Conjugated and nonconjugated diynes can be readily converted to poly(phenylene)‐ethynylene derivatives and polyalkynylenes by acyclic diyne metathesis. The catalyst for these condensation reactions is [(tBuO)3 WCtBu], and they proceed with cleavage of volatile alkynes such as 2‐butyne and 3‐hexyne. The chain lengths of the polymers are controlled by reaction temperature and pressure.

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We report the synthesis of novel phenylenevinylene derivatives that allow for the introduction of meta versus para connections on the phenylene rings, as well as the incorporation of nitrogen atoms within the conjugated backbone and the attachment of electroactive substituents. We assess the impact of the various derivatization schemes on the electronic and optical properties by means of gas-phase ultraviolet photoelectron spectroscopy (UPS) and optical absorption and emission measurements; the evolution of the experimental data is further supported by the results of quantum-chemical calculations. We demonstrate that the electronic and optical properties of phenylenevinylene chains, and by extension those of many conjugated materials, can be tuned over a large energy range by a tailored design of the molecular structures.

The initiation and propagation of isobutylene (IB) polymerization initiated by 1,2-epoxi-2,4,4-trimethylpentane (TMPO-1)/TiCl 4 was monitored by a new fiber-optic transmission mid-IR probe. The real-time IR data provided insight into the initiation mechanism. Polyether formation, isomerization of the TMPO-1 into 2,4,4-trimethylpentanal, and its complexation by TiCl4 were observed, which occurred simultaneously with initiation of IB polymerization. The proposed initiating mechanism involves the formation of tertiary carbocations, which has been claimed to occur in the cationic polymerization of epoxides by the SN1 mechanism. On the basis of our results, the competitive occurrence of both SN1 and SN2 pathways is proposed. Interestingly, ketone/TiCl4 systems were found to initiate IB polymerization, albeit with very low efficiency. IR monitoring of these systems gave additional insight into the initiating mechanism. IB polymerization was monitored by following the disappearance of the second overtone of the C-H wag in the dCH2 group in IB at 1780 cm -1 and the CdC stretch at 1655 cm -1 . The linearity of first-order monomer consumption plots and the production of nearly uniform polyisobutylenes (PIBs) (Mw/Mn ) 1.06-1.13) indicated living conditions.

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Konjugierte und nichtkonjugierte Diine können durch acyclische Diinmetathese mit dem Carbinkomplex [(tBuO)3WCtBu] zu Poly(phenylen)ethinylenen bzw. Polyalkinylenen umgesetzt werden. Durch Variation der Reaktionsparameter Druck und Temperatur kann die Abspaltung niedermolekularer, flüchtiger Reaktionsprodukte und damit die Kettenlänge der Polymere gesteuert werden.

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