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Transforming how plastics are made, unmade, and remade through innovative research and diverse partnerships that together foster environmental stewardship is critically important to a sustainable future. Designing, preparing, and implementing polymers derived from renewable resources for a wide range of advanced applications that promote future economic development, energy efficiency, and environmental sustainability are all central to these efforts. In this

Macrocyclic poly(glycidyl phenyl ether) (pGPE) synthesized via zwitterionic ring opening polymerization is typically contaminated by chains with linear and tadpole architecture. Although mass spectrometry (MS) analysis can readily confirm the presence of the linear byproduct, due to its unique mass, it is unable to differentiate between the cyclic and tadpole structures, which are constitutional isomers produced by backbiting reactions in monomeric or dimeric chains, respectively. To overcome this problem, ultraperformance reversed-phase liquid chromatography interfaced with electrospray ionization tandem mass spectrometry (UPLC-ESI-MS/MS) was employed. The separation achieved by UPLC revealed that the tadpole isomer elutes before the cyclic structure because of the increased polarity afforded by its distinctive substituents. The ratio of tadpole to cyclic species increased with the degree of polymerization, in agreement with the synthetic method used, as the potential for forming tadpole structures by backbiting is entropically favored in longer polymer chains. Once separated, the two isomers could be independently characterized by tandem mass spectrometry. The macrocyclic and tadpole species exhibit unique fragmentation patterns, including structurally diagnostic fragments for each structure., Support from the National Science Foundation (CHE-1808115 to C. W.) is gratefully acknowledged.

We have achieved breakthroughs for the efficient synthesis of linear polydicyclopentadiene (pDCPD) via photoredox mediated metal-free ring-opening metathesis polymerization (MF-ROMP). Molecular weight control from 1 to 16 kDa can be targeted in a straightforward manner. Assisted by this method, the Tg–Mn dependence of linear pDCPD is investigated and reported for the first time.

Unlike their more common linear counterparts, cyclic polymers have a ring-like structure and a lack of chain ends. Because of their topology, cyclic polymers exhibit a unique set of properties when compared with linear or branched macromolecules. For example, cyclic homopolymers exhibit a reduced hydrodynamic volume and a slower degradation profile compared with their linear analogues. Cyclic block copolymers self-assemble into compact nanostructures, as illustrated by their reduced domain spacing when cast into thin films and their reduced micellar size in solution. Although methods for preparing well-defined cyclic polymers have only been available since 1980, the extensive utilization of the cyclic topology in nature highlights the vital role that a cyclic architecture can play in imparting valuable physical properties, such as increased chemical stability or propensity towards self-assembly. This Review describes the major developments in the synthesis of cyclic polymers and provides an overview of their fundamental physical properties. In this context, preliminary studies exploring potential applications will be critically assessed and the remaining challenges for the field delineated.

Photo-redox mediated ring-opening metathesis polymerization (photo-ROMP) is an emerging ROMP technique that uses an organic redox mediator and a vinyl ether initiator, in contrast to metal-based initiators traditionally used in ROMP. The reversibility of the redox-mediated initiation and propagation steps enable spatiotemporal control over the polymerization. Herein, we explore a simple, inexpensive means of controlling molecular weight, using alpha olefins as chain transfer agents. This method enables access to low molecular weight oligomers, and molecular weights between 1 and 30 kDa can be targeted simply by altering the stoichiometry of the reaction. This method of molecular weight control was then used to synthesize a functionalized norbornene copolymer in a range of molecular weights for specific materials applications.

Cyclic polymers have garnered increasing attention in the materials community as lack of free-chain ends in cyclic polymers results in significant differences in structure, thermodynamics, and dyna...

Unlike their more common linear counterparts, cyclic polymers have a ring-like structure and a lack of chain ends. Because of their topology, cyclic polymers exhibit a unique set of properties when compared with linear or branched macromolecules. For example, cyclic homopolymers exhibit a reduced hydrodynamic volume and a slower degradation profile compared with their linear analogues. Cyclic block copolymers self-assemble into compact nanostructures, as illustrated by their reduced domain spacing when cast into thin films and their reduced micellar size in solution. Although methods for preparing well-defined cyclic polymers have only been available since 1980, the extensive utilization of the cyclic topology in nature highlights the vital role that a cyclic architecture can play in imparting valuable physical properties, such as increased chemical stability or propensity towards self-assembly. This Review describes the major developments in the synthesis of cyclic polymers and provides an overview of their fundamental physical properties. In this context, preliminary studies exploring potential applications will be critically assessed and the remaining challenges for the field delineated.

The electrophilic zwitterionic ring expansion polymerization of monosubstituted epoxides initiated by tris(pentafluorophenyl)borane [B(CF)] is investigated to reveal the effect of substituents on the generation of functional macrocyclic polyethers and to understand the formation of topological impurities for better control of architectural purity during polymerization. With this aim, different families of monofunctional epoxides were polymerized, and the products were analyzed by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-ToF MS). The data revealed that side reactions coexist with the macrocyclization reaction, including chain transfer reactions to the monomer. With the detailed MALDI-ToF MS analysis, it was possible to ascertain structural assignments of major and minor products and propose corresponding reaction mechanisms. Substituent effects were also studied to probe the functional group tolerance of this polymerization. Finally, computational studies were performed to examine the chemical interaction between the monomer and B(CF) catalyst, which corroborated the experimental results by providing insight into the likelihood of generating noncyclic byproducts. By using both analytical and computational tools, the polymerization could be optimized to generate macrocyclic polyethers with substantially increased purity., The authors gratefully acknowledge support from the Basque Government (PIBA 2018-34 and IT-1175-19) and the Spanish Ministry “Ministerio de Ciencia, Innovacion y Universidades ́”, PGC2018-094548-B-I00 (MICINN/FEDER, UE). F.M.H. thanks the DIPC for its invitation and accommodation as a visiting researcher. F.M.H. and S.M.G also thank the Joseph H. Boyer professorship, the Smart MATerials Design, Analysis and Processing consortium (SMATDAP) under cooperative agreement IIA-1430280, and the National Science Foundation for funding the MALDI-ToF MS instrument (MRI 0619770).

Rhodamine amides are known to function as an important platform for molecular probe formation. The use of rhodamine-based probes has focused on the equilibrium between the off to on opening of the lactam form to the amide form. Herein, a series of four structurally similar rhodamine lactam derivatives is studied to show that the rate of conversion from the lactam form to the amide form can vary greatly ( 12 h) and that the rate trend is different from the trend for the absorbance measured at equilibrium. Slow or varying rates of ring opening for structurally similar rhodamine derivatives could produce inaccurate results. Rates were studied with both trifluoroacetic acid (TFA) and iron III. The rate of conversion changed depending on the structure of the substituent attached to the lactam nitrogen. Interestingly the rate of conversion varied even for compounds with similar absorbance at equilibrium. This work will help with the development of more effective rhodamine-based molecular probes.

The physical properties of cyclic polymers can be perturbed by the presence of architectural impurities, even in trace amounts. As a result, it is important to develop techniques for quantifying and improving the purity of cyclic polymer samples. The zwitterionic ring-expansion polymerization (ZREP) of glycidyl phenyl ether (GPE) with B(CF) is a convenient, one-step method to generate cyclic polyethers in large amounts. However, the obtained cyclic samples are inherently contaminated by architectural impurities, which in this study are detected, identified, quantified, and successfully removed by a >click-scavenging> approach. The analytical techniques employed included matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), quantitative Fourier transform infrared spectroscopy (FTIR), and gel permeation chromatography/multiangle light scattering (GPC-MALS). The end-group functionalization of the architectural impurities was a particularly useful method in the identification of tadpole and linear polymers in cyclic poly(glycidyl phenyl ether) samples of M = 1.1 and 11.7 kg/mol. Moreover, differential scanning calorimetry (DSC) measurements demonstrated that the presence of architectural impurities cause only a small reduction (1.4-2.0 °C) of the glass transition temperature (T) of the cyclic polyether; an effect that is corroborated in this investigation by means of dielectric spectroscopy. The segmental and local dynamics of cyclic samples are shown to be only slightly modified by the presence of a small percentage of architectural impurities., We gratefully acknowledge support from MINECO (MAT2012-31088) and Basque Government (IT-654-13). S.M.G. and F.M.H. acknowledge the NSF (CHEM-1412439), the ACS-PRF (53980-ND7), and the Joseph H. Boyer professorship for support as well as NSF (MRI-0619770) for enabling MALDI−TOF MS characterization.