Effect of Biphenyl Spacers on the Anionic Polymerization of 2‑(4′-Vinylbiphenyl-4-yl)pyridine

The pyridine-containing monomer 2-(4′-vinylbiphenyl-4-yl)­pyridine (VBPPy), synthesized by the Suzuki coupling reaction, was successfully polymerized using diphenylmethylpotassium (DPM-K) as an initiator within 360 min at −78 °C, resulting in 100% yield and polydispersity <1.3, as with the living anionic polymerization of 2-vinylpyridine (2VP) and 2-(4-vinylphenyl)­pyridine (VPPy). By the block copolymerization of VBPPy with 2VP, VPPy, and methyl methacrylate (MMA), it was proven that the nucleophilicity of living poly­(2-(4′-vinylbiphenyl-4-yl)­pyridine) is between that of living poly­(2-(4-vinylphenyl)­pyridine) and that of living poly­(methyl methacrylate). Among the block copolymers, PVBPPy-b-PMMA was used to make nanocomposites in which gold (Au) nanoparticles (NPs) were present only in the PVBPPy zone of the phase-separated PVBPPy-b-PMMA) (fVBPPy = 0.23) film

Facile Synthesis of Amphiphilic Bottlebrush Block Copolymers Bearing Pyridine Pendants via Click Reaction from Protected Alkyne Side Groups

We present the facile synthetic platform for the production of amphiphilic bottlebrush block copolymers bearing pyridine pendants through combination of living anionic polymerization (LAP), ring-opening metathesis polymerization (ROMP), and copper-catalyzed azide–alkyne cycloaddition (CuAAC). ω-Norbornenyl poly­(4-((trimethylsilyl)­ethynyl)­styrene) (NBPTMSESt) with controlled molecular weights (Mn = 3–4 kDa) and low dispersity (Đ = 1.03–1.08) was synthesized by LAP and the subsequent end-capping reaction with exo-N-(n-decyl-10-phenylacrylate)-5-norbornene-2,3-dicarboximide. Well-defined bottlebrush block copolymers (Mn = 134–548 kDa, Đ = 1.04–1.14) were achieved through sequential ROMP of ω-norbornenyl polystyrene with NBPTMSESt and subsequently deprotected with the clickable alkyne group. Amphiphilic bottlebrush block copolymers were obtained by the click reaction of alkyne and azide functional pyridines in the presence of the organic-soluble catalyst/ligand system of CuBr­(PPh3)3 and N,N,N′,N″,N″-pentamethyldiethylenetriamine. These polymers exhibited the three-dimensional ordered porous films through breath-figure self-assembly

Well-Defined Block Copolymers with Triphenylamine and Isocyanate Moieties Synthesized via Living Anionic Polymerization for Polymer-Based Resistive Memory Applications: Effect of Morphological Structures on Nonvolatile Memory Performances

The anionic block copolymerization of 4,4′-vinylphenyl-<i>N</i>,<i>N</i>-bis­(4-<i>tert</i>-butylphenyl)­benzenamine (<b>A</b>) with <i>n</i>-hexyl isocyanate (<b>B</b>) was performed using potassium naphthalenide (K-Naph) in THF at −78 and −98 °C in the presence of sodium tetraphenylborate (NaBPh₄) to afford the well-defined block copolymers for investigating the effect of morphological structures on electrical memory performances. The well-defined functional block copolymers (P<b>BAB</b>) with different block ratios had predictable molecular weights (<i>M</i>_n = 17 700–79 100 g/mol) and narrow molecular weight distributions (<i>M</i>_w/<i>M</i>_n = 1.14–1.19). It was observed from transmission electron microscopy (TEM) that the block copolymers showed different morphological structures depending on block ratios. Although all memory devices fabricated from the resulting block copolymers with different block compositions equally exhibited nonvolatile resistive switching characteristics, which are governed by the trap-controlled space-charge-limited current (SCLC) conduction mechanism and filament formation, it was found that electrical memory performances of each device varied depending on morphological structures of the block copolymer films

End-Capping Reaction of Living Anionic Poly(benzyl methacrylate) with a Pentafluorophenyl Ester for a Norbornenyl-ω-End Macromonomer with a Long Flexible Spacer: Advantage in the Well-Controlled Synthesis of Ultrahigh-Molecular-Weight Bottlebrush Polymers

12-(cis-5-Norbornene-exo-2,3-dicarboximido)­dodecanoate pentafluorophenyl ester (exo-NBC12-PFP) was used as a norbornene-substituted end-capping terminator of living anionic polymers. Polystyrene with a terminal 1,1-diphenylethyllithium (PSt­(DPE)−Li+), poly­(2-vinylpyridine) with a terminal 2-pyridinylethyllithium (P2VP–Li+), and poly­(benzyl methacrylate) with a terminal lithium ester enolate (PBzMA–Li+) reacted with exo-NBC12-PFP under appropriate reaction conditions to generate norbornenyl-ω-end macromonomers, NBC12-PSt, NBC12-P2VP, and NBC12-PBzMA, respectively, each with a 12-carbon spacer. To estimate the efficiency of end-capping, these macromonomers were polymerized by grafting-through ring-opening metathesis polymerization (ROMP). The end-capping reaction of PSt­(DPE)−Li+ and P2VP–Li+ suffered from side reactions resulting in low end-capping efficiencies and the generation of by-products. On the other hand, the side reactions were minimal in the end-capping reaction of PBzMA–Li+, resulting in a high end-capping efficiency of 95%. The ROMP of NBC12-PBzMA allowed the synthesis of poly­[12-(5-norbornene-exo-2,3-dicarboximido)­dodecanoylate]-graft-poly­(benzyl methacrylate)­s (PNBC12-g-PBzMAs) with a wide range of controlled molecular weights (Mn = 436–4048 kDa, Đ = 1.07–1.23)

Experimental Formulation of Photonic Crystal Properties for Hierarchically Self-Assembled POSS–Bottlebrush Block Copolymers

Rodlike “POSS–bottlebrush block copolymers” (POSSBBCPs) containing crystalline polyhedral oligomeric silsesquioxane (POSS) pendants in A block and amorphous polymeric grafts in B block were utilized to create one-dimensional (1D) photonic crystals (PCs). 3-(12-(<i>cis</i>-5-Norbornene-<i>exo</i>-2,3-dicarboximido)­dodecanoylamino)­propyl­heptaisobutyl POSS (<b>NB-A16-POSS</b>, M_A) and <i>exo</i>-5-norbornene-2-carbonyl-end poly­(benzyl methacrylate) (<b>NBPBzMA</b>, M_B) were employed in sequential ring-opening metathesis polymerization to afford poly­[3-(12-(<i>cis</i>-5-norbornene-<i>exo</i>-2,3-dicarboximido)­dodecanoylamino)­propyl­heptaisobutyl POSS]-<i>block</i>-poly­(<i>exo</i>-5-norbornene-2-carbonylate-<i>graft</i>-benzyl methacrylate)­s, <b>P­(NB-A16-POSS)-</b><i><b>b</b></i><b>-P­(NB-</b><i><b>g</b></i><b>-BzMA)</b>s, with well-modulated block compositions (<i>f</i>_A = 34, 50, and 67 wt %) and overall degrees of polymerization (DP = 323–939). The <b>P­(NB-A16-POSS)-</b><i><b>b</b></i><b>-P­(NB-</b><i><b>g</b></i><b>-BzMA)</b>s hierarchically self-assembled to form highly ordered 1D PC films with periodic lamellar arrays that can reflect visible light with particular wavelengths. Their reflectance bandwidths, reflectivities, and ranges of peak reflectance wavelnegth (λ_peak) were largely dependent on the block composition. The 1D PC films based on lamellar <b>P­(NB-A16-POSS)-</b><i><b>b</b></i><b>-P­(NB-</b><i><b>g</b></i><b>-BzMA)</b>s demonstrated the capability of formaulation of λ_peak as linear functions of initial polymerization parameter ([M]₀/[I]₀)

Hydrogen Bonding-Mediated Phase Transition of Polystyrene and Polyhydroxystyrene Bottlebrush Block Copolymers with Polyethylene Glycol

A simple strategy was explored to systematically control the phase transition of an amphiphilic bottlebrush block copolymer (AmBBCP), poly­[(norbornene-graft-styrene)-block-(norbornene-graft-hydroxystyrene)], with polymeric additives, such as poly­(ethylene glycol) methyl ether (mPEG), poly­(2-vinylpyridine) (P2VP), and poly­(methyl methacrylate) (PMMA). The precursor polymers, poly­[(norbornene-graft-styrene)-block-(norbornene-graft-4-tert-butoxystyrene)], were synthesized by sequential ring-opening metathesis polymerization of ω-end-norbornyl polystyrene and poly­(4-tert-butoxystyrene). Acid hydrolysis of the tert-butyl groups in the precursor resulted in the AmBBCP with an ultrahigh molecular weight (∼2880 kDa) and relatively low dispersity (∼1.21). The disordered structures of neat AmBBCP were transformed to ordered lamellae by solvothermal annealing. AmBBCP and mPEG blended well because of H-bonding, maintaining well-ordered lamellae up to 40 wt % mPEG. The phase transition from ordered to disordered state occurred when increasing more than 50 wt %. The AmBBCP blended with P2VP and PMMA was compared. The effect of mPEG on phase transition, domain size, and refractive index and the photonic properties were determined

Molecular Design of an Interfacially Active POSS-Bottlebrush Block Copolymer for the Fabrication of Three-Dimensional Porous Films with Unimodal Pore Size Distributions through the Breath-Figure Self-Assembly

We compared the interfacial activity of two classes of POSS-bottlebrush block copolymers (POSSBBCPs) in the breath-figure (BF) self-assembly. Poly­[3-(5-norbornene-exo-2,3-dicarboximido)­propyl-heptaisobutyl POSS]-block-poly­(exo-5-norbornene-2-carbonylate-graft-benzyl methacrylate) (P1-b-P­(NB-g-BzMA)) and poly­[3-(2-(5-norbornene-exo-2,3-dicarboximido)­ethylamino)­propyl-heptaisobutyl POSS]-block-poly­(exo-5-norbornene-2-carbonylate-graft-benzyl methacrylate) (P2-b-P­(NB-g-BzMA)), which contain nonfunctionalized and secondary-amino-functionalized POSS-based blocks, respectively, were prepared by sequential ring-opening metathesis polymerization of norbornenyl monomers (P1-b-P­(NB-g-BzMA) with fP1 = 50 wt % (1–50): Mn = 213 kDa, Đ = 1.12; P2-b-P­(NB-g-BzMA)s with fP2 = 5/11/20/50 wt % (2–5/11/20/50): Mn = 2464/1043/581/268 kDa, Đ = 1.46/1.26/1.24/1.20). Of 1–50 and 2–50, only 2–50 afforded the three-dimensional porous films with unimodal pore size distributions. At high wet thickness, the efficient encapsulation of water droplets through the adsorption of water by the secondary amino groups allowed the 2–50 chains to stabilize the solvent–water interfaces, thus preventing the formation of giant pores. The interfacial activity of P2-b-P­(NB-g-BzMA) was enhanced by increasing the weight fraction of the P2 block from 5 to 50 wt %

Discovery of a New Sulfonamide Hepatitis B Capsid Assembly Modulator

Hepatitis B virus (HBV) remains a major health concern with 260 million people having been infected globally, and approximately 680,000 deaths have occurred annually from cirrhosis and liver cancer. The modulation of HBV capsid assembly has emerged as a promising therapeutic approach for curing chronic HBV infection. Small-molecule capsid assembly modulators (CAMs) can broadly be classified as heteroaryldihydropyrimidines and sulfamoylbenzamides (SBAs). SBAs are capsid activators that inhibit viral replication by achieving capsid assembly before polymerase encapsulation. Herein, we report a novel series of HBV CAMs based on NVR 3-778, a potent CAM belonging to the SBA class. The lead compound (KR-26556) exhibited improved pharmacological activity and was examined through molecular docking studies

Bis(β-ketoimino)nickel(II) Complexes for Random Copolymerization of Norbornene and Methyl 5‑Norbornene-2-carboxylate with Controlled Ester Group Incorporation

A series of bis­(β-ketoimino)­nickel­(II) complexes with p-substituted N-phenyl groups, Ni­[CH3C­(O)­CHC­(NPhR)­CH3]2 (Ni1: R = −OCH3; Ni2: R = −CH3; Ni3: R = −CF3), were synthesized, and their general coordination geometry was elucidated by single-crystal X-ray diffraction analysis of Ni3. These complexes were paired with tris­(pentafluorophenyl)­borane (B­(C6F5)3) to catalyze the vinyl addition copolymerization of norbornene (NB) and methyl 5-norbornene-2-carboxylate (NBE). All the catalyst systems exhibited high catalytic activities (>105 gpolymer molNi–1 h–1) at NBE feed contents of up to 50 mol %, resulting in the production of copolymers with high molecular weights (Mw = 135–355 kg mol–1, Đ = 1.78–2.12). In addition, the content of polar ester groups was precisely controlled by the feed ratio of the monomers. For Ni3, two monomer reactivity ratios were found to be close to unity (Fineman–Ross method: rNB = 0.951, rNBE = 0.903; Kelen–Tüdös method: rNB = 1.15, rNBE = 0.978). Since the copolymerization behaviors were revealed to be independent of the electronegativity of p-substituent, all the catalyst systems of Ni1–Ni3/B­(C6F5)3 were considered to serve the random copolymerization of NB and NBE. The resulting poly­(norbornene-random-methyl 5-norbornene-2-carboxylate)­s exhibited the dielectric and surface properties well tunable by compositional modulation