Functionalized polymers, reactive homopolymers

If one is able to control precisely the formation of end-functionalized polymers carrying groups of the proper reactivity and philicity, this scheme should open efficient and diversified new ways of access to interesting block copolymers. The basic problem remains accordingly a catalytic one, i.e. the quantitative end-functionali-zation of growing homopolymer chains by efficient termination or transfer reactions that is fortunately a rapidly improving field. 

Among the fluorine-containing polymers of commercial importance, our polymer of choice was PCTFE, the homopolymer of chlorotrifluoroethylene. The reason for choosing this polymer was the assumption that the chloride group would have sufficient reactivity to allow chemical modifications (Equation 1), but, in the most likely case that such modifications were incomplete, would be inert toward the ultimate reagents and substrates when the functionalized polymers were applied in their subsequent uses in carrying out organic reactions. 

Reactive Homopolymers. Types of Reactions. In the typical ringopening polymerization mentioned previously see Preparation of Siloxane-Type Polymers), reactive hydroxyl groups are automatically placed at the ends of the chains (7, 13). Substitution reactions carried out on these chain ends can then be used to convert them into other functional groups. These functionalized polymers can undergo a variety of subsequent reactions (Table III). 

In situ compatibilization is based on a specific chemical reaction between two functional polymeric components during blending, and thus is also known as reactive blending [5, 17]. Scheme 7.1 exemplifies reactions that take place at the interface between reactive functional polymers. Because the chemical reaction takes place within the interphase, the copolymer is produced in situ, where it is necessary, with segments from the two homopolymers. The process needs (i) sufficient... 

A/ -Vinylformamide (NVF), a reactive functional monomer with novel physical and chemical properties and favorable toxicology (1,2) has shown significant promise in a number of application areas. It is highly reactive under free radical or cationic reaction conditions. The free radically prepared homopolymer is readily water soluble and can be hydrolyzed in a controllable fashion to give cationic or free base amine functional polymers. NVF, like other vinylamides, also copolymerizes well with most commercially available monomers, especially vinyl acetate, acrylamides, and acrylates (2). NVF s moderate toxicity enables the material to be used in applications where there is some possibility of worker exposure. However, it is difficult to obtain with NVF alone the broad range of physical and chemical properties needed for many applications requiring different glass transition temperatures and variable hydrophilic and hydrophobic characteristics. Also, there are situations where the toxicity profile of the monomer system is a primary concern and NVF may not be considered adequately safe. 

The key to solve problems of coarse morphology is to reduce interfacial tension in the melt and to enhance adhesion between the immiscible phases in the solid state. One solution is to select the most suitable blending technique so that co-continuous phase morphology can be obtained, which results in direct load sharing. The second solution is the addition of a third homopolymer or block or graft copolymer or low molecular reactive compounds, which is miscible with either of the two phases. This can be considered as non-reactive compatibilization. The third way is to blend suitably functionalized polymers, which are capable for specific interactions or chemical reactions (reactive compatibilization) [35],... 

A monomer is a reactive molecule that has at least one functional group (e.g. -OH, -COOH, -NH2, -C=C-). Monomers may add to themselves as in the case of ethylene or may react with other monomers having different functionalities. A monomer initiated or catalyzed with a specific catalyst polymerizes and forms a macromolecule—a polymer. For example, ethylene polymerized in presence of a coordination catalyst produces a linear homopolymer (linear polyethylene) ... 

Chemical modification of polymers (J.) still remains a field of continuously increasing importance in macromolecular chemistry. In spite of its high diversification, it may be divided into 2 distinct but complementary main research lines a) the fundamental study of the chemical reactivity of macromolecular chains b) the synthesis of new homopolymers and copolymers, and the functionalization of linear or crosslinked polymers. Some of these facets have been reviewed in the last years (2-6), and the purpose of this presentation is to illustrate a number of characteristic topics both from fundamental and applied points of view, through some literature data and through our own studies on nucleophilic substitution of polymethylmethacrylate (PMMA). 

In conclusion, the AB benzocydobutene monomers can be polymerized to form polymers with a broad range of mechanical properties. The properties of the polymers depend not only upon the type of reactive functionalities but also the nature of the linking group between functionalities. Based upon the properties presented for these homopolymers, it would seem that a broad spectrum and combination of unique thermal and mechanical properties can be obtained from these relatively simple molecules. 

These data point to the specific behaviour of grafted PS chains in polymer-analogous conversions. As a rule, the functional groups of grafted macromolecules appear to be far more reactive than their homopolymer counterparts. 

Becker et al. [64] functionalized a peptide, based on the protein transduction domain of the HIV protein TAT-1, with an NMP initiator while on the resin. They then used this to polymerize f-butyl acrylate, followed by methyl acrylate, to create a peptide-functionahzed block copolymer. Traditional characterization of this triblock copolymer by gel permeation chromatography and MALDI-TOF mass spectroscopy was, however, comphcated partly due to solubility problems. Therefore, characterization of this block copolymer was mainly hmited to ll and F NMR and no conclusive evidence on molecular weight distribution and homopolymer contaminants was obtained. Difficulties in control over polymer properties are to be expected, since polymerization off a microgel particle leads to a high concentration of reactive chains and a diffusion-limited access of the deactivator species. The traditional level of control of nitroxide-mediated radical polymerization, or any other type of controlled radical polymerization, will therefore not be straightforward to achieve. 

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