Polymer Analog Reactions

There are a variety of reaction systems that allow the formation of cellulose trinitrate [9046-47-3]. HNO in methylene chloride, CH2CI2, yields a trinitrate with essentially no degradation of the cellulose chain (53). The HNO /acetic acid/acetic anhydride system is also used to obtain the trinitrate product with the fiber stmcture largely intact (51,52). Another polymer analogous reaction utilises a 1 1 mixture of HNO and H PO with 2.5% P2O5 to achieve an almost completely nitrated product (54). 

The chemical modification of poly (2,6-dimethyl-l,4-phenylene oxide) (PPO) by several polymer analogous reactions is presented. The chemical modification was accomplished by the electrophilic substitution reactions such as bromination, sulfonylation and acylation. The permeability to gases of the PPO and of the resulting modified polymers is discussed. Very good permeation properties to gases, better than for PPO were obtained for the modified structures. The thermal behavior of the substituted polymers resembled more or less the properties of the parent polymer while their solution behavior exhibited considerable differences. 

In order to determine the necessity and/or the length of the spacer that is required to achieve liquid crystalline behavior from flexible vs. rigid polymers, we have introduced mesogenic units to the backbones of a rigid [poly(2,6-dimethyl-l,4-phenylene oxide) (PPO)] and a flexible [poly(epichlorohydrin) (PECH)] polymer through spacers of from 0 to 10 methylene groups via polymer analogous reactions. 

The attachment of mesogenic units to a polymer backbone via polymer analogous reactions is not a new concept, although they are much less frequently used than the polymerization of mesogen containing monomers. Liquid crystalline polyacrylates,... 

In contrast to the substituted PPO s, It Is theoretically possible to obtain the same substituted PECH s by homopolymerization of the corresponding mesogenic oxirane, or by its copolymerization with epichlorohydrin. We have attempted these polymerizations in order to better interpret the thermal behavior of the more complicated copolymers that we have obtained by polymer analogous reactions. Homopolymerization would be instructive because the incorporation of nonmesogenic units into liquid crystalline homopolymers doesn t as a rule change the type of mesophase obtained (5). 

These results demonstrate that side-chain liquid crystalline polymers can be synthesized by polymer analogous reactions from theoretically any polymer backbone. When the polymer backbone is rigid, as in the case of PPO, a long spacer is required both to decrease the Tg of the parent polymer and to partially decouple the... 

The synthesis of block copolymers with blocks of ultralow cohesion energy densities on the basis of polystyrene-6-polybutadiene via two highly efficient polymer analogous reactions has been presented. 

We are able to functionalize our polyphenylene dendrimers via three different methods the use of functionalized cyclopentadienones, polymer-analogous reactions (group conversions), and electrophilic aromatic substitution. 

Scheme 15. Polymer-analogous reactions on polyphenylene dendrimers...

To obtain PVA, PVAc is saponified in a polymer analogous reaction using methanolic sodium hydroxide. The reaction 5 in Fig. 2, which is better described as a transesterification rather than a simple basic hydrolysis, leads to PVAs with different degrees of saponification (see Fig. 4). 

The third possibility for synthesizing polymeric substances is the modification of existant natural or synthetic macromolecules (see Chap. 5). These processes can either be chemical or physical. Chemical modifications are reactions on macromolecules without degradation of the main chain (macromolecular substitution routes, polymer-analogous reactions ) like, for example, hydrolysis. 

Table 2.5. Modification of macromolecules via polymer analogous reactions...

This is as a rule not possible as these data are not available for high-molecular-weight samples. In order to be able to exclude the influence of the distribution of degree of polymerization for various polymer structures, polymer analogous reactions may be carried out, where polymers of differing chemical structures and molecular weights, but with the same distribution of degree of polymerization are obtained (e.g., Kulicke, Horl 1985). Of particular interest in this report are polyelectrolytes. 

Reactions of intermediates with cellulose will be polymer-analogous reactions. The reaction will occur more or less randomly along the polymer chain and will thus likely be difficult to prove or to relate to specific locations along the polymer chain. 

This article surveys the research work on the synthesis and modification reactions of poly(ethyleneimine) as well as its applications to metal complexation processes. Poly-(ethyleneimine), one of the most simple heterochain polymers exists in the form of two different chemical structures one of them is branched, which is a commercially available and the other one linear which is synthesized by cationic polymerization of oxazoline monomers and subsequent hydrolysis of polyf(/V acylimino)cthylcne]. The most salient feature of poly(ethyleneimine) is the simultaneous presence of primary, secondary, and tertiary amino groups in the polymer chain which explains its basic properties and gives access to various modification reactions. A great number of synthetic routes to branched and linear poly(ethyleneimine)s and polymer-analogous reactions are described. In addition, the complexation of polyfethyleneimine) and its derivatives with metal ions is investigated. Homogeneous and heterogeneous metal separation and enrichment processes are reviewed. 

A sulfur atom can be introduced into the side chain of PS-g-PEI by polymer-analogous reaction with ethylene sulfide [83]. 

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