Sol–Gel Preparation of Initiator Layers for Surface-Initiated ATRP: Large-Scale Formation of Polymer Brushes Is Not a Dream

Abstract

We demonstrated for the first time a facile and reproducible preparation of large-scale (∼40 m2) initiator layers for surface-initiated atom transfer radical polymerization (SI-ATRP) using a simple sol–gel solution of (p-chloromethyl)­phenyl­trimethoxysilane and tetraethoxysilane. Highly smooth and transparent initiator layers could be formed on various inorganic/organic substrates via a spin-, wire-bar-, or roll-to-roll-coating without any marked change in surface morphology or bulk properties at room temperature. Combining the advantages of this sol–gel approach and subsequent “paint on” SI-ATRP using a variety of waterborne monomers, we have succeeded in the formation of polymer brushes on large-scale real-life substrates (i.e., maximum 50 × 50 cm2) under ambient conditions (room temperature and open to the air) without any complicated apparatus or harsh reaction conditions.

Translating Surface-Initiated Atom Transfer Radical Polymerization into Technology: The Mechanism of Cu0-Mediated SI-ATRP under Environmental Conditions

“…Previously reported oxygen-tolerant SI-ATRP processes have involved the application of reducing agents, which simultaneously consume oxygen and generate catalytically active Cu Ibased species. [6][7][8][9][10][11][12] Photo-active compounds were also recently applied as oxygen scavengers and polymerization catalysts for metal-free SI-ATRP, enabling the synthesis of microstructured brushes under ambient conditions, with excellent temporal and spatial control. 13 An alternative, highly efficient approach to circumventing the need for deoxygenation relies on the use of zerovalent copper, Cu 0 , which acts as a source of active catalyst, 14,15 simultaneously consuming dissolved oxygen when the polymerization mixture is not directly exposed to air.…”

Growing Polymer Brushes from a Variety of Substrates under Ambient Conditions by Cu0-Mediated Surface-Initiated ATRP

“…Specifically, by exploiting activators regenerated by electron transfer (ARGET) ATRP, various waterborne monomers could be successfully polymerized from large polymeric films in the presence of oxygen, 31 while the application of photocatalysts in light-mediated, metal-free SI-ATRP enabled the fabrication of micropatterned brushes over entire silicon wafers, with high resolution and without the need for deoxygenation of reaction mixtures. 30 Apart from the use of organic "additives" to improve the tolerance of SI-ATRP towards oxygen, Jordan et al demonstrated that Cu 0 -coated plates placed upon initiator-bearing substrates within polymerization mixtures could efficiently act as sources of catalyst, 32 simultaneously consuming oxygen 33 and triggering the rapid growth of a variety of compositionally different brushes.…”

Polymer Brush Coating and Adhesion Technology at Scale

“…Nevertheless, the paint-on method represents the most relevant process industrially, where large surfaces with different geometries may be polymer brush-functionalized. Furthermore, in a recent study by Sato et al, they demonstrated a roll-to-roll coating method using a low-concentration sol–gel solution to functionalize large poly(ethylene terephthalate) (PET) films (0.4 × 100 m 2 ) with an ATRP initiator, at a coating speed of 5 m min −1 ( Figure 3 B) [ 54 ]. Subsequently, “paint-on”-ATRP was demonstrated by spreading a 0.02 mL cm -2 polymerization solution on 40 × 40 cm 2 initiator-functionalized PET films, with another film placed on top, in a sandwich structure.…”

“…Copyright 2019 Elsevier. ( B ) Illustration of a roll-to-roll coating process on poly(ethylene terephthalate) (PET) film, reprinted with permission from Sato et al [ 54 ]. copyright 2018 ACS.…”