Telechelic macromolecule

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... 

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... 

Schemes 64 and 65 outline the synthesis of bifunctional telechelic macromolecules using methylene chloride as a comonomer or chain extender. In the first procedure, the phenolic polymer chain ends are end capped with an electrophilic compound containing a functional group such as p-chloromethylstyrene. The order of the rate constants shown in Scheme 64 is self-explanatory. In the second procedure, the chloromethyl ether chain ends are end capped with a nucleophilic compound containing a functional group such as 2-(p-hydroxyphenyl)-2-oxazoline. " ...

J. H. K. K. Hirschbeig, F. H. Beijer, H. A. van Aert, P. C. M. M. Magusin, R. P. Sijbesma, E. W. Meijer, Supramolecular polymers from linear telechelic siloxanes with quadruple hydrogen bonded units , Macromolecules 1999, 32, 2696-2705. 

Note 1 The term halato-telechelic polymer is used to denote a polymer composed of macromolecules having stable (long-lived) ionic or ionizable groups, such as carboxylate... 

Lou X, Detrembleur C, Jerome R (2002) Living cationic polymerization of 5-valerolactone and synthesis of high molecular weight homopolymer and asymmetric telechelic and block copolymer. Macromolecules 35 1190-1195... 

Hirschberg JHKK, Beijer FH, van Aert HA, Magusin PCMM, Sijbesma RP, Meijer EW. Suptamolecular polymers from linear telechelic siloxanes with quadniple-hydrogen-bonded units. Macromolecules 1999 32 2696-2705. 

Muller M, Dardin A, Seidel U, Balsamo V, Ivan B, Spiess HW, Stadler R. Junction d3mamics in telechelic hydrogen bonded polyisobutylene networks. Macromolecules 1996 29 2577-2583. 

Functionally terminal polymers are valuable material intermediates. The di- and polyfunctional varieties (telechelic polymers) have found theoretical (e.g., model network) and commercial (e.g., liquid rubber) applications (1, ). On the other hand, macromolecules with a functional group at one chain end (semitelechelic polymers) have been used to prepare novel macromolecular monomers (Macromers ), as well as block and graft copolymers ( -8). 

The problem of molecular weight distribution (MWD) and functionality type distribution (FTD) belongs by definition to an extensive problem of molecular heterogeneity of polymers. In the synthesis of a polymer with the requested properties, e.g. a telechelic polymer, one is always faced with different types of polydispersity the macromolecules can be of different length, they can have a different number of functional groups, i.e. be mono-, bifunctional, etc., they can be branched (star-, comb- or tree-like) and, finally, they can be cyclic. 

The fn value provides information on the average functionality of oligomers, but does not characterize at all their functional polydispersity. For instance, fn = 2, in some cases an ideal indicator for a telechelic oligomer, can be simulated by the presence of an equal number of mono- and trifunctional macromolecules. 

For the investigated type of telechelic polymer (preferably a sample containing only nonfunctional macromolecules so that retention volumes are close to V0 + Vp), it is first of all necessary to choose two solvents, in one of which (polar solvent b with E0b) the exclusion mode is operative and in the other (nonpolar solvent a with s ) the adsorption mode. The solvents must be able to dissolve readily the analyzed samples and satisfy the detection conditions. 

Telechelic polymers are defined as macromolecules with reactive sites on the polymer chain, usually as endgroups on linear polymers [106]. This macro-molecular architecture has successfully produced a wide variety of block copolymers using macroinititated polymerizations. Living anionic polymeriza-... 

Figure5.21 Viscosity versus shear rate for 1.0 wt% HEUR =51,000Mt /M — 1.7) telechelic polymers with hexadecanol end caps at 22°C. The illustrations show the structural transitions that are thought to occur as the shear rate is increased. First, the bridging chains are stretched, producing shear thickening. Then, many bridging chains are pulled out at one end from the micelles to which they were attached, and shear thinning occurs. (Reprinted with permission from Yekta et al.. Macromolecules 28 956. Copyright 1995 American Chemical Society.)...

Hara M, Wu J, Jerome RJ, Granville M. Salt-free polyelectrolyte behavior of halato-telechelic ionomers in polar solvent. Macromolecules 1988 21 3330-3331. 

On the other hand, a functionality of 1 on each chain end will be related to telechelic compounds (Scheme 1). This includes diols, diamines, and diacides. Of course it also comprises diolefin compounds that usually lead to gels or networks. We can also note that when the G and G functional groups are different at each chain end, the appropriate term becomes heterotelechelic (Table 1). It is also necessary to specify the particular case of macromolecules bearing a well-identified G functionality at one chain end and a thermally reactivated group at the G chain end. These groups can be nitroxides, an iodine atom, xanthate, etc.and are commonly used in living radical polymerizations (LRP). These compounds may be classified as monofunctional oligomers (Table 1). 

Thus, it is possible to use this reaction to obtain new macromolecules (di-ols or diamines) with low glass-transition temperature (Tg) and no crystalline phase. Earlier works suggested the synthesis of hydroxy-telechelic oligomers by radical addition of thiol onto dienes. But, the products obtained showed poor solubility in organic solvents and a high melting point. Our process, however, improves the properties of diol compounds (better solubility and decrease of the melting point). 

In spite of the relatively low performance/cost ratio of the respective products, application of reactions on polymers are of continuous interest for synthesis of amine functionalized polymers. The technique of modification of solid polymers by exploitation of their reactive moieties under heterogeneous conditions allows properties to be tailored and optimized according to specific needs and requirements. Telechelic polymers are used for the synthesis of materials with predictable and controlled properties. Application of carefully designed macromolecules provides systems with functional groups dispersed along the polymer chain or bond at the end of macromolecules. 

Lairez D, Adams M, Carton J P, Raspaud E. 1997. Aggregation of telechelic triblock copol5miers from animals to flowers. Macromolecules 30 6798 6809. 

Tsarevsky, N.V. Sumerlin, B.S. Matyjaszewski, K. Step-growth click coupling of telechelic polymers prepared by atom transfer radical polymerization. Macromolecules 2005, 38 (9), 3558-3561. 

Oligomers and polymers with reactive functional groups have been used extensively to prepare a great variety of polymeric materials. In many cases the behavior of these functional homopolymers is largely dependent on the nature and number of functional groups. In a number of important applications the functional groups are located at the end of the polymer chain macromolecules with terminal functional groups are usually termed telechelics or macromonomers . To characterize them it is necessary to have information not only about their molar mass but also on their functionality. 

GR1 Gregg, C.J., Stein, P.S., and Radosz, M., Phase behavior of telechelic polyisobutylene (PIB) in subcritical and supercritical fluids I., Macromolecules, 27, 4972, 1994. 

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