Telechelic polymers olefins

Diol-functionalized telechelic polymers have been desired for the synthesis of polyurethanes however, utilizing alcohol-functionalized a-olefins degrades both 14 and 23. Consequently, in order for alcohols to be useful in metathesis depolymerization, the functionality must be protected and the oxygen atom must not be /3 to the olefin or only cyclic species will be formed. Protection is accomplished using a/-butyldimcthylsiloxy group, and once protected, successful depolymerization to telechelics occurs readily. 

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). 

In order to synthesize telechelic polymers, the ROMP reaction is carried out in the presence of acyclic olefins that act as chain transfer agents to regulate the molecular weight of the polymers produced. 

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]. 

Polystyrene and Derivatives. Telechelic polystyrene, poly(2,4,6-trimethylst5Tene), poly(p-methylstyrene), and poly(p-chlorostyrene) can be prepared by living carbocationic polymerization (269-271) or by inifer method (272). While end-quenching the living carbocationic polsrmerization gave quantitatively polymers with sec-benzylic termini, the diciunyl chloride/BClg inifer system yielded a,with olefine end groups were also prepared by dehydrochlorination (272,273). 

Preparations of macro-initiators or telechelic polymers by cationic methods have been executed primarily by polymerizing isobutylene in the presence of a co-initiator that also functions as a chain transfer agent. A typical reaction sequence is shown in Scheme 1, outlining the synthesis of difunctional polyisobutylene (PIB), which is then used to initiate the polymerization of a-methyl styrene (ffi-MS) to produce an A-B-A type block copolymer. By similar methods, polyisobutylenes with phenol, phenyl, cyclopentadiene, and olefin termini have been synthesized. 

The exo-olefin is a precursor to a variety of chain-end-functionalized polymers via postpolymerization reaaions as shown in Scheme 37. Hydroxy-functionalized PIB has been utilized as a precursor for the preparation of RAFT macromo-lecular CTAs and carboxylic acid end-fimctionalized polymers. Telechelic PIB diols have been prepared using p-dicumyl chloride/BCU initiator system followed by dehydro-chlorination, hydroboration, and alkaline peroxide oxidation. Aldehyde end-fiinctionalized PIBs have been used to prepare carboxyl- and hydroxyl-terminated poly-mers. Carboxylic acid-functionalized PIBs have also been prepared from the oxidation of the methyl ketone-functionalized PIBs." The hydroxyl-functionalized PIBs have also been used to prepare methacrylate macromonomers by their reaction with methacryloyl chloride in the presence of triethylamine. The homopolymerization and copolymerization of these maaomonomers with methyl methacrylate were also reported. Cyanoacrylate-funaionalized PIBs prepared via the hydroxyl-functionalized PIB were also reported by Kennedy et al. ... 

A broad variety of difunctional allylic olefins have been used for the synthesis of amino-, carboxyl-, and halide-terminated polybutadienes by means of the Grubbs catalyst I (396-398). With the same catalyst, commercially interesting hydroxy telechelic polybutadienes could be obtained by the cleavage of the acetyl end-capped polymer or the copolymer, as depicted in Figure 14 (399,400). 

ADMET has been used to prepare unsaturated telechelic oligomers of PBD by reacting 1,5-hexadiene with an appropriate mono or difunctional olefin [176b, 178]. Alternatively, 1,5-hexadiene may undergo ADMET polymerization to form ADMET PBD and subsequently be reacted with an appropriate functionalized olefin. This reaction is believed to proceed through a cyclic intermediate of the PBD followed by CM of the cyclic polymer with the functionalized olefins (Figure 13.23) [179]. In some cases, the formation of telechelics is incomplete. 

The control over the molecular weight is possible in particular either by addition of acyclic olefins acting as chain transfer agents [111,232,233] or by adjusting the monomer/ initiator ratio [145,181]. The former strategy enables also a simple and efficient synthesis of telechelic ROM polymers [234-238]. Moreover, telechelics were synthesized by degradation of suitable ROM copolymers [239]. 

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