Course Of Copolymerization Research Articles

Optically active porous hybrid particles constructed by alkynylated cellulose nanocrystals, helical substituted polyacetylene, and inorganic silica for enantio-differentiating towards naproxen.

This article reports on a novel type of ternary chiral porous hybrid particles (TCPHPs) constructed by alkynylated cellulose nanocrystals (A-CNCs), helical substituted polyacetylene, and inorganic silica. The resulting TCPHPs combine the respective advantages of the three components. A-CNCs serve as stabilizer, co-monomer, and chiral source simultaneously and transfer their chirality to the resulting helical substituted polyacetylenes in the course of copolymerization with achiral acetylenic monomer following "sergeants and soldiers rule". Helical substituted polyacetylenes form chiral helical structures and thus endow TCPHPs with the anticipated optical activity. Inorganic silica constitutes the rigid framework and is covalently bonded with the organic components through hydrolysis of Si-O-Et groups. Phase separation between the organic and inorganic components renders TCPHPs with abundant pores. Scanning electron microscope (SEM) images confirm the formation of spherical particles with porous structures. Circular dichroism spectra demonstrate the optical activity of the chiral hybrid particles. The as-prepared TCPHPs exhibit capacity for enantio-differentiating performance towards chiral naproxen.

Thermal hazard evaluation of styrene-methyl methacrylate bulk copolymerization by differential scanning calorimetry and accelerating rate calorimetry

Thermal runaway primarily occurs during the course of copolymerization due to the release of large amounts of heat. In this paper, the thermal risk associated with styrene-methyl methacrylate bulk copolymerization was firstly investigated by differential scanning calorimetry (DSC) and accelerating rate calorimetry (ARC). The result found that the exothermic behavior was greatly affected by the initiator concentration, in contrast the exothermic enthalpy was not. This exothermic behavior was firstly illustrated via polymerization mechanism. The temperature and pressure have changed dramatically during the adiabatic runaway copolymerization, which demonstrated a great potential risk of thermal runaway. Kinetic parameters, such as TNR, TSADT was calculated accordingly, which provided guidance for the safety of storage and transportation. This study will provide a helpful safety assessment for the styrene-methyl methacrylate bulk copolymerization, which is widely used in industry.

Radical copolymerization of higher alkyl methacrylates with acrylic esters and amides in toluene: influence of monomer association on copolymer composition

A strong concentration effect was found in a course of copolymerization of higher N-alkylacrylamides with higher alkyl acrylates in toluene, where the fraction of amide functions in copolymers obtained at low degrees of conversion decreases significantly with an increase in total concentration of monomers in solution. It was established that the observed effect is independent of the structure of alkyl substitutes for both types of monomers. The data gathered with the aid of IR spectroscopy and computer modeling show that this concentration effect relates to the formation of amide associates in solution. The concentration effect was absent for the copolymerization of higher alkyl methacrylates and higher alkyl acrylates.

A Detailed Model on Kinetics and Microstructure Evolution during Copolymerization of Ethylene and 1-Octene: From Coordinative Chain Transfer to Chain Shuttling Polymerization

We introduce a theoretical model based upon the kinetic Monte Carlo (KMC) simulation approach capable of quantifying chain shuttling copolymerization (CSP) of ethylene and 1-octene in a semibatch operation. To make a deeper understanding of kinetics and evolution of microstructure, the reversible transfer reaction is first investigated by applying each of the individual catalysts to the reaction media, and the competences and shortcomings of a qualified set of CSP catalysts are discussed based on coordinative chain transfer copolymerization (CCTP) requirements. A detailed simulation study is also provided, which reflects and compares the contributions of chain transfer reversibility and other chain breaking reactions in controlling distribution fashion of molecular weight and chemical composition. The developed computer code is executed to capture developments in dead chain concentration and time-driven composition drift during CCTP. Also, the effect of chain shuttling agent (CSA) on the copolymerization kinetics is theoretically studied by simultaneous activation of both catalysts. In this way, it is attempted to make control over comonomer incorporation in the course of copolymerization. The molecular-level criteria reflecting copolymer properties, i.e., ethylene sequence length distribution and longest ethylene sequence length, as the signature of CSA performance, are virtually simulated in the presence and absence of hydrogen to capture an image on gradient copolymers in CCTP and blocks with gradually changing composition in CSP.

Cationic copolymerization of racemic -β-butyrolactone with L,L-lactide: One-pot synthesis of block copolymers

Cationic copolymerization of racemic-β-butyrolactone (β-BL) with l,l-lactide (LA) initiated by alcohol and catalyzed by trifluoromethanesulfonic acid proceeding by activated monomer (AM) mechanism was investigated. Although both comonomers were present from the beginning in the reaction mixture, polymerization proceeded in sequential manner, with poly-BL formed at the first stage acting as a macroinitiator for the subsequent polymerization of LA. Such course of copolymerization was confirmed by following the consumption of both comonomers throughout the process as well as by observing the changes of growing chain-end structure using 1H NMR. 13C NMR analysis and thermogravimetry revealed the block structure of resulting copolymers. The proposed mechanism of copolymerization was confirmed by the studies of changes of 1H NMR chemical shift of acidic proton in the course of copolymerization, providing an indication that indeed protonated species and hydroxyl groups are present throughout the process, as required for AM mechanism. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4873–4884

Nonlinear Method for Determining Reactivity Ratios of Ring-Opening Copolymerizations

A nonlinear errors-in-variables-model (EVM) regression method was used to determine reactivity ratios for enzyme-catalyzed ring-opening copolymerizations of ε-caprolactone (ε-CL) and δ-valerolactone (δ-VL). The cumulative copolymer composition model accurately described the experimental data, indicating that conventional models can be used to describe enzyme-catalyzed copolymerizations. Reactivity ratios were calculated from Raman spectroscopic data collected in situ and the model of monomer feed drift over the course of copolymerization. The analysis was combined for multiple experiments to improve the estimate. For the lipase-catalyzed copolymerization, the calculated reactivity ratios were rε-CL = 0.27 and rδ-VL = 0.39. Compared to conventional linearization techniques, the EVM method reduced the experimental work required and reduced the measurement error, as indicated by the 95% joint confidence region. In addition, the EVM method is influenced less by the apparent induction period of δ-VL. The conventional methods rely on low conversion data where the induction period is significant. The EVM method presented here determines reactivity ratios rapidly, saving both time and material waste.

Study of the kinetics of styrene copolymerization with divinyl sulfide and the structure of macromolecules

The kinetics of the free-radical copolymerization of styrene with divinyl sulfide in the presence of N,N′-bis(vinyloxyethyl)thiuram disulfide as an iniferter has been studied. The rate of polymerization is shown to decrease with increasing iniferter concentration. The structure of the copolymers isolated in the course of copolymerization has been investigated by electron microscopy and compared with that of the copolymers synthesized using AIBN as an initiator. Evolution in the morphology of the polymer phase during the process, which consists in self-organization of the secondary supramolecular structure into spheroids with diameters of 0.1–10 μm, has been revealed. The stages of the formation of polymer particles of various structures are described by the scheme of morphogenesis.

Oxidative Copolymerization of Aniline with o- and p-Nitroaniline by Ammonium Per Sulfate: Kinetic and Pathway

The kinetic study on the oxidation of aniline with o- and p-nitroaniline by ammonium persulfate (APS) has been carried out. The course of copolymerization was investigated by UV-vis spectroscopy and structural characterization was studied by FTIR spectral analysis. The electronic spectra of the copolymers poly(aniline-co-p-nitroaniline) and poly(aniline-co-o-nitroaniline) show hypsochromic shift. The shift has been observed in the bands corresponding to π → π* transition as well as in the exciton transition. The presence of nitro-group not only affects the oxidative polymerization window but also brings about the remarkable changes in the optical and electronic properties of parent polymer polyaniline. The poly(aniline-co-nitroaniline) has been shown multiple color transition (yellow → lightgreen → darkgreen) as the pH of the system changes with progress of polymerization reaction. The increase in absorbance recorded at various time intervals with increasing concentration of aniline, o- and p-nitroaniline, which indicates the growth of polymer formation. The first order kinetics is suggested as the degradation curve is consistent well byan exponential decay of APS. The resulting first-order rate constant was used to calculate the rate of poly(aniline-co-nitroaniline) formation using the rate equation –d[A]/dt = kcn. The reaction shows first-order dependence for each reactant.

Synthesis and properties of poly(sodium acrylate‐co‐2‐acryloylamino‐2‐methyl‐1‐propanesulfonic acid)/attapulgite as a salt‐resistant superabsorbent composite

AbstractA novel salt‐resistant superabsorbent composite was prepared by copolymerization of partially neutralized acrylic acid, 2‐acryloylamino‐2‐methyl‐1‐propanesulfonic acid (AMPS) and attapulgite (APT). To enhance the swelling rate (SR) of the copolymer, sodium bicarbonate was used as a foaming agent in the course of copolymerization. Furthermore, for improving the properties of swollen hydrogel, such as strength, resilience and dispersion, the copolymer was surface‐crosslinked with glycerine and sodium silicate, and then the surface‐crosslinked copolymer was blended with aluminum sulfate and sodium carbonate in post treatment process. The influences of some reaction conditions, such as amount of AMPS, APT, and initiator, and neutralization degree of acrylic acid on water absorbency in 0.9 wt% NaCl aqueous solution both under atmospheric pressure (WA) and load (WAP, P ≈ 2 × 103 Pa) were investigated. In addition, the effect of them on SR was also studied. The WA and WAP of the superabsorbent composite prepared under optimal conditions in 0.9 wt% NaCl aqueous solution were 52 g·g−1 and 8 g·g−1, respectively. Besides, the SR was fast, and it could reach 0.393 mL·(g·s)−1. Moreover, the swollen hydrogel possessed excellent salt resistance, hydrogel resilience and dispersion. POLYM. ENG. SCI., 2009. © 2008 Society of Plastics Engineers

Concentration Effect in Copolymerization of Sodium 2-Acrylamido-2-methylpropanesulfonate with N-Vinylpyrrolidone in Aqueous Solutions

The kinetics of copolymerization of sodium 2-acrylamido-2-methylpropanesulfonate with N-vinyl-pyrrolidone in aqueous solutions in the presence of potassium persulfate at 40 – 70°C and the molecular characteristics of the resulting complexes were studied, as influenced by the total concentration of the initial monomer mixture, comonomer ratio, temperature, and conversion. The kinetic data were explained taking into account the state of the ionic groups, electrostatic interactions between the reacting particles, and complexation of comonomers in the course of copolymerization.

Polystyrene-graft-poly(ethylene oxide) copolymers prepared by macromonomer technique in dispersion. 2. Mechanism of dispersion copolymerization

The reaction mechanism of dispersion copolymerization of methacryloyl-terminated poly(ethylene oxide) macromonomer and styrene in the polar media is discussed. The copolymerization products were analyzed by means of liquid chromatography. This analysis revealed presence of rather large amount of polystyrene in the final polymer product. It is assumed that the system undergoes phase separation in the course of copolymerization. The graft copolymer created in the first stage of polymerization acts as a detergent (amphiphile). The hydrophobic phase is hardly accessible for hydrophilic macromonomer but well dissolves styrene and benzoylperoxide initiator. Therefore, polystyrene homopolymer is intensively formed in this reaction locus. Its molar mass is rather low because of high initiator and low monomer concentration at the reaction loci. We suppose existence of at least two different polymerization loci; the continuous phase and the particle core. The existence of third polymerization locus, viz. particle surface layer cannot be excluded, either.

Kinetics and mechanism of glycolide and ethylenoxalate copolymerization. Characteristics of the copolymers formed and mechanism of the biodegradation

The study of glycolide (GL) and ethylenoxalate (EO) copolymerization with the use of SnCl2 2 H2O as a catalyst was carried out by 1H NMR spectroscopy. Monomer reactivities are found to be close and equal to 1,1 and 1,11 for GL and 0,71 and 0,85 for EO at 150 and 170 °C, respectively. Kinetic data obtained show that the reaction proceeds without induction period up to entire consumption of every monomer. The detailed identification of 1H spectra enables to follow the polymer microstructure in the course of copolymerization. Thermal properties of copolymers and their biodegradation abilities have been studied. The biodegradation rate is shown to increase with growing EO proportion in the copolymer. The lactone biodegradation mechanism where the electrophility of carbon and nucleophility of OH group are playing the most important role, is suggested. The correlation between the biodegradation rate and the chemical shift in 13C NMR spectra of the carbon atom of the carbonyl group has been established.

Synthesis of novel hydrolytically degradable hydrogels for controlled drug release

This paper describes synthesis of hydrolytically degradable gels based on N-(2-hydroxypropyl)-methacrylamide copolymers with high potential for use in the synthesis of new drug release systems. The first part deals with a study of the dependence between conditions of crosslinking copolymerization, the course of copolymerization and final properties of hydrogels thus formed. The second part is devoted to the study of hydrolytic degradation of hydrogels and in vitro studies of doxorubicin and polymer-doxorubicin conjugate release from hydrogel matrix. We have shown that the hydrogels under study were stable under acidic conditions (in buffers at pH 5 and lower) and hydrolytically degradable at physiological pH (7.4). Both drug forms, free doxorubicin and its conjugate with water-soluble polymeric drug carrier, can be released from the hydrogel matrix at a rate depending on the rate of drug diffusion from the hydrogel, or the rate of hydrogel degradation, or at a rate controlled by a combination of both processes. In all cases the hydrogel matrix was degraded and a hydrophilic water-soluble polymeric product was formed. Biological evaluation of drug-hydrogel systems described in this paper is under way.

Copolymerization and Copolymers of Acrylonitrile with Some Brominated Phenylmaleimides

Abstract Acrylonitrile (AN) was copolymerized with N-(4-bromophenyl)-maleimide (BPMI) or N-(2,4,6-tribromophenyl)maleimide (TBPMI) in toluene solution using azobisisobutyronitrile as the free radical initiator. The monomer reactivity ratios were found to be for BPMI (M1)-AN (M2), r1=0.44 ± 0.082 and r2 = 1.82 ± 0.125, and for TBPMI (M1)-AN (M2), r1 = 0.053 ± 0.051 and r2 = 4.71 ± 0.275. The e and Q values were also calculated. The course of copolymerization to high conversion is characterized by a remarkable decrease of the initial reaction rate as well as of overall conversion as the fraction of brominated monomer in the monomer mixture is increased. However, these values are somewhat higher when BPMI is used as a comonomer. The resulting copolymers show a higher thermal stability than that of polyacrylonitrile, and the glass transition temperature increases markedly with increasing BPMI or TBPMI content.

Copolymerization and copolymers of N‐(2,4,6‐tribromophenyl)maleimide with methyl acrylate and methyl methacrylate

AbstractN‐(2,4,6‐Tribromophenyi)maleimide (TBPMI) was copolymerized with methyl acrylate (MA) or methyl methacrylate (MMA) in toluene solution using 2,2′‐azoisobutyronitrile as free‐radical initiation. The copolymerization reactivity ratios were found to be for the system TBPMI/MA r1 = 0,095 ± 0,045 (TBPMI) and r2 = 2,17 ± 0,142 (MA) and for the system TBPMI/MMA r1 = 0,037 ± 0,042 (TBPMI) and r2 = 4,32 ± 0,230 (MMA); Q and e values were also calculated. The initial rate of copolymerization, Rp, for TBPMI/MA sharply decreases as the content of TBPMI in the monomer mixture increases but the composition of the feed does not have a strong influence on Rp for the TBPMI/MMA copolymerization system. The course of copolymerization to high conversion is characterized by an increase of conversion up to a mole fraction of TBPMI of 0,7 in the monomer mixture, when MA was used as the comonomer. An opposite behaviour was found with MMA. Its copolymers show a considerable increase of thermal stability as well as of the glass transition temperatures with increasing TBPMI content.

Copolymer‐monomer miscibility during copolymerization

AbstractSignificant drift in the compositions of copolymer and of unreacted monomer mixture is predicted to occur during the bulk copolymerization of N‐vinyl‐2‐pyrrolidone (VP) with butyl acrylate (BA), when the inital feed mixture contains 75 wt.‐% VP. The drift in copolymer composition has been confirmed by 1 the optical appearance and glass transition (Tg) behaviour of the products of the γ‐ray initiated copolymerization at various fractional conversions (C) and 2 the Tg behaviour of low‐conversion samples of poly(VP‐co‐BA) blended in propertions so as to simulate the overall composition of material that would be present cumulatively at selected values of C during an actual copolymerization. The compositions of unreacted monomer mixtures co‐existing with copolymer at selected conversions have been calculated and intrinsic viscosities [η] of blends dissolved in these VP/BA mixtures have been measured. Theta conditions for the blends have been established turbidimetrically in chloroform/heptane and the corresponding values of [η]Θ measured. The chain expansion factors thereby derived from [η] and [η]Θ show a decreasing affinity of copolymer for residual monomer during the course of copolymerization.

Special Features of Network Formation by Chain Crosslinking Copolymerization

Special features of free-radical crosslinking copolymerization and the structure of the resulting products have been reviewed. Characteristic is the effect of spatial correlations on the apparent reactivity of pendant double bonds. These correlation make the apparent reactivity in the course of copolymerization to increase (cyclization) and decrease (steric hindrances). At intermediate and higher concentrations of the crosslinker, compact structures are formed which are internally crosslinked. Only pendant double bonds in the peripheral layer are able to take part in polymerization reactions whereas the internal ones cannot react. The state of theoretical simulations of this structure growth is discussed with a special emphasis on the development of the kinetic (coagulation) network formation theories so that the above mentioned features may be taken into account. Also, the important role of the presence of a diluent during polymerization id discussed. It can result in a change of network chain conformations necessary for networks exhibiting volume phase transitions. Alternatively, it can induce liquid-gel phase separations resulting in inhomogeneous networks having a variety of morphologies.

Copolymerization and Copolymers of Styrene N-(2,4,6-Tribromophenyl) Maleimide with Styrene

Abstract Kinetic studies of the free radical copolymerization of N-(2,4,6- tribromophenyl) maleimide (TBPMI) with styrene in solution were carried out. The thermal and flammability characteristics of the resulting polymers were also investigated. The monomer reactivity ratios were found to be r 1 = 0.006 ± 0.0026 (TBPMI) and r 2 = 0.086 ± 0.0023, and the activation energy of the copolymerization reaction was Ea = 73.6 kJ/mol. The resulting copolymers showed an alternating structure regardless to the monomer feed composition. The molecular weights of the copolymers obtained are relatively high and gradually increase by increasing the TBPMI fraction in the feed, whereas the Tg's showed similar values (540 K) for the equimolar ratio of the comonomers. The course of copolymerization up to high conversion was followed by microcalorimetry and is characterized by a remarkable increase of the initial reaction rate as the fraction of TBPMI was increased; it is also higher at higher total monomer concentrations. Ho...

Aspects of the copolymerization of ethylene with acetylene on complex organometallic catalysts

The effect of various factors on the kinetics of the consumption of the comonomers during polymerization of ethylene with acetylene on vanadium- and titanium-containing complex catalysts and on the structure of the products formed has been studied. The kinetic method shows that the reactivity of acetylene in the course of copolymerization on complex catalysts exceeds that of ethylene. The copolymerization products of ethylene with acetylene are coloured, contain conjugated and vinyl double bonds, attach ozone, bromine, iodine and maleic anhydride, display paramagnetism and contain a considerable quantity of the crystalline phase. All this indicates that they are block copolymers of ethylene with acetylene. It is shown that the block copolymers in the course of combined polymerization of the two monomers can form only with the condition k 12→0 and k 21→0.

Sulphur‐containing polyacrylates. III: UV‐induced copolymerization of methyl methacrylate with some dimethacrylates containing ether or thioether linkage

AbstractThe UV‐induced copolymerization of methyl methacrylate (MM) with 2,2′‐thiobisethanol dimethacrylate (TEDM) and MM with 2,2′‐oxybisethanol dimethacrylate (OEDM) was investigated for a wide range of the diester content (6‐80 mol%) in the initial mixture. The influence of the feed composition on the course of copolymerization was determined. It was found that there exists a minimum on the plot of maximum yield of soluble copolymer versus diester content at a diester content of 30 mol%. The total copolymer yields were lower in the case of mixtures containing TEDM comonomer. Determination of the reactivity ratios gave the following values: for MM + TEDM ra = 0·21, rb = 4·59 and for MM + OEDM ra = 0·55. rb = 4·42. A possible explanation of the results obtained is discussed.