Block copolymers approach

Fig. 5. Illustration of the block copolymer approach to nanofoam formation...

The successful implementation of the block copolymer approach to polyimide nanofoams requires the judicious combination of polyimide with the thermally labile coblock. The material requirements for the polyimide block are stringent and require thermally stable, high Tg polyimides which can be readily... 

The hard-soft block copolymer approach employed to produce segmental PUs (Section 7.6) has also been used with polyesters, with the hard block formed from 1,4-butadienediol and terephthalic acid while the soft block is provided by oligomeric (approximate molecular weight of 2000 Da) poly(tetramethylene glycol) and is sold under the trade name Hytrel. 

The generation of nanofoam materials by the self-assembled block copolymer approach has been demonstrated. The nanofoam approach has been shown to work for a variety of different polyimide matrices, in combination with a variety of different thermally labile coblocks. Numerous synthetic approaches were surveyed as a means to appropriately functionalized thermally labile coblocks, including group transfer, anionic, ROP living free radical and others. (The block copolymers were prepared either by the poly(amic acid) or poly(amic alkyl ester) precursor to the polyimide.) In each case, microphase separated morpholo-... 

S.-S. Sun, et al. Photovoltaic enhancement of organic solar cells by a bridged donor-acceptor block copolymer approach. Applied Physics Letters, 2007. 90(4) p. 043117. 

Poly(phenylquinoline) (PPQ) is a well-known n-type semiconductor and is used as an electron transport and emission layer in light-emitting diodes (LEDs). ° Its poor solubility led Jenekhe et al to explore the block copolymer approach to improve the processability of PPQ. The authors studied the self-assembling behavior of rod-coil copolymer 43 consisting of PPQ as the rod block and PS as the coil block (Figure 10). 

Carneiro, K. M., F. A. Aldaye, and H. F. Sleiman. 2010. Long-range assembly of DNA into nanofibers and highly ordered networks using a block copolymer approach./Am Chem Soc 132(2) 679-85. 

The block copolymer approach to prepare cychc polymers is very robust. Even at a final polymer concentration of 5.0mg/mL, no crosslinked micelle peak was observed. 

Finally, this chapter discussed the use of block copolymers to examine local relaxations. Relationships between polymer motion, polymer dynamic modes, and paths for extracting regiospecific dynamic information by use of dielectric relaxation spectroscopy were considered. Quantitative applications of the block copolymer approach presented in this chapter are very demanding on the calibration, accuracy, and sensitivity of the dielectric apparatus and on the synthetic precision of the polymer chemist. 

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