Nanometer-Scale Precision Polymer Patterning of PDMS: Multiscale Insights into Patterning Efficiency Using Alkyldiynamines

Abstract

Most high-resolution interfacial patterning approaches are restricted to crystalline inorganic interfaces. Recently, we have shown that it is possible to generate 1 nm resolution functional patterns on soft materials, such as polydimethylsiloxane (PDMS), by creating highly structured striped patterns of functional alkyldiacetylenes on a hard crystalline surface, photopolymerizing to set the molecular pattern as a striped-phase polydiacetylene (sPDA), and then covalently transferring the sPDAs to PDMS. Transfer depends on the diacetylene polymerization, making it important to understand design principles for efficient sPDA polymerization and cross-linking to PDMS. Here, we combine single-molecule and fluorescence-based metrics for sPDA polymerization and transfer, first to characterize sPDA polymerization of amine striped phases, and then to develop a probabilistic model that describes the transfer process in terms of sPDA–PDMS cross-linking reaction efficiency and number of reactions required for transfer. We illustrate that transferred patterns of alkylamines can be used to direct both adsorption of CdSe nanocrystals with alkyl ligand shells and covalent reactions with fluorescent dyes, highlighting the utility of functional patterning of the PDMS surface.

Nanostructured Surface Functionalization of Polyacrylamide Hydrogels Below the Length Scale of Hydrogel Heterogeneity

“…In contrast with PDMS, which exhibits background fluorescence at 514 nm, PAAm exhibits a peak near 584 nm (Figure e, right panel, gray trace). μCP-TCD-NH 2 fluorescence intensities are lower than those for full TCD-NH 2 sPDA layers (Figure e,f), consistent with the smaller average molecular domain sizes achieved by μCP in comparison with LS transfer, and our previous observation that transfer efficiency increases with increasing sPDA length …”

“…Figure c–e illustrates this process using both full sPDA monolayers and square patterns of TCD-NH 2 sPDAs assembled on HOPG by microcontact printing (μCP, see the Experimental Methods section for details, and larger fluorescence micrographs of both LS and μCP surface preparation, Figure S2) and then transferred. Fluorescence emission spectra acquired over areas with transferred sPDAs (Figure e) can be fitted to a primary peak near 548 nm, and a set of longer-wavelength peaks, similar to those we have observed previously for sPDAs transferred to PDMS . In contrast with PDMS, which exhibits background fluorescence at 514 nm, PAAm exhibits a peak near 584 nm (Figure e, right panel, gray trace).…”

“…Energy minimized models (Figure b,c) illustrate an edge-to-edge lamellar width of 5.6 nm (Figure c) for the polymerized system, in good agreement with the 5.6 nm periodicity observed by atomic force microscopy (AFM), in Figure d. During polymerization, the relatively weak amine headgroup dimers can break as the DA rehybridizes to form the PDA, leading to modest variability in the lamellar structure in comparison with COOH sPDAs; here, we illustrate the H-bonded form of the sPDA for simplicity.…”

“…We carried out a series of experiments to examine transfer efficiency in relation to PAAm composition. Recently, we have examined the relationship between sPDA polymer length and the efficiency of transfer to PDMS, parametrizing the per-unit reaction probability with the PDA, and the number of linkages to the PDA required to exfoliate it with the bulk PDMS . The previous models were developed by comparing transfer efficiency for molecules with known populations of polymer lengths.…”

“…(g and h) Projected differences in probability of reaction per PDA unit ( p rxn ) and (i) average distance between cross-links ( d cross‑link ), for the range of %T tested. Panel (a) adapted from ref with permission. Copyright 2022 American Chemical Society.…”