Telechelic liquid polymer

Polymerization methods for preparing telechelic liquid polymers (TLPs) have been described in the patent and technical literature. An excellent review article by D. M. French on functionally terminated butadiene polymers was published in 1969 [272]. 

The radical containing an hydroxyethyl group which is formed (9.5), initiates the formation of polymeric chains which, by recombination, give hydroxy-telechelic polymers (reactions 9.6 and 9.7). Based on the principles mentioned various hydroxy-telechelic polymers were obtained by radical polymerisation of styrene [9], acrylonitrile [10], butyl acrylate or butadiene [10-14]. Of course, the oligo-polyols derived from styrene and acrylonitrile are solid and difficult to use in PU, but butyl acrylate and butadiene lead to liquid polymers with terminal hydroxyl groups, which are useful in polyurethane manufacture. 

More recently, ring opening metathesis polymerization (ROMP) has been used to prepare telechelic liquid crystalline polymers that carry azide end groups which can be crosslinked with a triacetylene species using the well known copper catalyzed click chemistry [22]. 

The carboxyl-terminated liquid polymers (CTBN) are telechelic polymers ranging in comonomer acrylonitrile content from 0 to 27 percent. Table 2 gives the characterization of these polymers. They are solvent-free and range in M from 3400 to 4000. The higher acrylonitrile-containing CTBN type possesses the best balance of oil- and solvent-resistant properties. 

The industrial interest in telechelics was stimulated by the development of thermoplastic elastomers (TPE) consisting of ABA triblock and multiblock copolymers. Liquid polymers (telechelics) are the basis of the reaction injection molding (RIM). The use of liquid telechelics that can be converted into networks offers both processing advantages and (in some cases) improved properties. ... 

Anionic polymerization has also been used to make telechelic polymers (Greek telos, end, and chele, claw), i.e., polymers with reactive terminal groups.We coined the term, telechelic in 1957 and it has been accepted ever since in technical as well as patent literature. Liquid carboxy- and hydroxy telechelic polybutadienes initiated with difunctional organolithium initiators are commercially produced since 1962. Some of the physical properties,production details and uses as in solid rockets... 

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 problems of determining molecular weight and functionality distributions using liquid chromatography have been analyzed in detail in a recent review116a>. Also, results obtained for various telechelic polymers have been summarized there. 

Utilization of the single hydrogen bond between pyridine and benzoic acids in SLCP s has been a source of inspiration for other groups in the development of main-chain supramolecular polymers based on diacids and dipyridines.53-56 Supramolecular rod-coil polymers have been developed by assembly of 4,4 -bipyridines and telechelic polypropylene oxide with benzoic acid end-groups, which show highly ordered liquid crystalline phases.57 The use of tartaric acid derivatives in combination with bipyridine units resulted in the formation of hydrogen-bonded, chiral main-chain LCP s, as has been shown by circular dichroism measurements, optical microscopy, and X-ray data.58,59... 

Fundamental studies directed toward the elucidation of the mechanism of olefin i.e.f isobutylene, polymerizations yielded a new method for the synthesis of novel linear and tri-arm star telechelic polymers and oligomers [1,2]. The synthesis involves the use of bi- or tri-functional initiator/transfer agents, so called inifers (binifers and trinifers), in conjunction with BCI3 coinitiator and isobutylene, and gives rise to polyisobutylenes carrying exactly two or three terminal -CH2-C(CH3)2Cl groups. These liquid telechelic polyisobutylene chlorides can be readily and quantitatively converted to telechelic polyisobutylene di- or tri-olefins [2,3] which in turn can quantitatively yield by hydroboration/oxidation telechelic polyisobutylene di- and triols [4,5]. 

The polymerisation processes described in the previous section are the classical processes used for producing the bulk commercial polymers. Newer processes have been and are being developed with a variety of aims in mind. These involve the production of novel polymer topologies (see box) precise control over chain length and over monomer sequences in copolymers control of isomerism (see section 4.1) production of polymers with special reactive end groups, the so-called telechelic polymers, production of specially designed thermally stable polymers and liquid-crystal polymers with a variety of different structures and properties. Other developments include the production of polymers with very precisely defined molar masses, and of networks with precisely defined chain lengths... 

Yan TZ, Schroter K, Herbst F, Binder WH, Thum-Albrecht T (2014) Nanostructure and rheology of hydrogen-bonding telechelic polymers in the melt fixjm micellar liquids and solids to supramolecular gels. Macromolecules 47(6) 2122-2130... 

The production of liquid short-chain difunctional polymers by anionic polymerization is of considerable technological interest and importance, and has attracted much attention in recent years, since it offers an analogous technology to that of the polyethers and polyesters used in urethane polymers. Such liquid telechelic polydienes could thus lead, by means of chain extension and crosslinking reactions, directly to castable polydiene networks [161,162]. 

Reasonably early however in the development of telechelic polybutadiene/acrylonitrile, Brenner and Drake (22) showed that mercaptan- and carboxyl-terminated liquid polybutadiene/acrylonitrile did respond to electron-beam (1-5 megarads) and cure (2-3 seconds/pass) from the liquid to the solid state. The mercaptan polymer (3.1% RSH, 23% bound acrylonitrile, Mn 1700) cured more readily. CTBN as expected required 50-100% higher irradiation dosage levels. With both MTBN and CTBN-type products of higher acid content (6% vs 3%), gum rubber properties of 13.8-34.5 mPa were obtained with 60-100% elongation. The E-beam cures were carried out in air at ambient temperature. Thus, unformulated telechelic polybutadienes were shown to be substantive to cure in the presence of ionizing radiation. 

Leir, C. M. Galkiewicz, R. K. Kantner, S. S. Mazurek, M., Telechelic SUoxanes with Hydrogen-Bonded Polymerizable End Groups. I. Liquid Rubbers and Elastomers. J. Appl. Polym. Sci. 2010,117,756-766. 

Industrial interest in telechelics was stimulated hy the development of thermoplastic elastomers, which consist of ABA block and multiblock copolymers. Liquid telechelic polymers are the basis for reaction injection molding. Liquid telechelics that can be used for network formation offer processing advantages and may result in materials with improved properties (10). 

Hydroxyl-terminated polybutadiene (HTPB) can be produced by such reactions. Such elastomers of low molecular weight (3000-10,000) are used as binders and liquid rubbers. Telechelic polymers (that is, polymers with reactive end groups), containing one or more end groups with the capacity to react with other molecules, can be prepared in this way. 

Because of its relative ease of synthesis from inexpensive starting materials, the ureido pyrimidinone (UPy) supramolecular motif has been widely exploited in recent years (Figure la). Appending UPy residues at the terminal positions of telechelic polymers such as end-functional polysiloxanes and polyethylene-co-butylene (pE-co-B), transforms previously free flowing, liquid starting materials into tough, elastomeric solids (Scheme 1). 

At this point, it is worth mentioning that the possibility exists to assemble main-chain, hydrogen-bonded polymers from covalent polymers with sticky ends, that is, hydrogen-bonding telechelic polymers. For example, Lenz and coworkers have proposed that the liquid-crystalline behavior of... 

Reaction of hydroxy telechelic poly(ethylene butylene) (M 3500, degree of functionalization 1.93) with this synthon led to product with <0.2% residual OH groups [23]. The mechanical properties of the product are dramatically different from those of the starting material. Whereas the starting material is a viscous liquid, the UPy-functionalized polymer is a rubber-like material with a Young s modulus of 5 MPa (Figure 5). 

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