Polymers difunctional reagents

Most aromatic difunctional reagents react with N3P3Cl6 to afford spirocyclic products (20,176,180,181,189,190). With catechol, the trispiro product is observed (190). This product was shown to function as a host in the formation of several inclusion adducts, including polymers (191). Ring degradation of the cyclophosphazene ring occurs in the reaction with o-amino phenol as well as in the reaction with catechol in the presence of a triethylamine (192). 

These structures are well defined by conducting the polymerization in the presence of appropriate mono- and difunctional reagents. They are of considerable interest for the preparation of segmented block copolymers.24,25 For instance, the fluorinated macrodiols 21 have already been used to prepare an interesting new series of partially fluorinated segmented polyurethanes,26 and we are investigating other novel polymers that can be prepared from these intermediates. 

Two different polymers can also be linked together using difunctional reagents which react with the end groups of both polymers... 

This work was extended to difunctional reagents, such as adiponitrile, to give a linear polymer ... 

To determine the extent of reaction of the monomers at gelation, p, it is necessary to determine the critical concentrations of Mj and M2 when the number of crosslinks per chain is 0.5. If the polymer had not contained the difunctional reagent, it would have attained a weight-average degree of polymerization DP under the conditions of polymerization. The gelation condition is then... 

The most obvious synthesis route to such polymers is the use of a difunctional reagent in the macromolecular substitution step. However, this method cannot be employed. For example, the reaction of poly(dichlorophosphazene) with NaOCH2CH2NH2 leads to crosslinking of the chains (Scheme II). Even a small amount of crosslinking in the initial stages of a macromolecular substitution will result in precipitation of the polymer, and this will prevent further halogen replacement. Avoidance of this comphcation requires die use of two alternative strategies. 

The objective of the experiments of the proceeding section was monoprotection of a difunctional reagent. Usually simultaneous single and double binding of the difunctional reagent could not be avoided. A few experiments have been performed to test how many doubly bound species can be formed deliberately, and to create shape-sdective cavities in the polymer, as described in detail in the chapter by Wulff. 

A variety of polyesters can be prepared by varying the diols and dicarboxylic acids. This principle is quite general and can be applied to any system of difunctional reagents that can react with each other. Some of the other important types of condensation polymers are disctissed in the following sections. 

A different strategy from the above consists in the incorporation of silylamino groups on ferrocene. Condensation of such difunctional reagents with disilanols leads to the formation of polymers where the ferrocene groups are separated by organosilicon spacers [28] (Fig. 8.7). 

As with Volume 1 in the series, this Chapter will deal specifically with polyesters, polycarbonates, polyamides, and polyimides. The four groups form a cohesive unit for a number of reasons the kinetics and techniques of synthesis are frequently similar, indeed the same difunctional reagents appear repeatedly as starting materials for synthesis, and their characteristic functional groups form an integral part of the polymer backbone. 

Acid chlorides are useful reagents, but when the pyrazole is N- unsubstituted a dimerization occurs and the diketopiperazine (254) is isolated (Section 4.04.2.3.3(x)). However, (254) reacts with many compounds as an acid chloride would, for example with amines to yield amides (67HC(22)l). The difunctional pyrazole derivative (441) affords polymers by reaction with diphenols (69RRC763). Cyanopyrazoles can be hydrolyzed to the corresponding carboxylic acids (68CB829). 

Typically, the most common precursors to new Si-N-P systems are simple silylaminophosphines (eq 1). The difunctional character of these compounds, which is due to the nucleophilic site at phosphorus and a complementary electrophilic site at silicon, makes them very versatile reagents. They have been used in a new synthesis of alkyl and/or phenyl substituted phospha-zenes (R2PN)jj ( ) and have led to the preparation of promising precursors to potentially electrically conducting polymer systems of general formula (RPN)n>... 

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