Facile Horner−Emmons Synthesis of Defect-Free Poly(9,9-dialkylfluorenyl-2,7-vinylene)

Abstract

This paper describes a simple new strategy for preparing poly(9,9-dialkylfluorenyl-2,7-vinylenes) (PFVs) having high molecular weights and no detectable saturated defects along the conjugated backbone. The new route utilizes a modified Horner-Emmons method by coupling suitably designed comonomers to form the targeted conjugated polymers. The newly prepared PFVs were directly compared to PFVs prepared via a previously established Gilch polymerization route. The structure and optical properties of all PFVs were characterized by gel permeation chromatography (GPC), NMR spectroscopy, UV-vis, fluorescence, and photoluminescence spectroscopy. The findings indicate that the modified Horner-Emmons route gave PFVs with lower molecular weights but substantially higher yields and fewer defects than those prepared by using the Gilch route.

Acyclic Diene Metathesis (ADMET) Polymerization for Precise Synthesis of Defect-Free Conjugated Polymers with Well-Defined Chain Ends

“…(Mn = 32,000, Mw/Mn = 2.0). The spectrum prepared by the ADMET polymerization displays two absorption bands at 427 and 455 nm, which can also be attributed to π-π* transitions of the conjugated backbone [31]. Three absorption peaks at 455, 427, and 400 nm are attributed to 0-0, 0-1, and 0-2 transitions [32], respectively, with corresponding emission peaks at 465, 496, and 530 nm (described below, Figure 2b).…”

McMurry coupling of aryl aldehydes and imino pinacol coupling mediated by Ti(O-i-Pr)4/Me3SiCl/Mg reagent

“…7 Thus, a mixture of 1j 8 or 1k 9 with Ti(O-i-Pr) 4 (2.6 eq), Me 3 SiCl (2.6 eq), Et 3 N (5.2 eq) and Mg powder (4 eq) in THF was stirred for 48 h at 50 o C to produce polymers 5j (M n = 4.74 x 10 3 , M w /M n = 2.50, 51% yield) and 5k (M n = 6.94 x 10 3 , M w /M n = 2.15, 65% yield), respectively. In the region for longer wave length, the maximum absorption (λ max abs ) of 5j thus obtained was observed at 434 nm.…”

ADMET Polymerization: Greener Method for Synthesis of End-Functionalized Poly(Arylene Vinylene)s

“…The other methods such as the Gilch polymerization, Suzuki-Heck or Heck coupling, and Horner-Wittig-Emmons (HWE) reactions [7]- [13] have also been employed as the conventional methods. Gilch polymerization provides some advantages for placement of vinylene units along the polymer backbone with high molecular weights and low PDI (M w /M n ) index.…”

“…The resultant PFVs (and PPVs) prepared by these methods shown in Scheme 4 possessed rather low percentage of structural defects compared to those prepared by the Gilch method, however, the polymers possessed a mixture of cis-and trans-olefinic double bonds and control of molecular weight as well as removal of Pd (and exclusion of a possibility of cross linking even small percentage), which would affect the property (quantum efficiency), seemed difficult. Horner-Emmons method offers a simple strategy for preparing PFVs (Scheme 4(a)) [13]. The resultant PFVs by modified Horner-Emmons route possessed rather lower molecular weights compared to those prepared by established Gilch polymerization route, but relatively higher yields and fewer defects [13].…”

“…Horner-Emmons method offers a simple strategy for preparing PFVs (Scheme 4(a)) [13]. The resultant PFVs by modified Horner-Emmons route possessed rather lower molecular weights compared to those prepared by established Gilch polymerization route, but relatively higher yields and fewer defects [13]. Interestingly, the PFVs prepared by this route possessed no termination of the conjugation and cross-linking (compared to Gilch and Heck routes), and the resultant polymers thus possessed less structural defect that showed better properties compared to those especially by the Gilch method [13].…”