The Self-assembly Of Coil-rod-coil Block Copolymer In Solution

With the development of nanotechnology in twenty-firstCentury, the preparation of functional polymer nano materials become ahot research topic rapidly. The self-assembly of polymer has importantapplications in materials science, such as chemistry, catalysis, nanobionics and biomedical and other fields, therefore the research onself-assembly behavior of polymer has increasingly become animportant topic of functional polymer nanometer material preparationfield. Block copolymer is a type of special polymer that composed oftwo or more than two kinds of monomer sequence with differentchemical properties by covalent bond. It can also be a excellent chemicalproperties of various polymer together, so as to obtain the materialproperties of polymer is more excellent. Rod coil block copolymer is akind of special structure polymer block copolymers, and flexible chainand rigid rod block are containing in the block, the phase behavior ofliquid crystal rigid rod block and flexible chain free extension to thecompetition between the self-assembly, phase structure and thetraditional full coil block copolymers have vastly different. The rod coildiblock copolymers has been studied in-depth researchers, become one of the hottest topics in the materials field. This paper is mainly usingdissipative particle dynamics method (DPD) to systematic study the selfassembly of coil-rod-coil triblock of block copolymer in selectivesolvent.In the second chapter， we study coil-rod-coil triblockcopolymer self-assembly in selective solvent. In coil-selective solventcase, the morphological transitions of CRC solutions are induced byvarying the rod length Lr and the coil length Lc. The increase of rodlength makes the contact area between rods and solvents larger, and theinterface energy enhanced. To reduce the contact area and interfaceenergy, rod blocks tend toward aggregate. Two kinds of interestingphase structures（spherical phase and micellar phase）are observed byvarying the solvent preference (aCS)and rod length Lr. With the solventpreference aCSvaried from coil-selective to neutral and then torod-selective, the rod-rich-domains in spherical micelle move from theinterior to the surface and the number of rod-rich-domain layers ischanged. Also, the rod length influences the internal structure of thespherical phase and induces the phase transition between the differentspherical phases. The micellar phase includes segmented smectic micelleand rod helices-like micelle, where the rod blocks are arranged in theliquid crystal structure due to the anisotropy of the long rods. In the third chapter, we study the formation conditions andmechanism of coil-rod-coil block copolymer vesicles. Self-assembledvesicles formed by symmetrical coil-rod-coil triblock copolymer inselective solvents are investigated by dissipative particle dynamicsmethod. With varying the coil lengthLc and the rod lengthLr, kinds oftypically ordered phases are observed, including the special hollowstructure of vesicle, which are formed in the range of the rod block ratiof r30%~50%and the rod length Lr9. The kinetic process of vesicleformation is also observed. The micelles firstly experience the fusion,elongation, and deformation, and then encompass the solvents, andfinally close up to a vesicle membrane, where the bilayer disc isobserved as an intermediate phase transited from solid micelles tohollow vesicle. Furthermore, the effect of polymer concentrationf pandsolvent property are discussed. Meanwhile, the vesicle size exhibits awell linear increase with polymer concentration. The size of vesiclesdecreases with an increase in the interactionsa CSbetween coil blocksand solvents. Due to the interfacial energy increased witha CS, thesystem minimizes the interfacial energy by compressing the vesicle size.