Polymer-analogous Transformations

The possibility of carrying out not only fast polymerisation processes in turbulent flows, but also polymer-analogous reactions of polymer modification [18,20-22] was exemplified by butyl rubber (BR) chlorination in solution with molecular chlorine. 

Halobutyl rubber is one of the BR species (chlorinated and brominated rubber) having the advantage of being able to be vulcanised with any type of rubber [23]. Due to this, the demand for halobutyl rubber is constantly growing, whereas the demand for BR has dropped. Halobutyl rubber is an excellent raw material for the tyre industry in the manufacture of tubeless tyres, high temperature and conveyor belts, and so on. [24]. Chlorinated rubber is generally produced on a commercial scale. 

Chlorinated BR macromolecules predominantly contain exomethylene groups [structure (2)], up to 90%. The content of endomethylene groups [structure (1)] is about 9%. Macromolecules may also include saturated groups [structure (4)], up to 1%, which are generally formed at low temperatures. The relative content of structures (2) to (1) defines the performance characteristics of chlorobutyl rubber particularly, the thermal load stability and processing stability. Before introducing one chlorine atom per one isoprene unit, in the case of chlorinating BR, an increase of the chlorine content in the polymer (linear relationship) is observed. BR contains up to 50 mol% of the added chlorine. 

The chlorination of BR should be precisely monitored by the amount of chlorine atoms incorporated into the macromolecules. As one chlorine atom is introduced per C = C bond, the MW of a polymer decreases by not greater than 5-10%. If stronger chlorination occurs, a decrease in the C = C bond content in the macromolecules, as well as a high polymer degradation at the expense of the liquid products, is observed. 

Less strict requirements can be imposed on the reaction temperature in the case of BR chlorination in solution because temperature variation in the reaction zone, in the range of 10-55 °C, has a slight effect on the preparation process and the quality of the chlorinated polymer produced. Above 55 C, a fast degradation of chlorinated BR occurs. 

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The transformation of the hydrophobic periphery composed of bromo substituents into a hydrophilic wrapping of carboxylic acid functions was achieved by reacting 31 with (i) n-butyllithium and (ii) carbon dioxide. The polymer-analogous transformation provides water soluble, amphiphilic derivatives of 31 which constitute useful covalently bonded unimolecular models for micellar structures. 

Synthesis and Modification of New Acrylonitrile Polymers and Copolymers with the Use of Polymer-Analogous Transformations of the Nitrile Groups 115... 

In polymer chemistry, there are two known CDSD techniques (i) the chemical modification (polymer-analogous transformation) of homopolymers and (ii) the step-growth copolymerization of monomers with different properties under special conditions. We will address both these techniques. 

The idea of conformation-dependent sequence design via polymer-analogous transformation can be generalized in many respects [23]. Indeed, a special chemical sequence can be obtained not only from a globular conformation any specific polymer chain conformation can play the role of parent. 

The CDSD copolymerization essentially differs in principles and in results from the conformation-dependent polymer-analogous transformation [25]. Such a process can be considered as a variant of template polymerization (also called molecular imprinting) based on the noncovalent binding of polymerizing monomers to a template. 

Other important methods of synthesis of coordination compounds are discussed in detail [1,3,10,11,53,201,202,206,207,316,318,322,690]. In this respect, we emphasize the synthesis of metal-polymers [690,691] and preparation of complexes in the solid phase (mechano- or tribosynthesis) [10,201,202,206]. Additionally to the above-described techniques, the general methods and principles of synthesis of coordination compounds are used to obtain metal-polymers (immediate interaction of polymer ligands and metal salts, template electrosynthesis, polymer-analogous transformations). The last method consists of the polymerization of metal-monomers (metal-containing monomers) and fixation of metal complexes on the polymer... 

The Diels-Alder-route to ladder polymers is clearly a powerful method for the formation of the primary cycloaddition products. The key problem, however, is the polymer-analogous transformation of the primary macromolecules. 

As a consequence of the general chemistry of such a process polyelectrolyte brushes prepared by this technique always require a two-step approach where a neutral brush system is formed in a first step and then charged sites are introduced in a second step. However, one should be aware that such a post-synthetic modification process might lead to additional complications if the transformation is not quantitative or if side reactions occur. For a detailed understanding of the structural behavior of such brushes a homogeneous polymer-analogous transformation throughout the whole brush is a basic requirement. 

Polymers with side anisodiametric groups modeling the molecular structure of low-molecular liquid crystals csm be obtained either through synthesis of monomers with liquid crystalline (mesogenic) groups with subsequent polymerization or throui chemical attachment of molecules of low-molecular liquid crystalline compounds to a polymer chain by way of polymer-analogous transformations. As can be inferred from the bulk of works dealing with this problem, at present, the first of these two methods is used in most cases. 

Those not affecting DP. These involve reactions of functional groups already contained in the polymer molecules Some of these reactions are reversible and are referred to as polymer-analogous transformations. These reactions have been used in polymer-mediated organic syntheses and will be the subject of the bulk of this book. 

Some overlap between categories can occur. For example, the sequential synthesis of a polypeptide on a polymer support is equivalent to grafting the polypeptide onto the original polymer support, whereas each step of the solid-phase peptide synthesis can be regarded as a polymer-analogous transformation. 

Although it is more than two and a half decades since polymer-mediated syntheses were put into practice, few systematic kinetic studies of such reactions have been made. Even detailed kinetic studies of earlier known polymer-analogous transformations, such as the esterification of vinyl... 

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