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1. ipso ‐Arylative Ring‐Opening Polymerization as a Route to Electron‐Deficient Conjugated Polymers

   https://doi.org/10.1002/anie.201809610  

   Shih, Feng‐Yang ; Choi, Deokkyu ; Wu, Qin ; Nam, Chang‐Yong ; Grubbs, Robert B. ( December 2018 , Angewandte Chemie International Edition)

   ipso‐Arylative ring‐opening polymerization of 2‐bromo‐8‐aryl‐8H‐indeno[2,1‐b]thiophen‐8‐ol monomers proceeds to M_nup to 9 kg mol⁻¹with conversion of the monomer diarylcarbinol groups to pendent conjugated aroylphenyl side chains (2‐benzoylphenyl or 2‐(4‐hexylbenzoyl)phenyl), which influence the optical and electronic properties of the resulting polythiophenes. Poly(3‐(2‐(4‐hexylbenzoyl)phenyl)thiophene) was found to have lower frontier orbital energy levels (HOMO/LUMO=−5.9/−4.0 eV) than poly(3‐hexylthiophene) owing to the electron‐withdrawing ability of the aryl ketone side chains. The electron mobility (ca. 2×10⁻³ cm² V⁻¹ s⁻¹) for poly(3‐(2‐(4‐hexylbenzoyl)phenyl)thiophene) was found to be significantly higher than the hole mobility (ca. 8×10⁻⁶ cm² V⁻¹ s⁻¹), which suggests such polymers are candidates for n‐type organic semiconductors. Density functional theory calculations suggest that backbone distortion resulting from side‐chain steric interactions could be a key factor influencing charge mobilities.

    

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2. ipso ‐Arylative Ring‐Opening Polymerization as a Route to Electron‐Deficient Conjugated Polymers

   https://doi.org/10.1002/ange.201809610  

   Shih, Feng‐Yang ; Choi, Deokkyu ; Wu, Qin ; Nam, Chang‐Yong ; Grubbs, Robert B. ( December 2018 , Angewandte Chemie)

   ipso‐Arylative ring‐opening polymerization of 2‐bromo‐8‐aryl‐8H‐indeno[2,1‐b]thiophen‐8‐ol monomers proceeds to M_nup to 9 kg mol⁻¹with conversion of the monomer diarylcarbinol groups to pendent conjugated aroylphenyl side chains (2‐benzoylphenyl or 2‐(4‐hexylbenzoyl)phenyl), which influence the optical and electronic properties of the resulting polythiophenes. Poly(3‐(2‐(4‐hexylbenzoyl)phenyl)thiophene) was found to have lower frontier orbital energy levels (HOMO/LUMO=−5.9/−4.0 eV) than poly(3‐hexylthiophene) owing to the electron‐withdrawing ability of the aryl ketone side chains. The electron mobility (ca. 2×10⁻³ cm² V⁻¹ s⁻¹) for poly(3‐(2‐(4‐hexylbenzoyl)phenyl)thiophene) was found to be significantly higher than the hole mobility (ca. 8×10⁻⁶ cm² V⁻¹ s⁻¹), which suggests such polymers are candidates for n‐type organic semiconductors. Density functional theory calculations suggest that backbone distortion resulting from side‐chain steric interactions could be a key factor influencing charge mobilities.

    

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3. Ring-Opening Polymerization of Cyclic Esters in an Aqueous Dispersion

   https://doi.org/10.1021/acs.macromol.0c01300  

   Harrier, Danielle D. ; Kenis, Paul J. ; Guironnet, Damien ( October 2020 , Macromolecules)

   Aqueous polymer dispersions are commodity materials produced on a multimillion-ton scale annually. Today none of these materials are biodegradable because the process by which they are made is not compatible with the synthesis of biodegradable polymers. Herein, we report a droplet microfluidic encapsulation strategy for protecting a water incompatible ring opening polymerization (ROP) catalyst from the aqueous phase, yielding biodegradable polymer particles dispersed in water. Polymerization yields 300 μm sized particles comprised of biodegradable poly(δ-valerolactone) with molecular weights up to 19.5 kg mol−1. The success of this approach relies on simultaneous precise control of the kinetics of polymerization, the rate of mass transfer, and fluid mechanics. The power of this methodology was demonstrated by the synthesis of cross-linked polymer particles through the copolymerization of bis(εcaprolactone-4-yl)propane and δ-valerolactone, producing cross-linked polymer particles with molecular weights reaching 65.3 kg mol−1. Overall, this encapsulation technique opens the door for the synthesis of biodegradable polymer latex and processable, biodegradable elastomers. 

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4. Engineering bistetrazoles: ( E )-5,5′-(ethene-1,2-diyl)bis(1 H -tetrazol-1-ol) as a new planar high-energy-density material

   https://doi.org/10.1039/d2ma00664b  

   Singh, Jatinder ; Staples, Richard J. ; Shreeve, Jean'ne M. ( July 2022 , Materials Advances)

   Energetic properties of bistetrazole derivatives are improved by the step-by-step introduction of functionalities which improve heat of formation, density, and oxygen content. The incorporation of unsaturation between bis(1 H -tetrazol-5-yl) and bis(1 H -tetrazol-1-ol) derivatives leads to planarity which enhances the density of the final product. In this manuscript, we have synthesized compounds 1,2-di(1 H -tetrazol-5-yl)ethane (4), ( E )-1,2-di(1 H -tetrazol-5-yl)ethene (5), and ( E )-5,5′-(ethene-1,2-diyl)bis(1 H -tetrazol-1-ol), (6) using readily available starting materials. Their corresponding dihydroxylammonium salts 7, 8 and 9 are obtained by reacting two equivalents of hydroxylamine (50% in water). New compounds are analyzed using IR, EA, DSC and multinuclear NMR spectroscopy ( 1 H, 13 C and 15 N). The solid-state structures of compounds 6, 7, 8 and 9 are confirmed by single-crystal X-ray diffraction. The energetic performances are calculated using the EXPLO5 (v6.06.02) code and the sensitivities towards external stimuli such as friction and impact are determined according to BAM standard. Compound 6 {( E )-5,5′-(ethene-1,2-diyl)bis(1 H -tetrazol-1-ol)} exhibits a surprisingly high density of 1.91 g cm −3 at 100 K (1.86 g cm −3 at 298 K). Its detonation velocity (9017 m s −1 ) is considerably superior to those of RDX (8795 m s −1 ), which suggests it is a competitive high-energy-density material. 

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5. Controlled ring-opening polymerization of N -(3- tert -butoxy-3-oxopropyl) glycine derived N -carboxyanhydrides towards well-defined peptoid-based polyacids

   https://doi.org/10.1039/D0PY01395A  

   Barrett, Bailee N. ; Sternhagen, Garrett L. ; Zhang, Donghui ( March 2021 , Polymer Chemistry)

   null (Ed.)

   Polypeptoids bearing carboxylic acid groups on the N -substituent are useful building blocks for the construction of peptidomimetic supramolecular assemblies with stimuli-responsive properties. Towards this end, N -(3- tert -butoxy-3-oxopropyl) glycine derived N -carboxyanhydride ( t BuO 2 Pr-NCA) has been successfully synthesized and polymerized using primary amine initiators to produce the corresponding poly( N -(3- tert -butoxy-3-oxopropyl) glycine) with molecular weights ( M n ) of 5.6–59 kg mol −1 and a narrow molecular weight distribution (PDI = 1.003–1.026). The polymerization was shown to proceed in a controlled manner, evidenced by the good agreement of the experimental molecular weight ( M n ) with theoretical values and narrow molecular weight distribution in a wide range of monomer-to-initiator ratios ([M] 0  : [I] 0 = 25 : 1–200 : 1), the linear increase of M n with conversion and the second-order polymerization kinetics. The cloaked carboxyl groups on the poly( N -(3- tert -butoxy-3-oxopropyl) glycine) can be readily unveiled in mild acidic conditions to yield the poly( N -(2-carboxyethyl) glycine), a structural mimic of poly(glutamic acid). The poly( N -(2-carboxyethyl) glycine) polymer is a weak polyelectrolyte whose hydrodynamic size in water can be controlled by the solution pH. 

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