Telechelic molecule

Note A prepolymer molecule capable of entering into further polymerization through reactive end-groups, often deliberately introduced, is known as a telechelic molecule. 

ADMET depolymerizations with substituted alkenes have been done as well, thereby generating perfectly difunctional telechelic molecules. As an example, 1,4-polybutadiene has been depolymerized in an inert atmosphere with a 10-fold molar excess (based on the repeat unit) of either allyltrimethylsilane or allylchlorodimethylsilane (equation 23). In these examples, the chemistry can be driven to complete depolymerization to yield structures with either one, two, three, or four repeat units of 1,4-butadiene. The synthesis of perfectly difunctional oligomers by this chemistry offers significant opportunity, particularly for functional groups such as alcohols, esters, carboxylic acids, and amines. 

Problem 2.30 What is the scattering from a telechelic molecule in which two identical small spheres are attached to the end of a rodlike molecule of length L that is isorefractive with the solvent ... 

Another example of the flexibility of ADMET is the demonstration of successful polymerization of o /v-telechelic diene carbosilane macromonomers.45 The synthesis of macromonomer 30 is achieved using catalyst 23 and copolymerized with a rigid small-molecule diene, 4,4/-di-trans-l-propenylbiphenyl (Fig. 8.17). 

Note 2 The term halatopolymer is used for a linear polymer formed by the coupling of halato-telechelic polymer molecules, for example, for the linear polymer formed by the coupling of carboxylate end-groups with divalent metal cations [2]. 

The prepolymers described above are one type of telechelic polymer. A telechelic polymer is one containing one or more functional end groups that have the capacity for selective reaction to form bonds with another molecule. The functionality of a telechelic polymer or prepolymer is equal to the number of such end groups. The macrodiol and macrodiisocyanate telechelic prepolymers have functionalities of 2. Many other telechelic prepolymers were discussed in Sec. 2-12. (The term functional polymer has also been used to describe a polymer with one or more functional end groups.)... 

Telechelic polymers, containing one or more end groups with the capacity to react with other molecules, are useful for synthesizing block and other copolymers [Fontanille, 1989 Hsieh and Quirk, 1996 Nuyken and Pask, 1989 Pantazis et al., 2003 Patil et al., 1998 Quirk et al., 1989, 1996 Rempp et al., 1988]. Living anionic polymers can be terminated with a variety of electrophilic reagents to yield telechelic polymers. For example, reaction with carbon dioxide, ethylene oxide, and allyl bromide yield polymers terminated with carboxyl, hydroxyl, and allyl groups, respectively. Functionalization with hydroxyl or carboxyl groups can also be achieved by reaction with a lactone or anhydride, respectively. Polymers with amine end... 

These heterogeneities, which can be called elementary , can be superimposed one on the other, i.e. bifunctional molecules can be linear or branched, linear molecules can be mono- and bifunctional, etc. In order to characterize in an ideal way a telechelic polymer with respect to its subsequent transformation, it is necessary to know a set of functions (fj(M), the molecular weight distributions within each heterogeneity type. Clearly, it is very difficult in a general case to solve this characterization problem. 

Molecular or structural functionality, f, of any chemical compound and, specifically, a telechelic polymer should be understood as the number of functional groups in one molecule. If some of the functional groups are inactive, the practical or realizable functionality, f of this compound is lower than its molecular functionality ... 

In the previous sections, we have dealt only with telechelic oligomers containing linear non-, mono- and bifunctional molecules. In practice, however, oligomer systems containing components of higher functionality are often encountered. If the mean square distance between functional groups in the chain is greater than the pore size of the stationary phase, then... 

Usually the adjustment of properties is carried out by using mixtures of high molecular weight polydispersed telechelic prepolymers and simple low molecular weight molecules. Recently, we produced a review about the prepolymers mentioned above [8] which we will not describe in this paper. This work concerns the synthesis of low molecular weight monodispersed molecules, their properties and eventually their applications. 

Four main studies have been published on styrene in which the authors show that thiuram disulfides play the role of both initiator and counter radical. Otsu et al. [235] demonstrated with 51 and 52 (n = 2) compounds and model molecule 55 that the polymerization of styrene led to the formation of mono-and dithiuram telechelic PS with a behavior close to that of living radical polymerization ... 

The general types of step-growth polymerizations are shown in Eigure 5.21. Since the resulting polymers contain reactive functional groups on either/both ends, it is referred to as a telechelic macromolecule. Although water is typically released as a byproduct of these polymerizations, other small molecules such as alcohols and alkyl halides may also be generated based on the monomers that co-condense. In its most simplest form, condensation reactions result in linear polymers from the reaction of... 

Surfactants are long, we expect each chain to occupy a large patch of the micelle surface, compared to that occupied by a typical small-molecule surfactant. As a consequence, the aggregation number of telechelic micelles should be significantly smaller than that of a small-molecule micelle with a comparably sized hydrophobe. Using fluorescence decay studies, Yekta et al. (1995) have deduced a micelle aggregation number of 18-28... 

With MMA [73, 74] the authors showed that the telechelic oligomers from MMA were able to be cleaved between the two last carbon atoms and this was carried out from the model molecules ... 

The versatility associated with nitroxide-mediated polymerizations, in terms of both monomer choice and initiator structure, also permits a wide variety of other complex macromolecular structures to be prepared. Sherrington201 and Fukuda202 have examined the preparation of branched and cross-linked structures by nitroxide-mediated processes, significantly the living nature of the polymerization permits subtlety different structures to be obtained when compared to traditional free radical processes. In addition, a versatile approach to cyclic polymers has been developed by Hemery203 that relies on the synthesis of nonsymmetrical telechelic macromolecules followed by cyclization of the mutually reactive chain ends. In a similar approach, Chaumont has prepared well-defined polymer networks by the cross-linking of telechelic macromolecules prepared by nitroxide-mediated processes with bifunctional small molecules.204... 

The methods described above correspond to those attainable with conventional sol-gel chemistry. This strategy is simple, low cost, and yields amorphous hybrid materials, which can contain specific organic molecules, biocomponents or polyfunctional cross-linkable polymers (e.g., telechelic polymers). These materials exhibit an infinity of microstructures, can be transparent, and easily shaped as films or bulks (Fig. 2, Route A). However, they are generally poly-disperse in size and locally heterogenous in chemical composition. 

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