Larsen Ryan J, Zukoski Charles F
Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
Phys Rev E Stat Nonlin Soft Matter Phys. 2011 May;83(5 Pt 1):051504. doi: 10.1103/PhysRevE.83.051504. Epub 2011 May 13.
The glass transition temperature of a broad class of molecules is shown to depend on molecular size. This dependency results from the size dependence of the pair potential. A generalized equation of state is used to estimate how the volume fraction at the glass transition depends on the size of the molecule, for rigid molecule glass-formers. The model shows that at a given pressure and temperature there is a size-induced glass transition: For molecules larger than a critical size, the volume fraction required to support the effective pressure due to particle attractions is above that which characterizes the glassy state. This observation establishes the boundary between nanoparticles, which exist in liquid form only as dispersions in low molecular weight solvents and large molecules which form liquids that have viscosities below those characterized by the glassy state.
一大类分子的玻璃化转变温度被证明取决于分子大小。这种依赖性源于对势的尺寸依赖性。对于刚性分子玻璃形成体，使用广义状态方程来估计玻璃化转变时的体积分数如何依赖于分子大小。该模型表明，在给定压力和温度下，存在尺寸诱导的玻璃化转变：对于大于临界尺寸的分子，由于粒子吸引力而支持有效压力所需的体积分数高于表征玻璃态的体积分数。这一观察结果确定了纳米颗粒与大分子之间的界限，纳米颗粒仅以分散在低分子量溶剂中的液体形式存在，而大分子形成的液体的粘度低于玻璃态所表征的粘度。
