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Organocatalyzed atom transfer radical polymerization (O-ATRP) is a method of producing polymers with precise structures under mild conditions using organic photoredox catalysts (PCs). Due to the unknown toxicity of PCs and their propensity to introduce color in polymers synthesized by this method, removal of the PC from the polymer product can be important for certain applications of polymers produced using O-ATRP. Current purification methods largely rely on precipitation to remove the PC from the polymer, but a more effective and efficient purification method is needed. In this work, an alternative purification method relying on oxidation of the PC to PC

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The development of photoinduced organocatalyzed atom transfer radical polymerization (O-ATRP) has received considerable attention since its introduction in 2014. Expanding on many of the advantages of traditional ATRP, O-ATRP allows well-defined polymers to be produced under mild reaction conditions using organic photoredox catalysts. As a result, O-ATRP has opened access to a range of sensitive applications where the use of a metal catalyst could be of concern, such as electronics, certain biological applications, and the polymerization of coordinating monomers. However, key limitations of this method remain and necessitate further investigation to continue the development of this field. As such, this review details the achievements made to-date as well as future research directions that will continue to expand the capabilities and application landscape of O-ATRP.

Photoinduced organocatalyzed atom transfer radical polymerization (O-ATRP) is a controlled radical polymerization methodology catalyzed by organic photoredox catalysts (PCs). In an efficient O-ATRP system, good control over molecular weight with an initiator efficiency (I* = Mn,theo/Mn,exp × 100%) near unity is achieved, and the synthesized polymers possess a low dispersity (Đ). N,N-Diaryl dihydrophenazine catalysts typically produce polymers with low dispersity (Đ < 1.3) but with less than unity molecular weight control (I* ~ 60-80%). This work explores the termination reactions that lead to decreased control over polymer molecular weight and identifies a reaction leading to radical addition to the phenazine core. This reaction can occur with radicals generated through reduction of the ATRP initiator or the polymer chain end. In addition to causing a decrease in I*, this reactivity modifies the properties of the PC, ultimately impacting polymerization control in O-ATRP. With this insight in mind, a new family of core-substituted N,N-diaryl dihydrophenazines is synthesized from commercially available ATRP initiators and employed in O-ATRP. These new core-substituted PCs improve both I* and Đ in the O-ATRP of MMA, while minimizing undesired side reactions during the polymerization. Further, the ability of one core-substituted PC to operate at low catalyst loadings is demonstrated, with minimal loss of polymerization control down to 100 ppm (weight average molecular weight [Mw] = 10.8 kDa, Đ = 1.17, I* = 104% vs Mw = 8.26, Đ = 1.10, I* = 107% at 1000 ppm) and signs of a controlled polymerization down to 10 ppm of the catalyst (Mw = 12.1 kDa, Đ = 1.36, I* = 107%).

Radical cations of photoredox catalysts used in organocatalyzed atom transfer radical polymerization (O-ATRP) have been synthesized and investigated to gain insight into deactivation in O-ATRP. The stability and reactivity of these compounds were studied in two solvents, N,N-dimethylacetamide and ethyl acetate, to identify possible side reactions in O-ATRP and to investigate the ability of these radical cations to deactivate alkyl radicals. A number of other factors that could influence deactivation in O-ATRP were also probed, such as ion pairing with the radical cations, radical cation oxidation potential, and halide oxidation potential. Ultimately, these studies enabled radical cations to be employed as reagents during O-ATRP to demonstrate improvements in polymerization control with increasing radical cation concentrations. In the polymerization of acrylates, this approach enabled superior molecular weight control, a decrease in polymer dispersity from 1.90 to 1.44, and an increase in initiator efficiency from 78 to 102%. This work highlights the importance of understanding the mechanism and side reactions of O-ATRP, as well as the importance of catalyst radical cations for successful O-ATRP.

Core-modified N-alkyl phenoxazines were synthesized and evaluated as photoredox catalysts (PCs) in organocatalyzed atom transfer radical polymerization (O-ATRP). Each PC was characterized and found to strongly absorb UVA and visible light, undergo reversible oxidation to radical cation species, and exhibit high quantum yields of fluorescence (Φf > 77%). PCs found to exhibit intramolecular charge transfer in their excited state were capable of the controlled synthesis of poly(methyl methacrylate) with good molecular weight control (I* ~ 100%) and moderately low dispersity (Đ < 1.30).

Photoinduced organocatalyzed atom-transfer radical polymerization (O-ATRP) is a controlled radical polymerization technique that can be driven using low-energy, visible light and makes use of organic photocatalysts. Limitations of O-ATRP have traditionally included the need for high catalyst loadings (1000 ppm) and the narrow scope of monomers that can be controllably polymerized. Recent advances have shown that N,N-diaryl dihydrophenazine (DHP) organic photoredox catalysts (PCs) are capable of controlling O-ATRP at PC loadings as low as 10 ppm, a significant advancement in the field. In this work we synthesized five new DHP PCs and examined their efficacy in controlling O-ATRP at low ppm catalyst loadings. We found that we were able to polymerize methyl methacrylate at PC loadings as low as 10 ppm (relative to monomer) while producing polymers with dispersities as low as Đ = 1.33 and achieving initiator efficiencies (I*) near unity (102%). In addition to applying these PCs in O-ATRP, we carried out a thorough investigation into the structure–property relationships of the new DHP PCs reported herein and report new photophysical characterization data for previously reported DHPs. The insight into the DHP structure–property relationships that we discuss herein will aid in the elucidation of their ability to catalyze O-ATRP at low catalyst loadings. Additionally, this work sheds light on how structural modifications affect certain PC properties with the goal of bolstering our understanding of how to tune PC structures to overcome current limitations in O-ATRP such as the controlled polymerization of challenging monomers.

Investigation of the effects of a solvent on the photophysical and redox properties of the photoredox catalyst (PC), N,N-di(2-naphthyl)-5,10-dihydrophenazine (PC 1), revealed the opportunity to use tetrahydrofuran (THF) to modulate the reactivity of PC 1 toward achieving a controlled organocatalyzed atom transfer radial polymerization (O-ATRP) of acrylates. Compared with dimethylacetamide (DMAc), in tetrahydrofuran (THF), PC 1 exhibits a higher quantum yield of intersystem crossing (Φ(ISC) = 0.02 in DMAc, 0.30 in THF), a longer singlet excited-state lifetime (τ(Singlet) = 3.81 ns in DMAc, 21.5 ns in THF), and a longer triplet excited-state lifetime (τ(Triplet) = 4.3 μs in DMAc, 15.2 μs in THF). Destabilization of 1(•+), the proposed polymerization deactivator, in THF leads to an increase in the oxidation potential of this species by 120 mV (E(1/2)(0) = 0.22 V vs SCE in DMAc, 0.34 V vs SCE in THF). The O-ATRP of n-butyl acrylate (n-BA) catalyzed by PC 1 proceeds in a more controlled fashion in THF than in DMAc, producing P(n-BA) with low dispersity, Đ (Đ < 1.2). Model reactions and spectroscopic experiments revealed that two initiator-derived alkyl radicals add to the core of PC 1 to form an alkyl-substituted photocatalyst (2) during the polymerization. PC 2 accesses a polar CT excited state that is ~40 meV higher in energy than PC 1 and forms a slightly more oxidizing radical cation (E(1/2)(0) = 0.22 V for 1(•+) and 0.25 V for 2(•+) in DMAc). A new O-ATRP procedure was developed wherein PC 1 is converted to 2 in situ. The application of this method enabled the O-ATRP of a number of acrylates to proceed with moderate to good control (Đ = 1.15–1.45 and I* = 83–127%).

Anchote (Coccinia abyssinica) starch films were prepared by a solution casting method with glycerol, 1-ethyl-3-methylimidazolium acetate, sorbitol or triethylene glycol as plasticizers. The effect of these plasticizers and their concentration on film microstructure, thermal, and mechanical properties was investigated. Scanning electron microscopy revealed that regardless of plasticizer type, films possessing higher plasticizer content had more homogeneous morphologies than those with lower plasticizer content. The FTIR spectra of films plasticized with 1-ethyl-3-methylimidazolium acetate had higher intensity peaks at 3150, 1400 and 1000 cm−1 when compared to other film peaks. These data show that 1-ethyl-3-methylimidazolium acetate plasticized films have decreased molecular order which results in less hydrogen bonding. For this reason, films developed from 1-ethyl-3-methylimidazolium acetate were more flexible than the others. The effect of plasticizers on the thermal properties of the anchote starch films was investigated using thermogravimetric analysis (TGA). Films made from 30% (w/w) plasticizer concentration exhibited higher thermal stability for all types of plasticizer. Mechanical testing showed that sorbitol films had the highest tensile strength, approximately 2 times that of the triethylene glycol plasticized film and 3 times that of the film made from 1-ethyl-3-methylimidazolium acetate.

Phenochalcogenazines such as phenoxazines and phenothiazines have been widely employed as photoredox catalysts (PCs) in small molecule and polymer synthesis. However, the effect of the chalcogenide in these catalysts has not been fully investigated. In this work, a series of four phenochalcogenazines is synthesized to understand how the chalcogenide impacts catalyst properties and performance. Increasing the size of the chalcogenide is found to distort the PC structure, ultimately impacting the properties of each PC. For example, larger chalcogenides destabilize the PC radical cation, possibly resulting in catalyst degradation. In addition, PCs with larger chalcogenides experience increased reorganization during electron transfer, leading to slower electron transfer. Ultimately, catalyst performance is evaluated in organocatalyzed atom transfer radical polymerization and a photooxidation reaction for C(sp

ChemCatChem 14(17), e202200485 (2022). doi:10.1002/cctc.202200485 special issue: "Photocatalytic Synthesis – Catalysts, Catalytic Strategies, and Mechanistic Insights / Guest editors: Line Næsborg ; Bartholomäus Pieber ; Oliver Wenger", Published by WILEY-VCH Verlag, Weinheim

Photoinduced organocatalyzed atom transfer radical polymerization (O-ATRP) is a controlled radical polymerization methodology catalyzed by organic photoredox catalysts (PCs). In an efficient O-ATRP system, good control over molecular weight with an initiator efficiency (I* = M(n,theo)/M(n,exp) × 100%) near unity is achieved, and the synthesized polymers possess a low dispersity (Đ). N,N-Diaryl dihydrophenazine catalysts typically produce polymers with low dispersity (Đ < 1.3) but with less than unity molecular weight control (I* ~ 60–80%). This work explores the termination reactions that lead to decreased control over polymer molecular weight and identifies a reaction leading to radical addition to the phenazine core. This reaction can occur with radicals generated through reduction of the ATRP initiator or the polymer chain end. In addition to causing a decrease in I*, this reactivity modifies the properties of the PC, ultimately impacting polymerization control in O-ATRP. With this insight in mind, a new family of core-substituted N,N-diaryl dihydrophenazines is synthesized from commercially available ATRP initiators and employed in O-ATRP. These new core-substituted PCs improve both I* and Đ in the O-ATRP of MMA, while minimizing undesired side reactions during the polymerization. Further, the ability of one core-substituted PC to operate at low catalyst loadings is demonstrated, with minimal loss of polymerization control down to 100 ppm (weight average molecular weight [M(w)] = 10.8 kDa, Đ = 1.17, I* = 104% vs M(w) = 8.26, Đ = 1.10, I* = 107% at 1000 ppm) and signs of a controlled polymerization down to 10 ppm of the catalyst (M(w) = 12.1 kDa, Đ = 1.36, I* = 107%).

In this issue of Chem, Fors and co-workers describe an exciting approach to block copolymer synthesis by using electricity and light to mediate orthogonal polymerizations with temporal control. Through repeated cycling of each stimulus, multi-block copolymers with up to six blocks that were previously inaccessible by other methods are synthesized.

We report here a mild, safe, and user-friendly bromine radical catalysis system that enables efficient [3 + 2] cycloaddition of diversely substituted vinyl- and ethynylcyclopropanes with a broad range of alkenes, including drug-like molecules and pharmaceuticals. Key to the success is the use of photosensitizing triplet-state β-fragmentation of a judiciously selected precatalyst, cinnamyl bromide, to generate bromine radicals in a controlled manner using parts per million-level photocatalyst (i.e., 4CzIPN) loading.

Development of photocatalysts (PCs) with diverse properties has been essential in advancement of organocatalyzed atom transfer radical polymerization (O-ATRP). In this work, dimethyl-dihydroacridines are presented as a new family of organic PCs, for the first time enabling controlled polymerization of challenging acrylate monomers via O-ATRP. Structure-property relationships for seven PCs are established, demonstrating tunable photochemical and electrochemical properties and accessing a strongly oxidizing (2)PC(●+) intermediate for efficient deactivation. In O-ATRP, a combination of PC choice, implementation of continuous-flow reactors, and promotion of deactivation through addition of LiBr are critical to producing well-defined acrylate polymers with dispersities as low as 1.12. The utility of this approach is established through demonstration of the oxygen tolerance of the system and application to diverse acrylate monomers, including the synthesis of well-defined di- and triblock copolymers.

Phenothiazine, owing to its ease of oxidation and modularity with respect to facile functionalization, is an attractive central chemical unit from which to construct highly reducing organic photoredox catalysts. While design improvements have been made in the community, the yield of intersystem crossing (ΦISC), which determines access to the long-lived triplet excited state, has yet to be systematically optimized. Herein, we explore the impacts of N-aryl substituent variation on excited-state dynamics using picosecond to millisecond transient absorption and emission spectroscopies. Design principles are uncovered that center on controlling the energy of an intermediate charge transfer (CT) state within the singlet excited-state manifold, which, in turn, dictates the yield of CT-state formation and the rate constants for its depletion. Ultimately, we find ΦISC to be highly sensitive to the electron-withdrawing character of the N-aryl electron acceptor in the aforementioned CT state, with ΦISC ranging from ∼0 to 0.96.

Four series of brush block copolymers (BBCP), with near identical side chain compositions but varying backbone structures, were synthesized to investigate the effect of backbone structure on the process of thermal BBCP self-assembly to photonic crystals (PCs). Each of the self-assembled PC films were examined by reflection measurements, small angle X-ray scattering measurements, and scanning electron microscopy to compare the resulting properties of the polymeric photonic crystal and the nanostructured morphology impacted by the backbone structure. It was found that the composition of the brush backbone within a BBCP has a dramatic effect on the ability of the BBCP to self-assemble into ordered nanostructures and on the local ordering of the nanostructure morphology accessed with higher molecular weight (MW) BBCPs (> 1,500 kg/mol). BBCPs with a norbornene imide-based backbone were able to thermally self-assemble to longer wavelength reflecting PCs and had higher fidelity ordering of lamellar nanostructures with higher MW polymers. By analyzing the melt rheological responses of the backbone compositions, both as linear polymers and homobrush polymers, it was concluded that the inherent fragility of the backbone promotes enhanced local ordering in the lamellar nanostructure morphology as well as access to larger domain sizes.

An electrochemical variant of organocatalyzed atom transfer radical polymerization (O-ATRP) is developed and investigated. Inspired by electrochemically mediated atom transfer radical polymerization (eATRP), potentiostatic electrolysis is used to manipulate the catalyst’s redox states in O-ATRP to understand whether deactivation in O-ATRP can be enhanced to improve polymerization control. During the course of this work, several possible side reactions are investigated, and the electrochemical apparatus is optimized to reduce side reactions at the counter electrode. This electrochemically modified O-ATRP method (eO-ATRP) is then studied at different applied potentials, under different irradiation conditions, and with two photoredox catalysts to understand the impact of electrolysis on polymerization control. Ultimately, although electrolysis was successfully used to improve polymerization control in O-ATRP, some additional challenges have been identified. Several key questions are postulated to guide future work in this area.

Dual catalytic light-driven cross-coupling methodologies utilizing a Ni(II) salt with a photocatalyst (PC) have emerged as promising methodologies to forge aryl C–N bonds under mild conditions. The recent discovery that the PC can be omitted and the Ni(II) complex directly photoexcited suggests that the PC may perform energy transfer (EnT) to the Ni(II) complex, a mechanistic possibility that has recently been proposed in other systems across dual Ni photocatalysis. Here, we report the first studies in this field capable of distinguishing EnT from electron transfer (ET), and the results are consistent with Förster-type EnT from the excited state [Ru(bpy)(3)]Cl(2) PC to Ni-amine complexes. The structure and speciation of Ni-amine complexes that are the proposed EnT acceptors were elucidated by crystallography and spectroscopic binding studies. With the acceptors known, quantitative Förster theory was utilized to predict the ratio of quenching rate constants upon changing the PC, enabling selection of an organic phenoxazine PC that proved to be more effective in catalyzing C–N cross-coupling reactions with a diverse selection of amines and aryl halides.

In this study the chemical composition, morphology, crystallinity, thermal, and pasting properties of Anchote (Coccinia abyssinica) starch were compared with commercial potato and wheat starches. Anchote starch showed lower total starch content than that of potato starch. Their morphological properties were investigated using scanning electron microscopy. The mean granule width of potato starch was four times greater than anchote starch and two times greater than that of wheat starch. The x-ray powder diffraction analysis revealed that anchote starch had a B-type crystallinity pattern. Differential scanning calorimetric (DSC) results showed the significant differences between the gelatinization temperature of anchote, wheat, and potato starches. The onset, peak, and conclusion temperature of anchote starch were 66.58 °C, 70.18 °C, and 73.98 °C, respectively. The gelatinization temperature of potato and wheat starches were 56.53 °C and 55.56 °C for onset, 61.46 °C and 61.14 °C for peak, 68.47 °C and 67.06 °C for conclusion, respectively. These properties of anchote starch make it an attractive candidate for industrial use.

This study examined the relationship between how visual information is organized and people’s visual search performance. Specifically, we systematically varied how visual search information was organized (from well-organized to disorganized), and then asked participants to perform a visual search task involving finding and identifying a number of visual targets within the field of visual non-targets. We hypothesized that the visual search task would be easier when the information was well-organized versus when it was disorganized. We further speculated that visual search performance would be mediated by cognitive workload, and that the results could be generally described by the well-established speed-accuracy tradeoff phenomenon. This paper presents the details of the study we designed and our results.

JAEA-AMS-TONO has been in operation at the Tono Geoscience Center, Japan Atomic Energy Agency since 1998 and 20 years have passed from the beginning of its utilization. The AMS has been used to measure 14C, 10Be and 26Al. The main use is measurement of 14C in geological samples for dating studies in neotectonics and hydrogeology, in support of the research on geosphere stability applicable to the long-term isolation of high-level radioactive waste. In order to increase the speed of sample preparation, we introduced an automated graphitization equipment and made a gas-strip line to collect dissolved inorganic carbon in groundwater samples. Measurement of 10Be and 26Al has been used for geoscience studies and the detection limit in the measurement of 10Be was improved. Recently optimization of AMS settings for 129I-AMS has been progressed.

Organocatalyzed photoredox radical ring-opening polymerization (rROP) of vinylcyclopropanes (VCPs) is employed for the synthesis of polymers with controlled molecular weight (MW), dispersity, and composition. Herein, we report the study on the rROP of a variety of VCP monomers bearing diverse functional groups (such as amide, alkene, ketal, urea, hemiaminal ether, and so on) under organocatalyzed conditions with varying light sources and temperature. Notably, VCP monomers bearing natural product functionality or their derivatives can be polymerized in a controlled manner to produce poly(VCPs) with predictable MW, low dispersity, tunable composition, high thermal stability, and tailored glass transition temperature (T(g)), ranging 39 to 107 °C. Lastly, successful “grafting through” synthesis of molecular brush copolymers containing 1.0 or 5.0 kDa polydimethylsiloxane (PDMS) side chains from readily accessible EtVCP-PDMS macromonomers further demonstrates the robustness of this organocatalyzed photoredox rROP.

Organocatalyzed ATRP (O-ATRP) is a growing field exploiting organic chromophores as photoredox catalysts (PCs) that engage in dissociative electron transfer (DET) activation of alkyl halide initiators following absorption of light. Characterizing DET rate coefficients (kact) and photochemical yields across various reaction conditions and PC photophysical properties will inform catalyst design and efficient use during polymerization. The studies described herein consider a class of phenoxazine PCs where synthetic handles of core-substitution and N-aryl substitution enable tunability of the electronic and spin character of the catalyst excited state as well as DET reaction driving force ( ). Using Stern-Volmer quenching experiments through variation of diethyl 2-bromo-2-methylmalonate (DBMM) initiator concentration, collisional quenching is observed. Eight independent measurements of kact are reported as a function of for four PCs: four triplet reactants and four singlets with kact values ranging from 1.1´108 M-1s-1 where DET itself controls the rate to 4.8´109 M-1s-1 where diffusion is rate limiting. This overall data set, as well as a second one inclusive of five literature values from related systems, is readily modeled with only a single parameter of reorganization energy under the frameworks of adiabatic Marcus electron transfer theory and Marcus-Savéant theory of DET. The results provide a predictive map where kact can be estimated if is known and highlight that DET in these systems appears insensitive to PC reactant electronic and spin properties outside of their impact on driving force. Next, on the basis of measured kact values in selected PC systems and knowledge of their photophysics, we also consider activation yields specific to the reactant spin states as the DBMM initiator concentration is varied. In N-naphthyl-containing PCs characterized by near-unity intersystem crossing, the T1 is certainly an important driver for efficient DET. However, at DBMM concentrations common to polymer synthesis, the S1 is also active and drives 33% of DET reaction events. Even in systems with low yields of ISC, such as in N-phenyl-containing PCs, reaction yields can be driven to useful values by exploiting the S1 under high DBMM concentration conditions. Finally, we have quantified photochemical reaction quantum yields, which take into account potential product loss processes after electron-transfer quenching events. Both S1 and T1 reactant states produce the PC·+ radical cation with a common yield of 71%, thus offering no evidence for spin selectivity in deleterious back electron transfer. The sub-unity PC·+ yields suggest that some combination of solvent (DMAc) oxidation and energy-wasting back electron transfer is likely at play and these pathways should be factored in subsequent mechanistic considerations.

Engineering design has drawn inspiration from naturally occurring structures to advance manufacturing processes and products, termed biomimetics. For example, the mantis shrimp, order Stomatopoda, is capable of producing one of the fastest appendage strikes in the world with marginal musculoskeletal displacement. The extreme speed of the mantis shrimp's raptorial appendage is due to the non-Euclidean hyperbolic paraboloid (i.e., saddle) shape within the dorsal region of the merus, which allows substantial energy storage through compression in the sagittal plane. Here, investigation of 3D printed synthetic geometries inspired by the mantis shrimp saddle geometry has revealed insights for elastic energy storage (i.e., spring-like) applications. Saddles composed of either a stiff or a flexible resin were investigated for spring response to explore the geometric effects. By modulating the saddle geometry and testing the spring response, it was found that, for the stiff resin, the spring constant was improved as the curvature of the contact and orthogonal faces were maximized and minimized, respectively. For the flexible resin, it was found that the spring constant increased by less than 250 N/mm as the saddle geometry changed, substantiating that the flexible component of mantis saddles does not contribute to energy storage capabilities. The geometries of two saddles from the mantis shrimp species Odontodactylus scyllarus were estimated and exhibited similar trends to manufactured saddles, suggesting that modulating saddle geometry can be used for tailored energy storage moduli in spatially constrained engineering applications.

Neutrinos generated during solar flares remain elusive. However, after $50$ years of discussion and search, the potential knowledge unleashed by their discovery keeps the search crucial. Neutrinos associated with solar flares provide information on otherwise poorly known particle acceleration mechanisms during solar flare. For neutrino detectors, the separation between atmospheric neutrinos and solar flare neutrinos is technically encumbered by an energy band overlap. To improve differentiation from background neutrinos, we developed a method to determine the temporal search window for neutrino production during solar flares. Our method is based on data recorded by solar satellites, such as Geostationary Operational Environmental Satellite (GOES), Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI), and GEOTAIL. In this study, we selected 23 solar flares above the X5.0 class that occurred between 1996 and 2018. We analyzed the light curves of soft X-rays, hard X-rays, $\gamma$-rays, line $\gamma$-rays from neutron capture as well as the derivative of soft X-rays. The average search windows are determined as follows: $4,178$ s for soft X-ray, $700$ s for derivative of soft X-ray, $944$ s for hard X-ray ($100$-$800$ keV), $1,586$ s for line $\gamma$-ray from neutron captures, and $776$ s for hard X-ray (above $50$ keV). This method allows neutrino detectors to improve their sensitivity to solar flare neutrinos., Comment: 29 pages. Accepted for Solar Physics

Three series of well-defined norbornene imide-based polymers with different pendant groups were synthesized to investigate the effect of the pendant group on the polymer conformation in solution and bulk melt properties. Each of these three series was examined by analyzing the polymers' bulk z-average radius of gyration via static light scattering and the polymers' melt viscoelastic properties via oscillatory measurements and differential scanning calorimetry. Sterically bulky pendant wedge groups modestly increase the rodlike conformation of the norbornene-imide polymer, however, the inherent rigidity of the polymer main-chain can still be observed with less bulky substituents. In stark contrast, the different side groups significantly impacted the bulk viscoelastic and thermal properties. By increasing the pendant group size, the chain diameter of the polymer increases and lowers the entanglement modulus. Finally, as the wedge pendant group size increases, the segmental relaxation time and the fragility index of these norbornene-based polymers are decreased.