【作者】 王红；

【导师】 吕中元；

【作者基本信息】 吉林大学 ， 物理化学， 2011， 硕士

【摘要】 本文利用耗散粒子动力学（Dissipative Particle Dynamics, DPD）模拟方法,研究了梳型嵌段共聚物自组装形成囊泡的形态变化过程。主要内容包括:（1）囊泡自发形成过程的研究。我们发现梳型嵌段共聚物A₆ （ B₂ ）₃会自组装形成长管状囊泡。为了更好地比较聚合物结构对自组装形成囊泡形态的影响,我们同时研究了线型三嵌段共聚物A₃ B₆ A₃自发形成囊泡的过程,发现线型三嵌段共聚物A₃ B₆ A₃会自组装形成球形囊泡。虽然形成囊泡的形态不同,但自组装的动力学路径是一样的。（2）囊泡分裂及翻转过程的研究。我们发现线张力对囊泡的分裂起着至关重要的作用。在模拟中,我们确定了两条不同的分裂路径:一种路径是通过母体囊泡出芽然后闭合完成分裂,另外一种是在区域膜的边界处产生裂缝完成分裂。分裂完成后,相同组分的小胶束或小囊泡会自发融合,最终融合为两个大的囊泡。在囊泡的翻转过程的研究中,我们发现长管状囊泡翻转后变成了多层胶束结构,洋葱状囊泡翻转后得到的仍是一个结构完整的囊泡。更多还原

【Abstract】 Cells are common and essential structures in nature. They are closely related with the phenomenon of life and are basic units of organism. The primary roles of biomembranes are the separation between the inner and outer environments of the cell which is crucial for a variety of physiological functions, structural integrity and transmembrane transport of the cell. The complex biomembranes are deformed easily. So, it is very difficult to study the formation and structure transition of the biomembrane structures. However, the biomembranes are still membrane material, the physical and chemical nature of the self-assembly process is only connected with membrane characteristics. Therefore, it is very necessary to build a relatively simple membrane model to simulate some features of the biomembranes. Currently, the accepted model of membranemodel is vesicle obtained by molecular self-assembly. The characteristic of vesicle with hollow inner space has attracted much attention in the fields of drug and gene delivery, chemical and waste transport, and nanotechnology. The structure transitions of vesicle, such as fusion and fission, underlie the fundamental biological processes in normal and pathological conditions. Therefore, understanding the formation of various vesicle structures and elucidating the mechanism of their transitions has an important biological and technological significance.Computer simulation performed by establishing model based on real problems, select appropriate simulation method to depict the real process, and then obtain reinforce results for experiment and theoretical. In this dissertation, we carry out DPD simulations to study the thermodynamic influences on the vesicle structure transitions of a specific comb-like block copolymer. Within the DPD method, all the particles interact with each other through three pairwise forces: a conservative force, a dissipative force, and a random force. These forces are very soft, so the integration time steps can be very large. It is intrinsically embedded in the DPD model because of the pari-wise interactions which result the momentum of the system being conserved. DPD method has been applied on the study of microphase separation of the block copolymers, self-organizing of amphiphilic molecules into memberane, and the budding and fission of bionic micelles.The spontaneous vesicle structure transitions of comb-like block copolymers with semiflexible hydrophobic backbone are studied via Dissipative Particle Dynamics （DPD）.simulations. The main results are as follows:（1） The study of spontaneous vesicle formation. We can observe a well-formed long tube vesicle from the comb-like block copolymer A₆ （ B₂ ）₃ . It should be noted that for better comparing the influence of polymer architectures on the vesicle structures, we have also simulated a system composed of linear triblock copolymers A₃ B₆ A₃ and observe one well-generated spherical vesicle. Although the vesicle structures in these two systems are different, their vesicle formation pathways are rather the same.（2） The study of fission and reversal processes of vesicle. Line tension plays a decisive role on the fission of vesicles. We find two fission pathways: the first fission pathway is closely related to the domain budding outward from the parent vesicle, whereas the other fission pathway corresponds to the cleavage along the domain boundary. When we simulate long enough time, the separated small micelles or microvesicles are approaching to each other, and then fuse spontaneously. Finally, we can observe that the parent vesicle divides into two vesicles. We then study the vesicle reversal behavior by changing the solvent environment, and find that the tube-like vesicle forms special layered micelle structure and the onion-shape vesicle still form an onion-shape vesicle.更多还原