Interfacial Thermal Transport over Solid–Liquid Interfaces Mediated by Heterogeneous Self-Assembled Monolayers: A Molecular Dynamics Study

Interfacial thermal management plays a pivotal role in ensuring efficient heat dissipation in nanodevices with solid–liquid interfaces. Although sandwiching self-assembled monolayers (SAMs) that have heterogeneous chain lengths between solids and liquids is considered a promising strategy for enhancing interfacial thermal transport, it has received limited attention in the current research landscape. In this study, we systematically examine the effects of liquid-induced SAM stiffness and pattern densities of heterogeneous SAMs on interfacial thermal resistance (ITR) over SAM-mediated Au–polymer liquid interfaces with various SAM–liquid affinities using nonequilibrium molecular dynamics simulations. Our findings confirm that hydrophobic alkanethiol SAMs exhibit higher induced stiffness, while hydrophilic poly(ethylene glycol) (PEG)-COOH-functionalized SAMs are comparatively softer, thereby influencing the equilibrium structures of the patterned SAM surfaces. The structured arrangement of stiff heterogeneous alkanethiol SAMs is well-preserved, which increases the contact area utilized by liquids compared to that of nonpatterned systems, thereby resulting in smaller ITR. Thus, a dense arrangement of alternating SAM lengths is recommended for minimizing ITR. The softness of hydrophilic SAMs limits the potential increase in the contact area, making it challenging to further reduce ITR compared to that of nonpatterned systems, particularly under very high SAM–liquid affinity, where ITR can exceed that of nonpatterned configurations. The liquid adsorption density on SAM surfaces is a key factor governing the ITR in varying affinity cases. The hydrogen bond number density plays an additional role when hydrogen bonds form between the SAMs and liquid molecules. These insights highlight the importance of prioritizing induced stiffness in the molecular design of patterned SAM surfaces for efficient thermal management in nanodevices with multiple solid–liquid interfaces.界面热管理对于具备固液界面的纳米器件实现高效散热起着至关重要的作用。尽管在固液之间夹入具有非均相链长的自组装单分子层（self-assembled monolayers，SAMs）被认为是强化界面热输运的极具前景的策略，但当前研究领域对此关注有限。本研究采用非平衡分子动力学模拟，系统探究了在不同SAM-液体亲和性条件下，由SAM介导的金-聚合物液体界面中，液体诱导的SAM刚度以及非均相SAM的图案密度对界面热阻（interfacial thermal resistance，ITR）的影响。研究结果证实，疏水烷基硫醇SAMs表现出更高的诱导刚度，而亲水型聚乙二醇（PEG）羧基功能化SAMs则相对更柔软，这会对图案化SAM表面的平衡结构产生影响。刚性非均相烷基硫醇SAMs的结构化排列得以较好保留，相较于无图案化体系，其增大了液体可利用的接触面积，进而降低了界面热阻。因此，建议采用交替链长的高密度排列以最小化界面热阻。亲水SAM的柔软性限制了接触面积的潜在提升空间，相较于无图案化体系，进一步降低界面热阻颇具挑战，尤其是在SAM-液体亲和性极高的情况下，此时界面热阻甚至会高于无图案化配置。在不同亲和性条件下，SAM表面的液体吸附密度是调控界面热阻的关键因素。当SAM与液体分子间形成氢键时，氢键数密度会产生额外影响。这些研究结果凸显了在多固液界面纳米器件的高效热管理中，优先考虑图案化SAM表面分子设计中的诱导刚度的重要性。