A telechelic

polymer A polymer (; Greek '' poly-'', "many" + ''-mer'', "part") is a substance or material consisting of very large molecules called macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic a ...

oligomer In chemistry and biochemistry, an oligomer () is a molecule that consists of a few repeating units which could be derived, actually or conceptually, from smaller molecules, monomers.Quote: ''Oligomer molecule: A molecule of intermediate relativ ...

is a

prepolymer In polymer chemistry, the term prepolymer or pre-polymer, refers to a monomer or system of monomers that have been reacted to an intermediate-molecular mass state. This material is capable of further polymerization by reactive groups to a fully c ...

capable of entering into further

polymerization In polymer chemistry, polymerization (American English), or polymerisation (British English), is a process of reacting monomer, monomer molecules together in a chemical reaction to form polymer chains or three-dimensional networks. There are ...

or other reactions through its reactive end-groups. It can be used for example to synthesize block

copolymer In polymer chemistry, a copolymer is a polymer derived from more than one species of monomer. The polymerization of monomers into copolymers is called copolymerization. Copolymers obtained from the copolymerization of two monomer species are some ...

s. By definition, a telechelic polymer is a di-end-functional polymer where both ends possess the same functionality. Where the chain-ends of the polymer are not of the same functionality they are termed di-end-functional polymers. All polymers resulting from

living polymerization In polymer chemistry, living polymerization is a form of chain growth polymerization where the ability of a growing polymer chain to terminate has been removed. This can be accomplished in a variety of ways. Chain termination and chain transfer r ...

are end-functional but may not necessarily be telechelic. Telechelic polymers with different number of reactive end groups can be termed according to the number of end-groups as “hemi-” (one), “di-” (two),” and “tri-telechelic” (three) polymers. When it presents many end groups it is called “polytelechelic”. To prepare polymers by

step-growth polymerization Step-growth polymerization refers to a type of polymerization mechanism in which bi-functional or multifunctional monomers react to form first dimers, then trimers, longer oligomers and eventually long chain polymers. Many naturally occurring a ...

, telechelic polymers like polymeric diols and

epoxy Epoxy is the family of basic components or cured end products of epoxy resins. Epoxy resins, also known as polyepoxides, are a class of reactive prepolymers and polymers which contain epoxide groups. The epoxide functional group is also coll ...

prepolymers can be used. The main examples are: *

Polyether In organic chemistry, ethers are a class of compounds that contain an ether group—an oxygen atom connected to two alkyl or aryl groups. They have the general formula , where R and R′ represent the alkyl or aryl groups. Ethers can again be c ...

diols; *

Polyester Polyester is a category of polymers that contain the ester functional group in every repeat unit of their main chain. As a specific material, it most commonly refers to a type called polyethylene terephthalate (PET). Polyesters include natural ...

diols; *

Polycarbonate Polycarbonates (PC) are a group of thermoplastic polymers containing carbonate groups in their chemical structures. Polycarbonates used in engineering are strong, tough materials, and some grades are optically transparent. They are easily work ...

diols: Polyhexamethylene carbonate diol (PHMCD); * Polyalcadiene diols:

Hydroxyl-terminated polybutadiene Hydroxyl-terminated polybutadiene (HTPB) is an oligomer of butadiene terminated at each end with a hydroxyl functional group. It reacts with isocyanates to form polyurethane polymers. HTPB is a translucent liquid with a color similar to wax paper a ...

(PBHT)... Other examples of telechelic polymers are the halato-telechelic polymers or halatopolymers. The end-groups of these polymers are ionic or ionizable like

carboxylate In organic chemistry, a carboxylate is the conjugate base of a carboxylic acid, (or ). It is an ion with negative charge. Carboxylate salts are salts that have the general formula , where M is a metal and ''n'' is 1, 2,...; ''carboxylat ...

quaternary ammonium In chemistry, quaternary ammonium cations, also known as quats, are positively charged polyatomic ions of the structure , R being an alkyl group or an aryl group. Unlike the ammonium ion () and the primary, secondary, or tertiary ammonium cations ...

groups.

Synthesis

Telechelic polymers can be synthesized by different polymerization mechanisms. From vinyl monomers, among synthetic strategies are

controlled radical polymerization Living free radical polymerization is a type of living polymerization where the active polymer chain end is a free radical. Several methods exist. IUPAC recommends to use the term "reversible-deactivation radical polymerization" instead of "livi ...

and anionic polymerization. In the case of olefins, that is difficult to be functionalized, recent advances in insertion polymerization and post-polymerization can be used to produce telechelic polyolefins.

Application

Telechelic polymers is important in the preparation of block copolymers acting as building blocks for the structural design of these copolymers. Particularly, ABA triblock copolymers has received much industrial interest for development of

thermoplastic elastomers Thermoplastic elastomers (TPE), sometimes referred to as thermoplastic rubbers, are a class of copolymers or a physical mix of polymers (usually a plastic and a rubber) that consist of materials with both thermoplastic and elastomeric properties. ...

References

Polymers {{Polymer-stub