Highly Emissive, Optically Active Poly(diphenylacetylene) Having a Bulky Chiral Side Group

Abstract

A highly emissive, optically active poly-(diphenylacetylene) derivative, NpSi*-PDPA, was synthesized by introducing a bulky chiral pendant group into the polymer chain. NpSi*-PDPA exists in a glassy state having a highly disordered and amorphous structure. Hence, the fractional free volume is quite high, i.e., 0.29. NpSi*-PDPA emits a green light in solution and a yellow light in film. This polymer is quite emissive, as the photoluminescence (PL) quantum yield is 56.1% in solution and 6.2% in film, and the PL lifetime is relatively long, 1.71 ns in solution and 1.05 ns in film. NpSi*-PDPA shows the strongest circular dichroism (CD) signal at 384 nm, with a magnitude of circular polarization (g CD ) of 0.90 × 10 −3 and an optical rotation of 110°(4.30 × 10 −3 g mL −1 , in CHCl 3 ). The CD intensity is significantly increased by annealing at 80 °C, reaching an equilibrium at g CD of 7.10 × 10 −3 after 72 h.

Synthesis of Optically Active Poly(diphenylacetylene)s Using Polymer Reactions and an Evaluation of Their Chiral Recognition Abilities as Chiral Stationary Phases for HPLC

“…These results indicated that a predominantly one-handed helical conformation was induced in the polymer backbone by thermal annealing owing to the effect of the optically active pendants (h-poly-2S). A similar thermal annealing was necessary for poly-4S to form the preferred-handed helical conformation (h-poly-4S) [27,36]. This result was attributed to steric hindrance between the neighboring pendant phenyl rings, which was large enough to prevent poly-2S and poly-4S from being transformed into their preferred-handed helical conformations after the introduction of the optically active pendants.…”

“…These results indicated that a predominantly one-handed helical conformation was induced in the polymer backbone by thermal annealing owing to the effect of the optically active pendants (h-poly-2S). A similar thermal annealing was necessary for poly-4S to form the preferred-handed helical The circular dichroism (CD) spectrum of poly-2S showed almost no circular dichroism (CD) in the wavelength region longer than 300 nm ascribed to the absorption of the polymer backbone in N,N-dimethylformamide (DMF) immediately after the preparation of the sample (Figure 2a) [27,[32][33][34][35]. However, an apparent Cotton effect was observed around 400 nm after one day.…”

“…This result was attributed to steric hindrance between the neighboring pendant phenyl rings, which was large enough to prevent poly-2S and poly-4S from being transformed into their preferred-handed helical conformations after the introduction of the optically active pendants. conformation (h-poly-4S) [27,36]. This result was attributed to steric hindrance between the neighboring pendant phenyl rings, which was large enough to prevent poly-2S and poly-4S from being transformed into their preferred-handed helical conformations after the introduction of the optically active pendants.…”

“…for HPLC because of their preferred-handed helical conformation [17][18][19][20][21][22][23][24][25][26]. However, very few optically active poly(diphenylacetylene)s have been prepared to date, which has limited research towards evaluating the scope and efficiency of the chiral recognition abilities of these materials [27][28][29][30][31][32][33][34][35]. We recently reported the first example of an optically active poly(diphenylacetylene)-based CSP for HPLC [36].…”

Chiral Recognition Ability of an Optically Active Poly(diphenylacetylene) as a Chiral Stationary Phase for HPLC

“…21 Very recently, a similar thermal annealing effect on the CD intensity was reported for an optically active poly(diphenylacetylene) bearing a bulky pendant. 13 The chiral recognition abilities of poly-3 and h-poly-3 as CSPs for HPLC were evaluated by coating them on macroporous silica gel. The DMF solutions of poly-3 and h-poly-3 were coated on macroporous silica gel to give coated-type packing materials, 22 which were then packed into a stainless steel column (25 © 0.20 cm (i.d.))…”