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1. Effect of metallosupramolecular polymer concentration on the synthesis of poly[ n ]catenanes

   https://doi.org/10.1039/D1SC02450G  

   Tranquilli, Marissa M. ; Wu, Qiong ; Rowan, Stuart J. ( January 2021 , Chemical Science)

   null (Ed.)

   Poly[ n ]catenanes are a class of polymers that are composed entirely of interlocked rings. One synthetic route to these polymers involves the formation of a metallosupramolecular polymer (MSP) that consists of alternating units of macrocyclic and linear thread components. Ring closure of the thread components has been shown to yield a mixture of cyclic, linear, and branched poly[ n ]catenanes. Reported herein are investigations into this synthetic methodology, with a focus on a more detailed understanding of the crude product distribution and how the concentration of the MSP during the ring closing reaction impacts the resulting poly[ n ]catenanes. In addition to a better understanding of the molecular products obtained in these reactions, the results show that the concentration of the reaction can be used to tune the size and type of poly[ n ]catenanes accessed. At low concentrations the interlocked product distribution is limited to primarily oligomeric and small cyclic catenanes . However, the same reaction at increased concentration can yield branched poly[ n ]catenanes with an ca. 21 kg mol −1 , with evidence of structures containing as many as 640 interlocked rings (1000 kg mol −1 ). 

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2. Scalable synthesis of an architectural library of well‐defined poly(acrylic acid) derivatives: Role of structure on dispersant performance

   https://doi.org/10.1002/pola.29316  

   Lunn, David J. ; Seo, Sungbaek ; Lee, Sang‐Ho ; Zerdan, Raghida Bou ; Mattson, Kaila M. ; Treat, Nicolas J. ; McGrath, Alaina J. ; Gutekunst, Will R. ; Lawrence, Jimmy ; Abdilla, Allison ; et al ( January 2019 , Journal of Polymer Science Part A: Polymer Chemistry)

   The synthesis and systematic comparison of a comprehensive library of well‐defined polymer architectures based on poly(acrylic acid) is reported. Through the development of new synthetic methodologies, linear, single branched, precision‐branched comb, and star polymers were prepared and their performance as dispersants was evaluated. The ability to accurately control chain lengths and branch points allows the subtle interplay between structure and dispersant performance to be defined and affords critical insights into the design of improved polymeric additives for coating formulations. The general industrial relevance of ionic polymers and branched macromolecular architectures supports these design rules for a wide range of other applications and materials, including as additives for personal care products and in water treatment. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem.2019,57, 716–725

    

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3. Employing Heterocyclic Hypervalent Iodine Compounds with ICl Bonds as Initiators and Chain Transfer Agents in the Synthesis of Branched Polymers

   https://doi.org/10.1002/macp.201800471  

   Cao, Yakun ; Kumar, Rajesh ; Tsarevsky, Nicolay V. ( January 2019 , Macromolecular Chemistry and Physics)

   Heterocyclic hypervalent (HV) iodine(III) compounds with ICl bonds and various substituents at the N atom are synthesized and found to be very efficient chain transfer agents in the polymerization of styrene with transfer coefficients exceeding that of CCl₄by 2–3 orders of magnitude, depending on the structure. The chain transfer rate coefficients are also determined. Due to the presence of thermally labile HV bonds, the compounds degrade homolytically upon heating and can initiate radical polymerization. For instance, 1‐chloro‐2‐hexyl‐1,2‐benziodazol‐3(2H)‐one, is used in the polymerization of styrene, which yields low molecular weight polymers with alkyl chloride groups at the α‐ (initiation) and the ω‐chain ends (transfer). Chain‐end functionalization reactions with azide and chain extension under low‐catalyst‐concentration atom transfer radical polymerization (ATRP) conditions of the prepared telechelic polymers are carried out. The same initiator/chain transfer agent is successfully employed in the synthesis of highly branched polymers with multiple alkyl chloride‐type chain ends when added to mixtures of styrene and 1,4‐divinylbenzene containing 10–80 mol% of the divinyl crosslinker, or even pure crosslinker. In all cases, soluble hyperbranched polymers are obtained up to moderate monomer conversions. The effects of crosslinker and HV iodine(III) compound concentrations on the polymerization outcome are studied systematically.

    

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4. One‐Pot Synthesis of Depolymerizable δ ‐Lactone Based Vitrimers

   https://doi.org/10.1002/adma.202300954  

   Yue, Liang ; Su, Yong‐Liang ; Li, Mingzhe ; Yu, Luxia ; Montgomery, S. Macrae ; Sun, Xiaohao ; Finn, M. G. ; Gutekunst, Will R. ; Ramprasad, Rampi ; Qi, H. Jerry ( June 2023 , Advanced Materials)

   A depolymerizable vitrimer that allows both reprocessability and monomer recovery by a simple and scalable one‐pot two‐step synthesis of vitrimers from cyclic lactones is reported. Biobasedδ‐valerolactone with alkyl substituents (δ‐lactone) has low ceiling temperature; thus, their ring‐opening‐polymerized aliphatic polyesters are capable of depolymerizing back to monomers. In this work, the amorphous poly(δ‐lactone) is solidified into an elastomer (i.e.,δ‐lactone vitrimer) by a vinyl ether cross‐linker with dynamic acetal linkages, giving the merits of reprocessing and healing. Thermolysis of the bulkδ‐lactone vitrimer at 200 °C can recover 85–90 wt% of the material, allowing reuse without losing value and achieving a successful closed‐loop life cycle. It further demonstrates that the new vitrimer has excellent properties, with the potential to serve as a biobased and sustainable replacement of conventional soft elastomers for various applications such as lenses, mold materials, soft robots, and microfluidic devices.

    

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5. Chain‐growth polymerization of azide–alkyne difunctional monomer: Synthesis of star polymer with linear polytriazole arms from a core

   https://doi.org/10.1002/pola.29440  

   Gan, Weiping ; Cao, Xiaosong ; Shi, Yi ; Gao, Haifeng ( July 2019 , Journal of Polymer Science)

   This article reports a chain‐growth coupling polymerization of AB difunctional monomer via copper‐catalyzed azide–alkyne cycloaddition (CuAAC) reaction for synthesis of star polymers. Unlike our previously reported CuAAC polymerization of AB_n(n ≥ 2) monomers that spontaneously demonstrated a chain‐growth mechanism in synthesis of hyperbranched polymer, the homopolymerization of AB monomer showed a common but less desired step‐growth mechanism as the triazole groups aligned in a linear chain could not effectively confine the Cu catalyst in the polymer species. In contrast, the use of polytriazole‐based core molecules that contained multiple azido groups successfully switched the polymerization of AB monomers into chain‐growth mechanism and produced 3‐arm star polymers and multi‐arm hyperstar polymers with linear increase of polymer molecular weight with conversion and narrow molecular weight distribution, for example,M_w/M_n ~ 1.05. When acid‐degradable hyperbranched polymeric core was used, the obtained hyperstar polymers could be easily degraded under acidic environment, producing linear degraded arms with defined polydispersity. © 2019 Wiley Periodicals, Inc. J. Polym. Sci.2020,58, 84–90

    

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