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1. End‐To‐End FRET Enabling Direct Measurement of Oligomer Chain Conformations and Molecular Weight in Reaction Solutions

   https://doi.org/10.1002/marc.202400627  

   Valdez, Sara; Ismail, Syba; Wang, Yuming; Qiang, Zhe (January 2025, Macromolecular Rapid Communications)

   Abstract Förster resonance energy transfer (FRET) is an established tool for measuring distances between two molecules (donor and acceptor) on the nanometer scale. In the field of polymer science, the use of FRET to measure polymer end‐to‐end distances (R_ee) often requires complex synthetic steps to label the chain ends with the FRET pair. This work reports an anthracene‐functionalized chain‐transfer agent for reversible addition‐fragmentation chain‐transfer (RAFT) polymerization, enabling the synthesized chains to be directly end‐labeled with a donor and acceptor without the need for any post‐polymerization functionalization. Noteworthily, this FRET method allows for chain conformation measurements of low molecular weight oligomers in situ, without any work‐up steps. Using FRET to directly measure the averageR_eeof the oligomer chains during polymerization, the chain growth of methyl methacrylate, styrene, and methyl acrylate is investigated as a function of reaction time, including determining their degree of polymerization (DP). It is found thatDPresults from FRET are consistent with other established measurement methods, such as nuclear magnetic resonance (NMR) spectroscopy. Altogether, this work presents a broadly applicable and straightforward method to in situ characterizeR_eeof low molecular weight oligomers and theirDPduring reaction. 

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2. Versatile Production of Multivariate, Hyperdimensional End Group and Main Chain Functionalized Polyolefins

   https://doi.org/10.1002/anie.202304725  

   Fischbach, Danyon M.; Krstic, Katharina A.; Sita, Lawrence R. (June 2023, Angewandte Chemie International Edition)

   Abstract The (stereoselective) living coordinative copolymerization of 1‐alkenes with 4‐aryl‐1,6‐heptadienes, in both the absence and presence of multiple equivalents of a reversible chain transfer agent, is established as a highly versatile strategy for production of multivariate hyperdimensional functionalized semi‐crystalline or amorphous polyolefins that optionally possess either mono‐ or difunctionalized (telechelic) end‐groups in combination with a programmable level of incorporation of orthogonal functional groups within the main‐chain. The non‐conjugated diene comonomers are readily obtained from a diverse range of aryl carboxaldehyde precursors through a one‐step bis‐allylation process. These results serve to provide a new platform for exploring the science and technology of a vast new landscape of functionalized classes of polyolefins that are now accessible in practical and scalable quantities. 

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3. Chain End-Functionalized Dense Polymer Brushes from an Inimer Coating by SI-RAFT

   https://doi.org/10.1021/acs.langmuir.3c00733  

   Smith, Julia D.; Salas, Luis Adrian; Kreft, Carter; Hur, Su-Mi; Gopalan, Padma (June 2023, Langmuir)
4. Chain-End Functionalized Polymers for the Controlled Synthesis of Sub-2 nm Particles

   https://doi.org/10.1021/jacs.0c02244  

   Chen, Peng-Cheng; Liu, Yuan; Du, Jingshan S.; Meckes, Brian; Dravid, Vinayak P.; Mirkin, Chad A. (April 2020, Journal of the American Chemical Society)
5. Enhancing the Dielectric Breakdown Strength of Solid-State Polymer Capacitors by Chain End Manipulations

   Singh, Maninderjeet; Wu, Wenjie; Dong, Mei; Tran, David; Wooley, Karen L.; Pradhan, Nihar; Raghavan, Dharmaraj; Karim, Alamgir (March 2020, Bulletin of the American Physical Society)

   The need for high power density, flexible and light weight energy storage devices requires the use of polymer film-based dielectric capacitors. Theoretically, it has been shown that chain ends contribute adversely to electrical breakdown, resulting in low energy density in polymer capacitors. In this work, we enhanced the energy density of polymer capacitor by using well-ordered high molecular weight block copolymer (BCP), in which the chain ends are segregated to narrow zones. Cyclic homopolymers (no chain ends) and linear homopolymers having chemistry-controlled chain ends also show enhanced breakdown strength, resulting in higher energy density as compared to the linear counterparts. These novel insights into manipulating chain end distribution such as in BCPs and with molecular topology to increase the energy density of polymers will be helpful for fulfilling next-generation energy demands. 

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