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Controlled polymerization for the synthesis of structurally precise conjugated polymers remains a challenging problem in polymer chemistry. Catalyst-transfer polymerization (CTP) based on Pd-catalyzed Suzuki-Miyaura cross-coupling is one of the promising approaches toward solving this challenge. Recent introduction of N-methyliminodiacetic acid (MIDA) boronates as monomers for Suzuki-Miyaura CTP has extended this approach towards a broader variety of monomer structures and led to improved control over the polymerization, particularly for heteroaromatic systems (such as thiophenes). Previously, we found that MIDA-boronate monomers polymerization could be facilitated by Ag+-mediated reaction conditions due to shifting the Pd catalytic cycle toward a more efficient oxo-Pd transmetalation pathway where MIDA-boronates could participate in transmetalation directly, without prior hydrolysis to boronic acid. In this work, we continued studying this novel process, and investigated the dual role of the MIDA-boronate functional group in the case of less reactive fluorenyl (and potentially other all-carbon aromatic systems) monomers. With such monomers, MIDA-boronate group enables the controlled polymerization but also produces a hydrolysis byproduct hindering the polymerization. We also investigated the role of Ag+ acting to counteract this hindering effect. Steric bulkiness of the MIDA-boronate functional group may also slow down the Suzuki-Miyaura CTP process. These complications could reduce the synthetic value of MIDA-boronate monomers in Suzuki-Miyaura CTP, although better understanding of these implications and a proper choice of polymerization conditions and catalytic initiators could to some extent mitigate such problems. As part of this work, we also uncovered a "critical length" phenomenon which results in a dual molecular weight distribution of the resulting conjugated polymer, both with MIDA-boronate and boronic acid monomers. This phenomenon could account for the experimentally observed loss of polymerization control beyond formation of the polymer chains of a certain "critical length", even despite the formally "living" nature of the polymer chains. The generality of this phenomenon and whether it is restricted to using Pd catalytic systems based on Buchwald-type phosphine ligands remains to be studied. Overall, these new findings paint a sophisticated picture of the Suzuki-Miyaura CTP process with MIDA-boronate monomers where the mere presence of a Pd center on the polymer chain is not sufficient to sustain the polymerization (even if a chain could be considered "living" in a sense of possessing a Pd center), and the choice of phosphine ligand on the Pd center is an effective tool to overcome the "critical length" restriction. 

Thin films of poly(arylene ethynylene) conjugated polymers, including low-energy-gap donor–acceptor polymers, can be prepared via stepwise polymerization utilizing surface-confined Sonogashira cross-coupling. This robust and efficient polymerization protocol yields conjugated polymers with a precise molecular structure and with nanometer-level control of the organization and the uniform alignment of the macromolecular chains in the densely packed film. In addition to high stability and predictable and well-defined molecular organization and morphology, the surface-confined conjugated polymer chains experience significant interchain electronic interactions, resulting in dominating intermolecular π-electron delocalization which is primarily responsible for the electronic and spectroscopic properties of polymer films. The fluorescent films demonstrate remarkable performance in chemosensing applications, showing a turn-off fluorescent response on the sub-ppt (part per trillion) level of nitroaromatic explosives in water. This unique sensitivity is likely related to the enhanced exciton mobility in the uniformly aligned and structurally monodisperse polymer films. 

We have developed a convergent method for the synthesis of allylic alcohols that involves a reductive coupling of terminal alkynes with α-chloro boronic esters. The new method affords allylic alcohols with excellent regioselectivity (anti-Markovnikov) and an E/Z ratio greater than 200:1. The reaction can be performed in the presence of a wide range of functional groups and has a substrate scope that complements the stoichiometric alkenylation of α-chloro boronic esters performed using alkenyl lithium and Grignard reagents. The transformation is stereospecific and allows for the robust and highly selective synthesis of chiral allylic alcohols. Our studies support a mechanism that involves hydrocupration of the alkyne and cross-coupling of the alkenyl copper intermediate with α-chloro boronic esters. Experimental evidence excludes a radical mechanism of the cross-coupling step and is consistent with the formation of a boron-ate intermediate and a 1,2-metalate shift. 

Controlled preparation of structurally precise complex conjugated polymer systems remains to be a major synthetic challenge still to be addressed, and this push is stimulated by the improved device performance as well as unique fundamental characteristics that the well-defined conjugated polymer materials possess. Catalyst-transfer polymerization (CTP) based on Pd-catalyzed Suzuki-Miyaura cross-coupling reaction is currently one of the most promising methods towards achieving such a goal, especially with the recent implementation of N-methyliminodiacetic acid (MIDA) boronates as monomers in CTP. Further expansion and development of practical applications of CTP methods will hinge on a clear mechanistic understanding of both the entire process and the particular steps involved in the catalytic cycle. In this work, we introduced Ag⁺-mediated Suzuki-Miyaura CTP and demonstrated that presence of Ag⁺ shifted a key transmetalation step toward the oxo-Pd pathway, leading to direct participation of MIDA-boronates in the transmetalation step and hence in the polymerization process, and resulting in the overall more efficient polymerization. In addition, we found that, under Ag⁺-mediated conditions, MIDA-boronates can also directly participate in small-molecule cross-coupling reactions. The direct participation of MIDA-boronates in Suzuki-Miyaura cross-coupling has not been envisaged previously and could enable new interesting possibilities to control this reaction both for small-molecule and macromolecular syntheses. In contrast to MIDA-boronates, boronic acid monomers likely undergo transmetalation through an alternative boronate pathway, although they may also be directed to react via the oxo-Pd transmetalation pathway in Ag⁺-mediated conditions. The interplay between the two transmetalation pathways which are both involved in the catalyst-transfer polymerization, and the opportunity to selectively enhance one of them not only improves mechanistic understanding of Suzuki-Miyaura CTP process but also provides a previously unexplored possibility to gain more effective control over the polymerization to obtain structurally better-defined conjugated polymers. 

It has been recognized that jobs across different domains is becoming more data driven, and many aspects of the economy, society, and daily life depend more and more on data. Undergraduate education offers a critical link in providing more data science and engineering (DSE) exposure to students and expanding the supply of DSE talent. The National Academies have identified that effective DSE education requires both appropriate classwork and hands-on experience with real data and real applications. Currently significant progress has been made in classwork, while progress in hands-on research experience has been lacking. To fill this gap, we have proposed to create data-enabled engineering project (DEEP) modules based on real data and applications, which is currently funded by the National Science Foundation (NSF) under the Improving Undergraduate STEM Education (IUSE) program. To achieve project goal, we have developed two internet-of-things (IoT) enabled laboratory engineering testbeds (LETs) and generated real data under various application scenarios. In addition, we have designed and developed several sample DEEP modules in interactive Jupyter Notebook using the generated data. These sample DEEP modules will also be ported to other interactive DSE learning environments, including Matlab Live Script and R Markdown, for wide and easy adoption. Finally, we have conducted metacognitive awareness gain (MAG) assessments to establish a baseline for assessing the effectiveness of DEEP modules in enhancing students’ reflection and metacognition. The DEEP modules that are currently being developed target students in Chemical Engineering, Electrical Engineering, Computer Science, and MS program in Data Science at xxx University. The modules will be deployed in the Spring of 2021, and we expect to have immediate impact to the targeted classes and students. We also anticipate that the DEEP modules can be adopted without modification to other disciplines in Engineering such as Mechanical, Industrial and Aerospace Engineering. They can also be easily extended to other disciplines in other colleges such as Liberal Arts by incorporating real data and applications from the respective disciplines. In this work, we will share our ideas, the rationale behind the proposed approach, the planned tasks for the project, the demonstration of modules developed, and potential dissemination venues.