Dissipative particle dynamics study of multicompartment micellar solutions in a slit1.doc
《Dissipative particle dynamics study of multicompartment micellar solutions in a slit1.doc》由会员分享,可在线阅读,更多相关《Dissipative particle dynamics study of multicompartment micellar solutions in a slit1.doc(12页珍藏版)》请在三一文库上搜索。
1、精品论文推荐Dissipative particle dynamics study of multicompartment micellar solutions in a slit1Cui Yuanyuan, Liu Dahuan*, Zhong ChongliDepartment of Chemical Engineering, The Key Lab of Bioprocess of Beijing, Beijing University ofChemical Technology, Beijing, P. R. China (100029)E-mail:AbstractMulticomp
2、artment micelles are a new family of micelles that may find wide applications; however, due to their complexity, the knowledge on them is quite limited to date. In this work, dissipative particle dynamics simulations were performed to investigate the morphology and structure of multicompartment mice
3、llar solutions confined in two hydrophilic walls, as a function of slit width. The results show that pore width can influence largely the morphology and structure of multicompartment micellar solutions confined in hydrophilic walls, the commonly observed “confinement-induced alignment” also occurs i
4、n multicompartment micellar solutions, and confinement can induce new morphologies, which can also speed up and enhance the formation of large multicompartment micelles. In addition, this work shows that a strong external field can change the alignment of multicompartment micelles, leading to new we
5、ll-defined ordered structures. The information obtained may be useful for experimental investigations, as well as for understanding multicompartment micelles at molecular level.Keywords: Dissipative particle dynamics, multicompartment micelles, slit.1. I n tr o d u c tio nAmphiphilic block copolymer
6、s can self-assemble into various structures such as micelles and vesicles in a selective solvent.1-3 Recently, a novel class of micelles called multicompartment micelles explode an intriguing field of nanotechnology that shows great potential applications in drug delivery,4-6 as well as in many othe
7、r fields such as multi-functional nano-reactors.In the past decade, several groups have performed investigations on preparing and characterizing multicompartment micelles in aqueous medium.4,7-10 Recently, Lodge and co-workers not only prepared stable multicompartment micelles through the self-assem
8、bly of miktoarm star copolymers, but also succeeded in evidencing visually the formation of segregated compartments in a micellar core by means of cryo-transmission electron microscopy (cryo-TEM).11 However, the rigorous assessment of the morphology of inner core and the evolution of multicompartmen
9、t micelles by experiments are very difficult due to the structural complexity of the micelles, to which molecular simulation is a powerful tool. Unfortunately, molecular simulations on multicompartment micelles are very scarce to date,12-14 limiting to some extent the precise understanding of their
10、morphologies as well as the corresponding evolution mechanisms at a microscopic level.A systematic research toward a understanding of the formation and morphological transitions in multicompartment micelles at molecular level is being performed in our laboratory by using the dissipative particle dyn
11、amics (DPD) simulation technique.12-14 In our previous works,12,13 DPD simulations were performed to investigate the effect of block compositions and shear on the morphologies of multicompartment micelles formed from ABC miktoarm star copolymers in water. In this work, it was extended to study the e
12、ffect of confinement on multicompartment micellar solutions. It is well known that confinement plays an important role in the mesoscale morphology formation due to the surface interactions and the geometrical constraints, and new morphologies and ordered1 Support by Specialized Research Fund for the
13、 Doctoral Program of Higher Education of China (20040010002)-12-structures can be formed in confinement. Although there have been extensive investigations on the effect of confinement on nonionic and ionic micellar solutions, both experimentally15-21 and theoretically,22-28 investigations on the eff
14、ect of confinement on multicompartment micelles have not been performed. Therefore, it is valuable to perform a DPD simulation study to reveal the confinement effects as well as to make a comparison with other micellar solutions. This preview can provide useful information for both experiments and t
15、oward the complete understanding of the characteristics of multicompartment micelles.2. Me th od and sim u la t i on det a i l s2.1 Diss ip ativ e p a rtic le d y n a m i c s m e th o dThe DPD method, introduced by Hoogerbrugge and Koelman,30,31 is a particle-based mesoscopic simulation technique pa
16、rticularly suitable for complex fluids. It can be used to study systems over larger length and time scales than classical molecular dynamics and Monte Carlo simulations that has been successfully used to study microstructures and properties of polymers in melt state and in solvent.12-14,32-39 In thi
17、s method, a number of soft particles are considered interacting with each other and each particle represents a small volume of fluid containing many atoms. Details of the DPD method are given elsewhere,32,40 and only a brief introduction is given here.In the DPD method the force acting on a particle
18、 contains three parts, each of which is pairwiseadditive:40ij ij ijFi = ( F C + F D + F R )(1)j i where the sum runs over all other particles within a certain cutoff radius rc. The conservative force is asoft repulsion acting along the line of centers and is given bya (1 rF C =ij ijrc )rij(rij rc ,
19、is the frictioncoefficient, is the noise amplitude, and ijstatistics.The two weight functions can be taken simply as2is a randomly fluctuating variable with Gaussian2 (1 r r ) (r r ) D (r ) = R (r ) = B 2 = 2 k T ij c ij c0 (rij rc )(5) (6)To determine the conservative force FC, the repulsion parame
20、ter aij has to be known. In this work, the relationship between aij and the Flory-Huggins -parameter proposed by Groot and Warren isadopted:40aii + 3.27ij = 3aij = a+ 1.45 = 5(7) ii ijwhere is the density, aii is the repulsion parameter between particles of the same type, and its value isderived fro
21、m the compressibility of pure component byaii = 75kBT 2.2 M o del s a nd pa ra m e t e r s(8)In our previous work,12 the self-assembly of ABC star copolymers (Fig. 1) in water into multicompartment micelles was studied, and various morphologies were identified as a function of block composition. In
22、this work, we focused on the study of the effect of confinement on wormlike multicompartment micelles. Therefore, the A4B10C2 (A: weak hydrophobic block, B: hydrophilic block, and C: strong hydrophobic block) copolymer was selected since our previous work showed this copolymer could self-assemble in
- 配套讲稿:
如PPT文件的首页显示word图标,表示该PPT已包含配套word讲稿。双击word图标可打开word文档。
- 特殊限制:
部分文档作品中含有的国旗、国徽等图片,仅作为作品整体效果示例展示,禁止商用。设计者仅对作品中独创性部分享有著作权。
- 关 键 词:
- Dissipative particle dynamics study of multicompartment micellar solutions in slit1
链接地址:https://www.31doc.com/p-3617619.html