Polymers with sulfur-containing substitu

For example, there is considerable interest in the preparation of sulfur-nitrogen polymers that have organic substituents on the sulfur atoms.56 This could help alleviate the intractability problem mentioned, and could also give rise to a series of polymers that parallel the phosphazenes in their structural variability. A series of polymers with S-N backbones of this type has been prepared, but with oxygen atoms as some of the substituents. The basic structure has the repeat unit -RS(=0)(N)- or -FS(=0)(N)-but they have not yet been studied in detail. The fluorine-containing polymer, however, is known to be a tough elastomer which is unaffected by water, acids, or bases up to 100 °C.7... 

In general, the synthesis of polyphosphazene polymers is unique in that, in theory, an infinite number of polymers with a variety of properties can be derived from the common polymeric intermediate, poly(dichlorophosphazene) (PNCI2), by replacing the chlorines with different nucleophiles. If the polydichlorophosphazene precursor is reacted with the sodium salts of trifluoroethanol and a mixed fluorotelomer alcohol, a poly(fluoroaIkoxyphosphazene) elastomer (FZ elastomer) is obtained. It contains a small amount of an unsaturated substituent as a curing site. The polymer is a soft gum, which can be compounded with carbon blacks and fillers and cured with sulfur or peroxides or by radiation. 

This section is concerned with polymers derived from open-chain phosphazenes, phospha(thia)zenes and related cross-linked materials. Cyclolinear and cyclomatrix materials as well as carbon-chain polymers with cyclophasphazene substituents are covered in Section 3. General and specific reviews have appeared including an overview of recent development in inorganic polymers including poly(phosphazenes), a comprehensive survey of hybrid siloxane-phosphazene systems, water-soluble phosphazenes and related hydrogels, a brief survey of polymerization reactions and mechanisms, and sulfur containing poly(phosphazenes). ... 

Sulfur dioxide does not homopolymerize, but on reaction with olefins it yields copolymers.Terminal olefins react more readily than those with an internal double bond. The presence of various substituents affects the rate of polymerization. Conjugated dienes copolymerize with sulfur dioxide to give linear polymers containing residual double bonds. 

An alternative addition of mono- and dianhydrides led to PNl with N-(p-phenoxy) naphthalenecarboximide ortho substituents. PNI prepared by this method (Scheme 13, method B) had r d = 0.27-0.40 dl/g [M = (2.2-3.0) x lO ], and unlike PNl with N-naphthylimide ortho substituents, they showed a partial or complete, in the case of sulfur-containing polymers, solubility in chloroform. These polymers had Tg = 315-350 °C, and the temperatures of the 10% weight loss were in the 480-515 °C range. 

The polymers [S]n and [SN] have been mentioned in Chapter 1. Other sulfur-containing polymers that have already been dealt with so far include those that have P-N-S and P-N-S(O) units as well as those that contain alternate S(0)N and PN units in the polymer backbone. In this section we will briefly look at polymers containing alternate sulfur and nitrogen atoms in the polymer backbone. In these pol5nners sulfur is hexavalent. An oxygen atom and an alky or an aryl group is present as the side-chain substituents on sulfur. 

HPLC is one of the most universal methods for determining the enantiomeric composition of substances and mixtures in a short time frame. Its application is not restricted to molecules in which chirality is based on a quaternary carbon atom with four different substituents it can also be employed for compounds containing a chiral silicon, nitrogen, sulfur, or phosphorus atom. Likewise, asymmetric sulfoxides or aziridines, the chirality of which is based on a lone electron pair, can be separated. Chirality can also be traced back to helical structures, as in the case of polymers and proteins to the existence of atropiso-merism, the hindered rotation about a single bond, as observed, for example, in the case of binaphthol, or to spiro compounds. 

Organotin compounds with Sn-S bonds can be prepared by substituation at tin by sulfur nucleophile. There are many parallels between the chemistry of compounds containing Sn-S bonds and those containing Sn-0 bonds. An important difference between them is that whereas Sn-0 bonded compounds often self-associate to give oligomers or polymers with 5-coordinate tin, the sulfur compounds show fewer tendencies to associate. The Sn-S bonds also less easily cleaved in substitution (e. g. hydrolysis) and addition reactions [54,56]. 

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