Vinyl Polymerization Research Articles

Sequence-Defined Synthesis Enabled by Fast and Living Anionic Monoaddition of Vinyl Monomers.

The selective monoaddition of polymerizable vinyl monomers like styrenes and methacrylates in a living manner has been achieved for the flash-flow preparation of molecules in a defined sequence with high selectivity. We demonstrated the sequence-defined synthesis of multifunctional molecules using an initiator, functionalized styrenes, diarylethylenes, various methacrylates, and an electrophilic trapping reagent at the living terminus (six-component sequential connection at maximum) without any intermediate purification steps. The anionic living terminus of the vinyl monomers in the flow system described herein is active for polymerization, such that the styrene or methacrylate sequence can be expanded to afford highly dispersed oligomers without affecting other single units, which means that the unequivocal sequences were successfully inserted into the internal or terminal positions. The methodology described herein provides an adaptable method for the construction of new molecular spaces based on unimolecular sequence control and pinpoint functionalization.

Sequence‐Defined Synthesis Enabled by Fast and Living Anionic Monoaddition of Vinyl Monomers

The selective monoaddition of polymerizable vinyl monomers like styrenes and methacrylates in a living manner has been achieved for the flash‐flow preparation of molecules in a defined sequence with high selectivity. We demonstrated the sequence‐defined synthesis of multifunctional molecules using an initiator, functionalized styrenes, diarylethylenes, various methacrylates, and an electrophilic trapping reagent at the living terminus (six‐component sequential connection at maximum) without any intermediate purification steps. The anionic living terminus of the vinyl monomers in the flow system described herein is active for polymerization, such that the styrene or methacrylate sequence can be expanded to afford highly dispersed oligomers without affecting other single units, which means that the unequivocal sequences were successfully inserted into the internal or terminal positions. The methodology described herein provides an adaptable method for the construction of new molecular spaces based on unimolecular sequence control and pinpoint functionalization.

Double-stranded vinyl polymer with transformable side chains synthesized in a metal‒organic framework

AbstractPost-polymerization modification (PPM) via active ester chemistry is a valuable method for modulating side-chain structures without altering their main-chain topology. Herein, we synthesized a double-stranded vinyl polymer with an active ester by crosslinking radical polymerization within the nanochannels of a metal‒organic framework (MOF) with a pore diameter comparable to that of the duplex. The resulting double-stranded poly(1,1,1,3,3,3-hexafluoroisopropyl acrylate) (DPHFIPA) was readily converted into acrylates and acrylamides with side chains derived from the nucleophile used in the PPM. This approach offers a pathway for creating double-stranded vinyl polymers with repeating units that are otherwise difficult to synthesize, even when MOF-templated polymerization is used.

Carbon-Resource Recovery from Vinyl Polymers of Cyclic Ketene Acetal Esters Using High-Temperature Water

Carbon-Resource Recovery from Vinyl Polymers of Cyclic Ketene Acetal Esters Using High-Temperature Water

Radical Copolymerization of Thionoglycolide and Derivatives for Preparation of Degradable Vinyl Polymers

Radical Copolymerization of Thionoglycolide and Derivatives for Preparation of Degradable Vinyl Polymers

From π-Conjugated Rods to Shape-Persistent Rings, Wheels, and Ladders: The Question of Rigidity.

ConspectusRigid-rod oligomers and polymers are mostly based on (hetero)aromatic rings connected with each other, either directly or via ethynylene or butadiynylene linkers, or by a combination of both structural elements. Although they are much more rigid than vinyl polymers, they exhibit considerable structural flexibility, often more than would be expected merely from their chemical structure. This disparity holds for both linear as well as for cyclic structures. The flexibility of rigid-rod polymers, which is directly observable for defined oligomers of different lengths at the solid-liquid interface by means of scanning-tunneling microscopy, also impacts their optical and electronic properties. The flexibility can be used, for example, to control whether an oligomer with two different fluorescent end-groups emits from either the one or the other. The flexibility of shape-persistent macrocycles also has an impact on the overall thermal stability of mechanically interlocked molecular architectures. However, the degree of flexibility can be reduced when rigid struts are covalently mounted into the inside of the rings, leading to the formation of so-called molecular spoked wheels. The combination of these two elements─rings and rods─stiffens both of them: the ring perimeter is prevented from collapsing and the internal rods from bending. These compounds have been further developed as platform molecules, where three spokes stiffen the ring and together form a tripod-like platform, while a fourth arm points─after adsorption to a solid substrate─above the plane of the molecule. This pillar makes it possible to decouple a functional group at the end of the arm from the surface. Rigidity enhancement by the introduction of rigid spacer elements can also be applied to the case of rigid-rod polymers and is visualized by sophisticated molecular dynamics simulations. In this case, formation of single-stranded oligomers and polymers, and a subsequent zipping reaction to form ladder-like structures, directly allows, by means of single-molecule fluorescence spectroscopy, a comparison of the single- and double-stranded molecules. In particular in the case of the polymers, which can be up to 100 nm in length, the enhancement of rigidity is quite remarkable. Overall, the covalent connection of two or more rigid molecular entities has a self-reinforcing effect: all parts of the molecule gain rigidity. Since overall synthetic yields for such complex high-molecular weight covalently bound shape-persistent structures can still be low, scanning tunneling microscopy and single-molecule fluorescence spectroscopy are the methods of choice for structural analyses. Preliminary results illustrate how these compounds can serve as versatile sources of deterministic single photons on demand, since rigidity also enhances the intramolecular flow of excitation energy, and suggest a range of applications in optoelectronic devices.

Aqueous RAFT Dispersion Polymerization Mediated by an ω,ω-Macromolecular Chain Transfer Monomer: An Efficient Approach for Amphiphilic Branched Block Copolymers and the Assemblies.

Herein, an ω,ω-macromolecular chain transfer monomer (macro-CTM) containing a RAFT (reversible addition-fragmentation chain transfer) group and a methacryloyl group was synthesized and used to mediate photoinitiated RAFT dispersion polymerization of hydroxypropyl methacrylate (HPMA) in water. The macro-CTM undergoes a self-condensing vinyl polymerization (SCVP) mechanism under RAFT dispersion polymerization conditions, leading to the formation of amphiphilic branched block copolymers and the assemblies. Compared with RAFT solution polymerization, it was found that the SCVP process was promoted under RAFT dispersion polymerization conditions. Morphologies of branched block copolymer assemblies could be controlled by varying the monomer concentration and the [HPMA]/[macro-CTM] ratio. The branched block copolymer vesicles could be used as seeds for seeded RAFT emulsion polymerization, and framboidal vesicles were successfully obtained. Finally, degrees of branching of branched block copolymers could be further controlled by using a binary mixture of the macro-CTM and a linear macro-RAFT agent or a small molecule CTM. We believe that this study not only provides a versatile strategy for the preparation of branched block copolymer assemblies but also offers important insights into polymer synthesis via heterogeneous RAFT polymerization.

Fast and Selective Main-Chain Scission of Vinyl Polymers Using the Domino Reaction in the Alternating Sequence for Transesterification.

This communication reports on vinyl polymers capable of selective and fast main-chain scission (MCS). The trick is the domino reaction in an alternating sequence of methyl 2-(trimethylsiloxymethyl)acrylate and 5,6-benzo-2-methylene-1,3-dioxepane, a cyclic ketene acetal for radical ring-opening polymerization. Removal of the trimethylsilyl group using Bu4N+·F- readily led to MCS via irreversible transesterification of the ester backbone, affording a five-membered lactone fragment. The molar mass decreased drastically within 5 min, and no side reactions were observed. Control experiments suggest that the formation of a five-membered ring via a domino reaction is critical for fast and selective MCS. The terpolymers with methyl methacrylate and styrene also exhibited a large decrease in molar mass within 5 min. In addition, MCS was also observed for the heterogeneous reaction system in acidic aqueous media; treatment of the binary copolymer in a 50 wt % acetic acid solution resulted in a significant decrease in molar mass after 30 min. These results suggest efficient construction of degradable sites using a binary monomer system corresponding to the pendant trigger and ester backbone. Because this molecular design using a binary monomer system provides selective and fast MCS for terpolymers containing other vinyl monomers, it can provide various degradable vinyl polymers.

Step-growth irreversible deactivation radical polymerization: synergistic developments with chain-growth reversible deactivation radical polymerization

Abstract Recent advances in chain-growth reversible deactivation radical polymerization (CG-RDRP), i.e. the so-called “living radical polymerization”, have synergistically developed step-growth radical polymerizations via controlled formation of radical species from covalent bonds followed by irreversible deactivation of the resulting radical species. The monomers for radical polyaddition are thus designed to possess carbon–halogen or thioester bonds, which can generate radical species in the presence of transition metal catalysts and radical initiators, as well as carbon‒carbon double bonds, which will irreversibly form carbon–halogen or thioester bonds. Radical polycondensations are achievable via radical coupling reactions of carbon-centered radicals generated from carbon–halogen bonds or radical quenching reactions with nitroxides. Furthermore, radical addition-condensation polymerizations are achieved by a sequence of reactions, i.e. the formation of radical species from carbon–halogen bonds, radical addition to nitroso or thiocarbonylthio compounds, and coupling or quenching reactions with the resulting stable radical. These step-growth irreversible deactivation radical polymerizations (SG-IDRP) enable the synthesis of a variety of polymers, such as polyethers, polyesters, polyamides, and polyimides, which have aliphatic, aromatic, polar, and degradable groups in their main chains. Sequence-regulated vinyl polymer structures can also be constructed by designing monomers. Combinations with CG-RDRPs further lead to unique hybrid block, multiblock, graft, hyperbranched, and network polymers.

Mechanochemical Backbone Editing for Controlled Degradation of Vinyl Polymers.

The chemically inert nature of fully saturated hydrocarbon backbones endows vinyl polymers with desirable durability, but it also leads to their significant environmental persistence. Enhancing the sustainability of these materials requires a pivotal yet challenging shift: transforming the inert backbone into one that is degradable. Here, we present a versatile platform for mechanochemically editing the fully saturated backbone of vinyl polymers towards degradable polymer chains by integrating cyclobutene-fused succinimide (CBS) units along backbone through photo-iniferter reversible addition-fragmentation chain-transfer (RAFT) copolymerization. Significantly, the evenly insertion of CBS units does not compromise thermal or chemical stability but rather offers a means to adjust the properties of polymethylacrylate (PMA). Meanwhile, reactive acyclic imide units can be selectively introduced to the backbone through mechanochemical activation (pulse ultrasonication or ball-milling grinding) when required. Subsequent hydrolysis of the acyclic imide groups enables efficient degradation, yielding telechelic oligomers. This approach holds promise for inspiring the design and modification of more environmentally friendly vinyl polymers through backbone editing.

Mechanochemical Backbone Editing for Controlled Degradation of Vinyl Polymers

AbstractThe chemically inert nature of fully saturated hydrocarbon backbones endows vinyl polymers with desirable durability, but it also leads to their significant environmental persistence. Enhancing the sustainability of these materials requires a pivotal yet challenging shift: transforming the inert backbone into one that is degradable. Here, we present a versatile platform for mechanochemically editing the fully saturated backbone of vinyl polymers towards degradable polymer chains by integrating cyclobutene‐fused succinimide (CBS) units along backbone through photo‐iniferter reversible addition‐fragmentation chain‐transfer (RAFT) copolymerization. Significantly, the evenly insertion of CBS units does not compromise thermal or chemical stability but rather offers a means to adjust the properties of polymethylacrylate (PMA). Meanwhile, reactive acyclic imide units can be selectively introduced to the backbone through mechanochemical activation (pulse ultrasonication or ball‐milling grinding) when required. Subsequent hydrolysis of the acyclic imide groups enables efficient degradation, yielding telechelic oligomers. This approach holds promise for inspiring the design and modification of more environmentally friendly vinyl polymers through backbone editing.

Polyhedral Vinyl Polymer Particles Synthesized Via Solvent-Free Radical Polymerization.

Liquid marbles (LMs) with a cubic shape are created by using various vinyl monomers as an inner liquid and polymer plates with mm size as a stabilizer. The relationship between the surface tension of the vinyl monomers and formability of the LMs is investigated. LMs can be fabricated using vinyl monomers with surface tensions of 42.7-40.3 mN m-1. The cubic polymer particles are successively synthesized via free-radical polymerizations by irradiation of the cubic LMs with UV light in a solvent-free manner. In addition, controlling the number of polymer plates per one LM, the shape of the plate or the coalescence of the LMs can lead to production of polymer particles with desired forms (e.g., Platonic and rectangular solids) that correspond to the shapes of the original LMs.

Bending and compressive properties of glued-laminated timber composed of Japanese white birch wood using casein adhesive

ABSTRACT Size-reduced model glued-laminated timber (GLT) (1/8 cross-sectional size, six layers, 11 by 18 by 430 mm) was manufactured using birch (Betula platyphylla) wood and a casein adhesive to evaluate the possibility of producing the structural GLT without petrochemical-based adhesives in Mongolia. The same-sized solid lumber and GLT using aqueous vinyl polymer solution-isocyanate adhesives (API) that can be used for structural GLT production in Japan was prepared to evaluate the mechanical performance of GLT using casein adhesive. The effects of lamination configuration and patterns on the mechanical properties (dynamic Young's modulus, modulus of elasticity [MOE], modulus of rupture [MOR], bending work [energy until broken, W], and compressive strength [CS]) were also evaluated using mixed-effect model. Almost no significant differences in the bending and compressive properties were found between GLT using casein and API adhesives, suggesting that, in dry conditions, the bonding performance of casein adhesives closely matches that of API. Modeling results showed that lamina configuration influenced the W and CS even in the Young’s modulus was almost the same, suggesting that the basic wood properties, such as load and deflection characteristics, are important to enhance the mechanical properties of birch GLT with casein adhesive by laminae configurations.

Hydrophobic Aerogels from Vinyl Polymers Derived from Radical Polymerization: Proof-of-Concept.

Hydrophilicity is one important drawback of bio-based aerogels. To overcome this issue, a novel approach for the preparation of mesoporous, water repellent aerogels is introduced, which combines synthesis of cross-linked bio-based copolymers from methacrylate copolymerizations, followed by solvent exchange and supercritical drying steps. The influence of monomers with different nonpolar ester groups (methyl, vanillin, tetrahydrofurfuryl) on textural properties and water contact angles of the dry products is assessed. Final aerogels show generally high overall porosities (≈96%), low densities (0.07-0.11gcm-3) as well as fine, mainly mesoporous networks, and specific surface areas in the range of 120-240m2g-1. Hereby, choice of the methacrylate ester groups results in differences of the resulting pore-size distributions. Water repellency tests show stable static water contact angles in the hydrophobic range (≈100°) achieved for the substrate containing the vanillin ester group. On the contrary the other substrates absorb water quickly, which indicates a decisive role of the ester group. The presented approach opens up a new pathway to bio-based aerogels with intrinsic hydrophobicity. It is suggested that the properties are tailored by the choice of the monomer structure, hence enabling further adaption and optimization of the products.

Controlled switching thiocarbonylthio end-groups enables interconvertible radical and cationic single-unit monomer insertions and RAFT polymerizations

To emulate the ordered arrangement of monomer units found in natural macromolecules, single-unit monomer insertion (SUMI) have emerged as a potent technique for synthesizing sequence-controlled vinyl polymers. Specifically, numerous applications necessitate vinyl polymers encompassing both radically and cationically polymerizable monomers, posing a formidable challenge due to the distinct thiocarbonylthio end-groups required for efficient control over radical and cationic SUMIs. Herein, we present a breakthrough in the form of interconvertible radical and cationic SUMIs achieved through the manipulation of thiocarbonylthio end-groups. The transition from a trithiocarbonate (for radical SUMI) to a dithiocarbamate (for cationic SUMI) is successfully accomplished via a radical-promoted reaction with bis(thiocarbonyl) disulfide. Conversely, the reverse transformation utilizes the reaction between dithiocarbamate and bistrithiocarbonate disulfide under a cationic mechanism. Employing this strategy, we demonstrate a series of synthetic examples featuring discrete oligomers containing acrylate, maleimide, vinyl ether, and styrene, compositions unattainable through the SUMI of a single mechanism alone.

Predicting polymerization reactions via transfer learning using chemical language models

Polymers are candidate materials for a wide range of sustainability applications such as carbon capture and energy storage. However, computational polymer discovery lacks automated analysis of reaction pathways and stability assessment through retro-synthesis. Here, we report an extension of transformer-based language models to polymerization for both reaction and retrosynthesis tasks. To that end, we have curated a polymerization dataset for vinyl polymers covering reactions and retrosynthesis for representative homo-polymers and co-polymers. Overall, we obtain a forward model Top-4 accuracy of 80% and a backward model Top-4 accuracy of 60%. We further analyze the model performance with representative polymerization examples and evaluate its prediction quality from a materials science perspective. To enable validation and reuse, we have made our models and data available in public repositories.

Lipid-based systems with precipitation inhibitors as formulation approach to improve the drug bioavailability and/or lower its dose: a review.

Lipid-based systems, such as self-microemulsifying systems (SMEDDS) are attracting strong attention as a formulation approach to improve the bioavailability of poorly water-soluble drugs. By applying the "spring and parachute" strategy in designing supersaturable SMEDDS, it is possible to maintain the drug in the supersaturated state long enough to allow absorption of the complete dose, thus improving the drug's bio-availability. As such an approach allows the incorporation of larger amounts of the drug in equal or even lower volumes of SMEDDS, it also enables the production of smaller final dosage forms as well as decreased gastrointestinal irritation, being of particular importance when formulating dosage forms for children or the elderly. In this review, the technological approaches used to prolong the drug supersaturation are discussed regarding the type and concentration of polymers used in liquid and solid SMEDDS formulation. The addition of hypromellose derivatives, vinyl polymers, polyethylene glycol, polyoxyethylene, or polymetacrylate copolymers proved to be effective in inhibiting drug precipitation. Regarding the available literature, hypromellose has been the most commonly used polymeric precipitation inhibitor, added in a concentration of 5 % (m/m). However, the inhibiting ability is mainly governed not only by the physicochemical properties of the polymer but also by the API, therefore the choice of optimal precipitation inhibitor is recommended to be evaluated on an individual basis.

A novel high reactive initiator system of vinyl‐substituted hydridopolycarbosilane (VHPCS) for lower curing temperature and higher ceramic yields

AbstractVinyl‐substituted hydridopolycarbosilane (VHPCS) is widely studied for its low viscosity, abundance of active functional groups, rapid curing, and high ceramic yield. The curing reactions mainly involve the free radical polymerization of vinyl and hydrosilylation reactions, but these reactions typically require high temperatures such as 160–250°C. The curing behavior of VHPCS‐17 with a tert‐butyl peroxybenzoate/Nickel acetylacetonate (TBPB/NIAA) system is investigated using differential scanning calorimetry and in situ Fourier transform infrared. The properties of VHPCS‐17 with different initiator systems and VHPCS with different vinyl contents (under TBPB/NIAA system) are studied using thermogravimetric analysis and x‐ray diffraction. The results demonstrate that the TBPB/NIAA system can facilitate the free radical polymerization of vinyl; moreover, this system decreases the peak temperature of the curing reaction from 251 to 141°C and increases the ceramic yield from 80.49% to 89.88%. The ceramic yield of cured VHPCS increases gradually, reaching 89.88% when the vinyl content is 17%. The grain size of β‐SiC decreases continuously with the increase in vinyl content, while the high‐temperature oxidation‐resistant properties of SiC ceramics obtained from different VHPCSs are not negatively affected.

Multistimuli responsive hydrogels with shape fix/memory capability fabricated from gold nanorod‐conjugated amino acid‐based vinyl polymer networks

AbstractFabricating robust shape‐memory hydrogels that respond to multiple external stimuli is an important challenge in facilitating gel technology for versatile applications. In this study, we report a simple approach for constructing thermo‐, redox‐, and photo‐responsive hydrogels with high mechanical strength and shape fix/memory capability. Upper critical solution temperature (UCST)‐type amino acid‐based hydrogels were facilely prepared by radical copolymerization of N‐acryloyl glycinamide (NAGAm) with cystine‐derived divinyl acrylamides (ionic cystine [NAC] or nonionic cystine‐methyl ester [NACMe]) units at different monomer concentrations (1/2 M). These hydrogels were transparent and exhibited good mechanical strength (tensile strength of 0.3–0.4 MPa and breaking elongation of 400%–700%). All hydrogels showed UCST‐type swelling‐shrinking behaviors based on thermo‐driven reversible hydrogen bonds among the PNAGAm units, and thus could be fixed into variety of shapes and recovered to the original shape by temperature manipulation. The cystine‐based crosslinkers having SS bonds served as efficient redox‐sensitive and gold‐nanorod‐(AuNR)‐adsorbing moieties; thus, AuNR could be conjugated stably and evenly into the PNAGAm/NAC hydrogel. Moreover, upon light‐irradiation, the AuNR‐conjugated hybrid hydrogel exhibited shape‐memory behavior owing to the photothermal effect of the AuNRs. These multiresponsive/functional hydrogels composed of amino acid units have considerable potential for various applications in the fields of soft actuators and biomedicines.

Assembly Structure Formation in Bulk and Ultrathin Films of Poly(substituted methylene) Having an Azobenzene Side Chain.

The density of the side chain introduced to a polymer main chain greatly influences the properties and functions of the polymer. This work first reports on the packing structure and properties at an interface of a poly(substituted methylene) where an azobenzene side chain is introduced at every carbon atom in the main chain (C1PAz). The structure and properties are compared with those of a conventional vinyl polymer [poly(methacrylate)] possessing an identical side-chain structure (C2PAz). The packing structure in the bulk state analyzed by X-ray measurements revealed that C1PAz adopts a highly ordered rectangular unit cell structure, whereas C2PAz shows a less ordered lamellar one. Langmuir film balance experiments indicated that both polymers with the trans-azobenzene give essentially the identical 2D side-chain occupying area on water, which agrees well with the smectic B (hexatic packing) model based on the X-ray data. Upon transfer onto a solid substrate, only C1PAz shows a conformational transformation to a spread bilayer-type layer, most probably due to conformational frustration stemming from the crowding of the side chains. This study proposes new insights into the effects of side-chain density on the self-assembly and photoreaction of azobenzene-containing polymers, which are expected to expand the possibilities of polymer design for various applications.