Cationic Polymerization Reactions Research Articles

The effect of boron trifluoride complex on the preparation of mesophase pitch from FCC decant oil fractions with different compositions and molecular structures

The boron trifluoride complex catalyst can effectively facilitate the development of anisotropic structures in FCC decant oil (FCC-DO) through cationic polymerization reaction. However, the fractions of FCC-DO with different boiling points possess different molecular compositions and aromatic nuclei configurations. In this study, FCC-DO is separated into light fraction, middle fraction, and heavy fraction by vacuum distillation. The different carbonization reaction pathways and reactivity were systematically investigated for three narrow fractions with no or 5 wt% addition of boron trifluoride complex catalyst. The results show that the heavy fraction is dominated by 4 and 5 plus ring aromatics with short side chains and methylene-bridged bonds. The catalyst showed excellent catalytic activity for the heavy fraction, the resulting product (MP-HF-5) possessing a softening point of 307 °C and 3.06 wt% methylene-bridged hydrogen at 95.3 wt% mesophase content. However, the catalyst slightly facilitated the development of anisotropic structures in the middle fraction (rich in 3 and 4 rings aromatics with naphthenic structures), which provided mesogen molecules during the FCC-DO carbonization reaction. Finally, the 1 ∼ 3 ring aromatics with long alkyl side chains are mainly present in the light fractions. The catalyst did not show obvious catalytic activity for the light fraction, in contrast, the oxygen-containing functional groups in the catalyst reacted with the aromatic molecule to form a disordered oxidative cross-linked structure, resulting in an almost completely isotropic structure of MP-LF-5.

Facile access to redox responsive self-healing coating materials via living cationic block copolymerization of styrene and 2-chloroethyl vinyl ether

Poly(alkyl vinyl ether)-based functional copolymers have wide applications in many high-tech areas. However, their synthesis is still challenging which limits their applications. This article describes the synthesis of an unprecedented redox-responsive polystyrene-block-poly(2-thioethyl vinyl ether) (PSt-b-PTEVE) diblock copolymers via sequential “water tolerant” cationic polymerization of St and CEVE, followed by post-polymerization transformation of the pendant -CH2CH2Cl functionalities of PCEVE segment to -CH2CH2SH functionalities. The initiating system enabled controlled cationic polymerization of styrene (St), yielding well-defined PSt (at least up to 22500 g/mol) with relatively low dispersity (Đ ≤ 1.36) and polystyrene-block-poly(2-chloroethyl vinyl ether) (PSt-b-PCEVE) diblock copolymers with acceptable dispersity values (Đ ≤ 1.38) thereof, demonstrating high chain-end fidelity. The controlled character of the cationic polymerization reaction was confirmed by linear kinetic plots, linear increase of Mns (with low Đs) and synthesis of PSts of changing Mns simply by varying initial [St]0/[Initiator]0 feed ratio. The synthesized PSt-b-PTEVE diblock copolymers exhibited redox responsivity and self-healing behaviour. The self-healing property of the PSt-b-PTEVE diblock copolymer was studied by optical microscopy. For this, first, a mechanical cut was introduced in the cross-linked PSt-b-PTEVE thin films and then images were taken at regular intervals to investigate the healing. These promising PSt-b-PTEVE diblock copolymers might have potential applications in many emerging areas, including functional coating.

Functionalization Methodology for Synthesis of Silane-End-Functionalized Linear and Star Poly(aryl isocyanide)s by Combination of Cationic Polymerization and Hydrosilylation Reaction

The combination of metal-free borates or borane mediated nonliving cationic polymerization of aryl isocyanides and hydrosilylation reaction of hydrosilanes affords a general and effective functionalization methodology to synthesize silane-end-functionalized linear and star poly(aryl isocyanide)s. The configurations, end group types, and molecular weights of these silane-end-functionalized poly(aryl isocyanide)s can be easily tuned by varying the type and concentration of hydrosilanes. A variety of monofunctional hydrosilanes such as PhMe2SiH, (4-iPrC6H4)Me2SiH, Ph3SiH, Et3SiH, iPr3SiH, and (OEt)3SiH have been successfully applied to the synthesis of linear poly(aryl isocyanide)s with different silane-end-functional groups having a one-handed helical conformation or an aggregation-induced emission (AIE) characteristic (activity up to 1.5 × 107 g/(mol of cat.·h), Mn up to 8.4 × 105), while two multifunctional hydrosilanes PhSiH3 and 1,3,5-(Me2SiH)3C6H3 are conductive to prepare star poly(aryl isocyanide)s and copoly(aryl isocyanide)s having one central core of multifunctional silane with a one-handed helical conformation and/or an AIE characteristic (activity up to 3.4 × 106 g/(mol of cat.·h), Mn up to 9.1 × 104). 1H, 29Si, and 1H-29Si HMBC NMR, Fourier transform infrared spectroscopy (FT-IR), electrospray-ionization mass spectrometry (ESI-MS), and matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF-MS) analysis confirm the presence of silane-end-functional groups in these linear and star poly(aryl isocyanide)s. The mechanism study based on density functional theory (DFT) calculations suggests that hydrosilane plays a dual functional role of the chain transfer agent and regenerated cationic initiator in the [Ph3C][B(C6F5)4]-initiated cationic polymerization of aryl isocyanides.

Hydrogen Bond Donor Catalyzed Cationic Polymerization of Vinyl Ethers

AbstractThe synthesis of high‐molecular‐weight poly(vinyl ethers) under mild conditions is a significant challenge, since cationic polymerization reactions are highly sensitive to chain‐transfer and termination events. We identified a novel and highly effective hydrogen bond donor (HBD)–organic acid pair that can facilitate controlled cationic polymerization of vinyl ethers under ambient conditions with excellent monomer compatibility. Poly(vinyl ethers) of molar masses exceeding 50 kg mol−1 can be produced within 1 h without elaborate reagent purification. Modification of the HBD structure allowed tuning of the polymerization rate, while DFT calculations helped elucidate crucial intermolecular interactions between the HBD, organic acid, and polymer chain end.

Hydrogen Bond Donor Catalyzed Cationic Polymerization of Vinyl Ethers.

The synthesis of high-molecular-weight poly(vinyl ethers) under mild conditions is a significant challenge, since cationic polymerization reactions are highly sensitive to chain-transfer and termination events. We identified a novel and highly effective hydrogen bond donor (HBD)-organic acid pair that can facilitate controlled cationic polymerization of vinyl ethers under ambient conditions with excellent monomer compatibility. Poly(vinyl ethers) of molar masses exceeding 50 kg mol-1 can be produced within 1 h without elaborate reagent purification. Modification of the HBD structure allowed tuning of the polymerization rate, while DFT calculations helped elucidate crucial intermolecular interactions between the HBD, organic acid, and polymer chain end.

Indole Carbonized Polymer Dots Boost Full-Color Emission by Regulating Surface State.

SummaryCarbonized polymer dots (CPDs) are impressive imaging probes with great potential for enriching the library of metal-free fluorescent materials, yet current strategies have struggled to achieve products that emit full-color light in a single reaction system. Establishing an efficient and robust synthesis approach that unlocks the color barrier to the luminescence centers of specific CPDs remains a challenge. Herein, the surface-state engineering of pyridine and amide in the indole system to create a palette of resolvable full-color light-emissive CPDs is reported. Detailed structural analysis revealed that cationic polymerization and oxidation reactions potentially contribute to the formation of the main frameworks and emission centers of the final CPDs, with emissive oxygen- and nitrogen-based centers fixed by cross-linked polymer structures. This study provides valuable insight into the energy absorbance and photoluminescence mechanism of CPDs and introduces additional reactants (benzo heterocycle) into CPD research.

Biobased Cycloolefin Polymers: Carvone-Derived Cyclic Conjugated Diene with Reactive exo-Methylene Group for Regioselective and Stereospecific Living Cationic Polymerization.

Carvone, a naturally abundant chiral cyclic α,β-unsaturated carbonyl compound, was chemically transformed into cyclic exo-methylene conjugated dienes. The exo-methylene group had high reactivity in cationic polymerization and was efficiently polymerized in a controlled manner via regioselective 1,4-conjugated additions using initiating systems effective for living cationic polymerization of vinyl ethers. The obtained polymers with 1,3-cyclohexenyl units and tetra-substituted olefins in the main chain showed high glass transition temperatures over 110 °C. The chiral monomer underwent stereospecific polymerization to result in polymers with low solubility and weak packing of the rigid main chain in the lamellar layers. The racemic mixture resulted in soluble amorphous polymers, which were subsequently hydrogenated into cycloolefin polymers with enhanced thermal properties.

Simultaneous initiation of radical and cationic polymerization reactions using the “G1” copper complex as photoredox catalyst: Applications of free radical/cationic hybrid photopolymerization in the composites and 3D printing fields

This investigation presents the use of a photoredox catalyst "G1" as a photoinitiating system for free radical/cationic hybrid polymerization under mild irradiation conditions. The G1 system (G1/iodonium salt/N-vinylcarbazole), can simultaneously initiate the free radical and cationic polymerization reactions upon exposure to a visible (405 nm) light from a Light Emitting Diode (LED) source. The multicomponent G1 system is able to simultaneously generate radical and cationic species through a catalytic photoredox process. The curing of thin samples (25 μm), thick samples (1.4 mm) as well as the manufacture of hybrid system/glass fibers composites (˜2 to 4 mm thickness) was realized and the influence of the ratio of cationic/radical monomer blends on the polymerization kinetics was studied. The use of G1 in visible light photoinitiating system for the access to composites and 3D printing experiments was particularly outlined. G1 was also shown to have low levels of migration from the cured materials. When compared to reference materials ("F1", a similar copper complex and an anthracene derivative, dibutoxy anthracene), G1 showed better polymerization efficiency. The initiation efficiency was investigated through the real-time Fourier transform infrared (RT-FTIR) spectroscopy and optical pyrometry. Dynamical Mechanical Analysis has been used to determine the glass temperature transition of the cured hybrid system as a complementary technique.

Digital Luminescence Patterning via Inkjet Printing of a Photoacid Catalysed Organic-Inorganic Hybrid Formulation.

Accurate positioning of luminescent materials at the microscale is essential for the further development of diverse application fields including optoelectronics, energy, biotechnology and anti-counterfeiting. In this respect, inkjet printing has recently attracted great interest due to its ability to precisely deposit with high throughput and no contact, functional materials on different types of substrates. Here, we present a novel photoacid catalysed organic-inorganic hybrid luminescent ink. The formulation, containing monomers bearing epoxy and silane functionalities, a photoacid generator and a small percentage of Rhodamine-B, shows good jetting properties and adequate wetting of the deposited droplets on the receiving substrates. Ultraviolet exposure of the deposited material triggers the cationic ring-opening polymerization reaction of the epoxy groups. Concomitantly, if atmospheric water is available, hydrolysis and condensation takes place, overall leading to a luminescent crosslinked hybrid organic-inorganic polymeric material obtained through a simple one-step curing process, without post baking steps. Advantageously, protection of the ink from actinic light delays the hydrolysis and condensation conferring long-term stability to the ink. Digital patterning leads to patterned emissive surfaces and elements with good adhesion to different substrates, mechanical and optical properties for the fabrication of optical and photonic elements and devices.

A Charge‐Transfer Complex of Thioxanthonephenacyl Sulfonium Salt as a Visible‐Light Photoinitiator for Free Radical and Cationic Polymerizations

AbstractA new double chromophoric sulfonium salt photoinitiator possessing both thioxanthone and phenacyl groups, namely 2‐isopropylthioxanthonium phenacyl hexafluoroantimonate (ITXPhenS), was synthesized and characterized. ITXPhenS can form a charge‐transfer complex (CTC) with the donor N,N‐dimethyl aniline (DMA) with absorption characteristics in the visible range as confirmed by spectral analysis, cyclic voltammetry (CV) and density functional theory (DFT). The extension of the absorbance shift can be controlled by the ITXPhenS to DMA ratio. The ability of the CTC to initiate free radical and cationic polymerization reactions of various monomers under visible and natural sunlight is demonstrated. The proposed mechanism assumes the generation of radical and ionic species by the heterolytic and/or homolytic cleavage of ITXPhenS within the CTC followed by electron‐transfer reactions.

Precise synthesis of UCST-type amphiphilic diblock copolymers with pendant imidazolium ionic liquid segments and their thermosensitive physical gelation at extremely low concentrations in water

UCST-type amphiphilic diblock copolymers were synthesized via living cationic polymerization and subsequent polymer reaction and they exhibited thermosensitive physical gelation behavior at an extremely low concentration in water.

Effect of ligand structure in the trimethylene carbonate polymerization by cationic zirconocene catalysts: A “naked model” DFT study

DFT calculations were performed on the cationic ring-opening polymerization (CROP) reaction of trimethylene carbonate (TMC) by the “naked cation” zirconocene catalyst, [Cp2ZrMe]+. Two reaction steps of the CROP (initiation and chain propagation) are considered. Using a set of 29 catalyst structures that differ in electronic and steric properties, the effects of ligand modification on the catalyst performance are explored. The calculations support the activated chain-end mechanism of the process, providing structural, energetic and electronic properties of key cationic species involved. It is found that varying ligand structures tend to destabilize the complexation in the initiation step and lower the activity of the chain propagation. Furthermore, the stability and reactivity of CROP cannot be ascribed solely by electronic origin as steric effect between the ligand and monomer is also playing a role. The effect of solvent and dispersion on the CROP reactivity was also investigated with the results, indicating that it plays a dominant role in the initiation process. The results in this paper might contribute to further improvements of this catalytic system.

Cationic Photoinitiators for Near UV and Visible LEDs: A Particular Insight into One‐Component Systems

The observed development of one‐component photoinitiators of cationic polymerization reactions in the last forty years is briefly described. Cationic photoinitiators can usually be activated by short wavelengths (<300 nm) and relatively hard conditions (high intensity). The search for cheaper and safer light sources has led to the use of Light Emitting Diodes (LEDs). In this review, a special emphasis is provided on the most recent and promising cationic initiators operating under near UV and visible LEDs. Ferrocenium salts exhibit the broadest visible light absorption and are probably, from this point of view, the most versatile near UV and visible light cationic initiators. Excellent photoinitiation performance has been found with the ferrocenium salts as one‐component initiators, and the effect of ferrocenium salts based multi‐component photoinitiating systems on the relevant photoinitiation performance has also been investigated. image

Visible‐light‐sensitive photoredox catalysis by iron complexes: Applications in cationic and radical polymerization reactions

ABSTRACTThe development of iron complexes for the photoredox catalysis is a huge challenge. Indeed, Iron complexes can be ideal candidates due to their potential visible light absorption and redox properties but also because they are less toxic, inexpensive and environmentally friendly compared to other catalysts. In the present paper, a series of novel iron complexes have been synthesized and utilized to initiate the free radical promoted cationic polymerization of epoxides or the free radical polymerization of acrylates through photoredox catalysis processes upon exposure to near UV (385 nm) or visible violet (405 nm) light emitting diodes (LEDs). When combined with an iodonium salt and N‐vinylcarbazole, the iron complex‐based photoinitiating systems are able to generate radicals, cations, and radical cations. The initiation efficiency is investigated through real‐time Fourier transform infrared spectroscopy and a satisfactory initiating ability is found. The mechanisms for the generation of the reactive initiating species through photoredox catalysis are studied by different methods (steady state photolysis, cyclic voltammetry and electron spin resonance spin trapping techniques) and discussed in detail. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 2247–2253

Isotope Effect on the Melt–Isothermal Crystallization of Polyoxymethylene D/H Random Copolymers and D/H Blend Samples

We have successfully synthesized a series of polyoxymethylene (POM) random copolymers between the deuterated (D) and hydrogeneous (H) monomeric units by a cationic polymerization reaction. The randomness of D and H units in the copolymers was characterized by the quantitative analysis of 13C NMR and Fourier transform infrared spectral data. The equilibrium melting point T°m was estimated on the basis of Gibbs–Thomson equation using the experimental data of DSC melting points plotted against the crystallite thickness evaluated from the small-angle X-ray scattering data. The T°m of pure D-POM (208.5 °C) is higher than that of pure H-POM (homopolymer, 190.0 °C). The T°m changes systematically with the D content in the copolymer. The blend samples between D-POM and H-POM (homopolymer) show the similar D content dependence, but the T°m is as a whole higher than that of the copolymer. Another type of blend samples consisting of D-POM and H-POM containing small amount of ethylene oxide (Duracon) shows the similar but slightly different D content dependence of T°m, compared with homopolymer case, since Duracon’s melting point is about 5 °C lower than the latter. The kinetics of melt–isothermal crystallization behavior of these copolymers have been investigated using the time-dependent DSC data collected at the various isothermal crystallization temperatures, from which the crystallization rate constant (k) and growth dimension (n) were estimated on the basis of Avrami’s plot, where the induction time of nucleation was corrected. In parallel, the tangential line of Avrami’s curve at the crystallinity 0.5 was analyzed, from which the crystallization rate was estimated. These two methods of analysis were found to give almost the same results. By comparing the thus-obtained parameters among all the samples, several important results were obtained: (i) the POM-D shows the lowest crystallization rate compared with the POM-H samples; (ii) the crystallization rate decreased gradually with the increment of the D content in both the cases of D/H random copolymers and D/H blends when compared at the same ΔTc or the degree of supercooling; (iii) the existence of regimes I and II has been detected, the boundary temperature of which was found to change systematically depending on the D content. The crystallization rates were compared also between the two types of D/H blend samples, which showed remarkably different behaviors as a whole. In this way the isotopic effect on the thermal and crystallization behavior of D/H POM copolymers and blends has been revealed for the first time.

Panchromatic photoinitiators for radical, cationic and thiol-ene polymerization reactions: A search in the diketopyrrolopyrrole or indigo dye series

A series of diketopyrrolopyrrole derivatives (DPPs) and indigo derivatives (IDGs) are synthesized and applied as photoinitiators (PIs) for the cationic polymerization (CP) of epoxides, the free radical polymerization (FRP) of acrylates or the thiol-ene polymerization under different lights (purple, blue, green, yellow, red LEDs and green laser diode). The photochemical mechanisms involved in the presence of these PIs and additives (iodonium salt (Iod), N-vinylcarbazole (NVK), amine (MDEA) or 2,4,6-tris(trichloromethyl)-1,3,5-triazine (R-Cl)) are investigated by steady state photolysis, electron spin resonance spin trapping, fluorescence, cyclic voltammetry, and laser flash photolysis techniques. Real-time infrared spectroscopy studies reveal that DPP4/Iod/NVK is very efficient for both CP and FRP and, compared to two references (Eosin-Y and camphorquinone), displays noticeably higher polymerization efficiencies. Panchromatic curable formulations exhibiting an almost constant photosensitivity from the blue to the red are proposed.

Recent Developments of Versatile Photoinitiating Systems for Cationic Ring Opening Polymerization Operating at Any Wavelengths and under Low Light Intensity Sources.

Photoinitiators (PI) or photoinitiating systems (PIS) usable in light induced cationic polymerization (CP) and free radical promoted cationic polymerization (FRPCP) reactions (more specifically for cationic ring opening polymerization (ROP)) together with the involved mechanisms are briefly reviewed. The recent developments of novel two- and three-component PISs for CP and FRPCP upon exposure to low intensity blue to red lights is emphasized in details. Examples of such reactions under various experimental conditions are provided.

Photochemical Production of Interpenetrating Polymer Networks; Simultaneous Initiation of Radical and Cationic Polymerization Reactions

In this paper, we propose to review the ways to produce, through photopolymerization, interpenetrating polymer networks (IPN) based, e.g., on acrylate/epoxide or acrylate/vinylether blends and to outline the recent developments that allows a one-step procedure (concomitant radical/cationic polymerization), under air or in laminate, under various irradiation conditions (UV/visible/near IR; high/low intensity sources; monochromatic/polychromatic sources; household lamps/laser diodes/Light Emitting Diodes (LEDs)). The paper illustrates the encountered mechanisms and the polymerization profiles. A short survey on the available monomer systems and some brief examples of the attained final properties of the IPNs is also provided.

Spectroscopic characterization and microbial degradation of engineered bio-elastomers from linseed oil

Abstract The microbial degradation of elastomers synthesized through the cationic polymerization reaction of linseed oil, styrene, and divinylbenzene was investigated by using the Alkaliphilus oremlandii OhILAs strain. In Fourier transform infrared (FTIR) analysis, the bound oil content in the elastomers was found to vary from 29.63 to 45.5 wt%, whereas the percentage of unreacted oil in the elastomers were in the range of 12.9–38 wt%. In 1H nuclear magnetic resonance spectrum analysis, the unreacted oil and unreacted aromatic components in the elastomers were obtained in the ranges of 13.2–39 wt% and 6.8–16 wt%, respectively. The amount of unreacted oil in the elastomers enhanced the percentage of biodegradation, which varied from 26 to 51 wt%. The biodegradation of elastomers was also confirmed by FTIR and scanning electron micrograph analyses.

有機ビスマス化合物を用いた有機合成の最近の進展

Organic synthesis using organobismuth compounds has considerably advanced during the last 15 years. One of the bottlenecks using organobismuth compounds in organic synthesis was their limited accessibility because of lack of variety of synthetic methods. Several new synthetic methods for organobismuth compounds have recently been developed, which allowed the access to wider variety of organobismuth compounds useful in organic synthesis. Considerable advancement has been achieved in cross-coupling reactions forming C-C, C-O, C-N, C-S and C-Se bonds using organobismuth reagents. Not only the arylation reaction, but also alkenylation and alkylation reactions became possible. Stereoselective allylation reaction of carbonyl compounds as well as 1,4-addition reaction of α,β-unsaturated carbonyl compounds have also been developed. There was also noticeable advancement in oxidation reaction, in which highly reactive and selective oxidation reagents have been developed. Catalysis by organobismuth compounds including CO2 fixation reaction, cross-condensation reaction, radical and cationic polymerization reaction has also been achieved.