Beijing Chemical Lu Chao \”Sci.Adv.\”: Click chemistry rapid large scale production of polymer room temperature phosphorescence
Polymer at room temperature phosphorescence (RTP) of a material with good flexibility, ductility, and low cost, etc., in the field of organic electronics flexible attracted more and more attention. RTP-based polymeric material in two categories: the first category, called non-doped polymeric material, the phosphor material contained in the polymer backbone. The second category is achieved by embedding the phosphor in a polymer matrix (polymer doped RTP). Currently, most RTP doping material is achieved by interaction between the noncovalent the phosphor and the polymer matrix. Is disappointing, non-covalent interactions (e.g., van der Waals forces or electrostatic interactions) is a weak non-directional connection, phase separation often unavoidable. In contrast, covalent crosslinking can overcome these deficiencies. It is encouraging that is formed by Professor Zhaoyan Li strong C-O-C covalent interactions, that has developed a long-life non-heavy atom amorphous organic phosphorescent material (Sci. Adv. 4, eaas9732 (2018)). However, the material is prepared RTP under stringent reaction conditions. Moreover, occasionally a need for a catalyst or initiator to initiate the covalent reaction, and therefore, this method is not applicable to the production of materials RTP, since the catalyst is difficult to remove. A disadvantage of this covalent crosslinking reaction is hampered large-scale application of polymer-based material in RTP flexible electronics manufacturing. Recently, Beijing University of Chemical Technology, Professor Lu Chao in a speech entitled \” Science Advances \” \”Large-scale preparation for efficient polymer -based room-temperature via phosphorescence click chemistry \”article, a method of BO between the phosphor and the boronic acid-modified polyhydroxy polymer matrix prepared RTP click reaction mass material. Ab initio molecular dynamics simulations indicate that these phosphors are effectively fixed, thereby suppressing the non-radiative transition and activated RTP emission. Compared with several hours covalently bound reported time, this B-O bond reaction can be completed within 20 seconds of the environment. The strategy by introducing a simple click chemistry, polymer-based RTP simplifies the polymeric materialStructure, providing inspiration and possibilities for large-scale production RTP materials. Photo Introduction
1. Preparation and Luminescent Properties RTP Material
In order to establish the PVA matrix covalently B-O bonds, two acid-functional tetraphenylethene (TPEDB). TPEDB reaction without catalyst to PVA, but can be easily achieved under ambient conditions.
They studied the luminescent properties TPEDB-PVA polymeric material. Emission spectrum of the fluorescence emission at 450 nm, 535 nm at the RTP green emission (FIG. 2A). RTP life of up 768.6ms, traceable to the naked eye green phosphorescent 4S (FIG. 2B). They also found that the addition of PVA in TPEDB molecule, can improve the performance of RTP TPEDB-PVA material, indicating PVA as the base of the RTP has TPEDB activation. In addition, with the increase of PVA content, the strength of the RTP TPEDB-PVA polymeric material increases to a maximum and then decreases. Further, with the increase TPEDB content, growing the RTP intensity (Figure 2C). When the content is too high TPEDB, PVA is insufficient by hydroxy B-O covalent bond TPEDB targeting molecules, molecular movement results in energy dissipation TPEDB free, reduced RTP strength.
2. B-O covalent bond action
To verify the importance of the B-O covalent interactions, performed control experiment of polymer in the absence of hydroxyl or acid groups in the case. In the absence of a hydroxyl group, RTP TPEDB polymeric material strength decreased. TPE with no boronic groups PVNeither form a covalent bond between A molecule can not form hydrogen bonds, resulting in RTP TPE-PVA material emission may be weak. These results demonstrate that the covalent bond and the hydroxyl group formed boronic necessity for a stable and efficient material RTP. Therefore, they studied the effects of different degree of hydrolysis of PVA alcohol to the RTP. The results showed that, of the polyvinyl alcohol solution increased from 72% to 98% results in improved fluorescence properties and RTP (FIG. 3 A and B) TPEDB-PVA polymeric material. XRD and IR analysis, PVA increased the number of hydroxyl groups, provides more attachment sites for the covalent and hydrogen bonding system to provide a more favorable environment for the movement and activation of limitations thereof phosphor RTP.
3. Emitting mechanism
Figure 5B shows the calculated and TPEDB PVA and ground state (S0), the first excited singlet state (S1) and the first excited triplet state (T1 ) energy level. For TPEDB, relative to vacuum level, S0, S1 and T1 energy level were -5.728, -3.266 and -3.757eV. The results showed that, TPEDB electrons excited under irradiation from S0 to S1, and then transferred back from T1 to S1 to S0, thereby generating RTP effective radiation. In contrast, PVA of S0, S1 and T1 energy level were -6.716, -2.751 and -2.318eV. Polyvinyl alcohol is higher than T1 S1 state energy states, so forbidden intersystem crossing. Thus, the source of phosphorescence is TPEDB, PVA as a non-emissive polymeric matrix TPEDB stable molecule.
To explore the effect on the phosphorescent benzene rotation of TPEDB – polymer material (TPEDB-PVA100, TPEDB-PVA67, TPEDB-PVA50, TPEDB-PDDA, TPEDB-PSS and TPEDB-PVDF) simulation for AIMD . Each model simulation process AIMD d dihedral distribution shown in Figure 5D. d TPEDB distribution less than PVA embedded embedding PDDA, PSS and PVDF d, show inhibition of rotation of the covalent PVA TPEDB provided superior inhibitory non-rotating non-covalent bonds provide hydroxyl polymer. Furthermore, as the degree of hydrolysis of PVA, restriction effect is enhanced. Thus, RTP performance TPEDB-PVA polymeric material may be conveniently regulated by the number of hydroxyl groups in PVA.
4. The data encryption and security applications
They achieve large-scale preparation TPEDB-PVA polymer material in the dish, the polymeric material TPEDB-PVA radius of 0.5, 1.0 and 2.5cm (FIG successfully prepared 6C). Further, also implements data encryption TPEDB-PVA polymer materials. The number \”8\”, showed a strong cyan fluorescence (FIG. 6D) at the ultraviolet excitation encoding TPEDB-PVA PVA having a degree of hydrolysis of different alcohols. After removal of the light source, after a different time delays, the green afterglow can distinguish the number \”3\” and \”a.\” TPEDB-PVA polymers having a different degree of alcoholysis in different RTP lifetime PVA chain, in order to achieve a different digital display. Further, TPEDB PVA can be used as a substrate for the security ink. TPEDB with clear boundary can be printed on the PVA substrate immediately on the figure \”123\” (FIG. 6E). Under ultraviolet light, blue numbers may be observed. After removal of ultraviolet radiation, you can still see the green RTP.
In summary, the strategy of a simple click-step B-O, an efficient preparation of polymer-based material RTP. Effect of the covalent bond of the number of B-O performance by RTP. The method is simple, high production efficiency, can be large-scale production, etc., it may be provided for the preparation of innovative RTP polymer material. This facilitates the successful application of RTP materials in many applications, such as a light emitting device and data security. By adjusting the click reaction reagents can be extended to many other different materials in the RTP strategy. The full text link: https: //advances.sciencemag.org/content/6/21/eaaz6107