Poly block copolymer film

Only recently first reports appeared describing the potential of the nanostructured thin block copolymer films for lithographic etching. A thin film of polystyrene-block-polybutadiene with a hexagonal cylindrical morphology where the poly-(butadiene) cylinders were oriented perpendicular to the substrate was deposited on a silicon wafer and selectively decomposed by treatment with ozone or converted with osmium tetroxide. By a subsequent reactive ion etching process the pattern could be inscribed into the surface of the silicon wafer yielding small holes or islands with a lattice constant of 27 nm and hole/island sizes of 13 nm [305,312]. 

In another report, a 50 nm thick poly(styrene-h-methylmethacrylate) block copolymer film with spherical domains was prepared on a sodium chloride monocrystal and coated by a thin layer of gold, replicating the domain pattern. Similar results were also obtained with poly(styrene-h-2-vinylpyridines) [113]. 

Fig. 3.52 Left (a) Schematic of intermittent contact mode AFM and phase imaging right (b) intermittent contact AFM phase image of a 30 nm thin block copolymer films on silicon [(poly(isoprene)-b-poly(ferrocenyl dimethylsilane), 29 kg/mol/15 kg/mol], which displays a in-plane worm-like surface pattern of poly(ferrocenyl dimethylsilane) in a matrix of poly (isoprene). From the 2D FFT analysis (inset) an average repeat period of 33 nm was estimated. Reprinted with permission from [116]. Copyright 2000. American Chemical Society...

Local reactions take place, for instance, in unconventional lithography approaches. Here, the surface of a polystyrene-Woc -poly(ter/-butyl acrylate) (PS69o-fr-PtBA12io) block copolymer film comprising reactive ter/-butyl ester moieties at the film surface (skin layer of 8 nm thickness) is locally hydrolyzed by a reactant (trifluoro acetic acid) that is delivered by a soft elastomeric stamp, as shown in Fig. 4.38. Thus, the surface is locally modified to yield poly(acrylic acid), which possess higher friction forces than the unreacted tert-butylester region. 

Nagahama, K., Nishimura, Y., Ohya, Y. and Ouchi, T. (2007) Impacts of stereoregularity and stereocomplex formation on physicochemical, protein adsorption and cell adhesion behaviors of star-shaped 8-arms poly(ethylene glycol)-poly(lactide) block copolymer films. Polymer, 48, 2649-2658. 

Microphase-separated block copolymer films have been investigated by numerous authors (257,258). van den Berg and co-workers reported on the film structures of poly(styrene-6Zoc butadiene-6Zoc -styrene) (SBS) triblock copolymers of PB and PS (259). In particular, the effect of film thickness on the observed morphology was unraveled for this system. 

Nagahama K, Ohya Y, Ouchi T. Suppression of cell and platelet adhesion to star-shaped 8-armed poly(ethylene glycol)-poly(L-lactide) block copolymer films. Macromol Biosci 2006 6 412--119. 

Ni SR, Zhang P, Wang YC, Winnik MA (1994) Energy-transfer studies of the boundary-layer interphase in polystyrene poly(methyl methacrylate) block-copolymer films. Macromolecules 27(20) 5742-5750. doi 10.1021/ma00098a031... 

Hedrick et al. reported imide aryl ether ketone segmented block copolymers.228 The block copolymers were prepared via a two-step process. Both a bisphenol-A-based amorphous block and a semicrystalline block were prepared from a soluble and amorphous ketimine precursor. The blocks of poly(arylene ether ether ketone) oligomers with Mn range of 6000-12,000 g/mol were coreacted with 4,4,-oxydianiline (ODA) and pyromellitic dianhydride (PMDA) diethyl ester diacyl chloride in NMP in the presence of A - me thy 1 morphi 1 i nc. Clear films with high moduli by solution casting and followed by curing were obtained. Multiphase morphologies were observed in both cases. 

Gong, Y., Huang, H., Hu, Z., Chen, Y, Chen, D Wang, Z. and He, X. (2006) Inverted to normal phase transition in solution-cast polystyrene-poly(methyl methacrylate) block copolymer thin films. Macromolecules, 39, 3369-3376. 

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