Covalently attached graft polymer monolayer on organic polymeric substrate via confined surface inhibition reaction
作者：Yang P, Xie JY, Yuan J, Zhang L, Yang, WT
關鍵字：functionalization; inhibition; monolayer; polymer; surfaces
論文來源：期刊
具體來源：JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY
發表時間：2007年
A grafting technique was proposed for the preparation of polymer monolayer on polymeric substrate. On the basis of our recent work on polymer-supported inhibitor (PSI), hydroquinone (HQ) was first implanted onto polypropylene (PP) surface through UV-initiated grafting. The resulting immobilized HQ was used as PSI for the thermal-induced free radical polymerization (FRP) of acrylic acid (AA). The inhibition mechanism was similar to that of free HQ molecule, that is, polymer chain-carrying radical or peroxy radical could be deactivated by abstracting hydrogen atom from hydroxyl group of immobilized HQ, and the resulting oxyradical (semiquinone radical) combined with another active chain free radical. According to this mechanism, a devised redox initiator consisting of sodium hydrogen sulfite and ammonium persulfate was used to initiate FRP of AA in water at low temperature (50 degrees C). High crystalline biaxial oriented PP film with HQ immobilized was deliberately laid in this system as a radical trap to capture poly(acrylic acid) (PAA) short chain radical. Through X-ray photoelectron spectra (XPS) analysis it was found that the atom ratio of C-HQ (carbon in HQ) to C-COOH (carbon in COOH) decreased with prolonging polymerization time and became stable after about 30 min. The formed PAA short chain on the surface showed a distribution of monolayer, and the saturated thickness was calculated as 5-7 angstrom. The degree of polymerization of gaft chain in PAA monolayer was estimated as 15-20 through three different models. Relating to surface coverage being 100% in ideal densely packed PAA monolayer, real monolayer surface coverage in such reaction system was estimated as 12.3-18.5%. This method was expected to give us a general approach for constructing kinds of graft polymer monolayer on polymeric substrate, because the involved chemistry was only common inhibition reaction between immobilized inhibitor (HQ) and FRP system in solution (herein redox initiating system of AA). We named this grafting chemistry as confined surface inhibition reaction.