Comonomer Feed Composition Research Articles

Stepwise Gradient Copolymers of n-Butyl Acrylate and Isobornyl Acrylate by Emulsion RAFT Copolymerizations

Gradient copolymers of n-butyl acrylate (nBA) and isobornyl acrylate (IBA) were prepared using reversible addition-fragmentation chain transfer (RAFT) emulsion polymerization. Gradient copolymerizations were conducted using stepwise monomer addition such that the system was monomer-starved. Using the stepwise monomer addition process with a fixed comonomer ratio during the polymerization allows for pre-specified gradient compositions to be obtained. The structural properties of copolymers were confirmed via kinetic investigations and two-dimensional chromatography. 1H nuclear magnetic resonance (NMR) characterization revealed the gradient behavior of the prepared copolymers. The degree of change in monomer composition along the copolymer chain strongly affects the thermal properties of the final polymer product. Thus, gradient copolymers were examined to determine how the strength of the gradient impacts the glass-transition temperature (Tg). Comparisons were also made between the gradient copolymers and their corresponding statistical copolymers and homopolymers. Differential scanning calorimetry analysis of gradient copolymers demonstrated that such copolymers had much broader glass-transition regions compared to homopolymers and statistical copolymers. Furthermore, both the midpoint of the transition (i.e., Tg) and the breadth of the transition were found to be predeterminable through a judicious choice of the comonomer feed composition and the steepness of the comonomer feed in the subsequent monomer additions.

Determination of the Radical Reactivity Ratios of 2-(N-Ethylperfluorooctanesulfonamido)ethyl Acrylate and Methacrylate in Copolymerizations with N,N-Dimethylacrylamide by in Situ 1H NMR Analysis As Established for Styrene–Methyl Methacrylate Copolymerizations

A model system of styrene (St) and methyl methacrylate (MMA) was copolymerized in an NMR tube at 60 °C using 2,2′-azobis(isobutyronitrile) as the initiator and pyridazine as an internal standard to optimize an in situ 1H NMR spectroscopic method for determining reactivity ratios by generating data at hundreds of instantaneous comonomer compositions (244 data points from 8 to 91 mol % St) starting with only nine initial comonomer compositions. The radical reactivity ratios of styrene (rSt = 0.697 ± 0.010) and methyl methacrylate (rMMA = 0.491 ± 0.007) were determined by nonlinear least-squares fitting of a Mayo–Lewis plot of the instantaneous copolymer composition as a function of the comonomer feed composition using the terminal model and MINITAB statistical software, in which the copolymer composition was calculated by assuming that all comonomer consumed was converted to copolymer without side reactions; the results were similar to accepted literature values for the terminal and implicit penultimate models. After correcting for changes in the “lock” value at the initial stages of the copolymerization (because of solids formed in the sealed NMR tube), the same technique was used to determine the reactivity ratios of 2-(N-ethylperfluorooctanesulfonamido)ethyl acrylate (FOSA; rFOSA = 1.624 ± 0.048) and 2-(N-ethylperfluorooctanesulfonamido)ethyl methacrylate (FOSM; rFOSM = 2.876 ± 0.083) in their radical copolymerizations with N,N-dimethylacrylamide (DMA; rDMA = 1.126 ± 0.031 with FOSA; rDMA = 0.859 ± 0.026 with FOSM).

Alternating radical copolymerization of vinyl acetate and tert-butyl-2-trifluoromethacrylate

Alternating conventional radical copolymerization of tert-butyl-2-trifluoromethacrylate (a non-homopolymerizable fluoromonomer under radical conditions) with vinyl acetate, initiated by 2,2′-azo-bis(4-methoxy-2,4-dimethyl valeronitrile) at 40 °C is presented. The study of the kinetics of the copolymerization using various [VAc]0/[MAF-TBE]0 feeds showed that an equimolar feed of comonomers led to the highest apparent copolymerization rate (kapp = 4 × 10−4 s−1). The resulting copolymers had a nearly perfect alternating structure over a very wide range of comonomer feed compositions (fMAF-TBE = 0.05–0.95) until complete consumption of one of the monomers. The reactivity ratios were measured to be: rMAF-TBE = 0 and rVAc = 0.014 at 40 °C and the Alfrey and Price parameters for MAF-TBE were calculated (QMAF-TBE = 1.18 and eMAF-TBE = 1.84).

Organometallic-Mediated Alternating Radical Copolymerization of tert-Butyl-2-Trifluoromethacrylate with Vinyl Acetate and Synthesis of Block Copolymers Thereof.

Organometallic-mediated radical polymerization (OMRP) has given access to well-defined poly(vinyl acetate-alt-tert-butyl-2-trifluoromethacrylate)-b-poly(vinyl acetate) and poly(VAc-alt-MAF-TBE) copolymers composed of two electronically distinct monomers: vinyl acetate (VAc, donor, D) and tert-butyl-2-trifluoromethacrylate (MAF-TBE, acceptor, A), with low dispersity (≤1.24) and molar masses up to 57 000 g mol-1 . These copolymers have a precise 1:1 alternating structure over a wide range of comonomer feed compositions. The reactivity ratios are determined as rVAc = 0.01 ± 0.01 and rMAF-TBE = 0 at 40 °C. Remarkably, from a feed containing >50% molar VAc content, poly(VAc-alt-MAF-TBE)-b-PVAc block copolymers are produced via a one-pot synthesis. Such diblock copolymers exhibit two glass transition temperatures attributed to the alternating and homopolymer sequences. The OMRP of this fluorine-containing alternating monomer system may provide access to a wide range of new polymer materials.

Chiral copoly(methacrylate)s carrying amino acid pendants in the side-chains

Main chain chiral poly(methacrylate)s have been synthesized by controlled reversible addition–fragmentation chain transfer (RAFT) copolymerization of chiral monomer Boc-l-alanine methacryloyloxyethyl ester (Boc-l-Ala-HEMA, A) with Boc-d-alanine methacryloyloxyethyl ester (Boc-d-Ala-HEMA, B) and achiral monomer Boc-2-methylalanine-methacryloyloxyethyl ester (Boc-Aib-HEMA, C), and B with C by changing comonomer feed compositions. We systematically examined the role of l-alanine, d-alanine and 2-aminoisobutyric acid (Aib) as folding nuclei in our designed hybrid polymer-amino acid conjugates. Specific optical rotation and circular dichroism (CD) spectroscopy studies reveal that poly(Boc-l-Ala-HEMA) and poly(Boc-d-Ala-HEMA) formed entirely opposite handed helical structure stabilized by intramolecular hydrogen bonding among the pendant chromophores of the chiral monomers. Poly(Boc-Aib-HEMA) formed random coil structures conformation (unstructured conformation), whereas the resultant copolymers of C with A and B showed an unusual linear relationship of optical activity against comonomer composition, in sharp contrast with Green’s “majority” and “sergeant-and-soldier” rule. After Boc-group expulsion in acidic environment from the polymer side-chains, backbone retained its helicity. Variable temperature chiroptical properties investigation was also performed to examine the thermal stability of the homo and copolymer’s helical conformations. Additionally, pH induced conformational transformation was observed for the homo and copolymers.

Control of particle size by feed composition in the nanolatexes produced via monomer-starved semicontinuous emulsion copolymerization

Conventional batch and semicontinuous emulsion copolymerizations often produce large particles whose size cannot be easily correlated with the comonomer feed compositions, and are to some degree susceptible to composition drift. In contrast, we found that copolymer nanolatexes made via semicontinuous monomer-starved emulsion copolymerizations are featured with an average nanoparticle size being controlled by the feed composition, a high conversion achieved, and a high degree of particle composition uniformity. This was achieved because the rate of particle growth, during nucleation, was controlled by the rate of comonomer addition, and the copolymer composition, surfactant parking area on the particles, and nucleation efficiency determined by the comonomer feed composition. Two model systems, methyl methacrylate/styrene and vinyl acetate/butyl acrylate, with significant differences in water solubility were studied. Monomers were added to the aqueous solution of sodium dodecylsulfate and potassium persulfate at a low rate to achieve high instantaneous conversions.

Poly(N‐vinylpyrrolidone‐co‐2‐acrylamido‐2‐methylpropanesulfonate sodium): Synthesis, characterization, and its potential application for the removal of metal ions from aqueous solution

ABSTRACTIn the current study, poly(N‐vinylpyrrolidone‐co‐2‐acrylamido‐2‐methylpropanesulfonate sodium), poly(VP‐co‐AMPS), was prepared and used for the removal of Cu2+, Cd2+, and Ni2+ ions via a polymer‐enhanced ultrafiltration (PEUF) technique. The copolymer was synthesized by radical polymerization in an aqueous medium with a comonomer feed composition of 50:50 mol %. The molecular structure of the copolymer was elucidated by ATR‐FTIR and 1H NMR spectroscopy, and the average molecular weight was obtained by GPC. The copolymer composition was determined to be 0.42 for VP and 0.58 for AMPS by 1H NMR spectroscopy. The copolymer and homopolymers exhibited different retention properties for the metal ions. PAMPS exhibited a high retention capacity for all of the metal ions at both pH values studied. PVP exhibited selectivity for nickel ions. Poly(VP‐co‐AMPS) exhibited a lower retention capacity compared to PAMPS. However, for poly(VP‐co‐AMPS), selectivity for nickel ions was observed, and the retention of copper and cadmium ions increased compared to PVP. The homopolymer mixture containing PAMPS and PVP was inefficient for the retention of the studied metal ions. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41272.

Synthesis of glycidyl methacrylate containing diethanol amine and its binary copolymers with ethyl methacrylate and butyl methacrylate as nano‐size chelating resins for removal of heavy metal ions

AbstractOne of the most important applications of chelating and functional polymers is their capability to recover metal ions from their solutions. This study concerns the synthesis of a hydrophilic glycidyl methacrylate (GMA) monomer‐bearing diethanol amine (DEA) chelating group from the reaction of GMA and DEA. The formed adduct (A) was characterized via FTIR and mass spectra and subjected to homopolymerization and binary copolymerization with ethyl methacrylate and butyl methacrylate. The copolymerization process was carried out via a semi‐batch emulsion polymerization technique by using potassium persulphate/sodium bisulphite as a redox pair initiation system and sodium dodecyl benzene sulphonate as an emulsifier at 65°C. The obtained polymers were characterized via FTIR, thermal gravimetric analysis, and UV–VIS. Volume‐average diameters (Dv) in nanoscale range for the prepared polymers were confirmed by transmission electron microscope investigation. It was shown that the obtained nano‐size chelating polymers have a powerful adsorption character toward transition metal ions (Cu+2, Cr+3, Ni+2, and Co+2) and efficient selectivity for Cu+2 and Ni+2 ions at normal pH. The effects of pH, time, and different comonomer feed compositions on the uptake of metal ions were studied. The reaction between the obtained chelating resins and different metal ions was confirmed to be a second‐order reaction. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Dynamic Monte Carlo Simulation of ATRP in a Batch Reactor

AbstractA dynamic MC model was developed to simulate the polymerization kinetics and the detailed microstructure of copolymers made with ATRP in a batch reactor. The model was used to predict monomer conversion, average molecular weight, polydispersity index, and copolymer composition as a function of polymerization time. The model can also predict the distribution of molecular weight, chemical composition, and comonomer sequence length at any polymerization time or comonomer conversion. The simulation was used to explore the effects of rate constants and reactant stoichiometry on the microstructure of chains. Two copolymerization systems were chosen to demonstrate the effect of reactivity ratios and comonomer feed compositions on the final chemical composition distribution.magnified image

Gradient Copolymers by ATRP in Semibatch Reactors: Dynamic Monte Carlo Simulation

AbstractWe developed a dynamic Monte Carlo model for ATRP in semibatch reactors. Semibatch reactors can be used to produce gradient copolymers even if the difference between the reactivity ratios of the comonomers is not significant by using different comonomer feed policies. The model was used to predict average molecular weights, polydispersity index, copolymer composition and complete distributions of molecular weight, chemical composition, and comonomer sequence length at any polymerization time. Two case studies, poly[styrene‐co‐(methyl methacrylate)] and poly[acrylonitrile‐co‐(methyl methacrylate)], were chosen to demonstrate the effect of comonomer feed compositions on the final chemical composition distribution of the copolymer.magnified image

Mathematical Modeling of Atom‐Transfer Radical Copolymerization

AbstractA comprehensive mathematical model for atom transfer radical copolymerization in a batch reactor is presented using the concept of pseudo‐kinetic rate constants and the method of moments. The model describes molecular weight, monomer conversion, polydispersity index, and copolymer composition as a function of polymerization time. Model predictions were compared with experimental data for styrene and butyl acrylate copolymerization and excellent agreement was obtained. We have also tested the model with styrene‐acrylonitrile copolymerization data obtained in our laboratory. Finally, we used the model to study the effect of comonomer reactivity ratio, feed composition, activation and deactivation rate constants on the copolymer composition.magnified image

Mechanical Performance of Styrene-2-Ethylhexyl Acrylate Polymers Synthesized by Semicontinuous Emulsion Polymerization Varying Feed Composition

A semicontinuous emulsion process varying comonomer feed composition in the course of the reaction is used here to produce copolymer chains of different composition as conversion proceeds. Polymeric material global composition and evidence of branching are determined by 1H-NMR. The determined by GPC is beyond the range where the mechanical properties depend on molecular weight. Static and dynamic mechanical properties of variable composition copolymers exhibit highly improved copolymer type behavior for all tested compositions (styrene content between 30 and 85 wt%), showing high superiority of the mechanical performance in comparison with random copolymers and two-stage polymers of equivalent composition, synthesized also by emulsion polymerization.

Diphenyl-ditelluride-initiated alternating co-polymerization of N-vinyl-2-pyrrolidone with methyl methacrylate

The free radical co-polymerization of N-vinyl-2-pyrrolidone and methyl methacrylate was carried out at 60°C in the presence of diphenyl ditelluride using 1,4-dioxane as the solvent. The kinetic expression is R p ∝ [DPDT]0.5 [MMA][NVP]. The energy of activation has been computed as 50 kJ/mol. The presence of tellurium in the co-polymer has been confirmed by qualitatively, as well as induced coupled plasma mass spectroscopy (ICP-MS). The FT-IR spectrum of the co-polymer shows the bands at 1728 cm−1 and 1680 cm−1 due to ester and ketonic stretching of MMA and NVP, respectively. The monomer sequence distribution has been given by 13C-NMR spectroscopy. The co-monomer feed composition was observed to have a strong effect on the overall co-polymerization rate. The reactivity ratio of the binary system was determined, using the Kelen–Tüdos method, to be r (MMA) = 0.043 and r (NVP) = 0.016, indicating an alternating tendency in the formed co-polymer.

Bulk and Solution Copolymerization of Butyl Acrylate/Methyl Methacrylate at Elevated Temperatures

A series of bulk and solution (in toluene) copolymerizations of butyl acrylate/methyl methacrylate were performed independently at two laboratories. The runs were at elevated temperatures ranging from 90 to 140 °C conducted to high conversion levels, and samples were characterized for conversion, cumulative copolymer composition and number- and weight-average molecular weights and distribution. Variation of the comonomer feed composition, temperature, and the solvent, initiator and chain transfer agent concentrations was studied. Using a mechanistic model, conversion data were predicted to high conversions using terminal model kinetics at 90 and 115 °C. The copolymer composition data conformed to the terminal kinetic model over the entire temperature range. Solvent effects were reflected by changes in the butyl acrylate rate constants. Composition vs. conversion. Effect of feed composition for runs at 140 °C.

Inter and intramolecular structure predictions in 2-hydroxyethyl methacrylate– tert-butyl acrylate copolymers obtained at high conversion

Radical copolymerization at 50°C of 2-hydroxyethyl methacrylate and tert-butyl acrylate in a 3 mol l −1 N, N′-dimethylformamide (DMF) solution has been analysed over a wide range of conversion and monomer feed compositions with the purpose of predicting the variation of inter and intramolecular structures. To do this, the previously obtained monomer reactivity ratios along with the coisotactic and statistical parameters were used. Overall copolymerization rate coefficients and individual monomer conversions for each monomer on the full range of conversion were also obtained. From the results obtained it follows that the Mayo–Lewis terminal model (MLTM) provides an excellent prediction across the complete conversion range for all comonomer feed compositions.

Copolymerization of ethylene and styrene with monocyclopentadienyltitanium trichloride/methylalumoxane catalyst

AbstractA series of ethylene‐styrene copolymerizations was carried out in the presence of cyclopentadienyltitanium trichloride and methylalumoxane at 20°C and at different comonomer feed compositions. By sequential extraction a copolymeric material with a styrene units content up to 36 mol‐% can be separated from the homopolymeric products. Some considerations about the relative reactivity of the comonomers and the regioregularity of the styrene insertion are made on the basis of the 13C NMR spectra.

Radical-initiated copolymers of N-vinyl pyrrolidone and N-acryloxy succinimide: kinetic and microstructure studies

Abstract Kinetics of solution (co)polymerization of N-vinyl pyrrolidone (NVP, or V) and N-acryloxy succinimide (NAS, or A) have been investigated at 60°C in N, N-dimethylformamide with 4,4′-azobis(4-cyanopentanoic acid) as initiator. First, the k p √k i value for homopolymerization of A monomer was estimated as 0.87 10.5 mol−0.5 s−0.5. The comonomer feed composition was observed to have a strong effect on the overall copolymerization rate. Reactivity ratios of the binary system were determined to be rNAS = 0.27 ± 0.04 and rNVP = 0.01 ± 0.01, indicating a strong alternating tendency in the formed copolymer. Copolymers were then characterized as regards to composition (by ultraviolet spectrophotometry) and monomer sequence distribution (by 13C nuclear magnetic resonance spectroscopy). The presence of a small fraction of VVA triads was clearly evidenced which was not expected from simulation based on a terminal kinetic model; the occurrence of a more complex model has been discussed.

The dynamic behavior of continuous solution polymerization reactors—VIII. A full bifurcation analysis of a lab-scale copolymerization reactor

In a previous paper in this series a mathematical model describing the dynamic behavior of continuous free-radical solution copolymerization reactors was validated with experimental results obtained for the copolymerization of vinyl acetate (VA) and methyl methacrylate (MMA) in tert-butanol (TB). Dramatic effects of the feed composition on the reactor dynamic behavior were predicted and confirmed by experiment. The model is now used for a full bifurcation analysis in a broader range of the parameter space in order to determine how the bifurcation structure evolves when the comonomer feed composition changes. New bifurcation structures are presented and special attention is paid to the role of the boiling constraint.

The comppen model: A combined complex‐participation/penultimate effect model for free‐radical copolymerization

AbstractThe Comppen model for the mechanism of free‐radical copolymerization has been developed to account for both penultimate effects and the participation of 1:1 electron donor‐acceptor complexes during chain propagation. This was achieved by incorporating penultimate effects into the existing complex participation model of Cais, Farmer, Hill, and O'Donnell, using probability theory to derive new copolymer composition and sequence distribution equations that are solely functions of the reactivity ratios, the composition of the comonomer feed, and the equilibrium constant for 1:1 electron donor‐acceptor complex formation. The model was applied to experimental data from styrene/maleic anhydride copolymers prepared in methyl ethyl ketone at 50°C over a wide range of comonomer feed compositions, using nonlinear least‐squares curve fitting techniques to determine best estimates of the reactivity ratios. Copolymer compositions and sequence distributions for copolymers in this comonomer system were then predicted using the Comppen model and compared to those determined experimentally via 13C‐NMR spectroscopy. © 1994 John Wiley & Sons, Inc.

A stereochemical study of citraconic anhydride units in copolymers of styrene with citraconic anhydride via 13C-NMR spectroscopy

The configuration of citraconic (α-methylmaleic) anhydride units in styrene/citraconic anhydride copolymers prepared in methyl ethyl ketone at 50.0 ± 0.1° was determined over a wide range of comonomer feed compositions using 13C-NMR spectroscopy. It was found that the ratio of Z (zusammen) to E (entgegen) configurations of citraconic anhydride units in these copolymers increased with the degree of alternation of the comonomer units, reaching a constant value of approx. 1.3 when the comonomer units were almost completely alternating and the mole fraction of citraconic anhydride units in the copolymers approached 0.50. This result was found to be consistent with previous related work, suggesting the existence of a link between the stereoregularity and alternating tendency of comonomer units in copolymerisation systems where pairs of comonomer units can form 1:1 electron donor acceptor (EDA) complexes in the comonomer feed.