Controlled Synthesis of Concentrated Polymer Brushes with Ultralarge Thickness by Surface-Initiated Atom Transfer Radical Polymerization under High Pressure

Abstract

The synthesis of ultrathick concentrated poly-(methyl methacrylate) (PMMA) brushes by atom transfer radical polymerization (ATRP) was investigated. The reactions were performed with a catalyst system of Cu(I)Br/dinonyl-2,2′bipyridine (dN-bipy) and Cu(II)Br 2 /dN-bipy at 60 °C under a high pressure of 500 MPa. The equilibrium constant for this catalyst system was determined to be 1.5 × 10 −6 , which followed the kinetics study and indicated good polymerization rate control. Under the high pressure of 500 MPa, a micrometer scale thick PMMA brush was obtained. During chain growth under the high pressure, the concentration of the deactivator catalyst was demonstrated to significantly affect the graft density of PMMA brushes, which was correlated to the number of monomers added in activation−deactivation cycles. A novel "cutoff" experiment and gel permeation chromatography demonstrated similar propagation for free polymers and graft polymers even under high pressure.

Convenient Synthesis of Very-Thick Concentrated Polymer Brushes by Atom Transfer Radical Polymerization in an Ionic Liquid

“…Despite the origin of the IL effect still being debated, it is understood that the propagation reaction is enhanced by the high polarity and that termination is reduced because of the high viscosity. As was observed for the high-pressure strategy, the IL effect (i.e., higher k p and lower k t ) is expected to lead to very-thick polymer brushes; in this case, the synthesis can be achieved in a straightforward manner that does not require specialized equipment. To this end, we used N , N -diethyl- N -methyl- N -(2-methoxyethyl)­ammonium bis­(trifluoromethanesulfonyl)­imide (DEME-TFSI) , as the ATRP polymerization medium because of the following reasons: the hydrophobicity of DEME-TFSI makes it a good solvent for PMMA, it is easy to handle because of its relatively low viscosity (room-temperature dynamic viscosity: 120 mPa s), the TFSI anion is inert toward the ATRP copper catalyst, and the IL is commercially available.…”

“…In order to synthesize CPBs that are significantly thicker, faster polymerization is required without increasing the premature termination of the growing graft chains. Recently, we investigated the synthesis of PMMA brushes using high-pressure polymerization . By applying SI-ATRP under high-pressure conditions, we successfully increased PMMA brush thickness to the micrometer scale.…”

Durability Improvement of Concentrated Polymer Brushes by Multiscale Texturing

“…The detailed texture patterns are summarised in Section 2.2. CPBs based on poly(methyl methacrylate) (PMMA) were grafted onto the discs with and without surface textures via surface-initiated atom transfer radical polymerisation (SI-ATRP) [24]. The thickness of the CPBs under dry conditions was approximately 1000 nm, as measured via ellipsometry.…”

100th Anniversary of Macromolecular Science Viewpoint: Achieving Ultrahigh Molecular Weights with Reversible Deactivation Radical Polymerization

“…Thick surface coatings have low friction and are more wear-resistant. Recently, ultrathick coatings (1–2 μm) have been achieved on macroscopic silicon wafers by surface-initiated high-pressure ATRP …”

“…Recently, ultrathick coatings (1−2 μm) have been achieved on macroscopic silicon wafers by surfaceinitiated high-pressure ATRP. 65 Challenges and outlook: The field of UHMW polymer synthesis via RDRP is rapidly growing. Despite great success, one of the major current challenges is to further improve synthetic efficiency under metal-free and ever greener conditions.…”