Chain-growth Polymerization Research Articles

Chain-Growth Polymerization of Benzotriazole Using Suzuki-Miyaura Cross-Coupling and Dialkylbiarylphosphine Palladium Catalysts.

Electron-deficient (n-type) conjugated materials are commonly prepared via step-growth methods with limited control over the molecular weight and molecular weight distribution of the resulting polymers. In this communication, we demonstrate that Pd-dialkylbiarylphosphine catalysts enable the chain-growth polymerization of benzo[1,2,3]triazole using Suzuki-Miyaura coupling with molecular weight control and modest molecular weight distributions (Đ ∼ 1.2-1.6). The importance of a free ligand in the reaction mixture during polymerization was established by analysis of polymer samples using GPC and MALDI-TOF mass spectrometry. A block copolymer with poly(3-hexylthiophene) was also synthesized by sequential monomer addition. The success of these commercially available catalysts for polymerization of benzotriazole highlights their potential for chain-growth reactions with other bicyclic arenes in the future.

100th Anniversary of Macromolecular Science Viewpoint: Polymerization of Cumulated Bonds: Isocyanates, Allenes, and Ketenes as Monomers.

Polymer chemistry offers exciting opportunities to tailor the properties of soft materials through control of the composition of the polymers and their interaction with each other, additives, and surfaces. Ongoing advances in the synthesis of polymeric materials demonstrate the drive for materials with tailored properties for enhanced performance in the next generation of materials and devices. One class of small molecules that can serve as monomers in chain growth polymerization are cumulated double bonds of the general form X═Y═Z. The three most common classes of these molecules are isocyanates (N═C═O), allenes (C═C═C), and ketenes (C═C═O), each of which has been explored as monomers under a variety of conditions. The orthogonality of the two pi bonds of the cumulated double bonds (i.e., lack of conjugation) enables the formation of different polymer backbones from a single monomer, provided the regioreactivity is controlled. This Viewpoint outlines the use of these three cumulated double bonds as monomers, illustrating success and current limitations to established polymerization methods. We then provide an outlook to the future of cumulated double bonds as monomers for the generation of tailored polymer compositions.

Cascade Reactions in Chain-Growth Polymerization

While the design and implementation of cascade reactions in organic chemistry and enzymatic biosynthesis flourished in the past decades, cascade reactions in polymerization remain an emerging conce...

Overcoming acid–base copolymer neutralization using mesoporous carbon and its catalytic activity in the tandem deacetalization–Knoevenagel condensation reaction

Acid–base copolymer materials are of considerable interest because of their fundamental implications for acid–base bifunctional catalysis applications. However, quenching the acid and base sites of the copolymer with each other in free radical polymerizations is still challenging. Herein, we demonstrate that the polymerization of styrenesulfonic acid-co-4-vinylpyridine into the mesoporous carbon material (i.e., CMK-3) can control the chain growth polymerization and result in decreasing the interaction of the acid–base sites. The results showed that by using CMK-3, 40% of the acid and base sites of the copolymer remain in their original form while 60% of acid and base sites convert to the pyridinium and sulfonate forms. Furthermore, it is demonstrated that this material can be processed as a heterogeneous bifunctional acid–base catalyst in the tandem one-pot acid–base reaction (i.e., deacetalization–Knoevenagel condensation reaction) with a high catalytic activity in aqueous media.

The Introduction of the Radical Cascade Reaction into Polymer Chemistry: A One-Step Strategy for Synchronized Polymerization and Modification.

SummaryPolymerization and modification play central roles in polymer chemistry and are generally implemented in two steps, which suffer from the time-consuming two-step strategy and present considerable challenge for complete modification. By introducing the radical cascade reaction (RCR) into polymer chemistry, a one-step strategy is demonstrated to achieve synchronized polymerization and complete modification in situ. Attributed to the cascade feature of iron-catalyzed three-component alkene carboazidation RCR exhibiting carbon-carbon bond formation and carbon-azide bond formation with extremely high efficiency and selectivity in one step, radical cascade polymerization therefore enables the in situ synchronized polymerization through continuous carbon-carbon bond formation and complete modification through carbon-azide bond formation simultaneously. This results in a series of α, β, and γ poly(amino acid) precursors. This result not only expands the methodology library of polymerization, but also the possibility for polymer science to achieve functional polymers with tailored chemical functionality from in situ polymerization.

AB-alternating copolymers via chain-growth polymerization: synthesis, characterization, self-assembly, and functions.

An AB-alternating copolymer is distinctly unique in comparison with other copolymers (e.g., random, gradient, and block) because the structure is uniform in terms of sequence: there is no composition distribution among the chains, and there are no consecutive sequence such as AA or AAA in one chain. Various types of alternating copolymers have been synthesized via strategic monomer design and advanced control of the copolymerization process. They exhibit the unique self-assembly behaviors and properties derived from the sequence, which are different from random or block copolymers in some cases. In this review, four topics related to alternating copolymers synthesized via chain-growth polymerization are reviewed: (1) how to control the alternating sequence; (2) sequence characterization; (3) self-assembly; and (4) functions.

Catalyzed chain growth polymerisation of ethylene using lanthanidocenes/dialkylmagnesium: further developments and one pot synthesis of narrow dispersed high molecular weight fatty alcohols

Ethylene polymerisation was performed via an improved in situ Ln/Mg CCG process and applied to the synthesis of high Mn linear alcohols.

Functional Polymers and Polymeric Materials From Renewable Alpha-Unsaturated Gamma-Butyrolactones.

Sustainable chemistry requires application of green processes and often starting materials originate from renewable resources. Biomass-derived monomers based on five-membered γ-butyrolactone ring represent suitable candidates to replace sources of fossil origin. α-Methylene-γ-butyrolactone, β-hydroxy-α-methylene-γ-butyrolactone, and β- and γ-methyl-α-methylene-γ-butyrolactones bearing exocyclic double bond are available directly by isolation from plants or derived from itaconic or levulinic acids available from biomass feedstock. Exocyclic double bond with structural similarity with methacrylates is highly reactive in chain-growth polymerization. Reaction involves the linking of monomer molecules through vinyl double bonds in the presence of initiators typical for radical, anionic, zwitterionic, group-transfer, organocatalytic, and coordination polymerizations. The formed polymers containing pendant ring are characterized by high glass transition temperature (Tg > 195°C) and render decent heat, weathering, scratch, and solvent resistance. The monomers can also be hydrolyzed to open the lactone ring and form water-soluble monomers. Subsequent radical copolymerization in the presence of cross-linker can yield to hydrogels with superior degree of swelling and highly tunable characteristics, depending on the external stimuli. The five-membered lactone ring allows copolymerization of these compounds by ring opening polymerization to provide polyesters with preserved methylene functionality. In addition, both the lactone ring and the methylene double bond can be attacked by amines. Polyaddition with di- or multi-amines leads to functional poly(amidoamines) with properties tunable by structure of the amines. In this mini-review, we summarize the synthetic procedures for preparation of polymeric materials with interesting properties, including thermoplastic elastomers, acrylic latexes, stimuli-sensitive superabsorbent hydrogels, functional biocompatible polyesters, and poly(amidoamines).

Two-Step 3 D-Printing Approach toward Sustainable, Repairable, Fluorescent Shape-Memory Thermosets Derived from Cellulose and Rosin.

Efficiently converting biomass into multifunctional polymerized materials is a challenge to effect high-valued utilization of biomass resources. A two-step 3 D-printing approach has been developed to fabricate a class of robust, fluorescent shape-memory thermosets from cellulose and rosin-based photosensitive 3 D-printing resin solution. The stereolithography 3 D printing was first performed to form the first crosslinked network by UV-induced chain-growth polymerization, which fixed the shape of thermoset. Subsequently, isocyanate was applied to react with hydroxy in the monomer to form the second crosslinked network by thermally induced step-growth polymerization. The formation of a dual-cure network, leading to phase separation and increased crosslinking density, could greatly improve the mechanical and thermal properties of 3 D-printed thermosets and endow them with thermally triggered shape-memory properties and excellent repairability. The 3 D-printed thermosets are found to have strong luminescence resulting from aggregation-induced emission originating from rosin. In addition, these 3 D-printed thermosets could degrade in the presence of NaOH aqueous solution and in situ achieved a range of flexible conductive hydrogels that have important potential application in the flexible electronic materials and smart photoelectric materials.

Seeded Chain-Growth Polymerization of Proteins in Living Bacterial Cells.

Microbially produced protein-based materials (PBMs) are appealing due to use of renewable feedstock, low energy requirements, tunable side-chain chemistry, and biodegradability. However, high-strength PBMs typically have high molecular weights (HMW) and repetitive sequences that are difficult to microbially produce due to genetic instability and metabolic burden. We report the development of a biosynthetic strategy termed seeded chain-growth polymerization (SCP) for synthesis of HMW PBMs in living bacterial cells. SCP uses split intein (SI) chemistry to cotranslationally polymerize relatively small, genetically stable material protein subunits, effectively preventing intramolecular cyclization. We apply SCP to bioproduction of spider silk in Escherichia coli, generating HMW spider silk proteins (spidroins) up to 300 kDa, resulting in spidroin fibers of high strength, modulus, and toughness. SCP provides a modular strategy to synthesize HMW, repetitive material proteins, and may facilitate bioproduction of a variety of high-performance PBMs for broad applications.

Synthesis of sequence-controlled polymers via sequential multicomponent reactions and interconvertible hybrid copolymerizations

Synthesizing artificial polymers with precise sequence structures, such as their biological analogues, is a serious challenge and of great importance in polymer science. Recently, step-growth polymerization and chain growth polymerization have been the main synthesis methods for preparing artificial sequence-regulated polymers. However, it is difficult to obtain sequence-controlled polymers with sufficient molecular diversity via step-growth polymerization; on the other hand, chain-growth polymerization generally requires laborious repetitive monomer feeding. In this focus review, the sequential multicomponent reactions for preparing periodic sequence-controlled polymers with sufficient molecular diversity and complexity and the interconvertible hybrid copolymerizations producing hybrid multiblock copolymers rapidly in one pot are highlighted. We have developed sequential multicomponent reaction and interconvertible hybrid copolymerization methods to prepare sequence-controlled polymers. The sequential multicomponent reaction combines more than two different multicomponent reactions in one pot to prepare periodic sequence˗controlled polymers with sufficient molecular diversity. The interconvertible hybrid copolymerization method uses trithiocarbonate compounds to combine radical polymerization of vinyl monomers and anionic ring-opening polymerization of thiirane monomers, resulting in hybrid multiblock sequence-regulated polymers.

A Versatile Computational Procedure for Chain-Growth Polymerization Using Molecular Dynamics Simulations

Vinyl ester resins are generated via chain-growth polymerization and are widely used for structural composites. The lack of atomic-scale structural models for these industrially important materials makes the link between their structure and performance challenging to fully elucidate. Despite experimental advances, key questions regarding the structure/property relationship of these resins await atomic-scale explanations. As first steps to address this, we introduce a generalized computational procedure for modeling chain-growth polymerization to generate the structure of these resins and test their thermomechanical properties. Our approach uses an in situ dynamic bond-formation procedure and is informed by known reaction kinetics data. The process is applied to the vinyl ester/styrene resin system, producing structures and properties that are consistent with experimental data. We also introduce comprehensive structural analyses to enhance our interpretation of the predicted properties. Our procedure is broadly applicable to the design and testing of any polymer-based material based on a chain-growth mechanism.

Polyethylene Aerogels with Combined Physical and Chemical Crosslinking: Improved Mechanical Resilience and Shape-Memory Properties.

While the introduction of polymers into aerogels strongly enhances their toughness, truly elastic monolithic aerogels which restore their dimensions upon extensive compression are still challenging to synthesize. In this context hydrophobic semi-crystalline polymers with low glass transition temperatures, and combined stiffness and flexibility, have only recently attracted attention. Shown here is that polyethylene aerogels with a low density, and combined chemical crosslinking and high crystallinity, display high moduli and excellent mechanical resilience. To maximize the crystallinity of these aerogels while maintaining a high crosslinking density, polyethylene networks with well-defined segments were synthesized by hydrosilylation crosslinking of telechelic, vinyl-functionalized oligomers obtained from catalyzed chain-growth polymerization. Recoverable deformations both above and below the melting temperature of polyethylene affords remarkable shape-memory properties.

A robust nickel catalyst with an unsymmetrical propyl-bridged diphosphine ligand for catalyst-transfer polymerization

A new nickel diphosphine catalyst has been synthesized in which the bidentate ligand has two different phosphine donors, a typical PPh2 group and a stronger σ-donating PEt2 group. The catalyst was highly effective for the chain-growth polymerization of a 3-alkylthiophene monomer using a Suzuki–Miyaura cross-coupling. The catalyst is particularly effective for this polymerization in the presence of excess free ligand. The unsymmetrical diphosphine nickel complex reported here represents a new approach to tuning metal-ligand reactivity in the chain-growth polymerization of aromatic monomers. In addition, this new nickel catalyst exhibited increased hydrolytic resistance in the polymerization as compared to commercially available 1,3-bis(diphenylphosphino)propane nickel dichloride. A new nickel diphosphine catalyst was synthesized and evaluated for Suzuki–Miyaura cross-coupling polymerization. The diphosphine is comprised of two electronically and sterically distinct phosphine donors, a PPh2 group and a PEt2 group. The catalyst was employed to bring about controlled polymerization of a 3-hexylthiophene monomer to afford poly(3-hexylthiophene). The catalyst was particularly effective for bringing about this polymerization in the presence of excess free ligand. The catalyst resting state was also probed using NMR spectroscopy and an externally initiated catalyst.

Nanoporous poly(ether sulfone) from polylactide-b-poly(ether sulfone)-b-polylactide precursor

We report a route to synthesize polylactide-b-poly(ether sulfone)-b-polylactide (PLA-b-PES-b-PLA) containing PES and PLA, which provide a mechanically robust framework and a sacrificial template for pore formation, respectively. High-molar mass PES terminated with fluorine groups was synthesized by the step-growth nucleophilic aromatic substitution (SNAr) reaction, and the chain ends were transformed into benzylic hydroxyl groups by chain end modification. Growth of the PLA using the hydroxyl groups as initiating sites via chain-growth ring opening transesterification polymerization (ROTEP) produced the target triblock copolymer. Although the step-growth polymerization produced a PES middle block with high dispersity, small angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) analyses indicated the formation of an ordered lamellar morphology. We further demonstrated that a nanoporous PES with slit-like pores could be obtained by selective removal of the PLA.

Dual Organocatalysts Based on Ionic Mixtures of Acids and Bases: A Step Toward High Temperature Polymerizations.

Organocatalysis provides a powerful alternative in many polymerization reactions and nowadays has become a valuable tool for polymer chemists. The key reason for transitioning to organocatalysts is not only their ability to be effectively removed from resultant products, but also, their potential to exquisitely control the catalytic activity and selectivity of the polymerization processes. While organocatalysis has been largely implemented in research laboratories, its use in industrial bulk polymerization processes is still scarce. This is mostly due to the poor thermal stability of organocatalysts at temperatures (150-250 °C) usually employed for industrial polymerizations. In this Viewpoint, we highlight the recent advances of the use of acid-base ionic mixtures in high temperatures bulk polymerization reactions. First, we will focus on the synthesis, characterization, difunctional catalytic properties, and thermal stability of these acid-base mixtures. Afterward, we will emphasize the recent literature describing their use in chain growth and step-growth polymerizations. Moreover, the highlight will also draw attention to recent efforts in the use of these acid-base mixtures in polymer recycling by means of depolymerization.

Oligomerization of Silyl Ketene: Favoring Chain Extension over Backbiting

Silyl ketenes provide an interesting class of molecules to be used as building blocks for highly functional molecules and materials, including as monomers in chain growth polymerizations, whereas p...

Aggregating ability of ferric chloride in the presence of phosphate ligand

Complexing anions such as phosphate or silicate play an ambivalent role in the performance of hydrolyzing metal coagulants: On one hand, they significantly interfere with the hydrolytic pathway of conventional iron or aluminum coagulants, the associated destabilization mechanism remaining rather elusive; on the other hand, they have been shown to be key ingredients in the formulation of innovative coagulant solutions exhibiting improved removal efficiency, their action mechanism at the molecular scale being presently poorly understood. In this paper, we explore the effect of small additions of phosphate ligand on the chemical coagulation of silica nanoparticles with ferric chloride. Transmission Electron Microscopy-Energy Dispersed X-ray Spectroscopy (TEM-EDXS) combined with Extended X-ray absorption Fine Structure Spectroscopy (EXAFS) at the Fe K-edge are used to provide an insight into the nature of coagulant species, whereas jar-tests, laser diffraction, Small Angle X-ray Scattering (SAXS), and electrophoretic mobility, are used to investigate the aggregation dynamics of silica particles in the presence of phosphate ligand. We show that, in spite of a slight increase in the consumption of iron coagulant, the addition of phosphate significantly improves the formation of silica aggregates provided that the elemental Fe/P ratio remains above 7. Such effects originate from both a large increase in the overall number of coagulant species, the binding of a phosphate ligand terminating the growth of polymeric chains of edge-sharing Fe octahedra, and a change in the nature of the coagulant species that evolves with the Fe/P ratio, small polycations built-up from Fe-oligomers linked by phosphate tetrahedra being eventually formed. Those non-equilibrium nanosize Fe–P coagulant species assemble the silica nanoparticles to form hetero-aggregates whose structure is consistent with a Diffusion-Limited Cluster Aggregation mechanism.

Mechanically Initiated Bulk-Scale Free-Radical Polymerization.

Mechanical initiation of polymerization offers the chance to generate polymers in new environments using an energy source with unique capabilities. Recently, a renewed interest in mechanically controlled polymerization has yielded many techniques for controlled radical polymerization by ultrasound. However, other types of polymerizations induced by mechanical activation are rare, especially for generating high-molecular-weight polymers. Herein is an example of using piezoelectric ZnO nanoparticles to generate free-radical species that initiate chain-growth polymerization and polymer crosslinking. The fast generation of high amounts of reactive radicals enable the formation of polymer/gel by ultrasound activation. This chemistry can be used to harness mechanical energy for constructive purposes in polymeric materials and for controlled polymerizations for bulk-scale reactions.

Paclitaxel-Promoted Supramolecular Polymerization of Peptide Conjugates.

Spontaneous association above a threshold concentration is a hallmark of supramolecular polymerization, in which monomeric units self-assemble into polymeric aggregates through noncovalent interactions. This self-initiated supramolecular process differs from the conventional covalent chain-growth polymerization in that the latter often involves the use of a different chemical entity as an initiator to trigger/control the polymerization process. We report here the use of a small molecule hydrophobe, paclitaxel (PTX), as an effective promoter to induce the supramolecular polymerization of a peptide-paclitaxel conjugate, Spheropax (Spax). We found that Spax monomers alone in water self-assemble into spherical micelles of approximately 6.5 nm in diameter but, in the presence of free PTX, undergo a supramolecular polymerization process to form filamentous assemblies of several micrometers in length. Increasing the ratio of promoter to monomer (PTX/Spax) induces Spax's directional polymerization and expedites its kinetic process. We believe these findings provide important insight into the initiator-controlled supramolecular polymerization process.