Polystyrene, reactive functional

A great variety of suitable polymers is accessible by polymerization of vinylic monomers, or by reaction of alcohols or amines with functionalized polymers such as chloromethylat polystyrene or methacryloylchloride. The functionality in the polymer may also a ligand which can bind transition metal complexes. Examples are poly-4-vinylpyridine and triphenylphosphine modified polymers. In all cases of reactively functionalized polymers, the loading with redox active species may also occur after film formation on the electrode surface but it was recognized that such a procedure may lead to inhomogeneous distribution of redox centers in the film... 

Sophiamma, P. N. Sreekumar, K. Polystyrene-Based Hydroxamic Esters Preparation and Application as Acyl Transfer Reagents, Reactive Functional Polymers 1997, 35, 169. 

Next to ion exchange resins, the polymeric supports most likely to be used for catalysts are other cross-linked polystyrenes or silica gels. Both are inexpensive, easy to functionalize, and void of other reactive functional groups. Their limitations are the thermal and physical stability of polystyrene and the solubility of silica in alkali. Polystyrene can be derivatized by almost every known reaction of mononuclear aromatic hydrocarbons, and the conditions for those reactions on polymers have been published and reviewed (2D- The surface of silica gel can be covered with a wide range of organic materials by reaction of its hydroxyl groups with silyl esters and chlorosilanes f381. 

The first resins used for sequencing were derived from cross-linked polystyrene beads, primarily because of their availability and chemical stability and ease of introducing reactive functional groups [synthetic methods are discussed in more detail by Laursen (1975b)]. Two polystyrene-based supports have been used, aminopolystyrene (1) (Laursen et a/., 1975) and TETA polystyrene (2) (Horn and Laursen, 1973), both of which are derived from... 

Nevertheless, such reactive functions from pre-stages on a modified support may interfere later on with steps of the Merrifield peptide synthesis causing unforeseen troubles. From this shortly depicted complex of problems of subsequent modification of polystyrene supports, the following consequences may be deduced ... 

In this way, the esterification of an amino acid as well as the complete transformation of reactive functions, can be controlled by conventional analysis, independent from reaction conditions on polymeric phase. Furthermore, the problem of the fixation of a carboxylic compound to the polymer support is reduced to the smooth reaction of a primary amine to chloromethyl functions on cross-linked polystyrene, which were found to be com-... 

Molecules of a difiinctional monomer such as X-R-Y (where X and Y are mutually reactive functional groups) are polymerized via the elimination of small molecule by-products of XY, a linear condensation polymer with a general formula of X-(-R-)w-Y is formed, whereas when molecules of an olefinic monomer such as H2C=CHR are polymerized, a vinyl polymer with a structure of -[-H2C-CH(R)-]w- is produced. The difunctional and olefinic monomers have been the major monomer sources, and their step and chain polymerization reactions have been the main synthetic routes to the conventional polymers such as polyester and polystyrene, respectively [27]. 

An alternative approach is to incorporate reactive functional groups Into the elastomer, producing an in-situ graft copolymer. This reduces interfacial tension, improving dispersion in processing, and improves the adhesion of the rubber to the thermoplastic In the solid state. A maleated polystyrene/poly(ethylene-co-butylene)/polystyrene triblock copolymer (SEES) has been used successfully to toughen polyamides and polyesters. 

Addition polymerization involves the addition of a reactive functionality such as a radical or an ion to a double or triple bond such as an olefin or a carbonyl (Figure 13.12 B). Many strategies exist, mostly based on chemistries we have described earlier in Chapter 10. A number of well known polymers can be formed by addition reactions, including polyethylene, polypropylene, polystyrene, polyvinylchloride (PVC), polyacrylonitrile (Orion), poly-tetrafluoroethylene (Teflon), and poly(methyl methacrylate) (Plexiglas, Lucite). 

A novel and versatile method for preparing polymer-supported reactive dienes was recently developed by Smith [26]. PS-DES (polystyrene diethyl-silane) resin 28 treated with trifluoromethanesulfonic acid was converted to a polymer-supported silyl triflate 29 and then functionalized with enolizable a,jS-unsaturated aldehydes and ketones to form silyloxydienes 30 and 31 (Scheme 4.4). These reactive dienes were then trapped with dienophiles and the Diels Alder adducts were electrophilically cleaved with a solution of TFA. 

Even in solution the relative rigidity of the polymer support can play a significant role in the reactivity of attached functional groups. Contrasting studies conducted with chloromethylated derivatives of poly(arylene ether sulfone) (Tg 175°C), phenoxy resin (Tg= 65°C) and polystyrene (Tg= 105°C) allow evaluation of chain rigidity effects. We have shown that the rates of quaternization of chloromethylated poly(arylene ether sulfones) and phenoxy resin deviate from the anticipated second order process at... 

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