-N₃;3.通过在极稀浓度下,进行分子内关环反应制备了环状聚苯乙烯-b-环状聚己内酯。用DSC研究其热性质,发现环状结构降低了PCL的结晶能力。5.发展了一种制备分子量可控、分子量分布窄的θ形共聚物的方法。首先,通过开环聚合、原子转移自由基聚合和端基转化制备了在PCL链段带有两个端炔基、在两个聚苯乙烯链段分别带有一个端叠氮基团的AB₂杂臂星形聚合物,α,α’-diacetylene-PCL)（ω-azido-PS）₂;然后,在极稀浓度下,进行分子内两步点击反应,成功制备了一系列不同分子量的θ形共聚物。用DSC对热性质进行了研究,发现由于θ形共聚物中PCL链段受到两个PS链段的限制,其与星形聚合物相比结晶能力降低。更多还原

【Abstract】 Cyclic topological polymers including single and multiple cyclic polymers have gained growing interest due to their unique properties unlike branched and linear topological polymers.In contrast with the significant achievement obtained in the investigation of branched polymers,an efficient and practical synthesis of a variety of cyclic topological copolymers is still a challenge due to the inherent synthetic difficulty.Most of the studies on cyclic polymers focused on the synthesis and characterization of single-loop cyclic polymers and only a few literatures reported the preparation of multi-loop cyclic copolymers.The most general synthetic approach of cyclic topological polymers is intramolecular cyclization of multifunctional precursor bearing two series of complementary functional groups under high dilution.All the synthetic methods mentioned above are based on anionic,cationic or ring-expansion polymerizations,rigorous operation conditions are needed.Controlled radical polymerization techniques and "click" reaction facilitate the preparation of polymers with predetermined molecular architectures,such as block,grafted,star,cyclic and hyperbranched polymers at less stringent conditions and offers exceptional versatility of monomers comparing with living ionic polymerizations.Based on the researches of the precursors,this dissertation described several outspread works in the synthesis of cyclic topological copolymers:a series of multifunctional initiators were prepared at first,and they were used as the initiators for the synthesis of linear or star copolymers bearing two different kinds of functional group by the combination of controlled radical polymerization and ring-opening polymerization;after the intermolecular click reaction of the precursors under high dilution,a series of multiple cyclic copolymers, such as tadpole-shaped,figure-of-eight-shaped,theta-shaped copolymers were prepared and their physical properties were primary investigated.All these facts are the origin and impetus of this thesis.The main results obtained in this thesis are as follows:1.The tadpole-shaped amphiphilic linear poly（N-isopropylacrylamide）- block-cyclic polystyrenes（LPNIPAAM-b-CPS） have been successfully synthesized by combination of reversible addition-fragmentation chain transfer（RAFT） polymerization and "click" reaction.A linear acetylene-terminated PNIPAAM-b-PS with a side azido group at the junction between two blocks was prepared at first;and then intramolecular cyclization reaction produced the cyclic PS block using "click" chemistry under high dilution.The difference of surface property between linear-cyclic block copolymer and its linear precursor was observed,and the water contact angles on the former surface are larger than that of the latter surface.2.A synthetic route to well-defined eight-shaped polystyrenes（PSs） with controlled molecular weight and narrow polydispersities has been developed.The synthesis involves two steps:1.Preparation of a linear tetrafunctional PS with two azido groups one at each end of the polymer chain and two acetylene groups at the middle of the chain;2.Intramolecular cyclization of the linear tetrafunctional PS at very low concentration through a "click" reaction to produce the eight-shaped polystyrenes.The glass transition temperatures（T_gs） were determined by differential scanning calorimetry（DSC） and it was found that the decrease in chain mobility by cyclization resulted in higher T_gs for 8-shaped polystyrenes as compared to their corresponding precursors.3.Well-defined hetero eight-shaped copolymers composed of polystyrene（PS） and poly（ε-caprolactone）（PCL） were successfully synthesized,a tetrafunctional PS and PCL star copolymer with two PS and two PCL arms was prepared at first using the tetrafunctional initiator bearing two hydroxyl groups and two bromo groups;and then the terminal hydroxyl and bromo groups were translated to acetylene and azido groups through the reaction with 4-propargyloxybutanedioyl chloride and NaN₃ respectively;After the intramolecular cyclization reaction,the hetero eight-shaped copolymers was produced using "click" chemistry under high dilution.Their thermal behavior was investigated by DSC,and their crystallization behaviors of PCL were studied by polarized optical microscopy. The decrease in chain mobility of the eight-shaped copolymers restricts the crystallization of PCL and the crystallization rate of PCL is slower in comparison with their corresponding star precursors.4.Cyclic polystyrene（PS）-b-cyclic poly（ε-caprolactone）（PCL）s,which is denoted as miktocycle figure eight-shaped copolymers have been successfully synthesized. The synthetic process involves three steps:（1） preparation of a tetrafunctional initiator with two acetylene groups,one hydroxyl group and a bromo group;（2） synthesis of diblock copolymers with two azido groups,one at each end of the two chains and two acetylene groups at the junction of two blocks, N₃-PCL-（CH≡C）₂-PS-N₃;（3） synthesis of cyclic PS-b-cyclic PCLs by the intramolecular cyclization of the linear diblock copolymers through a "click" reaction under high dilution.Their thermal behavior was investigated by differential scanning calorimetry and it was found that the decrease in chain mobility of cyclic-b-cyclic copolymers restricts the crystallization of PCL.5.A synthetic route to well-definedθ-shaped copolymers has been developed successfully.The AB₂ miktoarm star copolymers,which contain one PCL chain terminated with two acetylene groups and two PS chains with two azido groups at their one end,（α,α’-diacetylene-PCL）（ω-azido-PS）₂,were synthesized by ROP,ATRP and the terminal group transformation at first;and then well-defined pureθ-shaped copolymers were prepared by intramolecular cyclization of AB₂ miktoarm star copolymers using "click" chemistry under high dilution.Their thermal behavior was investigated by DSC.The mobility decrease of PCL chain across PS ring in the theta-shaped copolymers restricts the crystallization ability of PCL segment.更多还原