Telechelic polyesters

A methacryl-type polyester macromonomer was synthesized by lipase PF-catalyzed polymerizahon of DDL using vinyl methacrylate as terminator ( terminator method ), in which the vinyl ester terminator was present from the beginning of the reachon (Scheme 17). In using divinyl sebacate as terminator, the telechelic polyester having a carboxylic acid group at both ends was obtained. Various non-protected thiol compounds were used as inihator or terminator for the thiol end-funchonalizahon of poly(8-CL). ... 

A more general strategy to approach symmetrical telechelic polyesters consists of the control of both initiation and termination steps. Indeed, combination of a functional initiator for the (di)lactones ROP with an effective coupling... 

Such telechelic polyesters show typical surfactant behavior after neutralization with various amines (mono- and diethanol amine, etc...). Micellization has been studied by photon correlation spectroscopy. 

The UPy moiety has also been used by Long and co-workers to develop UPy telechelic polyesters to form linear SPs. Many more examples of isodesmic polymers based on a wide variety of multiple hydrogen-bonding interactions have been reported. 

Cadiz and co-workers [46] prepared telechelic polyester diols through two subsequent thiol-ene reactions. That is, a step growth polymerisation using allyl-lO-undecenoate and 3,6-dioxa-l,8-octanedithiol, followed by end-group post-polymerisation modification with 2-mercaptoethanol. Telechelics based on divinyl monomers are interesting materials with potential applications in the tailoring of polymer structures and properties. 

Single-step synthesis of polyester macromonomers was achieved by lipase-catalyzed polymerization of lactones in the presence of vinyl esters acting as terminator ( terminator method ) (187,188). A methacryl-type poly(DDL) macromonomer was obtained using vinyl methacrylate (12.5 or 15 mol% based on DDL) and lipase PF as terminator and catalyst, respectively. By the addition of divinyl sebacate, the telechelic polyester having a carboxylic acid group at both ends was synthesized. 

A monofunctional phosphine oxide containing the endcapping reagent, 4-car-boxyl-phenyl-diphenylphosphine oxide, was prepared for applications in the synthesis of telechelic polyester oligomers. The diphenyl-4-methylphenyl phosphine oxide obtained in Grignard reaction was subjected to oxidation to afford the carboxyl-phenyl derivative (Scheme 47). 

The enzymatic synthesis of a telechelic polyester having a hydroxy group, a prepolymer of polyurethane, at both ends was reported [38]. The lipase CA-catalyzed polymerization of adipic acid with an excess of 1,4-butanediol was performed imder reduced pressure. The content of water formed by dehydration polymerization greatly affected the enzyme activity and polymerization rates. 

The polymerization proceeds in a controlled manner, that is, the corresponding first-order kinetic plot is linear. The resulting polymer is a telechelic polyester The initiating end is derived from the a-bromoester used as the initiator and the propagating end bears benzyl bromide-type structure. The molecular weight increases linearly to monomer conversion, and the molecular weight distributions are narrow. 

Dimerized fatty acids (DFA) can be used as an alternative to polyether segments in TPE. The polyester elastomers based on DFA were first prepared by Hoeschele [42]. The properties affecting the degradation stability were improved, but the properties at lower temperatures were unsatisfactory, because the higher glass transition temperature was influenced by the lengths of the amorphous segments. DFA can be coupled with diols and diamines to synthesize telechelic polyesters (Scheme 14) and polyamides, respectively. 

Manuel H J and Gaymans R J (1993) Segmented block copol5Tners based on poly(but-ylene terephthalate) and telechelic polyesters and polyamides of dimerized fatty acids, Polymer 34 4325-4329. 

Table 1 Yields and properties of telechelic polyesters prepared from 1 and 4-tert.-butylbenzoic acid (2) or 1- and 4-tert.-butylphenol (3) in bulk at 8 h...

Table 2 Yields and properties of the telechelic polyesters S prepared from monomer 1 and acetylated bisphenol-P (4) in bulk at 270°C/4h...

Terminal-functionalized polymers such as macromonomers and telechelics are very important as prepolymer for construction of functional materials. Single-step functionalization of polymer terminal was achieved via lipase catalysis. Alcohols could initiate the ring-opening polymerizahon of lactones by lipase catalyst. The lipase CA-catalyzed polymerizahon of DDL in the presence of 2-hydroxyethyl methacrylate gave the methacryl-type polyester macromonomer, in which 2-hydroxyethyl methacrylate acted as initiator to introduce the methacryloyl group quanhtatively at the polymer terminal ( inihator method ).This methodology was expanded to the synthesis of oo-alkenyl- and alkynyl-type macromonomers by using 5-hexen-l-ol and 5-hexyn-l-ol as initiator, respechvely. 

Fig. 12. Enzymatic synthesis of polyester macromonomer and telechelics by terminator method...

Telechelic polymers rank among the oldest designed precursors. The position of reactive groups at the ends of a sequence of repeating units makes it possible to incorporate various chemical structures into the network (polyether, polyester, polyamide, aliphatic, cycloaliphatic or aromatic hydrocarbon, etc.). The cross-linking density can be controlled by the length of precursor chain and functionality of the crosslinker, by molar ratio of functional groups, or by addition of a monofunctional component. Formation of elastically inactive loops is usually weak. Typical polyurethane systems composed of a macromolecular triol and a diisocyanate are statistically simple and when different theories listed above are... 

Telechelic polymers are also used in the synthesis of many products including segmented PU and polyester products. 

A telechelic polystyrene containing two carboxyl groups at one end of a polymer can be used as a macromonomer in a step polymerization with a diol or diamine to yield a polyester or polyamide containing graft chains of polystyrene. The required telechelic polymer is obtained by radical polymerization of styrene in the presence of 2-mercaptosuccinic acid. 

Poly(oxytetramethylene), poly(tetrahydrofuran), may assume the state of a viscous oil, a wax, or a crystalline solid (melting range around 55 °C), depending on the molecular weight. Poly(tetrahydrofuran) telechelics prepared with two OH end groups and in molar masses of 500-4000 g/mol are used widely as soft block in segmented polyurethanes and polyesters (see Sect. 3.4.2.1). 

Synthesis of telechelic oligomers usable in the synthesis of multiblock polyesters or polyamides with different segments presenting specific physical properties... 

Again the efficiency is >0.9 and the ester functionality is exactly 2. The ester groups can be converted to carboxylic acids. The whole chain can be hydrogenated to obtain telechelic polyethylene with ester or hydroxyl end-groups. These telechelics can replace poly(tetrahydrofuran) in the modification of polyesters. The ester end-groups can be used directly in a transesterification process. 

The first urethane was synthesised, by this route, as early as 1849 by Wurtz [6,16,22,30]. In 1937, following very systematic and intensive research works at IG Farbenindustrie, in Germany, Dr. Otto Bayer synthesised the first polyurethane, by the reaction of a diisocyanate with a polyester having two terminal hydroxyl groups (called polyester diol, in fact an a,(o-telechelic polymer with terminal hydroxyl groups) [1,2] ... 

Appropriate telechelic polymers produced from a variety of monomers may be incorporated as reactive components in a variety of applications such as sealants, elastomers, foams, and fibers. Such telechelic polymers may impart almost any desired characteristic such as hydrophilic properties, elastomeric properties, dyeability, and solvent resistance. A dihydroxy telechelic polymer may be reacted with a telechelic polymer containing two carboxylic acid groups to produce a condensed polyester. Accordingly, from these telechelic entities one may produce block copolymers that will have alternating addition polymer residues of like or unlike repeat units. In addition, block copolymers can be produced by modifications of this procedure in which addition polymers are alternated with condensation polymer units. 

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