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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.

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...

Herein, the design, synthesis, and characterization of an unprecedented copolymer consisting of alternating linear and dendritic segments is described. First, a 4th-generation Hawker-type dendron with two azide groups was synthesized, followed by a step-growth azide-alkyne "click" reaction between the 4th-generation diazido dendron and poly(ethylene glycol) diacetylene to create the target polymers. Unequal reactivity of the functional groups was observed in the step-growth polymerization. The resulting copolymers, with alternating hydrophilic linear and hydrophobic dendritic segments, can spontaneously associate into a unique type of microphase-segregated nanorods in water.

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).

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.