The composition profiles of a series of model polystyrene/fullerene bilayers are measured, before, during and after thermal annealing, using in situ neutron reflectometry. In combination with grazing-incidence X-ray diffraction measurements, these experiments, which quantify layer compositions as a function of molecular weight using changes in both scattering length density and layer thickness, extend and corroborate recent measurements on ex situ annealed samples and demonstrate that the composition profiles rapidly formed in these systems correspond to two co-existing liquid–liquid phases in thermodynamic equilibrium. The measurements also demonstrate a clear and systematic onset temperature for diffusion of the fullerenes into the PS layer that correlates with the known glass-transition temperatures of both the polymer (as a function of molecular weight) and the fullerene, revealing that the molecular mobility of the fullerenes in these systems is controlled by the intrinsic mobility of the fullerenes themselves and the ability of the polymer to plasticise the fullerenes at the interface. Over the temperature range investigated (up to 145 °C), measurements of equilibrated composition profiles as a function of temperature (during gradual cooling) reveal no significant changes in composition profile, other than those associated with the known thermal expansion/contraction of polystyrene thin-films.

中文翻译：

---

聚合物-富勒烯混合物中的液-液平衡；原位中子反射率研究

使用原位中子反射仪在热退火之前，之中和之后测量一系列模型聚苯乙烯/富勒烯双层的组成分布。结合掠入射X射线衍射测量，这些实验通过使用散射长度密度和层厚度的变化来量化层组成作为分子量的函数，扩展并证实了最近的非原位测量退火的样品，并证明在这些系统中快速形成的成分分布与热力学平衡中的两种液相共存相对应。测量结果还表明，富勒烯扩散到PS层中的过程温度清晰而系统，该温度与聚合物（作为分子量的函数）和富勒烯的已知玻璃化转变温度相关，这表明富勒烯的分子迁移率这些体系中的富勒烯受富勒烯本身的固有迁移率以及聚合物在界面处增塑富勒烯的能力控制。在研究的温度范围内（最高145°C），