Polymer Chemistry Blog

Ben Zhong Tang is an Associate Editor for Polymer Chemistry and a Chair Professor in the Department of Chemistry, The Hong Kong University of Science & Technology (HKUST), China. His research focuses on the synthesis of new molecules and polymers with novel structures and unique functions and the exploration of their high-tech applications as advanced materials in life science, optoelectronic devices, etc.

You can find all Editorial Board’s Top Picks papers in our web collection

Focus on Luminogenic Polymers (Associate Editor: Prof. Ben Zhong Tang, HKUST, China)

1. A fluorescent supramolecular polymer with aggregation induced emission (AIE) properties formed by crown ether-based host–guest interactions
Dong Chen, Jiayi Zhan, Mingming Zhang, Jing Zhang, Jiaju Tao, Danting Tang, Ailin Shen, Huayu Qiu and Shouchun Yin
Polym. Chem. 2015, 6, 25–29.

Supramolecular polymers are a group of novel macromolecules with their monomeric units self-assembled together through monovalent interactions. S. Yin and coworkers at Hangzhou Normal University (China) and University of Maryland (USA) have synthesized a new supramolecular polymer by utilizing crown ether-based host–guest interactions. The supramolecular polymer shows aggregation-induced emission, thanks to the tetraphenylethene units imbedded in the macromolecular chain. Its fluorescence intensity is decreased dramatically on the addition of Pd²⁺ due to the coordination of the metal ion with the triazole group, enabling the polymer to find practical application as a fluorescent chemosensor.

2. Amphiphilic fluorescent copolymers via one-pot combination of chemoenzymatic transesterification and RAFT polymerization: synthesis, self-assembly and cell imaging
Zengfang Huang, Xiqi Zhang, Xiaoyong Zhang, Changkui Fu, Ke Wang, Jinying Yuan, Lei Tao and Yen Wei
Polym. Chem. 2015, 6, 607–612.

Fluorescent organic nanoparticles (FONs) have attracted much attention. Many FONs, however, are hydrophobic particles and have been fabricated by non-covalent strategies. Z. Huang and coworkers at University of Electronic Science & Technology of China and Tsinghua University have combined radical polymerization and enzymatic transesterification processes and developed a one-pot covalent procedure for the fabrication of FONs with aggregation-induced emission (AIE) attribute. The amphiphilic chains of the obtained polymers self-assemble into spherical FONs with the hydrophobic AIE cores covered by hydrophilic poly(ethylene glycol) shells. The FONs show excellent dispersibility in aqueous media, compatibility with biological species, and performance as bioimaging reagent.

3. Aggregation-induced circularly polarized luminescence of an (R)-binaphthyl-based AIE-active chiral conjugated polymer with self-assembled helical nanofibers
Shuwei Zhang, Yuan Sheng, Guo Wei, Yiwu Quan, Yixiang Cheng and Chengjian Zhu
Polym. Chem. 2015, 6, 2416–2422.

A number of polymers with atomic chirality have been found to emit circularly polarized luminescence (CPL). Polymers with axial chirality, however, have been rarely prepared. A team led by Y. Cheng and C. Zhu at Nanjing University (China) have synthesized a series of conjugated polymers containing (R)-binaphthylene and tetraphenylethene (TPE) units with axial chirality and aggregation-induced emission (AIE). All the polymers show AIE effects, thanks to the TPE units embedded in the polymer chains. When the polymers form aggregates in aqueous mixtures, a polymer with the “right” structure becomes CPL active. The aggregation-induced CPL effect of the polymer is tunable by changing the water content of the aqueous mixture.

Review article

Luminescent polymers and blends with hydrogen bond interactions
Shih-Hung Huang, Yeo-Wan Chiang and Jin-Long Hong
Polym. Chem. 2015, 6, 497–508.

Macromolecular luminogens with aggregation-induced emission (AIE) characteristics are useful functional materials because they emit strongly in the aggregate or solid state. As the restriction of intramolecular rotations of luminogens is the main cause for the AIE activity, it has been envisioned that hydrogen-bond interactions can be utilized to construct AIE-active polymers. J.-L. Hong and coworkers have summarized the research effort in the area of AIE study. Through appropriate choices of H-bonding units and sites, a variety of AIE-active polymers and blends have been conveniently generated. In the polymers containing multiple luminogen units, the entangling polymer chains and the intermolecular H-bonding interactions impose effective rotational restriction on the luminogens. In the hydrophilic polymers carrying single luminogens, ready aggregation of the hydrophobic luminogens from the phase-separated H-bonding sites reinforces the beneficial rotational restriction, resulting in AIE systems with intense light emissions. In the luminogenic polymer blends consisting of H-bonding donors and acceptors, the preferable intermolecular H-bond interactions effectively hamper the motion of the constituent components. Thanks to the effective intermolecular H-bond interactions, the blends emit more efficiently than their pure luminogen counterparts without H-bond interactions.

Wei You is an Associate Editor for Polymer Chemistry and an Associate Professor in the Department of Chemistry, University of North Carolina Chapel Hill, USA. His research focuses on the synthesis and characterization of novel multifunctional materials for a variety of applications, predominately in electronics and photonics. Wei’s group uses an interdisciplinary approach, interfacing chemistry, physics, materials science and engineering.

You can find all Editorial Board’s Top Picks papers in our web collection

Focus on Conjugated Polymers (Associate Editor: Prof. Wei You, UNC Chapel Hill, USA)

Conjugated polymers, due to their interesting optical and electrochemical properties, have found many applications, from solar cells, to light-emitting diodes, transistors, and sensors, to name a few. Design and synthesis of novel conjugated polymers have been a very research-active area, illustrated by the fact that Polymer Chemistry has published more than 450 contributions in the past five years (~10% of the total number of publications).

In my Editorial Board’s Top Picks, I highlight four papers, and two review articles:

1. Benzodifuran-alt-thienothiophene based low band gap copolymers: substituent effects on their molecular energy levels and photovoltaic propertiesLijun Huo, Zhaojun Li, Xia Guo, Yue Wu, Maojie Zhang, Long Ye, Shaoqing Zhang and Jianhui Hou
Polym. Chem., 2013,4, 3047-3056

Conjugated polymers for solar cells is one of hottest research areas in the past decade. Hou’s group took the conjugated backbone of benzodifuran-alt-thieno[3,4-b]thiophene (BDF-alt-TT) to carry out a comprehensive study on the impact of electron-withdrawing group on the optical and electrochemical properties of the parent polymer. It is an elegant study that covers design and synthesis, physical properties, computational modeling, and photovoltaic device characteristics. Such a comprehensive study of structure-property relationship is very impressive and useful to the field of conjugated polymer for solar cells.

2. Synthesis of donor–acceptor conjugated polymers based on benzo[1,2-b:4,5-b′]dithiophene and 2,1,3-benzothiadiazole via direct arylation polycondensation: towards efficient C–H activation in nonpolar solvents
Xiaochen Wang and Mingfeng Wang
Polym. Chem., 2014,5, 5784-5792

Though most conjugated polymers are made through Stille, Suzuki type polycondensations, recently, direct-arylation cross-coupling has emerged as an economically efficient and environment-friendly approach. Wang’s group focused on a particular polymer, PBDTBT, consists of alternating benzo[1,2-b:4,5-b0]dithiophene (BDT) as an electron donor (D) and 2,1,3-benzothiadiazole (BT) as the electron acceptor (A). What is really impressive is that they systematically investigated almost all reaction factors including catalysts, solvents, ligands, bases, additives, concentration of reactants and phase transfer agents. The great efforts had a good payoff: their optimized condition was able to achieve a weight averagemolecular weight (Mw) as high as 60 kg/mol in nearly quantitative yield and excellent C–H selectivity.

3. Optical and electrical properties of dithienothiophene based conjugated polymers: medium donor vs. weak, medium, and strong acceptors
Bijitha Balan, Chakkooth Vijayakumar, Akinori Saeki, Yoshiko Koizumi, Masashi Tsuji and Shu Seki
Polym. Chem., 2013,4, 2293-2303

Donor-acceptor to create conjugated polymers is the most popular approach to control the band gap and energy level of conjugated polymers. The Seki group conducted an interesting study to investigate the strength of acceptor (weak, medium and strong) with a fixed donor, dithienothiophene in deciding optical and electrochemical properties of the resulting polymers. Furthermore, they did the computational modeling and device mobilities with different methods. An elegant work with thorough synthetic details and comprehensive study.

4. Low band-gap benzothiadiazole conjugated microporous polymers
Shijie Ren, Robert Dawson, Dave J. Adams and Andrew I. Cooper
Polym. Chem., 2013,4, 5585-5590

Conjugated microporous polymers (CMPs), combining microporosity, high surface areas with extended conjugation, can find a range of potential applications, including light-harvesting and sensing. The Cooper group created a low band gap CMP by incorporating the popular benzothiadiazole unit, via transition metal catalyzed cross-coupling polycondensation. Most interestingly, the fluorescence of one of the polymers was quenched by the inclusion of C60 in the pores, demonstrating the potential applications of such materials in efficient light harvesting or energy conversion.

Review articles:

1. Controlled polymerizations for the synthesis of semiconducting conjugated polymers
Ken Okamoto and Christine K. Luscombe
Polym. Chem., 2011,2, 2424-2434

Conjugated polymers synthesize by chain-growth mechanism (directly or indirectly), though much less explored when compared with the more popular step-growth mechanism, offer a number of unique advantages, including controlled molecular weight, low dispersity, and ease of preparing block copolymers. This review by the Luscombe group provided a rather comprehensive review (up to 2011) on this topic, covering various controlled polymerization methods to synthesize conjugated polymers, including living anion polymerization, ring-opening metathesis polymerization and chain-growth condensation polymerization.

2. Well-defined two dimensional covalent organic polymers: rational design, controlled syntheses, and potential applications
Zhonghua Xiang, Dapeng Cao and Liming Dai
Polym. Chem., 2015,6, 1896-1911

Two-dimensional (2D) covalent organic polymers (COPs) and derivatives are an emerging category of conjugated polymers, which hold great potential for a large variety of applications, including gas storage, energy conversion and storage, and sensing. The Dai group reviewed the recent progress in this exciting field of research, covering the rational design, controlled syntheses and potential applications of 2D COPs with various well-defined structures and properties. An up-to-date review on this topic with many beautiful structures.