Catalytic Polymerization Research Articles

Facile Synthesis of Functionalised Hyperbranched Polymers for Application as Novel, Low Viscosity Lubricant Formulation Components.

A novel, previously unreported, method for synthesising hyperbranched (HB) materials is detailed. Their use as additives to produce lubricant formulations that exhibit enhanced levels of wear protection and improved low-temperature oil viscosity and flow is also reported. The lubricant formulations containing HB additives were found to exhibit both significantly lower viscosities and improved in-use film-forming properties than the current industry standard formulations. To achieve this, alkyl methacrylate oligomers (predominantly dimers and trimers) were synthesised using catalytic chain transfer polymerisation. These were then used as functional chain transfer agents (CTA) to control the polymerisation of divinyl benzene (DVB) monomers to generate highly soluble, high polydispersity HB polymers. The level of dimer/trimer purification applied was varied to define its influence on both these HB resultant structures and the resultant HB additives’ performance as a lubricant additive. It was shown that, while the DVB acted as the backbone of the HB, the base oil solubility of the additive was imparted by the presence of the alkyl chains included in the structure via the use of the oligomeric CTAs.

Influence of reaction conditions on kumada catalytic transfer polymerization for synthesis of poly(p-phenylene) for organic semiconductors

Influence of reaction conditions on kumada catalytic transfer polymerization for synthesis of poly(p-phenylene) for organic semiconductors

Simultaneous Enhancement of Polymerization Kinetics and Properties of Phthalonitrile Using Alumina Fillers.

Alumina particles are investigated as a potential catalyst for phthalonitrile polymerization and as a property enhancer. In this work, extensive characterizations were conducted on alumina-filled resorcinol-based phthalonitrile to differentiate between the catalytic effect and the filler effect. Thermal gravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectroscopy suggest the occurrence of chemical interaction between alumina fillers and phthalonitrile, which provides an insight into the better performance of alumina-filled phthalonitrile resins. This hypothesis is further supported by the additional Al–N peak observed in the X-ray photoelectron spectroscopy (XPS) analysis when alumina is added to phthalonitrile before curing, as well as the presence of an exothermic peak in the differential scanning calorimetry (DSC) analysis that indicates the catalytic polymerization of phthalonitrile. This catalytic phenomenon observed by the addition of alumina fillers is beneficial for the improvement of the conventionally slow curing process of phthalonitrile and, more importantly, is coupled with observable enhancement of thermomechanical properties of the composite.

Comparative Investigation of η6-Arene Tethered Ru(II) Complexes with Different Tethered Heteroatoms for Ethylene Polymerization Catalysis: Experimental and DFT Studies

Comparative Investigation of η⁶-Arene Tethered Ru(II) Complexes with Different Tethered Heteroatoms for Ethylene Polymerization Catalysis: Experimental and DFT Studies

Zirconium Permethylpentalene Amidinate Complexes: Characterization, Bonding, and Olefin Polymerization Catalysis

Zirconium Permethylpentalene Amidinate Complexes: Characterization, Bonding, and Olefin Polymerization Catalysis

In Situ Catalytic Polymerization of a Highly Homogeneous PDOL Composite Electrolyte for Long‐Cycle High‐Voltage Solid‐State Lithium Batteries

AbstractHigh energy density solid‐state lithium batteries require good ionic conductive solid electrolytes (SE) and stable matching with high‐voltage electrode materials. Here, a highly homogeneous poly(1,3‐dioxolane) composite solid electrolyte (CSE) membrane that can satisfy the above‐mentioned requirements by in situ catalytic polymerization effect of yttria stabilized zirconia (YSZ) nanoparticles on the polymerization of 1,3‐dioxolane (DOL), is reported. The well‐dispersed YSZ nanoparticle catalyst leads to the polymerization conversion of DOL monomers up to 98.5%, which enlarges its electrochemical window exceeding 4.9 V. YSZ also significantly improves the room temperature ionic conductivity (2.75 × 10−4 S cm−1) and enhances the cycle life of lithium metal anode. Based on this CSE, the Li(Ni0.6Co0.2Mn0.2)O2 (NCM622)‐based solid‐state lithium battery shows a long cycle life over 800 cycles. This investigation encourages polymer SE toward practical high energy solid‐state batteries.

Spotting Trends in Organocatalyzed and Other Organomediated (De)polymerizations and Polymer Functionalizations

Organocatalysis has evolved into an effective complement to metal- or enzyme-based catalysis in polymerization, polymer functionalization, and depolymerization. The ease of removal and greater sustainability of organocatalysts relative to transition-metal-based ones has spurred development in specialty applications, e.g., medical devices, drug delivery, optoelectronics. Despite this, the use of organocatalysis and other organomediated reactions in polymer chemistry is still rapidly developing, and we envisage their rapidly growing application in nascent areas such as controlled radical polymerization, additive manufacturing, and chemical recycling in the coming years. In this Review, we describe ten trending areas where we anticipate paradigm shifts resulting from novel organocatalysts and other transition-metal-free conditions. We highlight opportunities and challenges and detail how new discoveries could lead to previously inaccessible functional materials and a potentially circular plastics economy.

Spotting Trends in Organocatalyzed and Other Organomediated (De)polymerizations and Polymer Functionalizations.

Organocatalysis has evolved into an effective complement to metal‐ or enzyme‐based catalysis in polymerization, polymer functionalization, and depolymerization. The ease of removal and greater sustainability of organocatalysts relative to transition‐metal‐based ones has spurred development in specialty applications, e.g., medical devices, drug delivery, optoelectronics. Despite this, the use of organocatalysis and other organomediated reactions in polymer chemistry is still rapidly developing, and we envisage their rapidly growing application in nascent areas such as controlled radical polymerization, additive manufacturing, and chemical recycling in the coming years. In this Review, we describe ten trending areas where we anticipate paradigm shifts resulting from novel organocatalysts and other transition‐metal‐free conditions. We highlight opportunities and challenges and detail how new discoveries could lead to previously inaccessible functional materials and a potentially circular plastics economy.

Mechanochemical Suzuki polymerization for the synthesis of polyfluorenes

ABSTRACT Herein are reported the syntheses of poly(9,9-di-n-octylfluorenyl-2,7-diyl) (PF), poly(9,9-dioctylfluorene-alt-benzothiadiazole) (PFBT), and poly[(9,9-bis(3′-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] (PFN) by employing catalytic mechanochemical Suzuki polymerization in a ball mill. This mechanochemical synthesis technique can yield soluble functionalized polyfluorenes and its derivatives in 30 min or less. Furthermore, the polymer light emitting diode and photovoltaic interfacial electrolyte, poly(9,9-bis(3′-(N,N-dimethyl)-N-ethylammoinium-propyl-2,7-fluorene)-alt-2,7-(9,9-dioctylfluprene))dibromide (PFN-Br), was obtained via a facile mechanochemical quaternization reaction at the terminal amino groups of PFN.

Real-Time Polymer Viscosity-Catalytic Activity Relationships on the Microscale.

Polymer growth induces physical changes to catalyst microenvironments. Here, these physical changes are quantified in real time and are found to influence microscale chemical catalysis and the polymerization rate. By developing a method to "peer into" optically transparent living-polymer particles, simultaneous imaging of both viscosity changes and chemical activity was achieved for the first time with high spatiotemporal resolution through a combination of fluorescence intensity microscopy and fluorescence lifetime imaging microscopy techniques. Specifically, an increase in microenvironment viscosity led to a corresponding local decrease in the catalytic molecular ruthenium ring-opening metathesis polymerization rate, plausibly by restricting diffusional access to active catalytic centers. Consistent with this diffusional-access model, these viscosity changes were found to be monomer-dependent, showing larger changes in microenvironment viscosity in cross-linked polydicyclopentadiene compared to non-crosslinked polynorbornene. The sensitivity and high spatial resolution of the imaging technique revealed significant variations in microviscosities between different particles and subparticle regions. These revealed spatial heterogeneities would not be observable through alternative ensemble analytical techniques that provide sample-averaged measurements. The observed spatial heterogeneities provide a physical mechanism for variation in catalytic chemical activity on the microscale that may accumulate and lead to nonhomogeneous polymer properties on the bulk scale.

Post-Modification of Copolymers Obtained by ATRP for an Application in Heterogeneous Asymmetric Salen Catalysis.

Copolymers are valuable supports for obtaining heterogeneous catalysts that allow their recycling and therefore substantial savings, particularly in the field of asymmetric catalysis. This contribution reports the use of two comonomers: Azido-3-propylmethacrylate (AZMA) bearing a reactive azide function was associated with 2-methoxyethyl methacrylate (MEMA), used as a spacer, for the ATRP synthesis of copolymers, and then post-functionalized with a propargyl chromium salen complex. The controlled homopolymerization of MEMA by ATRP was firstly described and proved to be more controlled in molar mass than that of AZMA for conversions up to 63%. The ATRP copolymerization of both monomers made it possible to control the molar masses and the composition, with nevertheless a slight increase in the dispersity (from 1.05 to 1.3) when the incorporation ratio of AZMA increased from 10 to 50 mol%. These copolymers were post-functionalized with chromium salen units by click chemistry and their activity was evaluated in the asymmetric ring opening of cyclohexene oxide with trimethylsilyl azide. At an equal catalytic ratio, a significant increase in enantioselectivity was obtained by using the copolymer containing the largest part of salen units, probably allowing, in this case, the more favorable bimetallic activation of both the engaged nucleophile and electrophile. Moreover, the catalytic polymer was recovered by simple filtration and re-engaged in subsequent catalytic runs, up to seven times, without loss of activity or selectivity.

Hypervalent Chalcogenonium⋅⋅⋅π Bonding Catalysis

AbstractA proof‐of‐concept study of hypervalent chalcogenonium⋅⋅⋅π bonding catalysis was performed. A new catalytic strategy using 1,2‐oxaselenolium salts as chalcogen bond donors and alkenes as chalcogen bond acceptors is described. The feasibility of this concept is demonstrated by the use of trisubstituted selenonium salts in the metal‐free catalytic hydrofunctionalization and polymerization of alkenes via unconventional seleniranium ion‐like intermediates. The results indicate that counter anions have a significant effect on the catalysis based on hypervalent chalcogenonium⋅⋅⋅π bonding interactions.

Hypervalent Chalcogenonium⋅⋅⋅π Bonding Catalysis.

A proof-of-concept study of hypervalent chalcogenonium⋅⋅⋅π bonding catalysis was performed. A new catalytic strategy using 1,2-oxaselenolium salts as chalcogen bond donors and alkenes as chalcogen bond acceptors is described. The feasibility of this concept is demonstrated by the use of trisubstituted selenonium salts in the metal-free catalytic hydrofunctionalization and polymerization of alkenes via unconventional seleniranium ion-like intermediates. The results indicate that counter anions have a significant effect on the catalysis based on hypervalent chalcogenonium⋅⋅⋅π bonding interactions.

Stereogradient Poly(Lactic Acid) from meso-Lactide/L-Lactide Mixtures.

The production of L-lactide from L-lactic acid involves a substantial formation of meso-lactide as an impurity, and, upon polymerization with the industrial catalyst tin octanoate, results in poly(L-lactic acid) of reduced crystallinity due to stereoerrors randomly distributed along the polymer chains. We describe a new approach wherein, instead of avoiding stereoerrors by removing the meso-lactide prior to polymerization, the stereoerrors in the polymer are tolerated, by crowding them in a stereogradient copolymer. A zirconium complex of an amine tris(phenolate) ligand is found to exhibit very high syndioselectivity in the ring opening polymerization catalysis of meso-lactide at room temperature, and gives rise to stereogradient copolymers in the polymerization of mixtures of meso-lactide/L-lactide in the melt at 180 °C. Relative to the stereo-random copolymers obtained with tin octanoate, the stereogradient copolymers exhibit enhanced crystallinities manifested in lower solubilities and higher melting temperatures and enthalpies.

Stereogradient Poly(Lactic Acid) from meso‐Lactide/L‐Lactide Mixtures

AbstractThe production of L‐lactide from L‐lactic acid involves a substantial formation of meso‐lactide as an impurity, and, upon polymerization with the industrial catalyst tin octanoate, results in poly(L‐lactic acid) of reduced crystallinity due to stereoerrors randomly distributed along the polymer chains. We describe a new approach wherein, instead of avoiding stereoerrors by removing the meso‐lactide prior to polymerization, the stereoerrors in the polymer are tolerated, by crowding them in a stereogradient copolymer. A zirconium complex of an amine tris(phenolate) ligand is found to exhibit very high syndioselectivity in the ring opening polymerization catalysis of meso‐lactide at room temperature, and gives rise to stereogradient copolymers in the polymerization of mixtures of meso‐lactide/L‐lactide in the melt at 180 °C. Relative to the stereo‐random copolymers obtained with tin octanoate, the stereogradient copolymers exhibit enhanced crystallinities manifested in lower solubilities and higher melting temperatures and enthalpies.

Cost-effective, scalable and smartphone-controlled 3D-Printed syringe pump - From lab bench to point of care biosensing applications

Laboratories all over the word use syringe pumps every day for a multitude of purposes. The market of syringe pumps is limited, as it does not consider the broad range of specifications required by different researchers. In this work, we present a 3D printed syringe pump designed to be affordable, customizable, and extremely user friendly while still maintaining reliability and precision. The pump, thanks to its flexible design and smartphone-controlled interface, can be used in educational settings as well as in biological and chemical laboratories. The presented syringe-pump is used in this work to run a light catalyzed polymerization of butyl methacrylate using visible light, in a continuous flow setup.

Molecularly Defined Polyolefin Vitrimers from Catalytic Insertion Polymerization.

Vitrimers can combine the advantageous properties of cross-linked materials with thermoplastic processability. For the prominent case of polyethylene, established post-polymerization introduction of cross-linkable moieties results in extremely heterogeneous compositions of the chains. Here, we report the generation of functionalized polyethylenes directly by catalytic insertion polymerization, with incorporated cross-linkable aryl boronic esters or alternatively acetal-protected groups suited for cross-linking with difunctional boronic esters. In addition to the desired homogeneous in-chain distribution, the reactive cross-linkable groups are enriched at the chain ends. This enables the incorporation of all chains in the network, as also supported by simulations of all chains' compositions. The uniform molecular composition of the chains reflects in resulting vitrimers' material properties, particularly lack of leaching with solvents. At the same time, cross-linking is indeed fully reversible and the vitrimers can be recycled.

Suppression of Chain Transfer at High Temperature in Catalytic Olefin Polymerization

AbstractLiving polymerization by suppressing chain transfer is a very useful method for achieving precise molecular weight and structure control. However, the suppression of chain transfer at high temperatures is extremely challenging in any catalytic polymerization. This has been a severe limitation for catalytic olefin polymerization, which is one of the most important chemical reactions. Here, we report the unprecedented living polymerization of ethylene at 130 °C, with a narrow molecular weight distribution range of 1.04 to 1.08. This is a significant increase in the reaction temperature. Tailor‐made α‐diimine nickel catalysts that exhibit both the steric shielding and fluorine effects play an essential role in this breakthrough. These nickel catalysts are even active at 200 °C, and enable the formation of semi‐crystalline, ultrahigh‐molecular‐weight polyethylene at 150 °C. Mechanistic insights into the key chain transfer reaction are elucidated by density functional theory calculations.

Suppression of Chain Transfer at High Temperature in Catalytic Olefin Polymerization

Living polymerization by suppressing chain transfer is a very useful method for achieving precise molecular weight and structure control. However, the suppression of chain transfer at high temperatures is extremely challenging in any catalytic polymerization. This has been a severe limitation for catalytic olefin polymerization, which is one of the most important chemical reactions. Here, we report the unprecedented living polymerization of ethylene at 130 °C, with a narrow molecular weight distribution range of 1.04 to 1.08. This is a significant increase in the reaction temperature. Tailor-made α-diimine nickel catalysts that exhibit both the steric shielding and fluorine effects play an essential role in this breakthrough. These nickel catalysts are even active at 200 °C, and enable the formation of semi-crystalline, ultrahigh-molecular-weight polyethylene at 150 °C. Mechanistic insights into the key chain transfer reaction are elucidated by density functional theory calculations.

Site-Isolated Main-Group Tris(2-pyridyl)borate Complexes by Pyridine Substitution and Their Ring-Opening Polymerization Catalysis

Tris(2-pyridyl)borates are an emerging class of scorpionate ligands, distinguished as exceptionally robust and electron-donating. However, the rapid formation of inert homoleptic complexes with divalent metals has so far limited their catalytic utility. We report site-isolating tris(2-pyridyl)borate ligands, bearing isopropyl, tert-butyl, and mesityl substituents at the pyridine 6-position to suppress the formation of inert homoleptic complexes. These ligands form the first 1:1 complexes between tris(2-pyridyl)borates and Mg2+, Zn2+, or Ca2+, with isopropyl-substituted TpyiPrH showing the most generality. Single-crystal X-ray diffraction analysis of the resulting complexes and comparison to density functional theory (DFT) models showed geometric distortions driven by steric repulsion between the pyridine 6-substituents and the hexamethyldisilazide (HMDS-, -N(SiMe3)2) anion. We show that this steric profile is a feature of the six-membered pyridine ring and contrasts with more established tris(pyrazolyl)borate and tris(imidazoline)borate scorpionate complexes. TpyiPrMg(HMDS) (1) and its zinc analogue are moderately active for the controlled polymerization of l-lactide, ε-caprolactone, and trimethylene carbonate. Furthermore, 1 gives controlled polymerization under more demanding melt-phase polymerization conditions at 100 °C, and block copolymerization of ε-caprolactone and trimethylene carbonate. These results will enable useful catalysis and coordination chemistry studies with tris(2-pyridyl)borates, and characterizes their structural complementarity to more familiar scorpionate ligands.