Plasma induced grafting of PSt onto titanium dioxide powder. II

Electron beam irradiation grafting of metal-organic frameworks onto cotton to prepare antimicrobial textiles

Textiles modified with antimicrobial nanomaterials have excellent comprehensive performance. However, the shedding of nanoparticles often occurs in actual use. This not only reduces the service life of antimicrobial textiles, but also causes potential harm. Here, we report a new method to covalently immobilize a zinc-imidazolate MOF (ZIF-8) onto cotton fabric by electron beam irradiation to prepare antimicrobial textiles with excellent durability. A series of characterization analysis showed the electron beam irradiation did not damage the structure of the ZIF-8 nanoparticles and the particles were successfully introduced onto cotton fibers via poly hydroxyethyl acrylate (PHEA). The modified cotton fabric exhibited >99% inhibition of Escherichia coli, Staphylococcus aureus and Candida albicans. The results of dry cleaning and rub resistance tests showed that the prepared antimicrobial cotton fabric had significant durability which was attributed to the strong covalent binding between the MOF and textile.

Controlled nitroxide-mediated styrene surface graft polymerization with atmospheric plasma surface activation

Polymer layer growth by free radical graft polymerization (FRGP) and controlled nitroxide-mediated graft polymerization (NMGP) of polystyrene was achieved by atmospheric pressure hydrogen plasma surface activation of silicon. Kinetic polystyrene layer growth by atmospheric pressure plasma-induced FRGP (APPI-FRGP) exhibited a maximum surface-grafted layer thickness (125 A after 20 h) at an initial monomer concentration of [M] 0 = 2.62 M at 85 degrees C. Increasing both the reaction temperature ( T = 100 degrees C) and initial monomer concentration ([M] 0 = 4.36 M) led to an increased initial film growth rate but a reduced polymer layer thickness, due to uncontrolled thermal initiation and polymer grafting from solution. Controlled atmospheric pressure plasma-induced NMGP (APPI-NMGP), using 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO), exhibited a linear increase in grafted polystyrene layer growth with time due to controlled surface graft polymerization as well as reduced uncontrolled solution polymerization and polymer grafting, resulting in a polymer layer thickness of 285 A after 60 h at [TEMPO] = 10 mM, [M] 0 = 4.36 M, and T = 120 degrees C. Atomic force microscopy (AFM) surface analysis demonstrated that polystyrene-grafted surfaces created by APPI-NMGP exhibited a high surface density of spatially homogeneous polymer features with a low root-mean-square (RMS) surface roughness ( R rms = 0.36 nm), similar to that of the native silicon surface ( R rms = 0.21 nm). In contrast, polymer films created by APPI-FRGP at [M] 0 = 2.62 M demonstrated an increase in polymer film surface roughness observed at reaction temperatures of 85 degrees C ( R rms = 0.55 nm) and 100 degrees C ( R rms = 1.70 nm). The present study concluded that the current approach to APPI controlled radical polymerization may be used to achieve a grafted polymer layer with a lower surface roughness and a higher fractional coverage of surface-grafted polymers compared to both conventional FRGP and APPI-FRGP.

Inorganic surface nanostructuring by atmospheric pressure plasma-induced graft polymerization

Surface graft polymerization of 1-vinyl-2-pyrrolidone onto a silicon surface was accomplished by atmospheric pressure (AP) hydrogen plasma surface activation followed by graft polymerization in both N-methyl-2-pyrrolidone (NMP) and in an NMP/water solvent mixture. The formation of initiation sites was controlled by the plasma exposure period, radio frequency (rf) power, and adsorbed surface water. The surface number density of active sites was critically dependent on the presence of adsorbed surface water with a maximum observed at approximately a monolayer surface water coverage. The surface topology and morphology of the grafted polymer layer depended on the solvent mixture composition, initial monomer concentration, reaction temperature, and reaction time. Grafted polymer surfaces prepared in pure NMP resulted in a polymer feature spacing of as low as 5-10 nm (average feature diameter of about 17 nm), an rms surface roughness range of 0.18-0.72 nm, and a maximum grafted polymer layer thickness of 5.5 nm. Graft polymerization in an NMP/water solvent mixture, however, resulted in polymer feature sizes that increased up to a maximum average feature diameter of about 90 nm at [NMP] = 60% (v/v) with polymer feature spacing in the range of 10-50 nm. The surface topology of the polymer-modified silicon surfaces grafted in an NMP/water solvent mixture exhibited a bimodal feature height distribution. In constrast, graft polymerization in pure NMP resulted in a narrow feature height distribution of smaller-diameter surface features with smaller surface spacing. The results demonstrated that, with the present approach, the topology of the grafted polymer surface was tunable by adjusting the NMP/water ratio. The present surface graft polymerization method, which is carried out under AP conditions, is particularly advantageous for polymer surface structuring via radical polymerization and can, in principle, be scaled to large surfaces.