Monomer Feed Ratio Research Articles

Synthesis of Copolymers of Acrylamide and Acrylonitrile via Redox Polymerization

The redox copolymerization of acrylonitrile with acrylamide in N, N-dimethylformamide (DMF) containing K2S2O8 and AgNO3 was carried out. The resulting copolymers were soluble in this solution. A white floppy mass was obtained, when poltmerizing solution was poured in cold methanol. The copolymers were formed taking different feed ratios of monomers and concentrations of the initiators at 60°C. As the concentration of acrylamide increased in the feed ratio, copolymer yields consierably increased. The copolymerization was completely inhibited by 2, 2-diphenyl-1-picrylhydrazyl suggesting a free radical reaction.

Conducting Copolymers of N-methylaniline and o-aminophenol: Electrosynthesis and In Situ Spectroelectrochemical Characterization

Novel conducting copolymers of N-methylaniline (NMAn) and o-aminophenol (o-APh) were synthesized electrochemically with different feed ratios of the monomers in sulfuric acid solution. The obtained homopolymers and copolymers were characterized with cyclic voltammetry, scanning electron microscopy (SEM), in situ conductivity measurements, in situ UV-Vis., and FT-IR spectroscopy techniques. The influence of applied copolymerization potentials and monomer feed ratio on the optical properties and conductivity of the copolymers were discussed. The in situ UV-Vis. spectroscopy results revealed strong absorption bands at different applied electrode potentials. The conductivity of copolymers increased with increasing the o-APh concentration in feed ratios. The fundamental differences between the structures and morphology of the homo- and copolymers were observed from FT-IR spectroscopy and SEM analysis.

Spectroelectrochemistry of Intrinsically Conducting Selenophene-3-Chlorothiophene Copolymers

The electrochemical copolymerization between selenophene and 3-chlorothiophene monomers was successfully realized. The influence of the applied polymerization potential and the monomer feed ratio on the copolymer properties were investigated, and the results revealed that the obtained polymer films strongly depended on the polymerization conditions. The obtained copolymers showed good redox stability in acetonitrile-based electrolyte solution. Band gap energy of the homo- and copolymer films was estimated and the values were between 1.95-2.11 eV. The electrical conductivity measurements of selenophene-3-chlorothiophene copolymers were successfully achieved using a four-probe technique and generally increased with increasing temperature. Fourier transform infrared (FTIR) characterization disclosed that the bands of homopolymers were retained in the spectra of copolymers with typical assignments suggesting that α-positions in the polymer chains were involved in the polymerization.

Avoiding compositional drift during the RAFT copolymerization of N-(2-hydroxypropyl)methacrylamide and N-acryloxysuccinimide: towards uniform platforms for post-polymerization modification

Compositionally uniform copolymers: avoiding compositional drift during RAFT copolymerization by controlling monomer feed ratio and conversion.

Liquid crystal alignment behavior on sulfonated poly(arylene ether sulfone) films

A series of sulfonated poly(arylene ether sulfone) (PAES#, # is the feed monomer ratio of 3,3′-disulfonate-4,4′-dichlorodiphenylsulfone) derivatives were synthesized to investigate the liquid crystal (LC) alignment property of these polymer films.

UV-absorbent lignin-based multi-arm star thermoplastic elastomers.

Lignin-grafted copolymers, namely lignin-graft-poly(methyl methacrylate-co-butyl acrylate) (lignin-g-P(MMA-co-BA)), are synthesized via "grafting from" atom transfer radical polymerization (ATRP) with the aid of lignin-based macroinitiators. By manipulating the monomer feed ratios of MMA/BA, grafted copolymers with tunable glass transition temperatures (-10-40 °C) are obtained. These copolymers are evaluated as sustainable thermoplastic elastomers (TPEs). The results suggest that the mechanical properties of these TPEs lignin-g-P(MMA-co-BA) copolymers are improved significantly by comparing with those of linear P(MMA-co-BA) copolymer counterparts, and the elastic strain recovery is nearly 70%. Lignin-g-P(MMA-co-BA) copolymers exhibit high absorption in the range of the UV spectrum, which might allow for applications in UV-blocking coatings.

Ambient temperature living radical copolymerization of styrene and methyl methacrylate with sodium hypophosphite as reducing agent

A facile, safe and economical reducing agent, sodium hypophosphite (NaH2PO2·H2O), has been successfully employed for ambient temperature living radical copolymerization of styrene (St) and methyl methacrylate (MMA). Such effective reducing agent significantly improved the reactivity of low reactive St monomers during the copolymerization, where the reactivity ratios of St and MMA were determined to be 0.50 and 0.36 by Finemann-Ross method. Thus the copolymerizations proceeded fast and showed typical living/controlled features, as evidenced by pseudo first-order kinetics of polymerization, linear increase in molecular weight versus monomer conversion, and low polydispersity index values. Effects of the concentration of reducing agent and the monomer feed ratio on the copolymerization were investigated in detail. Furthermore, gel permeation chromatography and 1H-NMR analyses as well as chain extension experiments confirmed the high chain-end functionality of the resultant copolymer.

Estimating Monomer Sequence Distributions in Tetrapolyacrylates

Recently Ting et al. [ACS Macro Lett. 2013, 2, 770−774] described the syntheses of acrylic tetrapolymers with controlled molecular weights and tetramonomer compositions. Relative reactivity ratios of all monomer pairs were determined and used in the Walling–Briggs terminal copolymerization model along with Skeist’s equations to address the expected compositional drift in the monomer feed ratios. The anticipated control of monomer incorporation based on this approach was verified experimentally on several tetrapolyacrylates synthesized by RAFT polymerization, which additionally controlled their molecular weights. Their “new and simple paradigm combining both predictive models provides complementary synthetic and predictive tools for designing macromolecular chemical architectures with hierarchical control over spatially dependent structure–property relationships for complex applications” is extended here to the derivation of expected monad compositions, and diad, triad, and tetrad monomer sequence distributions. These were obtained directly from the comonomer reactivity ratios determined experimentally by Ting et al. Our motivation was twofold: (i) The similar chemical structures of the four acrylate monomers they selected (methyl, 2-carboxyethyl, 2-hydroxypropyl, and 2-propylacetyl acrylate) render the experimental determination of sequence distributions in the resulting tetrapolyacrylates problematic. (ii) Because they are spatially dependent structural parameters, the sequence distributions of monomer diads, triads, tetrads, etc., in co-, tri-, tetrapolymers, etc., are generally expected to correlate more closely with their properties than their overall compositions.

Unprecedented 3,4-Isoprene and cis-1,4-Butadiene Copolymers with Controlled Sequence Distribution by Single Yttrium Cationic Species

Precisely controlling the stereochemistry of a copolymerization by single catalyst, and achieving copolymers with predicted sequences, is a challenging project in organometallic and macromolecular sciences. This article reports that the copolymerization of isoprene and butadiene with the 3,4- and cis-1,4 different regioselectivities has been accessed through employing a pyridylmethylene functionalized fluorenyl ligated yttrium cationic species. The thus unprecedented regularity combination is attributed mainly to the backbiting interaction of the penultimate unit of the polymer chain to the active central metal ion according to the DFT calculation. Moreover, the compositions can be adjusted by regulating the monomer feed ratio according to the copolymerization kinetics study.

Conductivity Measurements of Electrochemically Synthesized Selenophene–Thiophene Conducting Materials: Effect of Temperature and Polymerization Solution

The electrical conductivity measurements of selenophene-thiophene copolymers were successfully achieved using a four-probe technique. The influence of the polymerization solution, the applied polymerization potential and the monomer feed ratio on the electrical conductivity was investigated. The conductivity of obtained films generally increased with increasing temperature, implying more electrons might acquire enough energy to move from the valence to the conducting band.

A high molecular weight acrylonitrile copolymer prepared by mixed solvent polymerization: I. effect of monomer feed ratios on polymerization and stabilization

A bifunctional comonomer β-methylhydrogen itaconate (MHI) was employed to prepare high molecular weight poly[acrylonitrile-co-(β-methylhydrogen itaconate)] [P(AN-co-MHI)] copolymers by radical polymerization in a mixed solvent of dimethyl sulfoxide/deionized water = 60/40 (wt/wt), which was used as a carbon fiber precursor instead of acrylonitrile terpolymers for improving the stabilization and spinnability simultaneously. The structure and stabilization of P(AN-co-MHI) copolymers with different monomer feed ratios were characterized by elemental analysis (EA), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The results show that both the polymerization conversion and molecular weight reduce with the increase of MHI content in the feed due to the larger molecular volume of MHI. The monomer reactivity ratios were calculated by Fineman–Ross and Kelen–Tüdõs methods and the reactivity of MHI is higher than that of AN. Two parameters Es = A1618 cm−1/A2244 cm−1 and SI = (I0 − Is)/I0 were defined to evaluate the extent of stabilization and the activation energy (Ea) of the cyclization. The FTIR, XRD and DSC results show that P(AN-co-MHI) copolymers exhibit significantly improved stabilization characteristics than the PAN homopolymer and poly(acrlonitrile–methyl acrylate–acrylic acid) terpolymer, such as a larger extent of stabilization, lower initiation temperature and smaller Ea of cyclization, which is attributed to the ionic initiation of the MHI comonomer and is beneficial for preparing high performance carbon fiber.

Electrochemical deposition and characterization of carboxylic acid functionalized PEDOT copolymers

Abstract

Acrylate copolymers containing benzimidazolium moieties: synthesis and antimicrobial applications

AbstractThe allylic monomer N-allyl-N-butylbenzimidazolium bromide (ABBB) was synthesized by reacting allyl bromide with benzimidazole and subsequent quaternization with 1-bromobutane. Copolymers of ABBB with butyl acrylate (BA) were prepared in dimethyl formamide solution at 70°C using a free-radical polymerization technique with different monomer feed ratios. Monomer reactivity ratios for the ABBB-BA pairs were evaluated by the Fineman-Ross (r1=0.40; r2=1.49) and Kelen-Tüdõs (r1=0.36; r2=1.46) linearization methods. Thermal behavior of the copolymers of different compositions was evaluated by thermogravimetric analysis. The copolymers were tested for antimicrobial properties against selected strains of bacteria and fungi and were found to be active against the strains. The growth-inhibitory effect of the copolymers varied according to the composition of the polymer: the effect increased with increasing content of the substituted benzimidazolium group in the polymer chain.

Electrocoated Films of Poly(N-Methylpyrrole-co-2,2′-Bithitiophene-co-3-(Octylthiophene)), Characterizations, and Capacitor Study

N-Methylpyrrole (N-MPy), 2,2′-bithiophene (BTh), and 3-(Octylthiophene) (OTh) were electrocopolymerized in 0.2 M NaClO4/CH3CN on glassy carbon electrode (GCE). The resulting terpolymers of N-MPy, BTh and OTh in different initial monomer feed ratios such as [N-MPy]0/[BTh]0/[OTh]0 = 1/1/1 and 1/2/5 were characterized by cyclic voltammetry (CV), Fourier-transform infrared attenuated total reflectance spectroscopy (FTIR-ATR), scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), and electrochemical impedance spectroscopy (EIS). The capacitive behaviors of the modified electrodes were defined via Nyquist, Bode-magnitude, Bode-phase, and Admittance plots. The equivalent circuit model of Rs(C dl1 (R 1 (QR 2 )))(C dl2 R 3 ) was performed to fit the theoretical and experimental data. The low-frequency capacitance (CLF) were obtained from initial monomer concentrations of 50 mM as CLF = ∼2.34 × 10−4 mFcm−2 for P(N-MPy), CLF = 5.06 × 10−4 mF cm−2 for P(BTh), CLF = 5.07 m F cm−2 for P(OTh), and CLF = ∼3.78 m Fcm−2 for terpolymer for [N-MPy]0/[BTh]0/[OTh]0 = 1/1/1. The terpolymer may be used as energy storage devices.

Reactivity ratios and sequence structures of the copolymers prepared by photo-induced copolymerization of MMA with MPMP

The copolymers were prepared by the photo-induced copolymerization of methyl methacrylate (MMA, M 1 ) with 4-methacryloyl-1,2,2,6,6-pentamethyl-piperidine (MPMP, M 2 ) in benzene solution at ambient temperature. The reactivity ratios for these monomers were measured by running a series of reactions at various feed ratios of initial monomers, and the copolymer compositions were determined by 1H NMR spectroscopy. The reactivity ratios of the monomers were found to be r 1 = 0.28 and r 2 = 1.63 by the application of extended Kelen-Tudos method. The results showed that, MMA preferred to copolymerization while MPMP tended to homopolymerization in the copolymerization system. The sequence structures of the MMA/MPMP copolymers were characterized by 1H NMR spectroscopy. The backbone structures of the MMA/MPMP copolymers were mainly composed of a syndiotactic and an isotactic configuration. Three kinds of the sequences of rr, rr’ and lr’ in the syndiotactic configuration and two kinds of the sequences of km’ and mm’ as the isotactic configuration were found. The sequential distribution and the sequence-length distribution in the MMA/MPMP copolymers were also obtained.

Synthesis and characterizations of waterborne poly(acrylate) latexes

Aqueous emulsions used as binders in solvent-free paint formulations have to cope with the challenge to guarantee an excellent film formation and appearance as well as good properties. One strategy to fulfill these contradictory requirements is the employment of pure poly(acrylate) resins synthesized by emulsion polymerization. Kinetic studies involving free radical emulsion polymerization of methyl methacrylate (MMA)- co- n-butyl acrylate (BA) are carried out, so that the effect of BA on polymerization of MMA can be interpreted. In this study, the effect of emulsifier and initiator on the kinetics of polymerization was studied. The polymers were characterized using different analytical tools. The surface tension and contact angle of latexes were also measured by varying the concentration of monomer feed ratios. The results indicated that the incorporation of comonomer enhances the properties of coating formulation of polyacrylates.

New electrochromic copolymers based on spiro bipropylenedioxythiophene and 3,4-ethylenedioxythiophene

Two alkylenedioxythiophene derivatives, spiro bipropylenedioxythiophene (Spiro-BiProDOT) and 3,4-ethylenedioxythiophene (EDOT), were integrated electrochemically in order to attain low band gap electrochromic copolymers. EDOT has a functionality of two, which causes a linear polymer, whereas Spiro-BiProDOT has a functionality of four and its polymerization results in a network polymer. Therefore, by playing the monomer feed ratio, the crosslink degree can be adjusted for the copolymers obtained electrochemically from EDOT and Spiro-BiProDOT monomers in an electrolyte solution of 0.1M tetrabutyl ammonium hexafluorophosphate dissolved in dichloromethane. It was found that copolymers showed different electrochemical and optical properties at their various redox states when compared to their homopolymers. For example, they could be switched from dark blue in the neutral state to reddish blue at intermediate state and finally to transparent blue in the oxidized state with 45–51% of the transmittance change at 575–595nm. π–π* transition bands of the copolymers can be shifted to higher wavelengths when compared to poly(Spiro-BiProDOT) by increasing the amount of the EDOT units in the polymer backbone. They have low band gaps in the range of 1.65 and 1.73eV.

Pd(II) complexes bearing di‐ and monochelate fluorinated β‐ketonaphthyliminato ligand and their catalytic properties towards vinyl‐addition polymerization and copolymerization of norbornene and ester‐functionalized norbornene derivative

Fluorinated β‐ketonaphthyliminate ligand CF3C(O)CHC[HN(naphthyl)]CH3 (L1) and Pd(II) complexes with dichelate fluorinated β‐ketonaphthyliminato ligand, {CF3C(O)CHC[N(naphthyl)]CH3}2Pd (C1), as well as with monochelate fluorinated β‐ketonaphthyliminato ligand, {CF3C(O)CHC[N(naphthyl)]CH3}Pd(CH3)(PPh3) (C2), were synthesized and their solid‐state structures were confirmed using X‐ray crystallographic analysis. The Pd(II) complexes were employed as precursors to catalyze norbornene (NB) homo‐ and copolymerization with ester‐functionalized NB derivative using B(C6F5)3 as a co‐catalyst. High activity up to 2.3 × 105 gpolymer molPd−1 h−1 for the C1/B(C6F5)3 system and 3.4 × 106 gpolymer molPd−1 h−1 for the C2/B(C6F5)3 system was exhibited in NB homopolymerization. Moreover, the Pd(II) complexes exhibited a high level of tolerance towards the ester‐functionalized MB monomer. In comparison with the C1/B(C6F5)3 system, the C2/B(C6F5)3 system exhibited better catalytic property towards the copolymerization of NB with 5‐norbornene‐2‐carboxylic acid methyl ester (NB‐COOCH3), and soluble vinyl‐addition‐type copolymers were obtained with relatively high molecular weights (3.6 × 104–7.5 × 104 g mol−1) as well as narrow molecular weight distributions (1.49–2.15) depending on the variation of monomer feed ratios. The NB‐COOCH3 insertion ratio in all copolymers could be controlled in the range 2.8–21.0 mol% by tuning a content of 10–50 mol% NB‐COOCH3 in the monomer feed ratios. Copolymerization kinetics were expressed by the NB and NB‐COOCH3 monomer reactivity ratios: rNB‐COOCH3 = 0.18, rNB = 1.28 were determined for the C1/B(C6F5)3 system and rNB‐COOCH3 = 0.19, rNB = 3.57 for the C2/B(C6F5)3 system using the Kelen–Tüdõs method. Copyright © 2014 John Wiley & Sons, Ltd.

Bio-based polyamide 11: Synthesis, rheology and solid-state properties of star structures

Polyamide 11 (PA11) is a bio-based technopolymer synthesized using 11-aminoundecanoic acid from castor oil. In this work star-shaped PA11 structures are obtained via one-pot copolycondensation of 11-aminoundecanoic acid with a multifunctional agent, either 3-functional bis hexamethylentriamine or tetra-functional 2,2,6,6-tetra[β-carboxyethylcyclohexanone]. A theoretical model predicting the macromolecular complexity of the star shaped polycondensates that result from the reaction is used to interpret the rheological behavior of the synthesized samples, that is found to be strongly affected by the presence of branching. It is shown that melt properties can be modulated, for easier processability, by simply controlling monomer feed ratio and conversion of the copolycondensation reaction. In the range of comonomer functionality and content explored, thermal properties do not significantly vary with changing macromolecular architecture. All star-shaped polyamide samples easily crystallize and their structural characterization above room temperature shows that upon heating they reversibly undergo the alpha-gamma crystal phase transition that is typical of linear PA11. Investigation of the effect of branching on the mechanical properties shows that careful selection of chain controller type and amount allows to obtain star-shaped PA11 samples with ad-hoc modulated melt viscosity and preserved material’s mechanical performance.

Synthesis and drug‐release studies of low‐fouling zwitterionic hydrogels with enhanced mechanical strength

AbstractReversible addition–fragmentation chain‐transfer polymerization was introduced to prepare a series of zwitterionic poly(hydroxyethyl methacrylate)‐g‐poly(sulfobetaine methacrylate) (PSBMA) hydrogels (HSGs) with different monomer feed ratios. Compared with PSBMA hydrogels, these hydrogels exhibited enhanced mechanical strengths. Then, the HSGs were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, and swelling measurements. We found that the equilibrium swelling ratios, mechanical strengths, and drug‐release behaviors were significantly affected by the feed ratios of the gels. The hydrophilic tetracycline hydrochloride release results suggest that the hydrophilic drug release from the HSGs could be prolonged by the variation of the hydroxyethyl methacrylate amount in the gel networks. The bovine serum albumin adsorption data showed that the zwitterionic HSG with 18.2 wt % sulfobetaine methacrylate exhibited good protein‐resistance properties. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 41041.