Sulfinyl polymers

A -sulfinylacetamide 297 in greater than 90% yield when a catalytic amount of methyltrioxorhenium is employed. Futhermore, the hetero-Diels-Alder adduct is highly soluble in both chlorinated and ethereal solvents. A detailed investigation of the retro-Diels-Alder reaction of 298 by thermogravimetric analysis revealed an onset temperature of 120 °C and complete conversion of bicycle 298 to pentacene 296 at 160 °C, which are temperatures compatible with the polymer supports typically used in electronics applications. The electronic properties of these newly prepared OTFTs are similar to those prepared by traditional methods. Later improvements to this chemistry included the use of A -sulfinyl-/< r/-butylcarbamate 299 as the dienophile <2004JA12740>. The retro-Diels-Alder reaction of substrate 300 proceeds at much lower temperatures (130 °C, 5 min with FlTcatalyst 150 °C, Ih with no catalyst). 

The most common nonionic surfactants are those based on ethylene oxide, referred to as ethoxylated surfactants. Several classes can be distinguished alcohol ethoxylates, alkyl phenol ethoxylates, fatty acid ethoxylates, sorbitan ester ethoxylates, fatty amine ethoxylates, and ethylene oxide-propylene oxide copolymers (sometimes referred to as polymer surfactants). Another important class of nonionics are the multihydroxy products such as glycol esters, glycerol (and polyglycerol) esters, glucosides (and polyglucosides), and sucrose esters. Amine oxides and sulfinyl surfactants represent nonionic with a small head group. 

Synthesis via the sulfinyl route led to a reduced number of defects on the MDMO-PPV donor polymer and showed some improved performances in MDMO-PPV PCBM bulk heterojunctions [ 167,168]. The lower defect density resulted in a more regioregular (head-to-taU) order within the MDMO-PPV, leading to charge carrier mobihty improvements and ultimately to an improved efficiency of 2.65% for MDMO-PPV PCBM based bulk heterojimc-tions [ 169]. This was accompanied by a fill factor of 71% [169], which to date has not been exceeded by any other polymer solar cell device. 

Alternatively, Liskamp s group [175] initially reported the use of j8-substituted sulfinyl chlorides 119 (Fig. 19) as activated monomers. NMM-mediated coupling to the polymer-bound amine led to the corresponding sulfinamide, which was further oxidized (Os04/A-methylmorpholine-iV-ox-ide) to sulfonamide on the solid support [66]. However, the yield of the oxidation step is highly dependent on the sequence of the peptidosulfon-amide. Hence the former method utilizing /3-sulfonyl chloride derivatives 117 is preferred [174]. 

Recently, a new synthetic route toward PPV and its derivatives has been reported in which the monomer is polymerized toward a dithiocarbamate precursor polymer by the additimi of a strong base. The corresponding conjugated polymer is obtained via a heart treatment of the precursor polymer. This dithiocarbamate precursor route represents a compromise between several straightforward but sometimes troublesome precursor routes and the more complex sulfinyl precursor route [134]. 

A number of potential drug carriers are described in the literature, e.g. polyphospha-zenes derivatives of poly(methacrylic acid) >, synthetic poIy(amino acids)polyvinyl analogs of nucleic adds , poly(ethylene oxide) copolymers of vinylpyrrolidone poly(amido-amines) and others. The structure of these polymers has been modified by the incorporation of hydrophobic units - >, sugar residues, sulfinyl groups to achieve, in a non-specific way, affinity for certain tissues. 

The sulfinyl precursor route is distinct from other radical/anionic polymerizations as the monomer is nonsymmetric (Scheme 7.2d). This means the polymer synthesis is more controlled and it is possible to achieve regiore-gular PPV materials. However, the monomers are more difficult to prepare (Scheme 7.3). Starting from the bis-sulfonium monomer 20, reaction with one... 

The first decision in choosing a synthetic method for a PPV material is the way in which the material will be processed (Scheme 7.8). The precursor routes will enable the preparation of solvent-resistant and more durable thin films of PPV. This is particularly desirable if a multilayer device structure is required for the application. When choosing different precursor methods, it is important to assess the criteria of the application. Most precursor methods involve a thermal elimination step to convert the precursor polymer to the PPV material. Sul-fonium precursors require higher-temperature elimination compared to sulfinyl precursors. This makes the sulfinyl route compatible with deposition on plastic substrates. Another factor to consider in precursor methods is the nature of the elimination byproducts. Sulfonium precursors convert to PPV with elimination of acids, such as HCl or HBr, which has been shown to be detrimental to device performance. Xanthate and dithiocarbamate routes involve the elimination of amine and CO2 and CS2, respectively. 

Sulfinyl or Louwet-VaruJerainde Precursor Route. The development of sulfinyl precursor polymers by Louwet et al. [996-998] has overcome many of the drawbacks of the previous precursor routes. 

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