Presence Of Dibenzyl Trithiocarbonate Research Articles

SYNTHESIS OF COPOLYMERS OF STEARYLMETHACRYLATE AND STEARYLACRYLATE WITH N-SUBSTITUTED ACRYLAMIDES IN THE PRESENCE OF REVERSIBLE CHAIN TRANSFER AGENTS AND STUDY OF THEIR EFFECT ON THE LOW-TEMPERATURE PROPERTIES OF DIESEL FUEL

The features of copolymerization of stearylacrylate (SA) and stearylmethacrylate with N-isopropylacrylamide and N,N-dimethylacrylamide in the presence of dibenzyltrithiocarbonate and 2-cyanoisopropyldodecyltrithiocarbonate as agents of reversible chain transfer have been studied. The choice of agents of reversible chain transfer (RAFT-agents) is due to the fact that sulfur-containing compounds with cyanoisopropyl radicals are most effective in the polymerization of methacrylic monomers, while benzyltrithiocarbonates are more active in the polymerization of acrylic monomers, as well as styrene and acrylonitrile. It has been established that polymerization of stearyl methacrylate (SMA) in the presence of RAFT-agents proceeds without a gel effect up to a high conversion. At the same time, although polystеarylmethacrylate samples are characterized by relatively high values of polydispersity coefficients (Mn/Mw) for controlled radical polymerization processes, they are nevertheless somewhat lower than for polymers of similar conversion synthesized in the absence of chain transfer agents. It has been shown that the process of copolymerization of stearyl acrylate and stearylmethacrylate with N-isopropylacrylamide and N,N-dimethylacrylamide in the presence of dibenzyltrithiocarbonate and 2-cyanoisopropyldodecyltrithiocarbonate proceeds without gelation to high conversions. The synthesized copolymers are characterized by a relatively narrow molecular weight distribution: the polydispersity coefficients of polymer samples vary from 1.18 to 1.57 in the case of using N-isopropylacrylamide and from 1.21 to 1.47 when using N,N-dimethylacrylamide as a comonomer to higher alkyl acrylates, which is typical for processes of radical polymerization proceeding in a controlled manner. At the same time, the synthesized copolymers exhibit a significant depressant effect when they are introduced into diesel fuel at a concentration of 1600 ppm. It has been established that copolymers of stearylmethacrylate and stearylacrylate with polar nitrogen-containing monomers have a more effective effect on the low-temperature properties of diesel fuel than homopolymers of stearylmethacrylate and stearylacrylate. At the same time, additives based on copolymers of stearylmethacrylate with N-isopropylacrylamide with a composition of 70/30 mol.% and stearylacrylate with N-isopropylacrylamide with a composition of 20/80 mol.% had the most significant effect on the low-temperature characteristics of the fuel.

ВЛИЯНИЕ ДИБЕНЗИЛТРИТИОКАРБОНАТА НА КИНЕТКУ РАДИКАЛЬНОЙ ПОЛИМЕРИЗАЦИИ 5-ВИНИЛТЕТРАЗОЛА

Radical polymerization with reversible chain transfer by the addition-fragmentation mechanism of 5-vinyltetrazole in the presence of dibenzyltrithiocarbonate was carried out. The kinetics of the polymerization was studied by NMR spectroscopy: data on the conversion of the monomer and dibenzyltrithiocarbonate, and the rate of polymerization were obtained and analyzed. A comparison was made with the kinetics of the classical radical polymerization of 5-vinyltetrazole

Kinetic analysis of the RAFT copolymerization of styrene and maleic anhydride by differential scanning calorimetry

A kinetic study of the copolymerization of styrene (S) and maleic anhydride (MA) in the presence of dibenzyl trithiocarbonate (DBTTC) as RAFT agent monitored by differential scanning calorimetry, is presented. The results obtained indicate that the polymerization proceeded in a controlled manner. The average activation energy (E) of the copolymerization obtained by Ozawa and Kissinger methods (62 ± 2 kJ mol−1) showed good agreement with the E value obtained by the isothermal method (67 ± 2 kJ mol−1). These values agree well with the value of 65 kJ mol−1 reported for the nitroxide-mediated copolymerization of S and MA. Calculations using isoconversional methods show that Ea is not constant within the whole conversion range. As the reaction proceeds and higher conversions are reached, Ea decreases to lower values due to diffusion-controlled effects. A first-order reaction model is applied to determine overall kinetic rate constants at different temperatures and different MA molar feed fractions. Polymerization rate increased approximately four orders of magnitude when temperature changed from 90 °C to 110 °C. Polymerization rate is also strongly affected by MA content. It increased by a factor of about three when MA changed from 30% to 50% molar content in the copolymer.

Kinetic modeling of pseudoliving free-radical styrene polymerization occurring via reversible addition-fragmentation chain transfer

A kinetic model has been constructed for 2,2′-azobisisobutyronitrile-initiated pseudoliving free-radical styrene polymerization occurring via reversible addition-fragmentation chain transfer in the presence of dibenzyl trithiocarbonate. The inverse problem of determining the unknown temperature-dependent rate constants of the elementary reactions of the kinetic scheme has been solved. The model has been validated by comparing the theoretical and experimental molecular weight characteristics of polystyrene. The model has been employed to investigate the effects of control factors of the process on the molecular weight characteristics of polystyrene.

Topological properties of poly(butyl acrylate) obtained by radical polymerization in the presence of dibenzyl trithiocarbonate

Topological properties of poly(butyl acrylate) obtained by radical polymerization in the presence of dibenzyl trithiocarbonate

Kinetic approach to modeling the radical polymerization of styrene in the presence dibenzyl trithiocarbonate

A mathematical model of the kinetics of the radical polymerization of styrene in the presence of dibenzyl trithiocarbonate by the reversible addition-fragmentation chain transfer mechanism with cross-termination of radicals and intermediates and quadratic termination of intermediates is developed. The adequacy of the polymerization mechanism underlying the model and the related mathematical formalism are tested by comparing the calculated and measured values of the average molecular-weight characteristics of resulting polystyrene.

Modeling of reversible addition-fragmentation chain transfer radical polymerization of styrene in the presence of dibenzyl trithiocarbonate

Modeling of reversible addition-fragmentation chain transfer radical polymerization of styrene in the presence of dibenzyl trithiocarbonate

Controlled Free‐Radical Copolymerization of N‐vinyl succinimide and n‐Butyl acrylate via a Reversible Addition–Fragmentation Chain Transfer (RAFT) Technique

AbstractSummary: Copolymerization of N‐vinyl succinimide and n‐butyl acrylate in the presence of dibenzyl trithiocarbonate as a reversible addition‐fragmentation chain transfer agent was investigated. The linear dependence of molecular mass on conversion and low values of polydispersity index confirmed pseudo‐living mechanism of the process. For the first time the soluble copolymers of N‐vinyl succinimide and n‐butyl acrylate with high composition homogeneity have been synthesized by copolymerization in bulk. The copolymerization kinetics was studied by NMR 1H spectroscopy; the reactivity ratios were determined: rVSI = 0.11, rBA = 2.54. The copolymer microstructure was estimated; it was shown that in conditions of RAFT polymerization gradient copolymers enriched with BA on the tails of the macromolecule and with VSI in the middle can be obtained. The method of elimination of trithiocarbonate fragment by the reaction with an excess of AIBN was proposed leading to formation of the simplest gradient structure of N‐vinyl succinimide – n‐butyl acrylate copolymer.

Preparation of Poly(acrylamide) with Configurational Sequences by Photo Living Polymerization

Abstract Poly(acrylamide) (PAM) with configurational sequences was synthesized under ultraviolet (UV) catalyzed by Lewis acid (here yttrium salts) and in the presence of dibenzyl trithiocarbonate (DBTTC). DBTTC is selected as the photoinitiator and also the chain-transfer agent to achieve a living manner for the polymerization process. A series of PAMs with narrow molecular weight distributions and different configurational sequences have been prepared. The catalysis effects on configurational control of different contents of the yttrium salts have been studied.

Stereocontrol during photo-initiated controlled/living radical polymerization of acrylamide in the presence of Lewis acids

Poly(acrylamide) (PAM) with controlled molecular weight and tacticity was prepared by UV-irradiation-initiated controlled/living radical polymerization in the presence of dibenzyl trithiocarbonate (DBTTC) and Y(OTf) 3. The rapid and facile photo-initiated controlled/living polymerization at ambient temperature led to controlled molecular weight and narrow polydispersity (M w /M n = 1.12–1.24) of PAM. The coordination of Y(OTf) 3 with the last two amide groups in the growing chain radical effectively enhanced isotacticity of PAM. The isotactic sequence of dyads ( m), triads ( mm) and pentads ( mmmm) in PAM were 70.32%, 50.95%, and 29.97%, respectively, which were determined by the resonance of methine (CH) groups in PAM under 13C NMR experiment. Factors affecting stereocontrol during the polymerization were studied, including the type of Lewis acids, concentration of Y(OTf) 3, and monomer conversion. It is intriguing that the meso tacticity increased gradually with chain propagation and quite higher isotacticity ( m = 93.01%, mm = 86.57%) was obtained in the later polymerization stage (conversion 65–85%).

A Novel Strategy to Synthesize Double Comb‐Shaped Water Soluble Copolymer by RAFT Polymerization

AbstractSummary: A double comb‐shaped water soluble copolymer, poly[poly(ethylene oxide) methyl ether methacrylate]‐block‐poly(N‐isopropylacrylamide)‐block‐poly[poly (ethylene oxide) methyl ether methacrylate], abbreviated as [P(MA‐MPEO)‐block‐PNIPAM‐block‐P(MA‐MPEO)], with a controlled molecular weight and narrow polydispersity was successively synthesized using a macromonomer technique. The 60Co γ irradiation polymerization of MA‐MPEO in the presence of dibenzyl trithiocarbonate (DBTTC) at room temperature afforded a polymer, P(MA‐MPEO)‐SC(S)S‐P(MA‐MPEO), which was subsequently used as a macro RAFT agent in the RAFT polymerization of N‐isopropylacrylamide, and water soluble double comb‐shaped copolymers, P(MA‐MPEO)‐block‐PNIPAM‐block‐P(MA‐MPEO), were successfully obtained.Structure of the double comb‐shaped copolymer.imageStructure of the double comb‐shaped copolymer.

“Gradient” Polymer Prepared by Complex-Radical Terpolymerization of Styrene, Maleic Anhydride, and N-Vinyl Pyrrolidone via γ-Ray Irradiation by Use of a RAFT Process: Synthesis, Mechanism, and Characterization

A novel “gradient” polymer, prepared by complex-radical terpolymerization of styrene (St), maleic anhydride (MA), and N-vinylpyrrolidone (NVP), was synthesized by use of a reversible addition−fragmentation chain transfer (RAFT) process. The terpolymerization was performed in tetrahydrofuran (THF) at room temperature under γ-ray irradiation in the presence of dibenzyl trithiocarbonate (DBTTC). The constants of complex-radical terpolymerization, complex formation, and some kinetic parameters for the monomer systems were studied by UV, 1H NMR, Kelen−Tudos methods, respectively. The equilibrium constant (K2) of 1:1 complex between MA and NVP was determined by UV method as 3.57 × 10-2 L/mol at 293.2 K in CHCl3. Obtained results show that the terpolymerization proceeded mainly through “complex” mechanisms in the state of near-binary copolymerization of St···MA (CTC1) and MA···NVP (CTC2) complexes. And as the big difference in the value of the reactivity ratios between the two complexes (r1 = 0.17 ± 0.01 and r2 ...

A novel strategy for synthesis of amphiphilic π-shaped copolymers by RAFT polymerization

The amphiphilic π-shaped copolymers with narrow molecular weight distribution ( M w/ M n = 1.04–1.09) based on polystyrene (PSt) and poly(ethylene glycol) have been synthesized successfully. The reversible addition-fragmentation transfer (RAFT) polymerization of St in the presence of dibenzyl trithiocarbonate and N, N′-azobis(isobutyronitrile) (AIBN) yielded macro RAFT agent PSt–SC( S)S–PSt, subsequent reaction with excess maleic anhydride (MAh) at 80 °C in tetrahydrofuran afforded the PSt–MAh–SC( S)S–MAh–PSt. It was used as RAFT agent in the RAFT polymerization of St, and finally the amphiphilic π-shaped copolymers were obtained by the reaction of MAh with hydroxyl-terminated poly(ethylene glycol methyl ether) at 90 °C for 48 h. Their structures were confirmed by FT-IR and 1H NMR spectra, and their molecular weight and molecular weight distribution were measured by gel permeation chromatography.

Photo-Initiated Living Free Radical Polymerization in the Presence of Dibenzyl Trithiocarbonate

The polymerizations of styrene (St), methyl acrylate (MA), and butyl acrylate (BuA), carried out under UV irradiation at room temperature in the presence of dibenzyl trithiocarbonate (DBTTC) were found to display living free-radical polymerization characteristics as evidenced by: narrow molecular weight distribution, linear increase of molecular weight with increasing conversion, well-controlled molecular weight, and first-order polymerization kinetics. The triblock copolymer, PMA-PSt-PMA, with narrow polydispersity and well-defined structure was successfully prepared using PMA-S-C(=S)-S-PMA as macro-photoinitiator under UV irradiation at room temperature. Based on GPC, NMR and FT-IR analyses, the structures of the polymers were obtained and the mechanism of the polymerization was proposed.

Photo-Initiated Living Free Radical Polymerization in the Presence of Dibenzyl Trithiocarbonate

Photo-Initiated Living Free Radical Polymerization in the Presence of Dibenzyl Trithiocarbonate

Controlled polymerization of acrylic acid under 60Co irradiation in the presence of dibenzyl trithiocarbonate

AbstractThe polymerization of acrylic acid (AA) was performed under 60Co irradiation in the presence of dibenzyl trithiocarbonate at room temperature, and well‐defined poly(acrylic acid) (PAA) with a low polydispersity index was successfully prepared. The gel permeation chromatographic and 1H NMR data showed that this polymerization displays living free‐radical polymerization characteristics: a narrow molecular weight distribution (Mw/Mn = 1.07–1.22), controlled molecular weight, and constant chain‐radical concentration during the polymerization. Using PAAS C(S)SPAA as an initiator, the extension reaction of PAA with fresh AA was carried out under 60Co irradiation, and the results indicated that this extension polymerization displayed controlled polymerization behavior. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3934–3939, 2001

60Co γ-Irradiation-Initiated “Living” Free-Radical Polymerization in the Presence of Dibenzyl Trithiocarbonate

The free-radical polymerization of vinyl monomers in the presence of dibenzyl trithiocarbonate (DBTTC) and under 60 Co γ-irradiation is of living character. Under 60 Co irradiation, the bonds between benzyl group and sulfur were cleaved, benzyl radicals initiate the polymerization. The propagating radical together with trithiocarbonate radicals form a dormant polymer chain. The fast equilibrium between propagation radical and dormant polymer chain controls the polymerization.