Living Vinyl Addition Polymerization of Substituted Norbornenes by a <i>t</i>‑Bu₃P‑Ligated Methylpalladium Complex

The vinyl addition polymerization of substituted norbornene (NB) monomers, via (<i>t</i>-Bu₃P)­PdMeCl activated by [Li­(OEt₂)_2.5]­B­(C₆F₅)₄, is investigated. NB monomers bearing alkyl, aryl, fluoroaryl, and even hexafluoroisopropanol substituents yield polymers exhibiting monomodal and narrow molecular weight distributions, with molecular weight controlled by reaction time and monomer to initiator ratio, demonstrating the living nature of these polymerizations. These polymers are soluble in common organic solvents and possess excellent thermal stability. Block copolymers are also prepared via sequential monomer addition; these are the first examples of well-defined block copolymers of substituted NB monomers enchained by vinyl addition polymerization

Vinyl Addition Copolymers of Norbornylnorbornene and Hydroxyhexafluoro­isopropylnorbornene for Efficient Recovery of <i>n</i>‑Butanol from Dilute Aqueous Solution via Pervaporation

The high energy cost to recover heavier alcohols, such as <i>n</i>-butanol, from dilute aqueous solution is a significant practical barrier to their large-scale bioproduction. Membrane pervaporation offers an energy-efficient alternative, provided membrane materials can be developed which provide both good alcohol selectivity and high flux. Previous work has revealed that vinyl addition polynorbornenes bearing substituentsespecially hydroxy­hexafluoroisopropylwith an affinity for <i>n</i>-butanol have potential in this application, as their high glass transition temperature allows the formation of thin but mechanically robust selective layers in thin-film composite (TFC) membranes. In the present work, we synthesize both microphase-separated gradient copolymers, and homogeneous random copolymers, of hydroxyhexafluoro­isopropyl­norbornene (HFANB) with norbornyl­norbornene (NBANB) and evaluate their <i>n</i>-butanol/water pervaporation performance. Compared with analogous copolymers of HFANB and <i>n</i>-butyl­norbornene (BuNB), the greater <i>n</i>-butanol permeability and selectivity of PNBANB vs PBuNB lead to a more-than-2-fold increase in membrane selectivity for <i>n</i>-butanol transport; the best HFANB–NBANB copolymers show <i>n</i>-butanol selectivities and fluxes which compare favorably with those of the best commercial TFC membranes, which contain cross-linked polydimethyl­siloxane selective layers. Moreover, vinyl addition copolymers offer a straightforward route to further flux enhancement, simply by reducing the selective layer thickness

Dual Effective Organic/Inorganic Hybrid Star-Shaped Polymer Coatings on Ultrafiltration Membrane for Bio- and Oil-Fouling Resistance

Amphiphilic organic/inorganic hybrid star-shaped polymers (SPP) were prepared by atom transfer radical polymerization (ATRP) using poly­(ethylene glycol) methyl ether methacrylate (PEGMA) and 3-(3,5,7,9,11,13,15-heptacyclohexyl-pentacyclo­[9.5.1.13,9.15,15.17,13]-octasiloxane-1-yl)­propyl methacrylate (MA-POSS) as monomers and octakis­(2-bromo-2-methylpropionoxypropyldimethylsiloxy)-octasilsesquioxane (OBPS) as an initiator. Star-shaped polymers (SPM) having PEGMA and methyl methacrylate (MMA) moieties were also prepared for comparative purposes. Polysulfone (PSf) ultrafiltration membranes coated with the SPP showed higher bio- and oil-fouling resistance and flux-recovery ability than the bare PSf membrane. Moreover, the SPP-coated membranes exhibited better antifouling properties than the SPM-coated membrane when they were used for oil/water emulsion filtration. The dual effective antifouling properties of the SPP were ascribed to the simultaneous enrichment of hydrophilic PEG and hydrophobic POSS moieties on the membrane surfaces resulting in the decrease in interactions with proteins and the increase in repellence to oils

Physical Properties of Poly(ether-thiourea)-Based Elastomer Formed by Zigzag Hydrogen Bonding and Slidable Cross-Linking

In this study, the effects of zigzag hydrogen bonding and slidable cross-linking on the design of stretchable elastomers were explored. Poly(ether-thiourea) (TU), capable of generating strong zigzag hydrogen bonds without crystallization, was introduced as the main chain in the non-cross-linked region of the developed elastomer. Consequently, the toughness of the TU-based elastomer was 14 times higher than that of elastomers formed using linear poly(ethylene glycol), despite the relatively low molecular weight of TU (∼3k). When a slidable polyrotaxane cross-linker was introduced into the TU-based elastomer, its flexibility became twice as high as that of the rigid polymer cross-linker. Moreover, the mechanical properties of the elastomer were prevented from deterioration against repeated deformation under the limited strain condition of 150%

Polymer Composite Electrolytes Having Core–Shell Silica Fillers with Anion-Trapping Boron Moiety in the Shell Layer for All-Solid-State Lithium-Ion Batteries

Core–shell silica particles with ion-conducting poly­(ethylene glycol) and anion-trapping boron moiety in the shell layer were prepared to be used as fillers for polymer composite electrolytes based on organic/inorganic hybrid branched copolymer as polymer matrix for all-solid-state lithium-ion battery applications. The core–shell silica particles were found to improve mechanical strength and thermal stability of the polymer matrix and poly­(ethylene glycol) and boron moiety in the shell layer increase compatibility between filler and polymer matrix. Furthermore, boron moiety in the shell layer increases both ionic conductivity and lithium transference number of the polymer matrix because lithium salt can be more easily dissociated by the anion-trapping boron. Interfacial compatibility with lithium metal anode is also improved because well-dispersed silica particles serve as protective layer against interfacial side reactions. As a result, all-solid-state battery performance was found to be enhanced when the copolymer having core–shell silica particles with the boron moiety was used as solid polymer electrolyte

Hydroxyhexafluoroisopropylnorbornene Block and Random Copolymers via Vinyl Addition Polymerization and Their Application as Biobutanol Pervaporation Membranes

Vinyl addition polymers of substituted norbornene (NB) monomers possess very high glass-transition temperatures, making them useful in diverse applications; however, until very recently, the lack of an applicable living polymerization chemistry has precluded the synthesis of such polymers with controlled architecture, or copolymers with controlled sequence distribution. In the present work, block and random copolymers of NB monomers bearing hydroxyhexafluoroisopropyl and <i>n</i>-butyl substituents (HFANB and BuNB) are synthesized via living vinyl addition polymerization, using (η³-allyl)­Pd­(<i>i</i>-Pr₃P)Cl activated by [Li­(OEt₂)_2.5]­B­(C₆F₅)₄ as the initiator. Both series of polymers are cast into the selective skin layers of thin film composite (TFC) membranes, and these organophilic membranes are investigated for the concentration of <i>n</i>-butanol from dilute aqueous solution via pervaporation. The block copolymers show well-defined microphase-separated morphologies, both in bulk and as the selective skin layers on TFC membranes, while the random copolymers are homogeneous. Both block and random vinyl addition copolymers are effective as <i>n</i>-butanol pervaporation membranes, with the block copolymers showing a better flux-selectivity balance; the optimal block copolymer, containing 19 wt % BuNB, showed a process separation factor of 21 and a flux of 4300 g m^–2 h^–1 with a 1.00 wt % aqueous <i>n</i>-butanol feed, at a selective layer thickness of 1.3 μm. While polyHFANB has much higher permeability and selectivity than polyBuNB, incorporating BuNB units into the polymer (in either a block or random sequence) limits the swelling of the polyHFANB and thereby improves the <i>n</i>-butanol pervaporation selectivity. An analogous block copolymer derived from ring-opening metathesis polymerization, which shows much greater swelling than the vinyl addition polymers, shows a correspondingly higher flux and lower selectivity

High-Performance Reverse Osmosis CNT/Polyamide Nanocomposite Membrane by Controlled Interfacial Interactions

Polyamide reverse osmosis (RO) membranes with carbon nanotubes (CNTs) are prepared by interfacial polymerization using trimesoyl chloride (TMC) solutions in <i>n</i>-hexane and aqueous solutions of <i>m</i>-phenylenediamine (MPD) containing functionalized CNTs. The functionalized CNTs are prepared by the reactions of pristine CNTs with acid mixture (sulfuric acid and nitric acid of 3:1 volume ratio) by varying amounts of acid, reaction temperature, and reaction time. CNTs prepared by an optimized reaction condition are found to be well-dispersed in the polyamide layer, which is confirmed from atomic force microscopy, scanning electron microscopy, and Raman spectroscopy studies. The polyamide RO membranes containing well-dispersed CNTs exhibit larger water flux values than polyamide membrane prepared without any CNTs, although the salt rejection values of these membranes are close. Furthermore, the durability and chemical resistance against NaCl solutions of the membranes containing CNTs are found to be improved compared with those of the membrane without CNTs. The high membrane performance (high water flux and salt rejection) and the improved stability of the polyamide membranes containing CNTs are ascribed to the hydrophobic nanochannels of CNTs and well-dispersed states in the polyamide layers formed through the interactions between CNTs and polyamide in the active layers

Mussel-Inspired Dopamine- and Plant-Based Cardanol-Containing Polymer Coatings for Multifunctional Filtration Membranes

A series of copolymers [PCD#s, where # is the weight percentage of dopamine methacrylamide (DMA) in polymers] containing mussel-inspired hydrophilic dopamine and plant-based hydrophobic cardanol moieties was prepared via radical polymerization using DMA and 2-hydroxy-3-cardanylpropyl methacrylate (HCPM) as the monomers. PCD#s were used as coating materials to prevent flux decline of the membranes caused by the adhesion of biofoulants and oil-foulants. Polysulfone (PSf) ultrafiltration membranes coated with PCD#s showed higher biofouling resistance than the bare PSf membrane, and the bactericidal properties of the membranes increased upon increasing the content of HCPM units in the PCD#s. Serendipitously, the PSf membranes coated with the more or less amphiphilic PCD54 and PCD74, having the optimum amount of both hydrophilic DMA and hydrophobic HCPM moieties, showed noticeably higher oil-fouling resistance than the more hydrophilic PCD91-coated membrane, the more hydrophobic PCD0-coated membrane, and the bare PSf membrane. Therefore, multifunctional coating materials having biofouling- and oil-fouling-resistant and bactericidal properties could be prepared from the monomers containing mussel-inspired dopamine and plant-based cardanol groups

Regional Control of Multistimuli-Responsive Structural Color-Switching Surfaces by a Micropatterned DNA-Hydrogel Assembly

Structural colors have advantages compared with chemical pigments or dyes, such as iridescence, tunability, and unfading. Many studies have focused on developing the ability to switch ON/OFF the structural color; however, they often suffer from a simple and single stimulus, remaining structural colors, and target selectivity. Herein, we present regionally controlled multistimuli-responsive structural color switching surfaces. The key part is the utilization of a micropatterned DNA-hydrogel assembly on a single substrate. Each hydrogel network contains a unique type of stimuli-responsive DNA motifs as an additional cross-linker to exhibit swelling/deswelling via stimuli-responsive DNA interactions. The approach enables overcoming the existing limitations and selectively programming the DNA-hydrogel to a decrypted state (ON) and an encrypted state (OFF) in response to multiple stimuli. Furthermore, the transitions are reversible, providing cyclability. We envision the potential of our method for diverse applications, such as sensors or anticounterfeiting, requiring multistimuli-responsive structural color switching surfaces