Nanoseparated Polymeric Networks with Multiple Antimicrobial Properties

Abstract

P(I-b-EO):The block copolymer P(I-b-EO) was synthesized using anionic polymerization as described in [11]. Characterization by GPC and 1 H NMR revealed a composition of 32 % poly(ethylene oxide) (PEO) by weight and molecular weight of 38 700 g mol ±1 (PDI < 1.1). Nanofabrication: (PaMS-b-HOST): A sample of the PaMS-b-HOST block copolymer was dissolved with a small amount of tetramethoxymethyl glycouril (4 wt.-%) as a crosslinker (CL) and triphenylsulfonium trifluorosulfonate (1.6 wt.-%) as a photoacid generator (PAG) in propylene glycol methyl ether acetate (PGMEA). Spincoating of the mixture onto a silicon substrate produced vertically aligned cylinder nanodomains over the entire substrate. By irradiation through conventional photomasks and subsequent mixed solvent development, a high resolution photopattern was generated. Subsequent strong UV irradiation on the developed pattern activated the depolymerization process of the PaMS building block, forming nanosized holes in spatially controlled micrometer-sized patterns. Photoimaging experiments were performed using a Nikon 248 nm stepper (numerical aperture (NA) = 0.42 and r = 0.5) equipped with a KrF excimer laser (Cymer CX-2LS) in the Cornell Nanofabrication Facility for the first exposure. Subsequent exposure with a JBA 1000 DUV Resist Cure Ramp (450 mJ cm ±2 at 250 nm) followed by heating (115 C for 60 s) was used to crosslink the PHOST matrix. A mixed solvent (cyclohexanone/isopropanol = 1:2 in volume) was used as a developer to form the negative-tone photoresist patterns. The thickness of the polymer films was examined with a P-10 profilometer. A second irradiation step (70 J cm ±2 at 365 nm) was carried out to remove the PaMS block at 80 C under high vacuum (~9 10 ±5 torr). (PaMS-b-I): Poly(a-methyl styrene-b-isoprene) was mixed with 3 wt.-% photoinitiator 2,4,6-trimethylbenzoyldiphenylphosphine oxide, provided by BASF (Product name: Lucirin TPO) to crosslink the poly(isoprene) matrix before the degradation of the cylindrical a-methyl styrene phase. This phosphine oxide is ideal because it has two main advantages over other types of photoinitiators: high light absorbance and fast photobleaching. A UV source (model SCU 110B from UVEX corporation) was used to crosslink the isoprene block using a peak intensity of k = 365 nm during exposure of 3 min. A film of the polymer was spin-coated from a solution of block copolymer and TPO in PGMEA. Subsequent strong UV irradiation on the polymer film activated the depolymerization process of the PaMS building block, forming nanometer-sized holes in spatially controlled micrometer-sized patterns.P(I-b-EO): Samples were prepared by spin-coating (CEE Model 100CB, velocity: 2000 rpm, duration: 53 s) onto silicon wafers from a 0.5 wt.-% PI-b-PEO polymer solution of equal weight THF/chloroform with a specific amount of added inorganic species (GLYMO/Al(O s Bu) 3 ). Crosslinking of the film was achieved in a vacuum oven at 130 C for 1 h. Subsequent calcination was carried out in a furnace at 500 C (temperature ramp: 5 C min ...

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