Marrying mussel inspired chemistry with photoiniferters: a novel strategy for surface functionalization†
Covalent tethering of well-defined polymer brushes to a surface is a very attractive tool for the tailoring and control of interfacial properties. Herein, a new catechol-based biomimetic photoiniferter agent Dopa-DETC is designed and used to prepare polymer layer modified surfaces through both “grafting to” and “grafting from” strategies. Dopa-DETC contains a catechol unit fragment for anchoring on substrates and N,N-diethyldithiocarbamate groups for photoinitiating polymerization of monomers. For the “grafting to” approach, N-isopropylacrylamide, 2-(dimethylamino)ethyl methacrylate and N-vinylpyrrolidone monomers were firstly polymerized in the presence of the Dopa-DETC agent via UV photoinitiated polymerization. The results of gel permeation chromatography (GPC) demonstrated that the range of polydispersity indices (PDI) of the resulting homopolymers is from 1.3 to 1.7. 1H NMR spectra and re-initiated photopolymerization indicated that the catechol and diethyldithiocarbamyl groups remained at each end of the homopolymer chains. Subsequent successful immobilization of the obtained dopamine end-functionalized polymers on titanium surfaces was characterized by X-ray photoelectron spectroscopy (XPS) and water contact angle measurements. On the other hand, for the “grafting from” method, the Dopa-DETC agent was firstly immobilized on gold surfaces through the aid of dopamine-hydrochloride in a weak alkaline solution (pH 8.5), the homopolymer brushes of poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) and block copolymer brushes of poly (2-(dimethylamino) ethylmethacrylate-b-(3-acrylamide)benzene boric acid) (P(DMAEMA-b-BA)) were grown from the gold surfaces under UV light. The resulting polymer films were characterized by X-ray photoelectron spectroscopy (XPS), contact angle measurements, ellipsometric measurements and reflectance Fourier transform infrared (FTIR) spectroscopy. Overall, the results obtained in the present work highlighted the efficiency of dopamine chemistry coupled with the photoiniferter based surface grafting strategy. We speculate that our approach may open an avenue to prepare functional interfaces.