Polymerization Reactivity Research Articles

A tridentate phenoxy-phosphine (POP) divalent chromium complex and its reactivities in olefin polymerization

We reported the synthesis and characterization of a Cr(ii) complex based on a tridentate phenoxy-phosphine ligand and studied its reactivities in ethylene and norbornene homopolymerization and ethylene copolymerization with norbornene or 1-octene.

Chemoselective ring-opening metathesis polymerization of cyclopropenes spirally appended with N-aryl saturated heterocycles

The nature of the substituents on cyclopropenes and catalysts could have a profound effect on the reactivity and selectivity of ring-opening metathesis polymerization (ROMP).

N-alkyl-β-ketoiminate zinc complexes: Synthesis, structure, and reactivity in ring-opening polymerization of lactide

A series of N-alkyl-β-ketoiminate monozinc complexes [{tBuCN(R)CHC(O)CtBu}2Zn] (R = Me, 2a; Et, 2b; Pr, 2c; iPr, 2d; Cy, 2e) were synthesized from the reaction of diethyl zinc with the corresponding β-ketimines. All these zinc complexes were characterized by NMR, elemental analysis and HRMS spectroscopy. The molecular structures of complexes 2b-2e were further confirmed by single-crystal X-ray diffraction. The structures exhibit that each zinc center is four-coordinate, and surrounded by two bidentate β-ketoiminate ligands, forming a distorted tetrahedral geometry. These homoleptic bis(β-ketoiminate) zinc complexes are active towards the ring-opening polymerization of rac-lactide in the absence of alcohol, yielding over 90 % conversions within 1 h at 70 °C in toluene with the ratio of monomer to catalyst being 100.

Preparation and characterization of photo‐decomposable ester‐containing semi‐alicyclic polyimide alignment layers for potential applications in in‐plane switching thin‐film transistor liquid crystal display devices

AbstractPoly(amic acid)s (PAAs) alignment agents have been prepared from the alicyclic dianhydrides, including 1,2,3,4‐cyclobutanetetracarboxylic dianhydride (CBDA, I), 1,3‐dimethyl‐1,2,3,4‐cyclobutanetetracarboxylic dianhydride (DMCBDA, II), and ester‐linked aromatic diamines, including 4‐aminophenyl‐4′‐aminobenzoate (APAB, a) and bis(4‐aminophenyl)terephthalate (BPTP, b), respectively. The derived PAAs, including PAA‐Ia (CBDA‐APAB), PAA‐Ib (CBDA‐BPTP), and PAA‐IIa (DMCBDA‐APAB) exhibited the preferable molecular weights, while the PAA‐IIb (DMCBDA‐BPTP) showed the low one due to the low polymerization reactivity both for the DMCBDA dianhydride and the BPTP diamine. All the PAA solutions except PAA‐IIb were adopted as the alignment components to fabricate liquid crystal (LC) minicells with a mode of in‐plane switching (IPS). The polyimides (PI) alignment layers derived from the thermal dehydration reaction of the PAA precursors at 230°C for 30 min showed good alignments effects to the LC molecules, which exhibited the pretilt angles (θp) from 0.09 to 0.15° after being exposed by the linear polarized ultraviolet light sources with the wavelength of 254 nm. In addition, the PI alignment layers afforded good optoelectronic features to the minicells, including the voltage holding ratio values over 97% at room temperature, and the residual direct circuit voltages lower than 1.0 V. The anchoring energy results indicated that the PI‐IIa (DMCBDA‐APAB) alignment layer showed the highest interaction with the LC molecules, and thus exhibited the highest threshold voltage (Vth) in the voltage‐transmittance (V‐T) measurements for the minicells.

Structural tuning enhanced catalytic activity of amido aluminum complexes for the ring-opening polymerization of ε-caprolactone

This work describes various coordination modes of aluminum complexes bearing amido-pyridinate and amido-benzene ligands. Utilizing pendant donating groups to switch the coordination behaviours of aluminum complexes and their catalytic activities. Noticeably, these Al complexes containing the methoxy group markedly showed reactivities in ring-opening polymerization of ε-caprolactone. Among them, complex 3 with the methoxy group coordinated to the metal center exhibited higher performance with lower catalyst loading at room temperature than other related amido aluminum complexes in literature.

Polymers from organosilicon derivatives of 5-norbornene-2-methanol for membrane gas separation

In this work, we have proposed a new strategy to the synthesis of norbornene-type monomers with Si–O–C structural motifs via a straightforward and selective dehydrogenative addition reaction between 5-norbornene-2-methanol and trialkylsilanes. As a result, a set of monomers with various trilalkylsiloxy groups (alkyl – CH3, C2H5, and n-C3H7) was synthesized with the yields of 89–90%. These monomers exhibited a high reactivity in both metathesis and vinyl-addition polymerization, affording high-molecular-weight products in yields up to 90%. The metathesis polymers were rubbery with glass transition temperatures from −29 to +23 °C, while related isomeric vinyl-addition polynorbornenes were glassy polymers. Permeability (P) and diffusion (D) coefficients for these polymers were systematically evaluated for permanent gases (He, H2, O2, N2, and CO2) and C1–C4 alkanes. Studying their gas transport properties allowed to establish new structure-property relationships. Particularly, the length of alkyl fragments in trilalkylsiloxy group affected differently gas permeability of metathesis (rubbery) and vinyl-addition (glassy) polymers. Besides, it was shown that the method of linking the Si–O–C-containing group to the main chains of polymers played very important role: Alk3SiO-substituted polynorbornenes are more permeable than isomeric (AlkO)Alk2Si-substituted ones. For the metathesis polynorbornenes, P(CO2) were in the range of 152–226 Barrer, and ideal selectivity (α) of CO2/N2 – 13-16; for the vinyl-addition polynorbornenes, P(CO2) = 230–500 Barrer, and α(CO2/N2) = 14–17. Among studied polymers, promising results for ethane/methane separation was demonstrated by metathesis polynorbornene bearing tri(n-propyl)siloxymethyl substituents: P(C2H6) = 138 Barrer and α(C2H6/CH4) = 2.4. The obtained polymers were also characterized by using TGA, WAXD, and nitrogen adsorption-desorption methods.

Strategies for Improving the Thermomechanical, Flame Retardancy and Dielectric Properties of Benzophenone‐Functionalized Polybenzoxazine

AbstractIn this work, two different approaches were proposed to obtain low‐dielectric material with self‐cleaning property from polybenzoxazine (Pbz). Initially, benzoxazine (Bzo) monomer with benzophenone functionality was synthesized. Then, Pbz/TiO2 composites were prepared using the synthesized bzo monomer and TiO2 nanoparticles (NPs). A simple Mannich reaction and thermal curing were effective for the synthesis of ring‐closing and ring‐opening benzoxazine using molecular structure and provided highly efficient products without the use of a special catalyst. DSC analysis showed that the benzoxazine monomer exhibits different polymerization reactivity as they possess different functional groups. The inclusion of an inorganic component into the organic polymer had a significant enhancing effect. Two important properties, viz., the low free surface energy of Pbz and the self‐cleaning property of TiO2 nanoparticles, were combined to develop a promising approach in the development of self‐cleaning materials. These properties are incorporated to produce a multifunctional superhydrophobic material, Pbz/TiO2 modified with different ratios of TiO2 by way of simple blending and subsequent thermal curing reactions. The resulting Pbz/TiO2 composite exhibits excellent thermomechanical strength (retention modulus 3.34G, thermal stability up to 352 °C) and strong water resistance (static water contact angle of 141°), as well as low dielectric constant (3.1).

Accelerated Post-Polymerization Amidation of Polymers with Side-Chain Ester Groups by Intramolecular Activation.

The catalytic conversion of esters to amides represents new opportunities in the synthetic diversification and upcycling of polymers, as esters are commonly featured in various polymer structures. Yet, direct amidation is typically hampered by poor reaction kinetics and the effects of polymer structure on the reactivity remain poorly understood. We report the accelerated amidation for amines with additional hydrogen bond donating or accepting groups. These amines facilitate the expeditious (co)amidation of polymers with pendant ester groups, displaying at least a 400-fold higher reactivity relative to polyesters with esters in the main chain. Furthermore, a positive correlation between the reactivity and degree of polymerization for poly(methyl acrylate) suggests a hydrogen-bond mediated intramolecular activation of the esters, which was confirmed by FT-IR spectroscopy and basic molecular mechanics modeling. The reported method paves the way to synthesize diverse (co)polymers with amide side chains from readily available polymeric precursors.

Accelerated Post‐Polymerization Amidation of Polymers with Side‐Chain Ester Groups by Intramolecular Activation

AbstractThe catalytic conversion of esters to amides represents new opportunities in the synthetic diversification and upcycling of polymers, as esters are commonly featured in various polymer structures. Yet, direct amidation is typically hampered by poor reaction kinetics and the effects of polymer structure on the reactivity remain poorly understood. We report the accelerated amidation for amines with additional hydrogen bond donating or accepting groups. These amines facilitate the expeditious (co)amidation of polymers with pendant ester groups, displaying at least a 400‐fold higher reactivity relative to polyesters with esters in the main chain. Furthermore, a positive correlation between the reactivity and degree of polymerization for poly(methyl acrylate) suggests a hydrogen‐bond mediated intramolecular activation of the esters, which was confirmed by FT‐IR spectroscopy and basic molecular mechanics modeling. The reported method paves the way to synthesize diverse (co)polymers with amide side chains from readily available polymeric precursors.

Polymerization of butadiene, isoprene and 1-substituted dienes using cobalt catalysts

Cobalt complexes carrying 6-(N-di-tert-butylphosphinoxide)-2-(2′-R-2H’-benzoimidazole)- aminepyridine (R = H, Co1; ethyl, Co2 and benzyl, Co3) ligand were prepared and characterized by FT-IR, UV–vis and elemental analysis. Single crystal X-ray diffraction analysis revealed that Co2 displayed a distorted trigonal bipyramid configuration via N, N, O-tridentate coordination to cobalt center. Activated with AlEt2Cl or MAO, all cobalt complexes are notably active in butadiene and isoprene polymerization, affording cis-1,4 polybutadiene and cis-1,4/3,4 polyisoprene, respectively. The formed catalysts are also efficient for 1-phenyl-1,3-butadiene and 1-(4′-methoxylphenyl)-1,3-butadiene polymerizations, but surprisingly result in partially cyclic product probably arising from Friedel-Craft reaction of formed internal olefin with pending aryl group. Copolymerization of isoprene with 1-substituted-1,3-butadiene is able to afford a series of high molecular weight copolymers with 1.4–8.7 mol-% incorporation rate that free of cyclization. The effects of the substitution pattern of monomer on the polymerization reactivity are also evaluated.

Synthesis of Pentaarylcyclobutenylrhodium(I) Complexes and Their Reactivity and Initiation Mechanism in Polymerization of Monosubstituted Acetylenes

Synthesis of Pentaarylcyclobutenylrhodium(I) Complexes and Their Reactivity and Initiation Mechanism in Polymerization of Monosubstituted Acetylenes

Solvent Degradation and Polymerization in the Li-Metal Battery: Organic-Phase Formation in Solid-Electrolyte Interphases.

The products of solvent polymerization and degradation are crucial components of the Li-metal battery solid-electrolyte interphase. However, in-depth mechanistic studies of these reactions are still scarce. Here, we model the polymerization of common lithium battery electrolyte solvents─ethylene carbonate (EC) and vinylene carbonate (VC)─near the anode surface. Being consistent with the molecular calculation, ab initio molecular dynamic (AIMD) simulations reveal fast solvent decompositions upon contact with the Li anode. Additionally, we assessed the thermochemical impacts of decarboxylation reactions as well as the lithium bonding with reaction intermediates. In both EC and VC polymerization pathways, lithium bonding demonstrated profound catalytic effects while different degrees of decarboxylation were observed. The VC polymerization pathways with and without ring-opening events were evaluated systematically, and the latter one which leads to poly(VC) formation was proven to dominate the oligomerization process. Both the decomposition and polymerization reactivities of VC are found to be higher than EC, while the cross-coupling between EC and VC has an even lower-energy barrier. These findings are in good agreement with experimental evidence and explanatory toward the enhanced performance of VC-added lithium-metal batteries.

Preparation and properties of a fluorinated epoxy resin with low dielectric constant

AbstractDemand for electronic materials with improved dielectric properties are increasing. One of the ways to reduce the dielectric constant is to incorporate fluorine atoms. In this article, a novel fluorinated epoxy resin (diglycidol ether of 2,4‐bis (1,1,1,3,3,3‐hexafluoroisopropyl) fluorobenzene (FB‐EP)) with 45.7 wt% fluorine content was synthesized from fluorobenzene, epichlorohydrin and hexafluoroacetone. The structures of desired monomers were characterized by NMR and FTIR. The epoxy resin FB‐EP was cured by copolymerization with hexahydrophthalic anhydride (HHPA) and by homopolymerization catalyzed with boron trifluoride ethylamine (BF3MEA), respectively. The curing reaction kinetics of the fluorinated epoxy and the properties of the cured materials were studied in comparison with those of common diglycidol ether epoxy resin (BADGE). The results of curing activation energy indicate that FB‐EP is reactive as the BADGE, and the four‐trifluoromethyl groups on FB‐EP do not negatively affect the cationic polymerization reactivity of the epoxy groups. The cured FB‐EP materials had lower moisture absorption, and especially lower dielectric constant (Dk, 2.23) and lower dielectric loss (Df, 0.011) in the frequency range of 8.2–12.4 GHz. This article provides a base for further study of fluorinated epoxy resin as advanced electronic materials.

Azaborine benzylic ion stability and reactivity in ionic polymerization.

Benzylic cations and anions are implicated in the mechanism of critical organic transformations, such as styrene polymerization. We investigate the influence of BN for CC bond substitution on the reactivity of benzylic ions and the effect on BN 2-vinylnaphthalene (BN2VN) ionic polymerization. Calculations suggest that the proximity of a N donor to a cation influences the stability of a BN benzylic cation, rationalizing unsuccessful protonation of BN2VN. Organolithium reagents undergo clean nucleophilic aromatic substitution with BN2VN and related BN naphthalenes via a hypothesized associative mechanism. These results suggest design principles for main group aromatic substitution.

N-Oxides amplify catalyst reactivity and isoselectivity in the ring-opening polymerization of rac-β-butyrolactone.

N-Oxides can amplify the performance of a lanthanum aminobisphenolate catalyst in the ring-opening polymerization (ROP) of rac-β-butyrolactone (rac-BBL) to unprecedented levels (TOF/Pm; At RT: 1900 h-1/0.73, At -30 °C: 200 h-1/0.82). Experiments and computations establish donor electronics control catalyst activity, while donor sterics control catalyst deactivation.

EPTFE reinforced, sulfonated aromatic polymer membranes enable durable, high-temperature operable PEMFCs

SummarySulfonated polyphenylene (SPP)-based ionomers have been developed for electrochemical applications in recent years due to their inherent thermal and chemical stability. However, the difficult synthesis, limited solubility, and rigid backbone obstructs their progress. Herein, a new monomer, 3,3″-dichloro-2′,3′,5′,6′-tetrafluoro-1,1':4′,1″-terphenyl (TP-f) with high polymerization reactivity was designed and polymerized with sulfonated phenylene monomer to prepare SPP-based ionomers (SPP-TP-f) with high ion exchange capacity up to 4.5 mequiv g−1. The resulting flexible membranes were more proton conductive than Nafion (state-of-the-art proton exchange membrane) even at 120°C and 20% RH. Unlike typical SPP ionomers, SPP-TP-f 5.1 was soluble in ethanol and thus, could be reinforced with double expanded polytetrafluorethylene thin layers to obtain SPP-TP-f 5.1/DPTFE membrane. SPP-TP-f 5.1/DPTFE showed superior fuel cell performance to that of Nafion, in particular, at low humidity (30% RH, > 100°C) and reasonable durability under the severe accelerated conditions combining OCV hold and humidity cycling tests.

A Robust Vanadium(V) Tris(2-pyridyl)borate Catalyst for Long-Lived High-Temperature Ethylene Polymerization

Soluble vanadium catalysts are highly coveted for their selectivity in olefin polymerization. However, their utility is limited by rapid deactivation, especially at scalable temperatures under which the polymer remains soluble (>100 °C). Reasoning that a highly σ-donating scorpionate ligand would stabilize the vanadium(V) against reductive deactivation, we developed vanadium tris(2-pyridyl)borate complexes and studied their reactivities in high-temperature homogeneous ethylene polymerization. Complex 1 shows exceptional ethylene polymerization longevity at high temperatures, with 1 h of activity at 105 °C. The low polydispersity, vinyl end groups, and concentration effects indicate single-site catalysis involving chain transfer to the monomer. These results provide a new platform for studying high-valent vanadium catalysts under demanding conditions.

EPTFE Reinforced, Sulfonated Aromatic Polymer Membranes Enable Durable, High-Temperature Operable PEMFCs

Sulfonated polyphenylene (SPP)-based ionomers have been developed for electrochemical applications in recent years due to their inherent thermal and chemical stability. However, the difficult synthesis, limited solubility and rigid backbone obstructs their progress. Herein, a new monomer, 3,3''-dichloro-2',3',5',6'-tetrafluoro-1,1':4',1''-terphenyl (TP-f) with high polymerization reactivity was designed and polymerized with sulfonated phenylene monomer to prepare SPP-based ionomers (SPP-TP-f) with high ion exchange capacity up to 4.5 mequiv g-1. The resulting flexible membranes were more proton conductive than Nafion (state-of-the-art proton exchange membrane) even at 120 °C and 20% RH. Unlike typical SPP ionomers, SPP-TP-f 5.1 was soluble in ethanol and thus, could be reinforced with double ePTFE thin layers to obtain SPP-TP-f 5.1/DPTFE membrane. SPP-TP-f 5.1/DPTFE showed superior fuel cell performance to that of Nafion, in particular, at low humidity (30% RH, > 100 oC) and reasonable durability under the severe accelerated conditions combining OCV hold and humidity cycling tests.

Theoretical insight into the opposite redox activity of iron complexes toward the ring opening polymerization of lactide and epoxide

The origin of opposite reactivity in the ring-opening polymerization of lactide (LA) and cyclohexene oxide (CHO) catalyzed by redox-switchable bis(imino)pyridine iron complexes has been computationally elucidated.

Divergent strategy for the synthesis of bottlebrush polymers via postpolymerization modification of macromonomer

AbstractA simple and divergent synthetic strategy of bottlebrush polymers (BBPs) is presented, consisting of postpolymerization modification of a macromonomer and grafting‐through polymerization. Beginning with a single macromonomer, its direct modification could build a library of macromonomers with an identical chain length, thus guaranteeing the precision in the synthesis of BBPs. In this study, a newly designed norbornenyl‐terminated poly(methyl acrylate) (NB‐PMA) is proposed as a chemically robust template. Ti‐mediated transesterification of NB‐PMA successfully produces structurally diverse polyacrylates while maintaining the terminal norbornenyl group intact. All macromonomers obtained from transesterification possess a good grafting‐through ring‐opening metathesis polymerization reactivity, furnishing homo, random, and block BBPs in a controllable manner. Moreover, atomic force microscopy analysis supports the controlled side‐chain length distribution in the resulting BBPs.