Poly -derived oligomers

The heterogeneously catalyzed disproportionation of 1,1,2,2-tetrachlorodimethyldisilane leads via oligo(chloromethylsilane)s to highly branched poly(chloromethylsilane)s. The disilane derived oligomer formation can be controlled by the nature of the Lewis base catalyst. 

Utesch, N. F., Diederich, F. Acetylenic scaffolding on solid support Poly(triacetylene)-derived oligomers by Sonogashira and Cadiot-Chodkiewicz-type cross-coupling reactions. Org. Biomol. Chem. 2003,1, 237-239. 

Tertiary amines like benzyldimethylamine, pyridine, and imidazole have been widely used as a base to initiate the anionic polymerization of PGE and its derivatives as well as for the synthesis of epoxy resins of diglycidyl ether of bisphenol A (DGEBA). Even if initiation occurs with amine alone, the introduction of an alcohol is a common procedure to suppress the observed induction period and increase the polymerization rate. Two initiation mechanisms have been proposed (Scheme 18) (1) direct nucleophilic attack of the amine onto the cyclic monomer to yield the zwitterion (a) and (2) formation of alkoxide (b) via proton transfer in the presence of alcohol. Fast exchange between dormant alcohol and active alkoxide allows chain growth from both initial amine (a) and alcohol (b). Poly(PGE) oligomers whose degree of polymerization does not exceed 5 are obtained. The presence of terminal double bonds indicates significant transfer to the monomer via... 

Oligomerization on solid phase via the Sonogashira reaction has also been carried out by Hwang and Tour in the preparation of 24 tetrameric oligo(phenylene ethynylene)s [104], as well as by Diederich and coworkers [105,106], who prepared poly(triacetylene)-derived oligomers displaying high fluorescence intensities. Triazene linkers, to attach the scaffold to a polystyrene resin, were also employed in these two cases. On-bead homo-... 

Decafluorobiphenyl [434-90-2] C F C F (mol wt, 334.1 mp, 68°C bp, 206°C), can be prepared by I Jllmann coupling of bromo- [344-04-7] chloro- [344-07-0] or iodopentafluorobenzene [827-15-6] with copper. This product shows good thermal stabiHty decafluorobiphenyl was recovered unchanged after 1 h below 575°C (270). Decafluorobiphenyl-based derivatives exhibit greater oxidative stabiHty than similar hydrocarbon compounds (271). Therm ally stable poly(fluorinated aryl ether) oligomers prepared from decafluorobiphenyl and bisphenols show low dielectric constant and moisture absorption which are attractive for electronic appHcations (272). 

Scheme 8. Oligomers and polymers with a poly(triacetylene) (PTA) backbone that are derived from tetraethynylethenes (TEEs)...

Most of the research on thioformaldehyde derivatives has been done on other products formed from formaldehyde and hydrogen sulfide. This reaction is quite complex and gives in addition to methanedithiol and bis(mercaptomethyl)sulfide, trithiane, thioformaldehyde oligomers, and poly(thioformaldehyde). 

Figure 7 illustrates the GPC curves of poly(TrMA) obtained by LiAn in toluene (A) and THF (B) Figure 8 is the GPC curves of the PMMA derived from the poly(TrMA) obtained with Sp-BuLi. Both polymers obtained in THF with LiAn and Sp-BuLi showed rather narrow distributions and initiator efficiency was about 100%. The polymerization in toluene was complicated and a large portion of the initiators was consumed for the formation of oligomers. 

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