Plasmon‐Polariton Induced, “from Surface” RAFT Polymerization, as a Way toward Creation of Grafted Polymer Films with Thickness Precisely Controlled by Self‐Limiting Mechanism

Abstract

field enhancement, surface plasmons also generate the so-called "hot electrons," arising from the nonradiative relaxation of the excited free electrons, which can activate the spatially close compounds. [7,8] Both phenomena become widely used in the field of plasmon-catalysis and chemical transformation. [9,10] Starting from the first observation of plasmon-induced amino or nitro groups transformations [11,12] the range of available plasmoninduced chemical reaction has grown exponentially and currently covers many essential fields of chemical technology and organic chemistry such as hydrogen dissociation, [13] water splitting, [14,15] hydrocarbon conversion, [16] click chemistry reaction, [17] just to mention a few.One of the more interesting and, so far, less explored avenues of plasmon-induced reactions is highly localized and controlled polymerization process. [18][19][20] First reports of plasmon-triggered polymerization refer to utilization of two-photon lithography and production of structures with subwavelength resolution in the common photoresist. [21,22] Plasmon-activated polymerization is not restricted to lithographic resist area. Recently the plasmon-assisted photopolymerization was also reported as a method for encapsulation of the noble metal nanoparticles by a variety of nonphoto-cross-linkable polymers. [23,24] The perfect control over the thickness of the polymer layer and the spatially resolved polymer growth was achieved by varying of illumination time, light wavelength, and monomers applied. [25,26] The plasmon-induced nature of the polymerization was convincingly confirmed by the comparison of plasmon intensity distribution and the volumes in which the polymer was formed. [27][28][29] So, the plasmon-induced polymerization can also be used to control polymer grafting to the plasmonic surface. [25,30] Moreover, it can be expected that the utilization of plasmon phenomena will facilitate the preparation of well-ordered polymer ad-layer with the plasmon defined thickness. In this paper, we propose the reversible addition-fragmentation chain-transfer (RAFT) polymerization as an example of plasmon inducing "from surface" polymerization. The RAFT polymerization is Plasmon-induced "from surface" reversible addition-fragmentation chain-transfer (RAFT) polymerization is reported for the first time. The gold grating surface, supporting the surface plasmon polariton excitation and propagation, is grafted with RAFT agent, immersed in the solution, containing the NIPAm monomer and AIBN and subsequently illuminated at a wavelength corresponding to plasmon absorption. The grafting of the polymer layer, its thickness, and morphology are characterized by several techniques (including the surface-enhanced Raman spectroscopy (SERS), scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM-EDX), X-ray photoelectron spectroscopy (XPS), nanomechanical atomic force microscopy (AFM) mapping, and goniometry). It is shown that the polymerization efficiently starts only under the surface plasmon-polar...

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“…The plasmon can be considered as one the most groundbreaking approach for the activation of organic reactions. [1][2][3][4][5][6][7][8] Nowadays, plasmon activation has been widely applied for the Pd-catalyzed cross-coupling reactions, [9][10][11] hydrogenation, [12][13][14][15] cycloaddition, 16,17 oxidative reactions, [18][19][20] polymerization, [21][22][23] methane reforming, 24 and so forth, whereby the utilization of plasmon allows achieving good yield of desired compounds under extremely mild conditions. Nevertheless, despite these impressive advances, the exact mechanism of plasmon activation of organic compounds has not been fully described yet.…”

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