Dissipative particle dynamics (DPD) simulation was performed to study the microphase separation and self-assembly dynamics of thermo-responsive amphiphilic triblock copolymer PCL16-PNIPAM63-PCL16 in aqueous solution. The effects of temperature and volume fraction of the copolymer on its phase behavior were investigated. The simulation results showed that different self-assembly morphologies, such as sphere, cylinder, laminar etc. , could be obtained by varying the volume fraction of the copolymer. Besides, it was found that temperature had a remarkable effect on the copolymer phase behavior in dilute solution. When temperature was low, a stable spherical core-shell micelle could be obtained with PCL as its core and PNIPAM as its shell. However, with the increase of temperature to a specific value, it was clearly seen that the spherical core-shell micelle formed at a low temperature changed to a multicompartment micelle whose surface was covered by several discontinuous micro-domains formed by PCL. This thermo-responsive phenomenon was captured in DPD simulation for the first time. Moreover, the lower critical solution temperature (LCST) obtained from the simulation was in good agreement with that determined by experiment. A more detailed explanation was given to illustrate this thermo-responsive phenomenon. This work demonstrated that dissipative particle dynamics could be used to study the influence of temperature and to reveal the mechanism and general rule of the phase behavior of thermo-sensitive amphiphilic block copolymers.%采用耗散粒子动力学模拟研究了由温敏性聚N-异丙基丙烯酰胺(PNIPAM)与聚己内酯(PCL)构成的两亲嵌段共聚物(PCL-PNIPAM-PCL)在水溶液中自组装的动力学过程及微相分离现象,考察了溶液浓度及温度对其相行为的影响.模拟发现不同体积分数的嵌段共聚物在水溶液中呈现出不同的自组装形貌,如球状胶束、柱状胶束、层状胶束等.温度对其在水溶液中的形貌及相变行为有着显著的影响.当温度较低时,PCL-PNIPAM-PCL于稀溶液中可形成稳定的以PCL为核,PNIPAM为壳的球形核壳胶束；而当温度升高到某一值时,在低温时所形成的球形核壳胶束将因温度的升高而转变为表面由PCL组成的多个不连续微区的多隔段胶束.这种温敏现象在耗散粒子动力学模拟中尚属首次被发现.另外,模拟中所得到的该体系的低临界溶解温度与实验测得的值也符合良好.对这一温敏现象作了较深入和细致的解释.本文工作表明耗散粒子动力学能用来研究温度对温敏性两亲嵌段共聚物相行为的影响并揭示其中的机制和一般规律.
展开▼
