Walker Christopher C, Genzer Jan, Santiso Erik E
Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina 27695, United States.
ACS Appl Mater Interfaces. 2020 Oct 21;12(42):47879-47890. doi: 10.1021/acsami.0c10747. Epub 2020 Oct 6.
Modulating a comonomer sequence, in addition to the overall chemical composition, is the key to unlocking the true potential of many existing commercial copolymers. We employ coarse-grained molecular dynamics (MD) simulations to study the behavior of random-blocky poly(vinyl butyral--vinyl alcohol) (PVB) melts in contact with an amorphous silica surface, representing the interface found in laminated safety glass. Our two-pronged coarse-graining approach utilizes both macroscopic thermophysical data and all-atom MD simulation data. Polymer-polymer nonbonded interactions are described by the fused-sphere SAFT-γ Mie equation of state, while bonded interactions are derived using Boltzmann inversion to match the bond and angle distributions from all-atom PVB chains. Spatially dependent polymer-surface interactions are mapped from a hydroxylated all-atom amorphous silica slab model and all-atom monomers to an external potential acting on the coarse-grained sites. We discovered an unexpected complex relationship between the blockiness parameter and the adhesion energy. The adhesion strength between PVB copolymers with intermediate VA content and silica was found to be maximal for random-blocky copolymers with a moderately high degree of blockiness rather than for diblock copolymers. We attribute this to two main factors: (1) changes in morphology, which dramatically alter the number of VA beads interacting with the surface and (2) a non-negligible contribution of vinyl butyral (VB) monomers to adhesion energy because of their preference to adsorb to zones with low hydroxyl density on the silica surface.
除了整体化学组成外，调节共聚单体序列是释放许多现有商业共聚物真正潜力的关键。我们采用粗粒度分子动力学（MD）模拟来研究无规嵌段聚（乙烯醇缩丁醛 - 乙烯醇）（PVB）熔体与无定形二氧化硅表面接触时的行为，该表面代表夹层安全玻璃中的界面。我们的双管齐下的粗粒度方法利用了宏观热物理数据和全原子MD模拟数据。聚合物 - 聚合物非键相互作用由融合球体SAFT - γ Mie状态方程描述，而键合相互作用则通过玻尔兹曼反演推导得出，以匹配全原子PVB链的键和角度分布。空间相关的聚合物 - 表面相互作用从羟基化的全原子无定形二氧化硅平板模型和全原子单体映射到作用于粗粒度位点的外部势。我们发现了嵌段参数与粘附能之间意想不到的复杂关系。对于具有中等VA含量的PVB共聚物与二氧化硅之间的粘附强度，发现对于具有适度高嵌段度的无规嵌段共聚物而非二嵌段共聚物最大。我们将此归因于两个主要因素：（1）形态变化，这极大地改变了与表面相互作用的VA珠子的数量；（2）乙烯醇缩丁醛（VB）单体对粘附能有不可忽略的贡献，因为它们倾向于吸附到二氧化硅表面羟基密度低的区域。
