【作者】 王龙；

【导师】 何学浩；

【作者基本信息】 天津大学 ， 材料化学工程， 2012， 博士

【摘要】 非线性高分子在溶解性、粘度、稳定性及多功能性等方面比线性分子具有明显的优势，因而在近些年的研究中受到青睐。采用计算机模拟的方法研究复杂的非线性聚合反应、分子的结构和性能，不仅具有重要的科学价值，同时对实验中控制反应及加速材料的应用也具有重要的指导意义。本论文中，我们对非理想超支化聚合反应、超支化分子的构象及ABC星形三嵌段共聚物的自组装进行了研究。研究的主要内容及结果如下：1、采用Monte Carlo方法，在三维键涨落格子模型中研究了分子链刚性及反应的可逆性对AB2和AB*型超支化聚合反应的影响。随着分子链的刚性增强，分子内成环的概率逐渐降低，环的尺寸逐渐增大，这导致分子的分子量和多分散指数在高转化率下逐渐增大。反应的可逆性对体系的平衡状态和动力学平衡过程有显著影响。在逆向反应发生的概率较大时，各参数同时达到平衡值；逆向反应发生的概率较小时，达到平衡转化率以后，重均聚合度和多分散指数继续增大。2、基于扩散限制凝聚模型，建立了扩散限制的聚合反应模型，并系统研究了具有不同支化程度的超支化分子的构象。分子的回转半径和聚合度具有指数关系，随着聚合度增加，有效指数趋近于0.4。同时，采用静态光散射技术和单元的径向分布表征了分子的内部结构。在低支化度下，分子具有紧密的中心核结构；在高支化度下，超支化分子呈现疏松-紧密-疏松的结构。3、结合分子动力学和Monte Carlo方法，建立了粗粒化反应模型，并对3,5-二羟基苯甲酸（DHBA）的本体聚合反应进行了定量研究。研究中，采用反Boltzmann迭代法分别提取单体与单体、大分子与大分子之间的非成键力场。单体和大分子之间的力场采用组合方式计算。通过迭代二分法，成功拟合了实验数据，并得到了与实验体系对应的最佳反应活性参数。在最佳的反应活性参数下，模拟中得到的聚合度和支化度与实验结果吻合得很好。此外，模拟可以提供聚合反应中其它参数的信息，包括多分散指数和分子内成环等。4、采用外势场动力学方法研究了ABC星形三嵌段共聚物在稀溶液中的自组装。结果表明，各嵌段的体积分数和两种疏溶剂嵌段的疏溶剂强度对胶束的内部结构具有显著影响。研究中发现了含有中心核的横向囊泡、点状镶嵌囊泡和多隔段笼型胶束三种新颖的胶束结构。在考察囊泡的形成机理时，发现多室囊泡都可以通过成核、归并、生长的路径形成。更多还原

【Abstract】 Nonlinear polymers attract many attentions recently because of their betterproperties in solubility, viscosity, stability and multi-functionalities than linearmacromolecules. Investigating complex nonlinear polymerizations andconformational properties of molecules by employing computer simulation methodnot only has significant value in scientific research, but also can provide meaningfulsuggestions for controlling polymerization reactions and accelerating the applicationof materials. In this dissertation, we have studied the reaction kinetics of nonlinearhyperbranched polymerizations, the conformational properties of hyperbranchedpolymers and the self-assembly of ABC star terpolymer. The research contents andresults are shown as follows.1. The reaction kinetics of nonideal hyperbranched polymerizations consideringthe chain rigidity and reaction reversibility are studied using the reactive3D bondfluctuation lattice model with Monte Carlo method. It is found that, with the increaseof chain rigidity, the formation probability of intramolecular rings decreases and lessintramolecular rings with larger size are formed. It results in the increase of thedegrees of polymerization and polydispersity index with the rise of chain rigidity athigher conversion. Furthermore, our simulation shows that the reversibility of reactionhas strong influences on the equilibrium state and kinetic process of hyperbranchedpolymerizations. When the ratio of reverse reaction probability is larger, eachparameter grows to the equilibrium value simultaneously. At smaller reverse reactionprobability, however, the weigh-average degree of polymerization and polydispersityindex further increase after approaching the equilibrium conversion.2. Based on the diffusion-limited aggregation model, we propose adiffusion-limited polymerization model and systematically study the conformationalproperties of hyperbranched polymers with different degrees of branching. The radiusof gyration and degree of polymerization show exponential relationship, and theeffective exponents approach0.4with the increase of the degree of polymerization.Meanwhile, the static light scattering technique and the radial distribution of units areapplied to characterize the internal structural property of polymers. It shows that themolecule has dense core structure at smaller degree of branching, andloose-dense-loose structure at larger degree of branching.3. Combining the molecular dynamics and Monte Carlo methods, we develop a coarse-grained reactive model to investigate hyperbranched polyesterification of3,5-Dihydroxybenzoic acid (DHBA) quantitatively. The iterative Boltzmann inversionmethod is employed to obtain the coarse-grained nonbonded force fields between twomonomers and two polymers respectively. Further, the interaction potentials betweencoarse-grained monomers and hyperbranched polymers are calculated by applying thecombining rule. The reactivity parameters are optimized according to theexperimental data using the iterative dichotomy method. At the optimized reactivityparameters, the degrees of polymerization and branching predicted in molecularsimulation agree well with experiments. Furthermore, more information such as thepolydispersity index and intramolecular cyclization are achieved quantitatively.4. The self-assembly of ABC star terpolymer in dilute solution is studied byusing the external potential dynamics method. The volume fraction of each block andthe solvophobicity of two solvophobic blocks have significant influence on theinternal structure of micelles. Three novel structures are observed including laterallystructured vesicle with a core, spotted vesicle with a core and segmented cage-likemicelle. There are three steps in the evolution pathway of multi-compartment vesicles,which are nucleation, coalescence and growth.更多还原