Copolymerization of N-carboxy Nϵ-carbobenzoxy L-lysine anhydride with N-carboxy β-benzyl L-aspartate anhydride in acetonitrile

Copolymerization of N-carboxy N^?-carbobenzoxy L -lysine anydride with N-carboxy β-benzyl L -aspartate anhydride was initiated with n-butylamine in acetonitrile. The copolymerization proceeded almost homogeneously except for the initial stage, when the proportion of N-carboxy anhydride (NCA) in the polymerization mixture varied from 25 to 75 mol %. This was due to the fact that the copolypeptides formed were soluble or highly swollen in the solvent, in contrast to the homopolymerization of NCAs such as N^?-carbobenzoxy L -lysine NCA and β-benzyl L -aspartate NCA in acetonitrile, which proceeds heterogeneously. The compositions of the copolymers obtained were, within experimental error, the same as their monomer feed compositions. The initial rates of copolymerization were almost the same as the rate of homopolymerization of β-benzyl L -aspartate NCA, which propagates with a nonhelical polypeptide, but were slower than the rate of homopolymerization of N^?-carbobenzoxy L -lysine NCA, which propagates with a helical polypeptide.     

Mechanism of alternating copolymerization of 4-hydroxy-4′-vinylbiphenyl with α-chloromaleic anhydride

The copolymerization of 4-hydroxy-4′-vinylbiphenyl (HVB) with α-chloromaleic anhydride (CMAn) was investigated in THF, 1,4-dioxane, and acetonitrile. The formation of the 1:1 charge transfer complex between HVB and CMAn was confirmed spectroscopically, and the corresponding equilibrium constant (K_eq) was determined as follows: K_eq = 0.19, 0.11, and 0.058 mol/L in THF, 1,4-dioxane, and CH₃CN, respectively. The copolymer composition is affected by the solvent, i.e., the content of HVB in the copolymer obtained in THF or 1,4-dioxane is lower than 50 mol % whereas the copolymer obtained in CH₃CN has excess of HVB units. The maximum rate of copolymerization was observed at a 1:1 initial comonomer mole ratio, irrespective of the solvent polarity. Plots of R_p/[HVB] vs. [HVB] gave a straight line with a slope and an intercept for the copolymerization in THF whereas a straight line in CH₃CN has no slope. On the basis of these results and ¹³C-NMR spectra of the copolymers, the mechanism of the predominant formation of alternating copolymers is discussed.     

Polymerization of α-amino acid N-carboxy anhydrides. III. Mechanism of polymerization of L- and DL-alanine NCA in acetonitrile

The polymerization of L - and DL -alanine NCA initiated with n-butylamine was carried out in acetonitrile which is a nonsolvent for polypeptide. The initiation reaction was completed within 60 min.; there was about 10% of conversion of monomer. The number-average degree of polymerization of the polymer obtained increased with the reaction period, and it was found to agree with value of W/I, where W is the weight of the monomer consumed by the polymerization and I is the weight of the initiator used. The initiation reaction of the polymerization was concluded as an attack of n-butylamine on the C₅ carbonyl carbon of NCA. The initiation, was followed by a propagation reaction, in which there was attack by an amino endgroup of the polymer on the C₅ carbonyl carbon of NCA. The rate of polymerization was observed by measuring the CO₂ evolved, and the activation energy was estimated as follows: 6.66 kcal./mole above 30°C. and 1.83 kcal./mole below 30°C. for L -alanine NCA; 15.43 kcal./mole above 30°C., 2.77 kcal./mole below 30°C. for DL -alanine NCA. The activation entropy was about ?43 cal./mole-°K. above 30°C. and ?59 cal./mole-°K. below 30°C. for L -alanine NCA; it was about ?14 cal./mole-°K. above 30°C. and ?56 cal./mole-°K. below 30°C. for DL -alanine NCA. From the polymerization parameters, x-ray diffraction diagrams, infrared spectra, and solubility in water of the polymer, the poly-DL -alanine obtained here at a low temperature was assumed to have a block copolymer structure rather than being a random copolymer of D - and L -alanine.     

Multichain copoly(α-amino acid). III. Multichain copoly(α-amino acid) prepared by the reaction of copoly(L-lysine γ-methyl-L-glutamate) with N-carboxy anhydride of β-benzyl L-aspartate

Graft copolymerization of N-carboxy anhydride of β-benzyl-L -aspartate onto copoly(L -lysine γ-methyl-L -glutamate) was carried out in N,N-dimethylformaide which contained 3 v/v% of dimethyl sulfoxide to obtain multi-N^ε-poly(β-benzyl-L -aspartyl)copoly(L -lysine γ-methyl-L gluta mate). The degree of polymerization of the branch chain attained was much influenced by the interval of the grafting sites of the copoly(L -lysine γ-methyl-L -glutamate). The solvent-induced two-step conformational transition of the multichain copoly(α-amino acid) was observed in the chloroform-dichloroacetic acid system at 25°C by the ORD technique. The stability of the α-helical conformation of the backbone polymer chain was decreased by the presence of poly(β-benzyl-L -aspartyl) branch chains that could form unstable α-helical conformations of opposite spirals.     

Radical copolymerization of maleimide with ethyl α‐ethylacrylate and α‐ethylacrylic acid via RAFT

The copolymerization of maleimide (MI) with α‐ethylacrylic acid (EAA) and with ethyl α‐ethylacrylate (EEA) in the presence of 2‐phenylprop‐2‐yl dithiobenzoate (PPDB) was investigated. The copolymerization of MI and EAA was difficult to conduct with the reversible addition–fragmentation chain transfer (RAFT) mechanism because reinitiation of expelled radicals by fragmentation chain transfer was inhibited by the association of EAA in polar solvent and the strong interaction of the imino of MI with the carboxyl of EAA between the propagation chains. When the carboxylic group of EAA was esterified, then the copolymerization went well via RAFT, and alternating copolymers with controlled molecular weight were obtained. Combining by electron spin resonance showed a different result. It was found that before 30% of the comonomer conversion had occurred, the copolymer poly(EEA‐co‐MI) showed increasing molecular weight with the conversion and a rather narrow molecular weight distribution; then the molecular weight of the copolymer began to retard. This phenomenon of retardation was aggravated at high temperature. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3828–3835, 2004     

Multichain copoly(α-amino acid). I. Multichain copoly(α-amino acid) prepared by reaction of copoly(L-lysine γ-methyl-L-glutamate) with N-carboxy anhydride of Nϵ-carbobenzyloxy-L-lysine

Polymerization of the N-carboxy anhydride of N^?-carbobenzyloxy-L -lysine in the presence of multifunctional polymeric initiator, copoly(L -lysine γ-methyl-L -glutamate) was studied in N,N-dimethylformamide containing 3% (v/v) of dimethyl sulfoxide. Multichain copoly(α-amino acid), i.e., multi-N^?-poly(N^?-carbobenzyloxy-L -lysine)copoly(L -lysine γ-methyl-L -glutamate), was obtained with linear poly(N^?-carbobenzyloxy-L -lysine) as by-product that could be removed by reprecipitation as was evidenced by gel-permeation chromatography. The degree of polymerization of the branch polymer chains estimated by the osmometric molecular weight determination and amino acid analysis was between 20 and 60, which decreased with increasing lysine content of the polymeric initiator. The stability of α-helical conformation of the multichain copoly(α-amino acid) was studied in the chloroform–dichloroacetic acid system at 25°C by the ORD technique. The α-helical conformation of poly(N^?-carbobenzyloxy-L -lysine) branches was less stable than those of linear poly(N^?-carbobenzyloxy-L -lysine) and the core molecular chains of the multichain copoly(α-amino acid).     

Emulsion copolymerization behavior of α-methylstyrene with methacrylonitrile

The emulsion copolymerization behavior of α-methylstyrene with methacrylonitrile is described. The effects of polymerization temperature, potassium persulfate initiator concentration, sodium lauryl sulfate emulsifier concentration on copolymer yield, molecular weight, and rate of copolymerization are described. The copolymer was found to have an azeotropic composition at 43 mole-% AMS. Reactivity ratios were determined to be 0.06 and 0.28 for AMS and MAN, respectively.     

Copolymerization of vinyl cyclohexane and α-methyl vinyl cyclohexane with acrylonitrile

Copolymerization of vinyl cyclohexane and α-methyl vinyl cyclohexane with acrylonitrile in the presence of a complexing agent AlEtCl₂ results in the formation of alternate copolymers. In the copolymerization of vinyl cyclohexane with acrylonitrile the copolymer composition depends on the ratio of acrylonitrile to AlEtCl₂. If this ratio is unity, alternating copolymers of the composition 1:1 are formed; with a ratio greater than unity statistical copolymers that contain more than 50% acrylonitrile units are produced. The ¹H-NMR spectroscopy measurements indicate that the interaction between the comonomers and the complexing agent leads to the formation of ternary donor–acceptor complexes of equimolar composition. The equilibrium constants of these complexes at ?60°C have been determined. The effects of temperature, nature of solvent and dilution on the yield, and composition of the copolymers of vinyl cyclohexane with acrylonitrile formed have been studied. By lowering the temperature the yield of copolymers increases but their composition remains equimolar. An increase in the polarity of the medium results in an increase in copolymer yield, whereas the yield decreases if the reaction is conducted in a donor-solvent medium. Dilution of the reaction mixture disrupts the alternation of units in the macrochain of copolymers. The kinetic pecularities of copolymerization have been investigated. The linear dependence of the copolymerization rate on the product of comonomer concentration is observed. The rate of copolymerization is proportional to the square root of the incident light intensity. Various additions of radical type and irradiation accelerate the process of copolymerization. The mechanism of alternating copolymerization of vinyl cyclohexane monomers with acrylonitrile in the presence of AlEtCl₂ is discussed in terms of homopolymerization of the comonomer complex.     

Polymerization of α-methylene-N-methylpyrrolidone

α-Methylene-N-methylpyrrolidone (α-MMP) was synthesized and homopolymerized by bulk and solution methods. The poly(α-MMP) is readily soluble in water, methanol, methylene chloride, and dipolar aprotic solvents at room temperature. Thermogravimetric analysis of poly(α-MMP) showed a 10% weight loss at 330°C in air. The kinetics of α-MMP homopolymerization and copolymerization were investigated in acetonitrile, using azobisisobutyronitrile (AIBN) as an initiator. The rate of polymerization R_p could be expresed by R_p = k[AIBN]^0.49[α-MMP]^1.3. The overall activation energy was calculated to be 84.1 kj/mol. The relative reactivity ratios of α-MMP (M₂) copolymerization with methyl methacrylate (r₁ = 0.59, r₂ = 0.26) in acetonitrile were obtained. Applying the Q-e scheme led to Q = 2.18 and e = 1.77. These Q and e values are larger than those for acrylamide derivatives.     

Alternating copolymerization of styrene and methyl α-chloroacrylate with diethylaluminum chloride

The alternating copolymerization of styrene and methyl α-chloroacrylate (MCA) with diethylaluminum chloride (Et₂AlCl) in benzene at 0°C has been investigated. The copolymer has an equimolar composition irrespective of the feed monomer composition, the copolymer yield and the amount of Et₂AlCl used. The copolymerization proceeds first very rapidly and then rather slowly after attaining a certain yield which varies proportionally to the amount of Et₂AlCl used. A maximum copolymer yield is observed at about 60% MCA feed composition. The ¹H-NMR analyses of dyad, triad, and pentad of the alternating deuterated α-d-St-MCA copolymer indicate that the configuration of this copolymer can be explained by a single parameter, coisotacticity σ(σ = 0.69). A favorable mechanism of the alternating propagation as well as of the stereoregularity control is discussed.     

Living polymerization of α‐amino acid‐N‐carboxyanhydrides

This article reviews recent developments in the polymerization of α‐amino acid‐ N‐carboxyanhydrides (NCAs) to form polypeptides. Traditional methods used to polymerize these monomers are described, and limitations in the utility of these systems for the preparation of polypeptides with controlled molecular weights and narrow molecular weight distributions are discussed. The development of transition‐metal‐based initiators, which activate the monomers to form covalent active species, permits the formation of polypeptides via the living polymerization of NCAs. In these systems, polymer molecular weights are controlled by monomer‐to‐initiator stoichiometry, polydispersities are low, and block copolypeptides can be prepared. The scope and limitations of these initiators and their key features and mode of operation are described in detail in this highlight. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3011–3018, 2000     

Poly(β-amino acid)s. IV. Synthesis and conformational properties of poly(α-isobutyl-L-aspartate)

Poly(α-isobutyl-L -aspartate) was prepared by the polycondensation reaction of p-nitrophenyl ester of α-isobutyl-L -aspartate and the conformation of the poly(β-amino acid) was investigated by X-ray diffraction, polarized infrared, circular dichroism (CD), optical rotatory dispersion (ORD), and NMR spectroscopy. α-Isobutyl β-p-nitrophenyl-L -aspartate hydrochloride and hydrobromide were used as monomers and dimethylformamide, chloroform, and chlorobenzene, as solvents. A high-molecular-weight polymer with [η] 1.0 dl/g (dichloroacetic acid, 25°C) was formed in the polymerization of the hydrochloride in chloroform at 25°C. The X-ray diagram and polarized infrared spectrum of the stretched polymer film obtained from a chloroform solution suggested a cross-β-form as the most probable structure in the solid state. The CD spectra of the polymer in a 2,2,2-trifluoroethanol (TFE) solution and its film cast from the solution showed a peak at 205 nm and a trough at 190 nm which were assigned to a β-structure. The polymer was associated in chloroform. The NMR and ORD spectra in chloroform were similar to those in TFE, which suggests that the polymer also exists in the β-structure in chloroform. The addition of small amounts of dichloroacetic acid and sulfuric acid to chloroform and TFE solutions, respectively, destroyed the β-structure. A random copolymer of α-isobutyl-L -aspartate with β-alanine was also prepared by polycondensation reaction. The copolymer apparently did not form an ordered structure in the solid state or in solution.     

γ-Ray-induced copolymerization of carbon monoxide with cyclic ethers

The γ-ray copolymerization of carbon monoxide with cyclic ethers, such as ethylene oxide, phenyl glycidyl ether, 1,3-dioxolane, 2-vinyl-1,3-dioxolane, terahydrofuran, 1,4-dioxane, and acetaldehyde was studied. A yellowish or brownish powdery copolymer was obtained in most of the cases examined. The infrared spectra showed that copolymers containing the ester structural unit were produced in the copolymerization with cyclic ethers which have no vinyl groups, and that a copolymer containing a ketone structure was produced from cyclic ether having vinyl group. It was found that the copolymer with ethylene oxide also had a β-propiolactone ring structure at the chain end or the side chain. The copolymers were confirmed to be partially crystalline from the x-ray diffraction diagrams. Further, a ring-opening polymerizability of the cyclic ether by γ-radiation was discussed. And it was found that as the bond dissociation energy between the carbon–oxygen linkage of the cyclic ether is small, the polymer yield both in the homopolymerization and copolymerization with carbon monoxide is high. A mechanism for the copolymerization is proposed on the basis of the results.     

Multichain copoly(α-amino acid). II. Preparation and properties of multi-Nϵ-poly(γ-benzyl-L-glutamyl)copoly(L-lysine γ-methyl-L-glutamate)

A number of multi-N^?-poly(γ-benzyl-L -glutamyl)copoly(L -lysine γ-methyl-L -glutamate)s with branches having various degrees of polymerization and with various intervals of the grafting sites in the core molecule were prepared in N,N-dimethylformamide containing dimethyl sulfoxide by the reaction of N-carboxy anhydride of γ-benzyl L -glutamate with random copoly(L -lysine γ-methyl-L -glutamate)s of different composition with various anhydride-initiator ratios. The relationship between the intrinsic viscosity measured in a coil solvent, dichloroacetic acid (DCA), and the number-average molecular weight determined by osmometry was found to be expressed by the Mark–Houwink–Sakurada equation for the multichain copoly(α-amino acid)s which were made from the same polymeric initiator. The observed α values of the multichain copoly(α-amino acid)s in the equation were lower than that of linear poly(γ-benzyl-L -glutamate). The solvent induced helix–coil transition of the multichain copolymer was investigated in the chloroform?DCA system by the ORD technique. Two kinds of transition regions were clearly distinguished: The α-helices of the core molecules underwent the transition at lower DCA concentration and those of the branch chains at higher DCA concentration. The reduced viscosity of the multichain copoly-(α-amino acid) increased slightly between the two transition regions, in contrast to the large decrease in the reduced viscosity of linear poly(γ-benzyl-L -glutamate) during the helix–coil transition.     

Room-temperature polycondensation of β-amino acid derivatives. V. Synthesis of hydrophilic polyamide by the polycondensation of β-amino acid derivatives

N-(Hydroxyalkyl) β-alanine ester which was obtained from amino alcohol and acrylate yielded polyamide at room temperature in the presence of a basic catalyst. Alkali and alkali earth metal alkoxides had a strong catalytic effect on the room-temperature polycondensation of N-(hydroxyethyl)-β-alanine esters. The catalytic activity of metal alkoxides decreased in the order: Li > Na > K > Cs and Ca > Zn > Mg. Aluminum and titanium alkoxide had a weak catalytic effect, while boron (III), tin (IV), antimony (V), and tellurium (VI) alkoxides did not show any catalytic activity for the polycondensation. It was also found that solvent had an effect on the course of the polycondensation of N-(hydroxyethyl)-β-alanine esters, and the highest molecular weight polymer was formed only in methanol solution. The solid-phase polycondensation of the low molecular weight prepolymer resulted in a high molecular weight polymer with an inherent viscosity of 1.0 in the presence of a catalytic amount of phosphoric acid. The polymer obtained is hydrophilic and its moisture absorption is more than twice that of nylon 6.     

Terpolymerization kinetics of amino acid N‐carboxy anhydrides

Based on their versatility with respect to amino acid type and sequence, polypeptides have become attractive for a number of biological applications such as drug delivery, biomineralization, and drugs. N‐carboxy anhydride (NCA) polymerization is a convenient way to rapidly prepare high‐molecular weight polypeptides with good control over molecular weight and polydispersity. However, the kinetics of the incorporation of NCA monomers into copolypeptides during random copolymerization are poorly understood. Here, kinetic data is presented that allows insight into the NCA polymerization of a terpolymer composed of three commercially relevant amino acids, namely, glutamic acid, lysine, and tyrosine. Furthermore, kinetic data and copolymerization parameters from the copolymerization of binary mixtures of these three amino acid NCAs is used to make predictions of the terpolymer composition. This study provides access to the information necessary to prepare functional copolypeptides with better‐defined sequence architecture that will be essential for the future development of polypeptide‐based materials. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1228–1236     

Copolymerization of styrene. V. Copolymerization with α-cyanocinnamamide

Copolymers of styrene with α-cyanocinnamamide were prepared by free radical initiation in bulk and in DMF solution and also by thermal initiation in bulk. The copolymerization parameters were determined by the conventional scheme of copolymerization and by an improved scheme taking into account the penultimate unit. Different values of the copolymerization parameters were obtained at the above mentioned different polymerization conditions, indicating the existence of a solvent effect. The influence of the comonomer on some of the basic properties, like intrinsic viscosity, solubility, melting range, and glass transition temperature and on some mechanical and behavior properties of the copolymers was studied in comparison with homopolystyrene.     

γ-Ray-induced copolymerization of ethylene and vinyl chloride in liquid carbon dioxide

The γ-ray-induced copolymerization of ethylene and vinyl chloride with the use of liquid carbon dioxide as a solvent was studied under a total pressure of 400 kg/cm², with a dose rate of 2.5 × 10⁴ rad/hr at 30°C. A rubberlike, sticky polymer is obtained when the molar concentration of vinyl chloride is less than 30% in the monomer mixture, and the polymer is a white powder at higher concentrations of vinyl chloride. Infrared, x-ray, and differential thermal analyses confirm that the polymerization products are noncrystalline, true random copolymers. The rate of copolymerization decreases markedly when a small amount of vinyl chloride is added to ethylene monomer. In the range of vinyl chloride concentration higher than 5%, however, the rate and the molecular weight of copolymer increase with increasing concentration of vinyl chloride. It has been concluded from kinetic considerations based on these results that the rate of initiation increases proportionally with the concentration of vinyl chloride. Further, the growing chain radicals are shown to be deactivated by the cross-termination reaction between the radicals with terminal unit of ethylene and vinyl chloride, and no transfer reaction occurs.     

Polymerization of α-amino acid N-carboxy anhydrides initiated by histamine in N,N-dimethylformamide

The polymerization of α-amino acid N-carboxy anhydrides (NCAs) initiated by 4-aminoethylimidazole (histamine) was studied in order to synthesize poly(amino acids) containing an imidazole nucleus at the end of polymer chain. On the basis of the kinetical measurements, it was found that the rate of polymerization is proportional to the first order in both NCA and initiator concentrations and that the initiation reaction is predominantly caused by the primary amine with the highest basicity in a histamine molecule. Binding of the histamine fragment to the end of polymer chain was confirmed by elementary analysis, nuclear magnetic resonance spectroscopy, and measuring the number-average molecular weight of the resulting polymers. It was thus possible to prepare poly(amino acids) with a pendant histamine. In addition, the lowering of the number-average degree of polymerization of the polymers prepared was observed under the condition that the initial molar ratio of NCA to histamine was larger. It was caused by the reinitiation of polymerization by the imidazole nucleus at the chain end.     

Electroinitiated copolymerization of indene and α-methylstyrene

Electroinitiated cationic copolymerization of indene and α-methylstyrene in dichloromethane has been investigated by constant potential electrolysis. The effects of copolymerization potential and the temperature on the copolymer composition was also studied. Constant potential electrolysis was found to be a suitable method to study the potential effects on copolymer compositions and the reactivity ratios of the monomers. The reactivity ratios were calculated according to integrated Lewis–Mayo equation.