Synthesis and Characterization of Polystyrene Brushes for Organic Thin Film Transistors

Abstract

We synthesized and characterized polystyrene brushes on a silicon wafer using surface-initiated atom transfer radical polymerization. The thickness of the polymer brush was controlled by adjusting the reaction time. We investigated monomer conversion as well as the molecular weight and density of the polymer brushes. When the monomer conversion reached 100%, the number-average molecular weight and film thickness reached 135,000 and 113 nm, respectively. The estimated densities of the synthesized polystyrene brushes were in the range 0.34-0.54 chains/nm2, high enough to be categorized in the "concentrated brush" regime. The synthesized polymer brush was used as an insulating layer in an organic thin-film transistor. Organic thin-film transistors were fabricated using pentacene as an active p-type organic semiconductor and a polystyrene brush on a SiO2 layer as a gate dielectric. The pentacene based organic thin-film transistor with the polystyrene brush exhibited a field-effect mobility microFET of 0.099 cm2/(V x s).

Facile one‐pot method of initiator fixation for surface‐initiated atom transfer radical polymerization on carbon hard spheres

“…Similarly graft densities of PMMA were calculated: 0.0068 and 0.0039 chains nm −2 with and without sacrificial initiator, respectively. One possible reason for this low density of polymer brushes relative to PSt brushes on silicon wafers (about 0.40 chains nm −2 ) and PMMA brushes on gold nanoparticles (about 0.30 chains nm −2 ) might be the presence of nanometer sized pores on the surface of CHSs resulting in narrow inner pore's surface areas that are incapable of grafting large polymer chains. It should be clarified that the above graft density calculations include the surface area of any pores or cavities that may be present on the outer surface.…”

Recent Advances in the Synthesis of Polymer-Grafted Low-K and High-K Nanoparticles for Dielectric and Electronic Applications

“…Pinto et al [ 97 ] employed SI-ATRP for grafting of PMMA brushes thinner than 50 nm on SiO 2 substrate for tunnel emitter transistor application at operating voltage below 5 V (which is an important requirement for industrial adoption). Hwang et al [ 98 ] employed SI-ATRP for grafting PS brushes on silica surface with controlled molecular weight (24,600–135,000 g/mol) as well as grafting density (0.34–0.54 chains/nm 2 ). The performance of pentacene-based thin-film transistor fabricated from PS-grafted SiO 2 as a gate dielectric was evaluated as a function of polymer brush thickness viz.…”

“…The OTFTs with the PS-grafted SiO 2 layer showed 2 times higher mobility (µ FET = 0.099 cm 2 /V·s) than that of bare SiO 2 layer (µ FET = 0.05 cm 2 /V·s). The electrode/active layer interface showed enhanced mobility which could be attributed to grafted PS influencing the morphology of pentacene by enhancing the crystalline structure [ 98 ]. Li and coworkers synthesized PMMA- g -SiO 2 NPs with ~10 nm PMMA brush onto the SiO 2 layer (~9 nm) via SI-ATRP.…”

Surface Modification of Silicon Nanowire Based Field Effect Transistors with Stimuli Responsive Polymer Brushes for Biosensing Applications

“…Lately, approaches have been made to combine the excellent transducing capability of SiNW FETs and the benefits from versatile polymer functionalization [44][45][46]. For instance, the switching events of brushes could be detected with FETs [47,48], dielectric materials were coated to create non-fouling surfaces [49,50], and chemical reactions were performed and transduced with polymer brush-FET systems [51,52].…”