Polymer chemical modification

The presence of allylic chlorines and tertiary chlorines and their influence on the thermal stability of PVC has now been established with some degree of confidence, and together they are considered to constitute the labile chlorine structures in the polymer. Numerous chemical modification methods involving the selective nucleophilic substitution of labile chlorines in PVC with other chemical moieties for identifying and quantifying labile structures have been reported in the literature. 

Although, the heat resistance of NBR is directly related to the increase in acrylonitrile content (ACN) of the elastomer, the presence of double bond in the polymer backbone makes it susceptible to heat, ozone, and light. Therefore, several strategies have been adopted to modify the nitrile rubber by physical and chemical methods in order to improve its properties and degradation behavior. The physical modification involves the mechanical blending of NBR with other polymers or chemical ingredients to achieve the desired set of properties. The chemical modifications, on the other hand, include chemical reactions, which impart structural changes in the polymer chain. 

To improve the dimensional stability of the oligoethyleneoxy phosphazene/ metal salt complexes, some attempts have been reported which concern the chemical modification of the parent polymers, their chemical or radiation cross-linking, or the use of blends. 

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. 

Munkholm C., Walt D.R., Milanovich F.P., Klainer S.M., Polymer modification of fiber optic chemical sensors as a method of enhancing fluorescence signal for pEl measurement, Analytical Chemistry 1986 58 1427-1430. 

The first section, Chemical Reactions on Polymers, deals with aspects of chemical reactions occurring on polymers—aspects relating to polymer size, shape, and composition are described in detail. One of the timely fields of applications comprises the use of modified polymers as catalysts (such as the immobilization of centers for homogeneous catalysis). This topic is considered in detail in Chapters 2, 3, 8, 9, and 11 and dealt with to a lesser extent in other chapters. The use of models and neighboring group effect(s) is described in detail. The modification of polymers for chemical and physical change is also described in detail in Chapters 2 (polystyrene) 4 (polyvinyl chloride) 5 (polyacrylic acid, polyvinyl alcohol, polyethyleneimine, and polyacrylamide) 6 (polyimides) 7 (polyvinyl alcohol) 8 (polystyrene sulfonate and polyvinylphosphonate) 10 (polyacrylamide) and 12 (organotin carboxylates). 

REACTIVE GASES AS REAGENTS FOR POLYMER FILMS CHEMICAL MODIFICATIONS... 

This book contains papers presented at the symposium on Polymer Modification held at the National American Chemical Society Meeting in Orlando, Florida, August, 1996. The chemistry presented is broad ranging, and includes grafting and chemical oxidation reactions, and many other chemical modifications. 

M. Langsam, M. Anand and E.J. Karwacki, Substituted Propyne Polymers I. Chemical Surface Modification of Poly [ 1 -(trimethylsilyl)propyne] for Gas Separation Membranes, Gas Sep. Purif. 2, 162 (1988). 

Polymer Structure Modification. Chemical modification of the polymer structure includes the use of tetrahalophthalic acids or anhydrides, diallylphenyl phosphonate, brominated allyl phosphates, chlorendic anhydride, and tetrakishydroxymethyl phosphonium chloride. 

The similarity of BBB and BBL to the vat dyestuffs suggests some alternate methods of forming solutions of these polymers by chemical modifications already well studied on the dyes. Both polymers can be... 

The heat resistance of ABS can be improved by adding a high- Tg polymer, by chemically modifying the SAN copolymer, or by removing low molecular weight plasticizers. This review will not cover the multiphase blend approach, exemplified by extruded mixtures of polycarbonate and ABS. The focus will concentrate on the chemical modification of ABS by the use of a different, continuous-phase styrenic copolymer. 

Hydrogels that are based on natural products are more acceptable from the standpoint of toxicity-related issues and are therefore preferable to azo-based polymers. However, chemical derivatization, if performed without proper understanding, can lead to modifications of the hydrogels to products that will not degrade readily in the colon because it is possible that the new structures will not be recognized by the colonic bacterial enzymes for degradation. Also, bulk degradation is preferred to surface erosion because it... 

These techniques demonstrate that it is possible to change the basic chemistry and, therefore, the properties of wood cell wall polymers through chemical reactions. These chemical modifications can greatly enhance the properties of wood products. 

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