Department of Polymer Science and Engineering, CAS Key Laboratory of Soft Matter Chemistry, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China.
J Chem Phys. 2009 Dec 28;131(24):244902. doi: 10.1063/1.3273418.
Using the off-lattice Monte Carlo simulation and replica-exchange method, we studied the behavior of nongrafted homopolymer adsorption by an attractive substrate from both the canonical and the microcanonical views. An adsorption transition is identified from the peak in canonical specific heat and compared with the conventional polymer adsorption with one end anchored on the surface of the substrate. Judging from the typical "backbending effect" and the negative specific heat in microcanonical ensemble, the transition is first-order-like when adsorption is relatively strong. However, it becomes second-order-like when the strength of adsorption becomes weak enough. Further study reveals that for a chain consisting of a limited number of monomers, the type of this transition becoming either first- or second-order-like depends not only on the interplay between monomer-monomer and monomer-substrate interaction, but also on the width of the gap in which it is confined.
使用无格子蒙特卡罗模拟和复制交换方法，我们从正则和微正则的角度研究了无支化均聚物从本体相中被有吸引力的基底吸附的行为。通过正则比热的峰值识别出吸附转变，并与传统的聚合物吸附进行比较，其中聚合物的一端固定在基底表面上。从典型的“回弯效应”和微正则系综中的负比热来看，当吸附较强时，转变是一级相变。然而，当吸附强度足够弱时，转变变为二级相变。进一步的研究表明，对于由有限数量的单体组成的链，这种转变是一级还是二级相变的类型不仅取决于单体-单体和单体-基底相互作用的相互作用，还取决于它被限制在其中的间隙的宽度。
