Conjugated example: poly

Alkadienes, alkatrienes, and alkatetraenes (poly-enes). These are unsaturated aliphatic hydrocarbons containing two, three, or four C = C double bonds, respectively. Alkadienes are also called diolefins or dienes, and alkatrienes are also known as triolefins or tricncs. Alkenes containing multiple double bonds fall under the general class of poly-enes. Double bonds that alternate with single bonds in a straight chain are said to be conjugated. Examples are... 

There have been very few examples of PTV derivatives substituted at the vinylene position. One example poly(2,5-thienylene-1,2-dimethoxy-ethenylene) 102 has been documented by Geise and co-workers and its synthesis is outlined in Scheme 1-32 [133]. Thiophene-2,5-dicarboxaldehyde 99 is polymerized using a benzoin condensation the polyacyloin precursor 100 was treated with base to obtain polydianion 101. Subsequent treatment with dimethyl sulfate affords 102, which is soluble in solvents such as chloroform, methanol, and DMF. The molar mass of the polymer obtained is rather low (M = 1010) and its band gap ( ,.=2.13 eV) is substantially blue-shifted relative to PTV itself. Despite the low effective conjugation, the material is reasonably conductive when doped with l2 (cr=0.4 S cm 1). 

The B block may consist of a water-soluble polymer, for example, poly(aspartic acid) P(Asp), that is rendered hydrophobic by the chemical conjugation of a hydrophobic drug (Yokoyama et al., 1992, 1993, 1996 Nakanishi et al., 2001), or is formed through the association of two oppositely changed polyions (polyion complex micelles) (Hatada etal., 1995,1998 Kataoka etal., 1996). Drugs used to couple the B block include cyclophosphamide, doxorubicin, cisplatin, pyrene, and iodine derivative of benzoic acid (Kwon and Kataoka, 1995 Trubetskoy et al., 1997 Yu etal., 1998). 

Conjugation to poly(ethylene glycol) (PEG), or PEGylation, is a well-established approach in protein stabilization (which is described in Section 8.2.3). PEGylation can also be used to increase the water solubility of drugs. For example, conjugation to PEG increases the aqueous solubility of paclitaxel and its derivatives [4] (Table 8.2 and Figme 8.2). The increase in solubility is... 

As an example of RBS applied to a polymer system, figure 3.22 shows the spectrum obtained from a sample of the conjugated polymer poly(phenylene, vinylene) after exposure to arsenic pentafluoride vapour (Masse et al. 1990). This dopant diffuses into the polymer and reacts with it to form an electrically conducting complex and RBS is well suited to following the kinetics of the doping process by providing concentration-depth profiles of the elemental components of the dopant as a function of time. The peaks in the spectrum... 

Poly (thiophene)s are of particular interest as electfochromic materials owing to their chemical stability, ease of synthesis and processability. For the most part, current research has been focused on composites, blends and copolymer formations of several conjugated polyheterocyclics, polythiophene and its derivatives, especially PEIX)T. In one example, poly(3,4-ethylenedioxythiophene) (PEDOT)/poly(2-acrylamido-2-methyl-l-propanesulfonate) (PAMPS) composite films were prepared by Sonmez et al. for alternative electrochromic applications [50]. Thin composite films comprised of PEDOT/PAMPS were reported to switch rapidly between oxidized and neufial states, in less than 0.4 s, with an initial optical contrast of 76% at A.max. 615 nm. Nanostructured blends of electrochromic polymers such as polypyrrole and poly(3,4-ethylenedioxythiophene) were developed via self-assembly by Inganas etal. for application as an electrochromic window [26]. Uniir etal. developed a graft-type electrochromic copolymer of polythiophene and polytetrahydrofuran for use in elecfiochromic devices [51]. Two EDOT-based copolymers, poly[(3,4-ethylenedioxythiophene)-aZ/-(2,5-dioctyloxyphenylene)] and poly[(3,4-ethylenedioxythiophene)-aft-(9,9 -dioctylfluorene)] were developed by Aubert et al. as other candidates for electrochromic device development [52],... 

Factors such as charge (Shen and Ryser, 1978), or the specific characteristics of the ligands and receptors (Salzman and Maxfield, 1989 Dunn et al, 1989 Tartakoff, 1987) will also influence endocytosis and the fate of endosomes. The conjugation of poly(L-lysine) to HRP, for example, has been observed to result in a 200-fold increase in uptake of the HRP by cultured mouse fibroblasts. This was concluded to be a result of the addition of a strong cationic charge to the HRP (Shen and Ryser, 1978). 

The foregoing paragraphs were concerned with the description of the redox behavior of the conducting polymers, but nothing was said about the influence of chemical substituents in the parent monomer and their influence on the redox activity. In fact, these have a considerable influence and a substantial amount of work has been done on this aspect. The main effect of the substituents is to disrupt the degree of conjugation in the polymer and thus decrease its conductivity. This in turn reduces the redox activity. For example, poly(yV-methylpolypyrrole) shows very reduced redox activity and poor electronic conductivity. 

All 7r-conjugated poly (ary lene)s change their color when electrochemically oxidized and reduced (cf. equation (5.10)). This phenomenon is called electro-chromism and much effort has been made to derive practical benefits from it [42]. For example, poly(vinyl alcohol) having PTh pendant group serves as an excellent polymer electrolyte showing electrochro-mism [43a,b] poly(vinyl alcohol) serves as an excellent... 

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