Molecularly Smooth Self-Assembled Monolayer for High-Mobility Organic Field-Effect Transistors

Abstract

Despite the need for molecularly smooth self-assembled monolayers (SAMs) on silicon dioxide surfaces (the most common dielectric surface), current techniques are limited to nonideal silane grafting. Here, we show unique bioinspired zwitterionic molecules forming a molecularly smooth and uniformly thin SAM in "water" in <1 min on various dielectric surfaces, which enables a dip-coating process that is essential for organic electronics to become reality. This monomolecular layer leads to high mobility of organic field-effect transistors (OFETs) based on various organic semiconductors and source/drain electrodes. A combination of experimental and computational techniques confirms strong adsorption (W > 20 mJ m), uniform thickness (∼0.5 or ∼1 nm) and orientation (all catechol head groups facing the oxide surface) of the "monomolecular" layers. This robust (strong adsorption), rapid, and green SAM represents a promising advancement toward the next generation of nanofabrication compared to the current nonuniform and inconsistent polysiloxane-based SAM involving toxic chemicals, long processing time (>10 h), or heat (>80 °C).

Mussel‐Inspired Surface Acrylation on Graphene Oxide Using Acrylic Surface Primers and Its Hydrogel‐Based Applications: Sustained Drug Release and Tissue Scaffolds

“…The mussel‐inspired phenolic (or catecholic) polymer binders are used for surface modification of silicon nanoparticles in high‐performance lithium‐ion batteries . The phenolic zwitterionic surfactants are used on nano‐grooved dielectric substrates as surface modifiers to produce organic field‐effect transistors . In our previous research, a single‐surface primer containing phenolic and acrylic groups enabled adherence to silica fillers that enhanced the toughness of the composite consisting of filler and polymer resin by interfacial bridging to the acrylic resin…”

Significant Performance Enhancement of Polymer Resins by Bioinspired Dynamic Bonding

“…The most common primers for mineral fillers in load-bearing polymer composites, such as those used in dental restorative applications, rely on silane-based chemistries. However, silane grafting involves uses of toxic chemicals [1,2] and difficult processing [3,4] and therefore there is a great demand for alternative strategies for surface priming.…”

“…[5] Inspired by the natural DOPA chemistry, numerous laboratories have exploited catechol functionalization in the translation of this bioadhesion to synthetic systems [10–12] and for various applications [1,13–15] such as functional materials; for example, catechol-functionalized polymers were used as binders for silicon lithium battery anodes, [15] and catecholic zwitterionic surfactants were employed as surface modifiers on nanogrooved dielectric substrates for organic field-effect transistors. [1] Although previous studies using catechol-decorated polymers have demonstrated improvements in adhesion, [5,12,16] the performance of such manmade polymers, [16] as well as isolated native mussel and engineered proteins [17] is still far lower than that of whole natural mussel plaques, in terms of the total energy required to dislodge a plaque from a surface. [18] These differences may arise from the lack of consideration given in previous work to the heterogeneous nature of the mussel plaque structures [19] and their impact on load transfer within the material.…”

“…By contrast, the use of the catecholic primers P 3 ( σ shear, max = 0.8 ± 0.2 and 4.2 ± 0.7 MPa, n = 10), P 4 ( σ shear, max = 0.9 ± 0.1 and 4.5 ± 0.5 MPa, n = 10) doubled the lap shear strength compared with the no-primer case. In fact, the measured strengths of the catechol-primed samples were equal, within experimental uncertainty, to that of the silane-primed surface ( σ shear, max = 0.9 ± 0.4 and 3.8 ± 1.1 MPa, n = 10), which is used as the industry standard despite of its low surface coverage, high energy consumption and toxic chemical usage [1,2] (Figure 3d,e; Figure S9, Supporting Information). On tooth enamel (Figure 3f), the lap shear strength measured using surfaces primed with P 3 ( σ shear, max = 3.0 ± 0.3 MPa, n = 10), and P 4 ( σ shear, max = 3.0 ± 0.3 MPa, n = 10) was almost double that of the no-primer case ( σ shear, max = 1.8 ± 0.1 MPa, n = 10), and equal, within experimental uncertainty, to that of MDP ( σ shear, max = 3.1 ± 0.2 MPa, n = 10), which is used as the dental industry standard despite the unfavorable pH dependency of phosphate-calcium binding.…”

“…bone) and in soft polymer networks [42] and have been attributed to the nanoscale rupture of sacrificial bonds which dissipate energy and provide hidden length and thus ductility. [1,43,44] We hypothesize that this pattern of saltatory stress decrease in the P 3 -treated samples might be correlated to the failure of the dynamic bonds formed between the catechol and mineral surfaces. [26,40,45] …”