Polymer modification reactions

If PTC is not used, then a polar aprotic solvent is essential to solubilize the ionic nucleophile well enough for efficient reaction to occur. Chen has used hexamethylphosphoramide as solvent for the esterification of poly(sodium acrylate) with bromoalkyl mesogens while Pugh and Percec used dimethyl formamide (DMF) for the etherification of sodium 4-methoxybiphenoxide with poly(epichlorohydrin). In a compromise between PTC and single-solvent approaches, Maa and Chen have reported the efficient esterification of acrylic polymers with bromoalkylmesogens in DMF after isolating the tetrabutylammonium salts of the polyac-rylates (tetrabutylammonium compounds are common PT catalysts). 

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An important polymer modification reaction is the grafting to or from a polymer backbone by some chemical method to produce a branched structure Q). The characterization of the products of these reactions is often somewhat less well defined than block copolymers (2) due to the complexity of the mixture of products formed. It is therefore useful to prepare and characterize more well defined branched systems as models for the less well defined copolymers. The macromonomer method (3 ) allows for the preparation of more well defined copolymers than previously available. 

In addition, the polymer modification reactions leading to acidic and ionomeric functionalities are described in detail. The derived ion-containing block copolymers may aid in the correlation of chemical architecture with ionomer morphology and properties. 

Apparatus. Since all the polymer modification reactions presented in this paper involved gas consumption, an automated gas consumption measuring system was designed, fabricated and used to keep constant pressure and record continuously the consumption of gas in a batch type laboratory scale reactor. Process control, data acquisition, and analysis was carried out using a personal computer (IBM) and an interface device (Lab-master, Tecmar Inc.). 

There also have been other reports of polymer-supported catalysts with incorporated boron moieties resulting from multistep polymer modification reactions to incorporate the boron moiety.76... 

Incorporation of nucleic acid bases by polymer modification reactions... 

Process whereby a polymeric monolith is produced through an in situ polymerization or polymer modification reaction. 

One of the time honored polymer modification reactions resulting in heterocyclic polymer formation is reaction of a poly(diene) with maleic anhydride or a maleimide (B-64MI11100). Two modification techniques have, in general, been employed—one catalyzed or initiated, the other not. Although most reports deal with modifications using maleic anhydride, A-alkylmaleimides are reported to behave in a completely analogous fashion. 

The synthesis of poly(vinyl acetals) (252) represents another example of generating a heterocycle, in this case the 1,3-dioxane nucleus, by application of a polymer modification reaction. Generally, the polymer modified is poly(vinyl alcohol) (180) or one of its copolymers. The 1,3-dioxane ring is generated (Scheme 122) by an acid-catalyzed acetalization reaction with an aldehyde, although ketones have also been reacted. A review (71MI11102) is available covering synthesis, properties and applications of the two most common and industrially important poly(vinyl acetals), poly(vinyl butyral) and poly(vinyl formal), as well as many other functional aldehydes that have been attached. 

The poly-L-lysine derivatives containing pendant nucleic add bases can be prepared alternatively by using a polymer modification reaction (Scheme 19). Carboxyeth derivatives of the bases were grafted onto poly-L-lysine by using the activated ester method . PoIy-L-lysine was aUowed to react in this case as trifluoroacetate . ... 

Use of Continuous System Modeling Program (CSMP) to Simulate Polymerization, Polycondensation, and Polymer Modification Reactions... 

This paper illustrates its application to problems encountered in studies on polymer modification reactions, polymer epimerization reactions, p-cresol-formaldehyde condensation reactions, and monomer-promoted polyaddition reactions. A 23-statement CSMP program was written, for example, to duplicate the predictor-corrector program of Bauer for simulating irreversible polymer modification reactions. 

Polymerization, polycondensation and polymer modification reactions are dynamic processes that are often represented by sets of differential equations. Analytical integration of such equations is often difficult or impossible and the solutions that are obtained often have complex forms that provide limited insight concerning the nature of the processes. This has been particular-... 

A large amount of theoretical work has been done on the problem of treating the kinetics of polymer modification reactions (9,10). In addition to the kinetics, the distributions of monomer units among the products of such reactions and the compositional heterogeneity of the products are of interest. The problem of treating irreversible polymer reactions is essentially solved,... 

TITLE REVERSIBLE POLYMER MODIFICATION REACTIONS / CALL ERRSET(209,100,=1,1)... 

The examples discussed herein show that very simple, easily written CSMP programs can be used to treat complex kinetic problems that are encountered in studies on polymerization, polycondensations and polymer modification reactions. It is obvious that CSMP is also applicable to problems involving polymer processing or the dynamic behavior of polymers in solution or bulk. Polymer scientists would be well advised to become familiar with this valuable program. It would also seem important to use CSMP in the classroom. We hope that the instructions and examples provided herein will help others to use CSMP programming effectively and with minimum difficulty. 

Extruders are mechanical devices used to melt and pump polymers. We discuss them here in the context of tubular reactors because extruders resemble them in many ways and may indeed more closely approximate a PER than an open tube. Chapter 16 in Paul et al. (2003) discusses extmders and other devices intended for mixing viscous liquids. Extruders are extremely expensive, provide very little volume for a chemical reaction, and are thus generally unsuited for polymerizations. They can be economically used for polymer modification reactions such as grafting. Although they... 

The same is true for other polymer modification reactions with acrylamide derivatives especially cationic structures for the formation of cationic surface layers. Furthermore acrylamide derivates like methylenediacrylamide are used in various polymerisation reactions and have to be determined in polymer solutions. The polycations formed by a radical polymerization and their reaction products with polyanions (symplexes) have to be characterized when they are used in polymer modification or other fields. 

In the area of enzymatic polymer synthesis, one can distinguish between enzymatic polymerization and enzymatic polymer modification. Of the six main enzyme groups (see Table 3.3), three have been used as catalysts for enzymatic polymerization and four have been used in enzymatic polymer modification reactions. 

References 1 through 7 are comprehensive reviews, and references 8 through 21 are some more specific papers that provide perspectives of these diverse applications. Another chapter in the present volume [2] has been specifically devoted to the polymerization and polymer modification reactions in near-critical and supercritical fluids. The present chapter is focused on miscibility and the kinetics of pressure-induced phase separation that are central to many of the applications. 

Kiran, E. (1998) Polymerization and polymer modification reactions in near and supercritical fluids. Presented at the NATO Advanced Study Institute on Supercritical Fluids, jcmcr, Turkey, July 12-24,1998 [Manuscript is included in this volume]. 

POLYMERIZATION AND POLYMER MODIFICATION REACTIONS IN NEAR AND SUPERCRITICAL FLUIDS... 

Another example of polymer modification reaction is the hydrolysis of cellulose in subcritical and supercritical water [40]. Cellulose is shown to hydrolyze rapidly (<1 s) in supercritical water in the absence of any catalysts to glucose, fructose, and oligomers (cellobiose, cellotriose, etc) with a hydrolysis product yield of about 75 % at 400 °C and... 

Chapter 10. Polymerization and polymer modification reactions in near and supercritical fluids E. Kiran... 

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