PS-fc-PMMA

The oxocarbenium perchlorate C(CH20CH2CH2C0+C104 )4 was employed as a tetrafunctional initiator for the synthesis of PTHF 4-arm stars [146]. The living ends were subsequently reacted either with sodium bromoacetate or bromoisobutyryl chloride. The end-capping reaction was not efficient in the first case (lower than 45%). Therefore, the second procedure was the method of choice for the synthesis of the bromoisobutyryl star-shaped macroinitiators. In the presence of CuCl/bpy the ATRP of styrene was initiated in bulk, leading to the formation of (PTHF-fc-PS)4 star-block copolymers. Further addition of MMA provided the (PTHF-fr-PS-fc-PMMA)4 star-block terpolymers. Relatively narrow molecular weight distributions were obtained with this synthetic procedure. 

Fig. 10 Schematic representation of the nanoreplication processes from block copolymers, a Growth of high-density nanowires from a nanoporous block copolymer thin film. An asymmetric PS-fc-PMMA diblock copolymer was aligned to form vertical PMMA cylinders under an electric field. After removal of the PMMA minor component, a nanoporous film is formed. By electrodeposition, an array of nanowires can be replicated in the porous template (adapted from [43]). b Hexagonally packed array of aluminum caps generated from rod-coil microporous structures. Deposition of aluminum was achieved on the photooxidized area of the rod-coil honeycomb structure (Taken from [35])...

Scheme 1 Synthesis of surface-immobifized dibfock copofymer brush (Si/Si02//PS-fc-PMMA) using a combination of carbocationic pofymerization and ATRP...

Fig. 1 AFM image of the tethered Si/Si02//PS-fc-PMMA brushes with 23 nm thick PS layer and 14 nm thick PMMA layer after treatment with dichloromethane at room temperature for 30 min and drying with a clean air stream...

Similar 2D surface micelles were observed at the water-air interface with nonionic block copolymers like PS-h-PnBMA, PS-fc-PtBMA, PS-h-PtBA [28, 29], PS-fc-PMMA [30], PODCMA-h-PMMA [31] and PS-fc-PEO [32]. 

PS-fc-PMMA Poly(styrene-fc/ocfc-methyl methacrjdate)... 

PS-fc-PMMA (diblock polystyrene polymethylmethacrylate) is one of title typical diblock polymers. " Nanostructure fabrication of direct self-assembly... 

PS-fc-PMMA is composed of 46.1 kg/mol PS and 21 kg/mol PMMA. PS-r-PMMA (random block polystyrene polymethylmethacrylate) is 5.3 kg/mol hydroxyl terminated PS copolymerized with 3.3 kg/mol PMMA at random. Solutions of PS-r-PMMA in toluene (1.5%) are spin-coated at 4000 rpm onto a cleaned Si wafer. The coated Si wafer is then annealed at 175°C for 2 days under vacuum. The substrates are sonicated in toluene to remove ungrafted polymer. On these Ps-r-PMMA grafted wafers, solutions of cylinder-forming Ps-l7-PMMA in toluene (1.0%) are spin-coated to produce films with the thickness of 20-25 nm. These coated thin films are annealed at 190°C for 1 day under vacuum to fabricate PMMA cylinders perpendicular to the substrate surface. The diameter and pitch of the PMMA cylinders are approximately 20 and 40 nm, respectively. This stripe pattern in the Ps-l7-PMMA layer is produced by the difference of surface tensions between PS and PMMA on hydroxyl-terminated PS-r-PMMA. Figure 3.22 shows nanoporous structures fabricated by DSA. Electron beam PS-I7-PMMA film is then exposed to the electron beam as shown in Figure 3.22b. PS is crosslinked by electron beam. 

The Russell group has applied the template synthesis approach to nanoporous films generated from UV-treated PS-fc-PMMA copolymers [43, 147,233,235,241], which were pre-aUgned perpendicular to the substrate by an electric field. Through direct current electrodeposition, they fabricated high-density vertical arrays of ferromagnetic cobalt nanowires (Fig. 10a) [43]. Through subsequent work, they also demonstrated the successful rephcation... 

There are of course some problems associated with the use of block copolymers for bit-patterned media. The first lies with the traditionally used block copolymer for most studies to date, PS-fc-PMMA. The relatively weak segregation strength of PS-( -PMMA (x = 0.06) (Russell etfll., 1990) means that an Lq of 20nm (Mn 30000g/mol) is the smallest critical dimension possible before the polymer will fail the condition > 10.5, meaning the polymer... 

When the homopolymer is comparable in size to the BC the homopolymer will segregate to the middle of the appropriate BC domain and produce a larger interlameUar spacing than the observed-for wet brush regime described previously. In this situation, described as dry brush the brush layer formed by the BC is not interpenetrated by the homopolymer. The latter forms a separate phase. This behavior has been illustrated in different mixtures, such as PS or PMMA homopolymers with symmetric short polystyrene-block-poly(methyl methacrylate) (PS-fc-PMMA) diblock copolymers where the... 

The miscibility in these types of blends is also governed by the subslrate/polymer interactions. Green et al. [189] examined the influence of this parameter on the miscibility and thus, the final morphology. Their study on PS/PS-fc-PMMA blends indicates that the PS component resides at the free surface while PMMA is in contact with the substrate. The thickness of the other layers increased with increasing PS (25 kD) homopolymer content (Figure 15.20). 

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