Crosslinking‐Induced White Light Emission of Poly(Hydroxyurethane) Microspheres for White LEDs

Abstract

Nonconjugated luminescent polymers with white light emission are promising for a wide range of applications in display and lighting devices, but their preparation remains a big challenge. Herein, a white‐light‐emitting nonconjugated poly(hydroxyurethane) microsphere (PHUM) synthesized from the crosslinking reaction of trimethylolpropane tri(cyclic carbonate) ether and 1,6‐hexanediamine in chloroform is reported. The resultant PHUMs possess uniform sizes ranging from 12.6 to 21.5 µm. It is proposed that a high crosslinking degree and various hydrogen‐bonding strengths induce the formation of carbamate clusters with different sizes and broad distributions, which result in a broad emission spectrum. The cluster‐size distribution effect leads to multiple n–π* transitions from various carbamate clusters via through‐space conjugation of carbamates, realizing white light emission. In addition, the application of PHUMs as single phosphor combined with a 365 nm UV chip is also demonstrated, with which a white‐light‐emitting diode with a high color rendering index of up to 95 is obtained. This work confirms that crosslinking can induce multiple emissions, which provides a new clusteroluminescence and polymerization‐induced emission system for tunable luminescence emission.

Clustering‐Induced White Light Emission from Carbonized Polymer Dots

“…[ 25 ] We have previously proposed a cluster‐size distribution effect to explain the luminescence of crosslinked poly(hydroxyurethane), according to which CPDs form nonuniform clusters of different sizes and bandgaps. [ 25,26 ] Based on this hypothesis, we propose that the luminescence of PF, CPD‐12, and CPD‐18 originates from clusters generated by the aggregation of CN and NHCOO on the surface of the carbon core and polymer chains. Due to different degrees of carbonization, the groups are aggregated in different ways and to different degrees, resulting in the generation of multiple clusters.…”

“…Second, the carbon core plays a role in restricting the motion of molecular chains, thus enhancing the interactions between the heteroatomic groups of poly(hydroxyurethane) chains, as in the case of crosslinking or hydrogen bonding interactions. [ 26 ] Therefore, we propose that multiple clusters of CPDs can be realized by carbonization. However, excessive carbonization leads to severe fluorescence quenching.…”

Rare Earth‐Free Luminescent Materials for WLEDs: Recent Progress and Perspectives

“…WLEDs with a high CRI of 95 were fabricated by combining PHUMs as single phosphors with a 365 nm UV chip (Figure 7a-c). [120] Lee and co-workers synthesized three different conjugated polymeric nanoparticles, also known as Pdots, with the same backbone but with different compositions of repeating units (phenylene and benzoselenadiazole). The dominant composition of phenylene units and a smaller amount of benzoselenadiazole in the polymer backbone enabled the Pdots to emit different fluorescence colors according to their condition (solution or solid), due to the difference in intermolecular electron transfer between the polymer backbones (Figure 7d,e).…”

“…[129] Recently, Wang et al synthesized poly(itaconic anhydride-covinyl caprolactam) (PIVC) and poly(itaconic anhydride-co-vinyl pyrrolidone) (PIVP) copolymers through a conventional free The previous parts were reproduced with permission. [120] Copyright 2020, Wiley-VCH. d) Synthetic route and e) GPC traces of the polymers.…”

Hydrated Hydroxide Complex Dominates the AIE Property of Nonconjugated Polymeric Luminophores

“…have received considerable attention due to their fundamental importance, promising applications. 5,6 NT-AIEgens with typical structural features of no traditional chromophores gradually developed into a new type of AIE luminophores, including nature and synthetic small molecules, 7-10 polymers [11][12][13][14][15][16] and metal clusters. [17][18][19][20][21] Among them, nonconjugated polymers, which are free of aromatic building blocks, have been intensively reported due to their unique clustering-triggered emission (CTE).…”