Random Statistical Copolymers

SCHEME 2.51 Synthesis of perylene-fluorene and a-cyanostilbene-fluorene copolymers via Yamamoto coupling. (From Klarner, G., Lee, J.-I., Davey, M.H., and Miller, R.D., Adv. Mater., 11, 115, 1999.) 

The emission wavelength of PF-PPV copolymer can be red-shifted and the band gap reduced by introducing alkoxy substituents, as demonstrated for compounds 344 [421], Consequently, the transport of both holes and electrons is facilitated and the PLED built in the configuration ITO/PEDOT/344/A1 produces an orange-red color (AEL = 574-592 nm) with a maximum brightness for 344b of 13 50 cd/m2 and a luminous efficiency of 0.51 cd/A, at a rather low turn-on voltage of 2.5 V (Chart 2.87.) 

Jenekhe and coworkers [430] synthesized a phenothiazine-containing alternating fluorene copolymer 352 by Suzuki coupling (Chart 2.89). The phenothiazine-3,7-diyl fragment in the polymer backbone interrupts the conjugation, and substantially blue shifts absorption 

Optical and Electronic Properties of the Fluorene-Perylene Copolymers 

A very efficient energy transfer (producing emission at 613 nm) was observed in PL spectra of the perylene end-capped polymer 361 in solid films. This material had the highest QE ( 60%) among the fluorene- perylene polymers, although the performance of its PLED has not yet been reported [434], 

---

Wang, R, Hickner, M., Kim, Y. S., Zawodzinski, T. A. and McGrath, J. E. 2002. Direct polymerization of sulfonated poly(arylene ether sulfone) random (statistical) copolymers Candidates for new proton exchange membranes. Journal of... 

Direct Copoiymerization of Sulfonated Monomers To Afford Random (Statistical) Copolymers 4595... 

Random copolymers are a special type of statistical copolymer in which the distribution of repeat units is truly random (some words of caution are necessary here because older textbooks and scientific papers often use the term random copolymer to describe both random and non-random statistical copolymers). A section of a truly random copolymer is represented below ... 

Samples tested were styrene copolymers of methacrylates, acrylates, vinyl acetate, and acrylonitrile, in addition to ethyl methacrylate-butyl methacrylate copolymers. These samples were dissolved in the initial mobile phase and the injection volume was 0.05-0.2 mL. These samples were prepared by solution polymerization at low conversion and have rather narrow CCD. These samples are random (statistical) copolymers. 

Novel approaches in PEM synthesis focusing on cheaper, usually fluorine-free PEMs and membranes capable of sustained fuel cell operation at elevated temperatures, have been reviewed in Ref. 75. Mature fuel cell membranes have been casted from sulfonated poly(arylene ether sulfone) (BPSH) random (statistical) copolymers [76]. 

A distinctive advantage of radical polymerization is that a variety of monomer pairs can readily be copolymerized into true random/statistical copolymers. 

A detailed structure characterization of isobutylene and 0-pinene copolymers has been carried out including homogeneity studies (by GPC), quantitative composition and sequence analysis (by PMR and reactivity ratios) and molecular weight determinations (by osmometry and viscometry). Analysis of our data leads us to conclude that isobutylene and 0-pinene can be readily copolymerized to reasonably high molecular weight materials and that the products are perfectly random, statistical copolymers showing no detectable tendency for blockiness . 

Figure 13.1 provides a classification scheme for combinations of two kinds of mers. (With only slight modification, three or more kinds of mers can be accommodated.) First are the random (statistical) copolymers and the alternating copolymers, which usually form one phase. While of great interest both theoretically and commercially, they will not be treated further in this chapter. Most of the remaining materials shown in Figure 13.1 normally exhibit phase separation. 

F. Wang, M. Hickner, Q. Ji, W. Harrison, J. Mecham, T. Zawodzinski, J. E. McGrath, Synthesis of highly sulfonated poly(arylene ether sulfone) random (statistical) copolymers via direct polymerization, Macromol. Symp. 175(1), 387-396 (2001). 

Wang, R, Hickner, M., Ji, Q., Harrison, W., Mecham, J., Zawodzinski, T. A., and McGrath, J. E. 2001. Synthesis of highly sulfonated poly(arylene ether sulfone) random (statistical) copolymers via direct polymerization. Macromol. Symp. 175 387-396. Wang, R, Ji, Q., Harrison, W., Mecham, J., Pormato, R., Kovar, R., Osenar, R, and McGrath, J. E. 2000. Synthesis of sulfonated poly(arylene ether sulfone)s via direct polymerization. Polym. Preprints 41(l) 237-238. 

---