Rate Constant Of Chain Propagation Research Articles

Mechanistic study on hydrogen effects in propylene polymerization with MgCl2-supported Ziegler-Natta catalysts: New evidences from active center counting and reaction kinetics

Propylene polymerizations catalyzed by MgCl2/Di/TiCl4-AlEt3/siloxane in the absence and presence of hydrogen were studied by determining the time-dependent changes of catalytic activity, number of active centers and active center distribution. Three types of active centers with high, medium and very low stereoselectivity were differentiated by fractionating the polymer into three parts. Chain propagation rate constant of each type of active centers was estimated by linear fitting/extrapolating the time-dependent change of apparent propagation rate constant. The centers with high (Ci*), medium (Cm*) and low (Ca*) stereoselectivity responded to addition of hydrogen differently. Adding hydrogen caused marked increase of Ci*, but its propagation rate constant (kpi) was evidently reduced. In contrast, numbers of Cm* and Ca* were only slightly affected, but their propagation rate constants were evidently enhanced by hydrogen. The different hydrogen responses of Ci* with those of Cm* and Ca* were explained by two kinds of hydrogen activation mechanisms.

Estimation of the chain propagation rate constants of propylene polymerization and ethylene‐1‐hexene copolymerization catalyzed with MgCl2‐supported Ziegler–Natta catalysts

AbstractIn olefin polymerization with MgCl2‐supported Ziegler–Natta (Z–N) catalysts, the apparent propagation rate constant (kp)a calculated by Rp = (kp)a [C*] CMe (CMe is equilibrium monomer concentration in the reaction system) declines with reaction time for gradually developed monomer diffusion limitation in the polymer/catalyst particles. In this work, a simplified multi‐grain particle model was proposed to build correlation between (kp)a and other kinetic parameters that can be determined experimentally. Rate profiles of propylene polymerization and ethylene‐1‐hexene copolymerization by three MgCl2‐supported Z–N catalysts were determined, and the (kp)a data was calculated using [C*] determined by quench‐labelling the propagation chains with acyl chloride. Decline of (kp)a in each polymerization process was precisely fitted by the linear correlation between lg(kp)a and [(ρcatmp)/(ρpmcat) + 1]1/3 developed on the particle model. Real propagation rate constant (kp) was estimated by extrapolating the fitting line to the starting point of polymerization, where no concentration gradient exists. According to the particle model, the slope of the lg(kp)a versus [(ρcatmp)/(ρpmcat) + 1]1/3 line (lgd) represents the degree of monomer diffusion limitation. Variations of parameter d found in the studied reaction systems can be reasonably explained based on the knowledge of olefin diffusion in the polymer phase.

Study on the polymerization process and monomer reactivity of EPEG‐type polycarboxylate superplasticizer

AbstractIn this study, the binary aqueous free radical copolymerization process of ethylene‐glycol monovinyl polyethylene glycol (EPEG) and acrylic acid (AA) was studied. The influence of monomer type and molar ratio on the conversion ratio of EPEG and the molar ratio of copolymer were investigated via gel permeation chromatography (GPC) by comparing the macromonomer molecular structures, side chain densities, and carboxyl group concentrations. According to the results, the reactivity of EPEG copolymerized with AA was higher than that of isoprenyl oxypoly (ethylene glycol) ether (IPEG, also referred to as TPEG) with AA. The copolymerization reaction between EPEG and AA could be completed within 30 min at 10–20°C. At the initial stage, the copolymer content quickly attained 60% within 15 min, reflecting the short induction period and high chain propagation rate constant. The fluidity tests in cement mortar revealed that polycarboxylate superplasticizers (PCEs) with short side chains and high conversion ratio exhibited better dispersion capacity than PCEs with long side chains.

Methods for Predicting Ethylene/Cyclic Olefin Copolymerization Rates Promoted by Single-Site Metallocene: Kinetics Is the Key.

In toluene at 50 °C, the vinyl addition polymerization of 4-vinyl-cyclohexene (VCH) comonomers with ethylene is investigated using symmetrical metallocene (rac-Et(Ind)2ZrCl2) combined with borate/TIBA. To demonstrate the polymerizations’ living character, cyclic VCH with linear-exocyclicπ and endocyclicπ bonds produces monomodal polymers, but the dispersity (Ɖ) was broader. The copolymers obtained can be dissolved in conventional organic solvent and have excellent thermal stability and crystalline temperature (ΔHm), and their melting temperature (Tm) varies from 109 to 126 °C, and ΔHm ranges from 80 to 128 (J/g). Secondly, the distribution of polymeric catalysts engaged in polymer chain synthesis and the nature of the dormant state are two of the most essential yet fundamentally unknown aspects. Comprehensive and exhaustive kinetics of E/VCH have shown numerous different kinetic aspects that are interpreted as manifestations of polymeric catalysts or of the instability of several types of active center [Zr]/[C*] fluctuations and formation rates of chain propagation RpE, RpVCH, and propagation rate constants kpE and kpVCH, the quantitative relationship between RpE, RpVCH and kpE, kpVCH and catalyst structures, their constituent polymer Mw, and their reactivity response to the endocyclic and exocyclic bonds of VCH. The kinetic parameters RpE, RpVCH, kpE, and kpVCH, which are the apparent rates for the metallocene-catalyzed E/VCH, RpE, and kpE values, are much more significant than RpVCH and kpVCH at 120 s, RpE and RpVCH 39.63 and 0.78, and the kpE and kpVCH values are 6461 and 93 L/mol·s, respectively, and minor diffusion barriers are recommended in the early stages. Compared with previously reported PE, RpE and kpE values are 34.2 and 7080 L/mol·s. VCH increases the RpE in the initial stage, as we are expecting; this means that the exocyclic bond of VCH is more active at the initial level, and that the chain transfer reaction of cyclic internal π double is increased with the reaction time. The tp versus Rp, kp, and [Zr]/[C*] fraction count may be fitted to a model that invokes deactivation of growing polymer chains. At tp 120–360 s higher, the incorporation rate of VCH suppresses E insertion, resulting in reduced molecular weight.

АКРИЛОВІ МОНОМЕРИ НА ОСНОВІ РОСЛИННИХ ОЛІЙ ІЗ ВИСОКИМ ВМІСТОМ ЕСТЕРІВ ОЛЕЇНОВОЇ КИСЛОТИ

New acrylic monomers were obtained via transesterification of olive, canola, and high-oleic soybean oils by N-hydroxyethylacrylamide. The kinetic features of homopolymerization of these monomers were studied and the influence of linoleic (C18: 2) and linolenic (C18: 3) acid esters on the polymerization rate and the molecular weight of homopolymers were compared. It was found that the chain transfer and propagation rate constants increase in monomer’s range: olive (CM = 0.016) <high-oleic soybean (CM = 0.018) <canola (CM = 0.025). Features of homopolymerization are associated with varying degrees of unsaturation of fatty acid fragments.

Kinetic and Thermal Study of Ethylene and Propylene Homo Polymerization Catalyzed by ansa-Zirconocene Activated with Alkylaluminum/Borate: Effects of Alkylaluminum on Polymerization Kinetics and Polymer Structure.

The kinetics of ethylene and propylene polymerization catalyzed by homogeneous metallocene were investigated using 2-thiophenecarbonyl chloride followed by quenched-flow methods. The studied metallocene catalysts are: rac-Me2Si(2-Me-4-Ph-Ind)2ZrCl2 (Mt-I), rac-Et(Ind)2ZrCl2 (Mt-II) activated with ([Me2NPh][B(C6F5)4] (Borate-I), [Ph3C][B(C6F5)4] (Borate-II), and were co-catalyzed with different molar ratios of alkylaluminum such as triethylaluminium (TEA) and triisobutylaluminium (TIBA). The change in molecular weight, molecular weight distribution, microstructure and thermal properties of the synthesized polymer are discussed in detail. Interestingly, both Mt-I and Mt-II showed high activity in polyethylene with productivities between 3.17 × 106 g/molMt·h to 5.06 × 106 g/molMt·h, activities were very close to each other with 100% TIBA, but Mt-II/borate-II became more active when TEA was more than 50% in cocatalyst. Similarly, Polypropylene showed the highest activity of 11.07 106 g /molMt·h with Mt-I/Borate-I/TIBA. The effects of alkylaluminum on PE molecular weight were much more complicated; MWD curve changed from mono-modal in Mt-I/borate-I/TIBA to bimodal type when TIBA was replaced by different amounts of TEA. In PE, the active center fractions [C*]/[Zr] of Mt-I/borate were higher than that of Mt-II/borate and average chain propagation rate constant (kp) value slightly decreased with the increase of TEA/TIBA ratio, but the Mt-II/borate systems showed higher kp 1007 kp (L/mol·s). In PP, the Mt-I/borate presented much higher [C*]/[Zr] and kp value than the Mt-II. This work also extend to investigate the mechanistic features of zirconocenes catalyzed olefin polymerizations that addressed the largely unknown issues in zirconocenes in the distribution of the catalyst, between species involved in polymer chain growth and dormant state. In both metallocene systems, chain transfer with alkylaluminum is the dominant way of chain termination. To understand the mechanism of cocatalyst effects on PE Mw and (MWD), the unsaturated chain ends formed via β-H transfer have been investigated by 1H NMR analysis.

Synthesis of a New Type of Star-Shaped Poly(2-alkyl-2-oxazolines) on the Basis of Sulfochlorinated Calix[8]arene

A new approach to the synthesis of sulfonyl chloride initiators with the calixarene core for the cationic polymerization of 2-oxazolines is developed. The kinetics of 2-ethyl-2-oxazoline polymerization with the synthesized octafunctional initiator at 100°С in sulfolane is studied. It is shown that the decelerated initiation of polymerization is observed in the system and the rate constant of chain propagation is kp = 1.20 × 10–3 L/(mol s). Using the cationic ring-opening polymerization of 2-alkyl-2-oxazolines initiated by calix[8]arene functionalized by sulfonyl chloride groups in the lower rim, star-shaped thermosensitive polymers are synthesized, and the molecular weight characteristics of the polymers are investigated. The critical micelle concentration of star-shaped poly(2-isopropyl-2-oxazoline) is determined (СCMC = 6.25 × 10–5 g/mL), and the solubilizability of the synthesized polymers is investigated using hydrophobic dye curcumin as an example.

Effects of titanium dispersion state on distribution and reactivity of active centers in propylene polymerization with MgCl2‐supported Ziegler‐Natta catalysts: A kinetic study based on active center counting

AbstractKinetics of propylene polymerization with two TiCl4/MgCl2 model catalysts of different Ti load (Cat‐1: Ti 0.1 wt%; Cat‐2: Ti 1.0 wt%) was investigated in this work. Time‐dependent variations of active centers fraction ([C*]/[Ti]) and active center distribution of the two catalysts were compared. In propylene polymerization with Cat‐1, [C*]/[Ti] was only 7.8 % in the initial stage, but increased for more than three times in reaction period of 600 s. Propylene polymerization with Cat‐2 had much lower [C*]/[Ti]. Active center distributions of the two catalysts were markedly different. Cat‐1 has evidently higher proportion of aspecific active centers and less isospecific ones than that of Cat‐2. These catalysts also showed different time‐dependent variations of active center distribution. The chain propagation rate constant of isospecific centers in Cat‐2 was evidently higher than that in Cat‐1, but propagation rate constants of either aspecific and medium‐isospecific centers were only slightly changed by enhancing Ti content of the catalyst. The results suggest that isospecific centers are mainly originated from clustered Ti species, but non‐clustered Ti species are the main source of active centers with lower stereoselectivity. By considering factors like dispersion states of Ti species and release of shielded active species through disintegration of catalyst particles, active center models have been proposed to explain the different kinetic behaviors of the two model catalysts.

Kinetics and mechanism of ethylene and propylene polymerizations catalyzed with ansa-zirconocene activated by borate/TIBA

Ethylene and propylene polymerizations catalyzed with two ansa-zirconocenes (rac-Me2Si(2-Me-4-Ph-Ind)2ZrCl2 (M-I) and rac-Et(Ind)2ZrCl2 (Mt-II)) activated by (Ph3C)B(C6F5)4/triisobutylaluminum were respectively conducted under the same conditions for different duration ranging from 0.5 to 30 min, and quenched with 2-thiophenecarbonyl chloride for determining the active center fraction ([C∗]/[Zr]). Variations of polymerization rate, molecular weight, isotacticity and thermal properties with time were also studied. The [C∗]/[Zr] fraction gradually increased with time in the first 20 min and then reached steady stage in all polymerization systems. [C∗]/[Zr] value in the steady stage of Mt-II catalyzed ethylene polymerization was significantly higher than that of propylene polymerization, similar to the phenomena previously observed in ethylene and propylene polymerizations catalyzed with Mt-II/methylaluminoxane. When M-I/borate was used as the catalyst, both ethylene and propylene polymerization showed higher steady stage [C∗]/[Zr] levels than those of the Mt-II/borate systems, and the influence of zirconocene structure on [C∗]/[Zr] of propylene polymerization was much stronger than that of ethylene polymerization. Change in zirconocene structure also significantly influenced apparent chain propagation rate constant (kp) and its time-dependent variations. By taking into consideration the time-dependent changes of [C∗]/[Zr], polymer’s molecular weight distribution and chain structure, presence of multiple active centers in the polymerization system and late activation of the centers with lower intrinsic reactivity are proposed to be the main reasons for steep decay of kp with time. Structure-performance relationships of the ansa-zirconocene catalysts have also been discussed based on the results of kinetic study.

Kinetics of Radical Chain Polymerization: 1. Time-Dependent Distributions of Macroradicals and Oligomers

Numerical and analytical solutions of kinetic equations and the relevant equations for the moments of distribution of macroradicals and oligomers during radical chain polymerization are presented. It has been shown that the initial chain growth occurs in the ballistic mode involving first-generation primary radicals. The chain transfer in which a macroradical, reacting with a solvent, forms an oligomer and the primary radical of the next generation, causes a transition from the ballistic to the diffusion mode in which distributions of chains of different generations are mixed. Time-dependent distributions have been found for chain propagation and transfer rate constants independent of chain length.

Calibration of Squalene, p-Cymene, and Sunflower Oil as Standard Oxidizable Substrates for Quantitative Antioxidant Testing.

The autoxidation kinetics of stripped sunflower oil (SSO), squalene (SQ), and p-cymene ( p-C) initiated by 2,2'-azobis(isobutyronitrile) at 303 K were investigated under controlled conditions by differential oximetry in order to build reference model systems that are representative of the natural variability of oxidizable materials, for quantitative antioxidant testing. Rate constants for oxidative chain propagation ( kp) and chain termination (2 kt) and the oxidizability ( kp/√2 kt) were measured using 2,6-di- tert-butyl-4-methoxyphenol, 2,2,5,7,8-pentamethyl-6-chromanol, BHT, and 4-methoxyphenol as reference antioxidants. Measured values of kp (M-1 s-1)/2 kt (M-1 s-1)/oxidizability (M-1/2 s-1/2) at 303 K in chlorobenzene were 66.9/3.45 × 106/3.6 × 10-2, 68.0/7.40 × 106/2.5 × 10-2, and 0.83/2.87 × 106/4.9 × 10-4, respectively, for SSO, SQ, and p-C. Quercetin, magnolol, caffeic acid phenethyl ester, and 2,4,6-trimethylphenol were investigated to validate calibrations. The distinctive usefulness of the three substrates in testing antioxidants is discussed.

Introducing electron-donating substituents on ligand backbone of α-diimine nickel complex and the effects on catalyst thermal stability in ethylene polymerization

A novel α-diimine nickel pre-catalyst Cat.1 with two electron-donating methyl substituents on the ligand backbone was synthesized and investigated for ethylene polymerization using methylaluminoxane as cocatalyst. Cat.1 exhibited higher polymerization activity and produced highly branched polyethylene with slightly higher molecular weight than that of the typical Brookhart catalyst (B-Cat) at elevated temperature. By tracing the changes of active center number in the polymerization process, Cat.1 was found to have higher ratio of activated nickel ([C∗]/[Ni]), longer catalyst lifetime and larger chain propagation rate constant (kp) as compared with B-Cat. The computational studies demonstrated the electron-donating methyl substituents can make a more electron-rich ligand to influence the catalytic properties of Cat.1. Stronger interactions between the electron-rich ligand and the nickel center should be the main reasons for longer catalyst lifetime and enhanced thermal stability of Cat.1. The production of polyethylene with higher molecular weight by Cat.1 can be explained by its larger kp value and more stable transition state for ethylene insertion than for chain transfer reaction due to the electron-donating ligand. Overall, the results of this work clearly support the importance of ligand electronic effects on the thermal stability and intrinsic reactivity of active centers in α-diimine Ni(II) catalysts.

Alkylsulfonyl Halides as Initiators of Cationic Polymerization of Oxazolines

The example of methanesulfonyl halides has shown the possibility of initiating cationic polymerization of 2-oxazolines by alkylsulfonic acid halides. Chain propagation rate constants and activation energy of the processes have been determined. The kinetic mechanisms suggest a slow initiation of polymerization followed by fast chain propagation. It has been shown that the polymerization of 2-ethyl-2-oxazoline initiated by aliphatic sulfonyl halides proceeds predominantly at the active centers of the ionic type. The synthesis of oligo(3-sulfonyl)methacrylate-graft-poly(2-isopropyl-2-oxazoline) is described as an example of using alkylsulfonyl halides for graft copolymers.

Mechanism of internal and external electron donor effects on propylene polymerization with MgCl2‐supported Ziegler–Natta catalyst: New evidences based on active center counting

ABSTRACTTwo TiCl4/Di/MgCl2 type supported Ziegler–Natta catalysts were prepared by loading dibutylphthalate or dicyclopentyldimethoxysilane (DCPDMS) (internal donor, Di) and TiCl4 on activated δ‐MgCl2 in sequence, and a blank catalyst was prepared by loading TiCl4 on the same δ‐MgCl2 without adding Di. These catalysts have similar specific surface area and pore size distribution, thus form a suitable base for comparative studies. Propylene polymerization with the catalysts was conducted in n‐heptane slurry using triethylaluminum (TEA) as cocatalyst, and the effects of Di as well as De (external donor, in this work it was DCPDMS) on the number of active centers, the distribution of active centers among three polypropylene (PP) fractions (isotactic, medium isotactic, and atactic PP chains), and chain propagation rate constants of the PP fractions were studied by counting the number of active centers in the PP fractions using a method based on selective quench‐labeling of the propagation chains by 2‐thiophenecarbonyl chloride. When De was not added in the polymerization, introducing a phthalate type Di in the catalyst evidently changed the active center distribution by enhancing the proportion of active centers producing isotactic PP (iPP) ( ), but scarcely changed reactivities of the three groups of active centers forming the three fractions. When the De was added in the polymerization system with TiCl4/phthalate/MgCl2 catalyst, further shifting of active center distribution in favor of took place, meanwhile reactivities of the three groups of active centers also remarkably changed in favor of . Mutual effects of these changes led to overwhelming dominance of iPP production in the TiCl4/Di/MgCl2–TEA/De system (Di = phthalate, De = alkoxysilane). In contrast, though using alkoxysilane as Di also caused shifting of active center distribution in favor of when De was not added, addition of alkoxysilane De caused reverse shifting of active center distribution in favor of those producing PP of lower stereoregularity. This unfavorable change largely counteracted the reactivity changes in favor of caused by the De, rendering the catalytic system rather poor isospecificity. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46605.

Kinetic parameters of cationic polymerization of 1,3-dienes

A new technique for the determination of the concentration of active centers of polymerization and propagation rate constants for processes of cationic polymerization of conjugated dienes was proposed. The method consists of the quantitative calculation from the 13C NMR spectra of the concentration of the initial units of the polymer chain polydienes synthesized at different monomer conversions and the subsequent extrapolation of the obtained values to the zero monomer conversion. Using the proposed procedure, the chain propagation rate constants were determined for the cationic polymerization of isoprene and 1,3-pentadiene in the presence of a titanium tetrachloride–tert-butyl chloride catalytic system.

Prediction of Chain Propagation Rate Constants of Polymerization Reactions in Aqueous NIPAM/BIS and VCL/BIS Systems.

Microgels have a wide range of possible applications and are therefore studied with increasing interest. Nonetheless, the microgel synthesis process and some of the resulting properties of the microgels, such as the cross-linker distribution within the microgels, are not yet fully understood. An in-depth understanding of the synthesis process is crucial for designing tailored microgels with desired properties. In this work, rate constants and reaction enthalpies of chain propagation reactions in aqueous N-isopropylacrylamide/N,N'-methylenebisacrylamide and aqueous N-vinylcaprolactam/N,N'-methylenebisacrylamide systems are calculated to identify the possible sources of an inhomogeneous cross-linker distribution in the resulting microgels. Gas-phase reaction rate constants are calculated from B2PLYPD3/aug-cc-pVTZ energies and B3LYPD3/tzvp geometries and frequencies. Then, solvation effects based on COSMO-RS are incorporated into the rate constants to obtain the desired liquid-phase reaction rate constants. The rate constants agree with experiments within a factor of 2-10, and the reaction enthalpies deviate less than 5 kJ/mol. Further, the effect of rate constants on the microgel growth process is analyzed, and it is shown that differences in the magnitude of the reaction rate constants are a source of an inhomogeneous cross-linker distribution within the resulting microgel.

Kinetics and Mechanism of Radical-Chain Oxidation of 1,2-Substituted Ethylene and 1,4-Substituted Butadiene-1,3

A combination of microvolumetry, the rotating sector method, ESR, 1H NMR, and IR allowed to establish a detailed mechanism of liquid-phase oxidation of vinyl compounds X1CH=CHX2 and X1CH=CH–CH=CHX2 (X1 and X2—a polar substitute: С6Н5–, CO–, СOO–) initiated by azobisisobutyronitrile. A distinctive feature of the mechanism is the fact that the oxidation chain is carried out by a low-molecular hydroperoxide radical joining the π-bond. For nine compounds in the temperature range of 303–353 K, relative chain propagation and termination rate constants were measured (k2•k3−0.5). Absolute values of k2 were obtained for diphenylethylene (110 L·mol−1·s−1), ethyl ether of trans-phenyl-pentadiene acid (13 L·mol−1·s−1), and methyl ether of trans-phenyl-pentadiene acid (14.2 L·mol−1·s−1) at T = 323 K. For the same conditions, 10−8k3 were calculated for diphenylethylene (0.87 L·mol−1·s−1) and methyl ether of trans-phenyl-pentadiene acid (1.21 L·mol−1·s−1). A cyclic mechanism of the oxidation chain termination on introduced antioxidants (stable nitroxyl radicals of the piperidine series (>NO●) and the transition metal compounds (Men)) was established. The inhibition factor (f) showing how many reaction chains are terminated by the one particle of the antioxidant is equal to 102. The cyclic chain termination is caused by the following reactions: HO2● + >NO● → NOH + O2, HO2● + NOH → >NO● + H2O2 (for >NO●) and HO2● + Men → Men+1 + HO2●−, HO2● + Men+1 → Men + H+ + O2 (for Men).

Kinetics and mechanism of metallocene‐catalyzed olefin polymerization: Comparison of ethylene, propylene homopolymerizations, and their copolymerization

ABSTRACTA series of ethylene, propylene homopolymerizations, and ethylene/propylene copolymerization catalyzed withrac‐Et(Ind)2ZrCl2/modified methylaluminoxane (MMAO) were conducted under the same conditions for different duration ranging from 2.5 to 30 min, and quenched with 2‐thiophenecarbonyl chloride to label a 2‐thiophenecarbonyl on each propagation chain end. The change of active center ratio ([C*]/[Zr]) with polymerization time in each polymerization system was determined. Changes of polymerization rate, molecular weight, isotacticity (for propylene homopolymerization) and copolymer composition with time were also studied. [C*]/[Zr] strongly depended on type of monomer, with the propylene homopolymerization system presented much lower [C*]/[Zr] (ca. 25%) than the ethylene homopolymerization and ethylene–propylene copolymerization systems. In the copolymerization system, [C*]/[Zr] increased continuously in the reaction process until a maximum value of 98.7% was reached, which was much higher than the maximum [C*]/[Zr] of ethylene homopolymerization (ca. 70%). The chain propagation rate constant (kp) of propylene polymerization is very close to that of ethylene polymerization, but the propylene insertion rate constant is much smaller than the ethylene insertion rate constant in the copolymerization system, meaning that the active centers in the homopolymerization system are different from those in the copolymerization system. Ethylene insertion rate constant in the copolymerization system was much higher than that in the ethylene homopolymerization in the first 10 min of reaction. A mechanistic model was proposed to explain the observed activation of ethylene polymerization by propylene addition. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem.2017,55, 867–875

Free Radical Polymerization Behavior of the Vinyl Monomers from Plant Oil Triglycerides

A one-step method of plant oil direct transesterification was used to synthesize new vinyl monomers from sunflower (SFM), linseed (LSM), soybean (SBM), and olive (OVM) oils. The degree of unsaturation in plant oil fatty acids was used as a criterion to compare the free radical polymerization behavior of new monomers. The number-average molecular weight of plant oil-based homopolymers synthesized in toluene in the presence of AIBN at 75 °C varies at 11 000–25 000 and decreases as follows: poly(OVM) > poly(SFM) > poly(SBM) > poly(LSM), corresponding to increasing degree of unsaturation in the monomers. Rate of polymerization depends noticeably on the degree of unsaturation in monomers. Due to the allylic termination, chain propagation coexists with effective chain transfer during polymerization. The obtained values of CM (ratio of chain transfer and propagation rate constants) depends on monomer structure as follows: CM(LSM) > CM(SBM) > CM(SFM) > CM(OVM). 1H NMR spectroscopy shows that the fraction of the r...

Atom transfer radical polymerization and copolymerization of isoprene catalyzed by copper bromide/2,2′-bipyridine

Abstract ATRP, as one of the most successful controlled/“living” radical polymerization techniques, has been applied to a large variety of monomers including styrenes, (meth)acrylates, (meth)acrylamides, acrylonitrile, and vinyl acetate. However, ATRP of isoprene still remains a challenge due to poor solubility of copper catalysts in isoprene and low chain propagation rate constant of the monomer. In this work, CuBr/2,2′-bipyridine was found to effectively mediate ATRP of isoprene at 100 °C, 130 °C, and 150 °C with ethyl 2-bromopropionate as an initiator. The polymerizations proceeded smoothly and reached 48.1%, 53.3%, and 71.0% conversions, respectively, in 72 h, producing polyisoprenes with molecular weights close to theoretical values and relatively narrow distributions. A block copolymer of polystyrene-b-polyisoprene was prepared using CuBr/2,2″-bipyridine as a catalyst and polystyrene as a macroinitiator. The 1 H NMR and 13 C NMR analysis of polyisoprene indicated that the polymer had 88.8% 1,4-addition structure and 63.9% of the polymer backbone units were in trans-configuration.