Prepolymers, telechelics

It was also shown that functional zinc alkoxides are also effective initiators for the ring-opening polymerization of -caprolactone imder very mild conditions via a polymerization mechanism described for aluminum alkoxides (345). Tin octoate, Sn(0(0)CCH(C2H5)C4H9)2, is another type of initiator to synthesize telechelics based on PCL. In particular, when it is used in conjunction with hydroxyl functional compounds or prepolymers, telechelics, linear and star-shaped block copolymers, or networks can be obtained via corresponding alkyl octoate formation (346-354). More recently, novel end-chain and mid-chain telechelics functionalized with photoactive groups of PCL were synthesized (355). 

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. 

Synthesis of PIB prepolymers. fm-Chlorine-telechelic PIB (Mn=4,000 MVf/Mn 1.09) (7), and an allyl-telechelic PIB (Mn=9,500 Mw/Mn 1.14) (7,8) were prepared by living carbocationic polymerizations. The tert-chlorine ended PIB was quantitatively dehydrochlorinated (9) to -C(CH3)=CH2 terminated polymer. Both olefin-telechelic PIBs were then hydroborated and oxidized (10) to prepare the primary hydroxyl termini. The hydroxyl-telechelic polymers were esterified with methacryloyl chloride to methacrylate-telechelic PIBs, MA-PIB-MA (11). 

Structural control of polymer terminal has been extensively studied since terminal-functionalized polymers, typically macromonomers and telechelics, are often used as prepolymers for synthesis of functional polymers. Various methodologies for synthesis of these polymers have been developed however, most of them required elaborate and time-consuming procedures. By selecting... 

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

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.)... 

A reactor was charged with poly[(R)-3-hydroxybutyrate], diethylene glycol, dibutyltin dilaurate, and diglyme and then heated overnight and the telechelic hydroxylated prepolymer isolated and used without further purification. 

Halogeno-telechelic polymers result from complete ionization of both ends of telechelic prepolymers. Teyssie et aL [38] developed a facile process of synthesizing dicarboxylato polymers based on Group IVb metal ions (Ti/Zr). Addition of a stoichiometric amount of tetra-n-butoxy-titanium Ti(0-nBu)4 to a carefully... 

Condensations of functionalized polymers or telechelics with AIBN or AIBN derivatives are the most frequently described examples of the al (see Sect. 4.2) type synthesis. Depending on the functionality of the reactants and their concentration ratio, a variety of prepolymers with different numbers of azo groups can be synthesised. 

The preparation of prepolymers [111] or macromers with functional end groups, so called telechelic polymers, is another approach to structurally unconventional architecture. The functional end groups are introduced either by functional initiation or end-capping of living polymers, or by a combination of the two. In this way, monomers that are not able to copolymerize can be incorporated in a copolymer. Telechelic prepolymers can be linked together using chain extenders such as diisocyanates [112]. In this process, it is essential that the structure and end groups of the prepolymers can be quantitatively and qualitatively controlled [113]. 

Star-shaped polymers can be prepared by using a multifunctional initiator, e.g., pentaerythritol and a catalyst which initiates ROP of the selected monomer. A second approach is to use telechelic prepolymers that are linked together after polymerization. 

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. 

The first part concludes with a discussion of the similarity between the mechanisms of initiation and chain transfer, the appreciation of which led to the inifer concept, which in turn yielded new telechelics, networks, sequential copolymers, etc. The second part of this presentation focuses on practical consequences of understanding details of the mechanism of initiation. The synthesis of a new family of telechelic linear and tri-arm star polyisobutylenes will be described. Among the new prepolymers are telechelic olefins, epoxides, aldehydes, alcohols, and amines. The preparation of new ionomers and polyisobutylene-based polyurethanes will be outlined and some fundamental properties of these new materials will be discussed. 

A. Synthesis of Linear Telechelic Polyisobutylene Diols. According to model calculations [5-7] efficient chain extension of telechelics can be carried out only with prepolymers having (number average... 

Scheme 14 Synthesis of telechelic oligomers by chemical modification of prepolymers previously obtained by ATRP...

Telechelic prepolymers having epoxide end-groups as well as telechelics containing amino end-groups and cyclooligomers were foxmd in the FAB mass spectra of epoxy-amine addition polymers. An FAB-MS study characterized in detail the oligomeric products formed in the synthesis of Novalak-type resin. ... 

Klee, J.E., Hagelle, K., and Przybylski, M., Mass Spectrometry Characterization of a 2,2-bis-4-(2,3-epoxy)phenylpropane-aniline Addition Polymer and its Telechelic Prepolymers, Macromol. Chem. Phys., 196, 937,1995. 

A monocyclic polymer with an emanating linear or branched segment - commonly referred to as tadpoles - constitute a group of simple, cyclic topologies. Previously, the ESA-CF process has been used to construct a variety of tadpole polymers, in which the self-assembly consists of two polymer components (i.e., one unit each of monofunctional and difunctional telechelic prepolymers) and a trifunctional counteranion, leading to the formation of a tadpole (Scheme 18.2a). Conversely, a... 

Scheme 18.5 Synthesis of 8-shaped poly- (d) Intramolecular metathesis conden-mers. (a) ESA-CF process (b) Intramolecular sation of a tv/in-tail tadpole prepolymer metathesis condensation of a four-armed (e) Intramolecular metathesis condensa-star telechelic precursor (c) Bimolecular tion of a monocyclic prepolymer having two...

Scheme 1S.6 Click chemistry between a monocyclic prepolymer having an alkyne group and linear telechelic precursor with azide end groups, resulting in the selective formation of a fcndged-dicyclic manacle-shaped polymer.

A monocyclic prepolymer having an alkyne group prepared by the ESA-CF process, as described in Section 18.3.3, was subjected to a dick reaction with a three-armed star telechelics having azide end groups this led to the selective formation of a tricyclic, paddle-shaped polymer (Scheme 18.8) [23]. 

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