True Copolymers Research Articles

The cyclopentadienyltitanium trichloride/MAO-catalysed polymerisation of methyl acrylate and copolymerisation with styrene and isoprene

The polar electron-deficient alkene methyl acrylate was readily polymerised in good yield by the CpTiCl3-MAO system to give a polymer with a relatively low molecular weight, but reasonable polydispersity. The polymer appears to be atactic. The same system also gave a random sequence 1:1 copolymer of methyl acrylate and styrene, which according to NMR and SEM studies was a true copolymer rather than a blend.

Spectroelectrochemistry of intrinsically conducting aniline–thiophene copolymers

Copolymers of aniline and thiophene prepared electrochemically were studied with elemental analysis, cyclic voltammetry, in situ UV–vis spectroscopy and conductivity measurements. The influence of the feed ratio, the mode and electrode potential of deposition and the composition of the deposition solution were studied in order to verify the obtained polymers as true copolymers or merely composites or mixtures.

Electrochemical synthesis of polylayer compositions from precursors of the thiophene series

Homopolymers based on 3,4-ethylenedioxythiophene (EDT) and bi(3,4-ethylenedioxythiophene) (BEDT) and polylayer compositions polymerized anodically from these precursors and bithiophene (BT) were studied electrochemically and spectroelectrochemically. The homopolymers obtained from EDT and BEDT were shown to have practically the identical properties although their polymerization potentials differ significantly. At close potentials, a true copolymer based on EDT and BT was formed. At different polymerization potentials (BEDT–BT system), a composition including numerical thin (up to 10 nm) polymeric layers was obtained potentiodynamically. In the electro- and spectroelectrochemical properties, this composition was like the true EDT–BT copolymer that was explained by the precursor copolymerization and the incorporation of one polymer into another. Independently of the polymerization potentials (EDT–BT, BEDT–BT systems), a composition from two- or four-thick (tens and hundreds nanometers) layers can be obtained galvanostatically. The first layer in such heterostructure always keeps the properties of its homopolymer. The properties of the second layer depend on the conductivity of the first layer in an oxidation region of the second layer. The first conducting layer facilitates the redox transformation of the second layer as compared to its homopolymer while the first isolating layer hinders this process.

Styrene copolymerization using diphenylzinc‐additive initiator systems: styrene/p‐substituted styrenes

AbstractCombined systems including diphenylzinc (Ph2Zn), a metallocene, and methylaluminoxane (MAO), have been employed to initiate the copolymerization of styrene (S) with p‐alkylsubstituted styrenes and with α‐olefins. The copolymerization processes depend largely on the comonomer, the nature of the metallocene included in the initiator system, the presence of Ph2Zn, the polymerization temperature and the solvent used. Titanocenes produced true copolymers for S/p‐substituted styrene, but not in S/α‐olefin copolymerization. On the other hand zirconocenes either did not copolymerize S/p‐substituted styrene or produced very low conversions, while they succeeded in copolymerizing S/α‐olefin, depending on the particular zirconocene employed. A low p‐methylstyrene (p‐MeS) content in the S/p‐MeS copolymer and a low p‐tertbutylstyrene (p‐ButS) content in the S/p‐ButS copolymer decreased Tm, making them easier to process material than s‐PS.

Microbial synthesis of poly(beta-hydroxyalkanoates) bearing phenyl groups from pseudomonas putida: chemical structure and characterization.

New poly(beta-hydroxyalkanoates) having aromatics groups (so-called PHPhAs) from a microbial origin have been characterized. These polymers were produced and accumulated as reserve materials when a beta-oxidation mutant of Pseudomonas putida U, disrupted in the gene that encodes the 3-ketoacyl-CoA thiolase (fadA), was cultured in a chemically defined medium containing different aromatic fatty acids (6-phenylhexanoic acid, 7-phenylheptanoic acid, a mixture of them, or 8-phenyloctanoic acid) as carbon sources. The polymers were extracted from the bacteria, purified and characterized by using (13)C nuclear magnetic resonance spectroscopy (NMR), gel permeation chromatography (GPC), and differential scanning calorimetry (DSC). Structural studies revealed that when 6-phenylhexanoic acid was added to the cultures, an homopolymer (poly-3-hydroxy-6-phenylhexanoate) was accumulated. The feeding with 8-phenyloctanoic acid and 7-phenylheptanoic acid leads to the formation of copolymers of the corresponding units with the n - 2 carbons formed after deacetylation, copoly(3-hydroxy-8-phenyloctanoate-3-hydroxy-6-phenylhexanoate) and copoly(3-hydroxy-7-phenylheptanoate-3-hydroxy-5-phenylvalerate), respectively. The mixture of 6-phenylhexanoic acid and 7-phenylheptanoic acid gave rise to the corresponding terpolymer, copoly(3-hydroxy-7-phenylheptanoate-3-hydroxy-6-phenylhexanoate-3-hydroxy-5-phenylvalerate). Studies on the chemical structure of these three polyesters revealed that they were true copolymers but not a mixture of homopolymers and that the different monomeric units were randomly incorporated in the macromolecular chains. Thermal behavior and molecular weight distribution were also discussed. These compounds had a dual attractive interest in function of (i) their broad use as biodegradable polymers and (ii) their possible biomedical applications.

Homo- and copolymerisation of norbornene and styrene with nickel bis(acetyl acetonate)/methylaluminoxane system

The homo and copolymerisations of norbornene and styrene with nickel bis(acetyl acetonate)/methylaluminoxane system were systematically investigated. This catalytic system shows a high activity towards homopolymerisation of both norbornene and styrene. For random copolymerisation, an increase in the initial styrene feed content leads to a gradual loss of activity relative to norbornene homopolymerisation. On the other hand, a drastic loss of activity, relative to styrene homopolymerisation, was found for very low norbornene feed contents. These results are qualitatively interpreted using the trigger coordination mechanism proposed by Ystenes. The structural characterisation of the polymers showed that norbornene polymerisation occurs via a 2,3 addition mechanism and that true copolymers are formed by random copolymerisation. At low styrene feed contents, only isolated styrene units or very short styrene sequences are present in the resulting copolymer. At higher styrene feed contents, short polystyrene sequences with more than eight styrene units may be formed. Determination of the reactivity ratios shows a much higher reactivity for norbornene ( r norbornene=17.8 and r styrene=0.16). Size exclusion chromatography measurements have shown that polynorbornenes possess high molecular weights. Relatively low molecular weights were observed for homopolystyrene and copolymers.

Electrochemical polymerization of aniline and toluidines on a thermally prepared Pt electrode

Abstract The polymerization of aniline (AN) and toluidines (o-toluidine (OTO)/m-toluidine (MTO)) was performed electrochemically on a Pt-coated titanium electrode in 1.0 M HCl using cyclic voltammetry. The results showed that the rate of polymerization was strongly dependent upon the type of monomer employed. The polymerization rate of these monomers on a Pt-coated electrode is in the order: AN>OTO>MTO. A kinetic expression for the autoacceleration process in the electrochemical polymerization of these aniline derivatives is expressed as v=k[p][M]+k′[M] in which k′, k, [M] and [p] are the initiation (nucleation process) rate constant, the rate constant when the polymer is deposited on the electrode, monomer concentration, and the total amount of polymer, respectively. The ratios of k′/k are 6.64×10−6, 3.23×10−6 and 3.15×10−6, respectively, for AN, OTO and MTO polymerization. The polymerization rate of these aniline derivatives is reduced with agitation of the monomeric solution. The experimental results of E1/2 for the first redox process showed that the AN–OTO or AN–MTO comonomer system generated true copolymers rather than the mixture of the corresponding homopolymers. The polymerization rates of these aniline derivatives on three different electrodes are in the order: IrO2>RuO2>Pt-coated electrode.

Homopolymerization and copolymerization of styrene and norbornene with Ni-based/MAO catalysts

The homopolymerization of styrene (Sty) and norbornene (NBE) was investigated in the presence of the nickel stearate (NiSt)/methylaluminoxane (MAO) catalytic system in toluene and in chlorobenzene at 20°C. The fully saturated structure of polynorbornene indicates that the two monomers polymerize by an ethylenic type addition reaction. The synthesis of true copolymers shows that one type of active species is operating for the tow monomers. Determination of reactivity ratios (rNBE = 20.8 and rSty = 0.02) indicates a much higher reactivity of NBE, which is interpreted by a coordination mechanism. The styrene-norbornene copolymers exhibit glass transition temperatures (Tg) which range from 100°C to 320°C and follow Kovacs' law. The absence of crystallinity and the homogeneous repartition of monomer units along the chains yield highly transparent materials of high thermal stability.

Homopolymerization and copolymerization of styrene and norbornene with Ni-based/MAO catalysts

The homopolymerization of styrene (Sty) and norbornene (NBE) was investigated in the presence of the nickel stearate (NiSt)/methylaluminoxane (MAO) catalytic system in toluene and in chlorobenzene at 20°C. The fully saturated structure of polynorbornene indicates that the two monomers polymerize by an ethylenic type addition reaction. The synthesis of true copolymers shows that one type of active species is operating for the tow monomers. Determination of reactivity ratios (rNBE = 20.8 and rSty = 0.02) indicates a much higher reactivity of NBE, which is interpreted by a coordination mechanism. The styrene-norbornene copolymers exhibit glass transition temperatures (Tg) which range from 100°C to 320°C and follow Kovacs' law. The absence of crystallinity and the homogeneous repartition of monomer units along the chains yield highly transparent materials of high thermal stability.

Electrochemical Polymerization of Aniline and Toluidine on RuO2‐Coated Titanium Electrodes

The polymerization of aniline (AN) and toluidines [o‐toluidine(OTO)/m‐toluidine(MTO)] was electrochemically performed on in 1.0 M HCl using cyclic voltammetry. The results showed that the rate of polymerization was strongly dependent upon the type of monomer employed. In comparison to the initial rates of AN polymerization, those were higher and lower for MTO and OTO, respectively. A kinetic expression for the autoacceleration process in the electrochemical polymerization of these aniline derivatives is expressed as in which k′, k, [M], and [p] are the initiation (nucleation process) rate constant, the rate constant when polymer deposited on the electrode, monomer concentration, and the total amount of polymer, respectively. The ratios of k′/k are , and , respectively, for AN, OTO, and MTO polymerization. The initial rate of polymerization for these aniline derivatives can be accelerated with slight agitation of the solution. The experimental results of E1/2 for the first redox process showed that the AN‐OTO or AN‐MTO comonomer system generated true copolymer rather than the mixture of the corresponding homopolymers.

Synthesis of Hydroxyl Group Containing Polyolefins with Metallocene/Methylaluminoxane Catalysts

Ethylene and propylene were copolymerized with 10-undecen-1-ol, using stereorigid Et[Ind]2ZrCl2, Me2Si[Ind]2ZrCl2, Me2Si[2-MeInd]2ZrCl2, and Me2Si[2-Me-4,5-BenzoInd]2ZrCl2 catalysts activated with methylaluminoxane (MAO). As a reference, ethylene copolymerization was also carried out with the nonstereospecific catalyst [Ind]2ZrCl2/MAO. Characterization of the copolymers by 13C and 1H NMR spectroscopy revealed that the polymerization product was a true copolymer and that the conversion of the polar comonomer was strongly favored by the chiral geometry of the catalyst. The pretreatment of 10-undecen-1-ol with MAO before initiating the copolymerization increased the ethylene polymerization rate markedly and slightly improved the reactivity of the polar comonomer. A major improvement in the polymerization rate of 10-undecen-1-ol was obtained when the polymerization temperature and Al/Zr mole ratio were increased.

Equation-of-State Analysis of Binary Copolymer Systems. 1. Screening Effect

The screening effect is introduced into the recently presented perturbed hard-sphere-chain (PHSC) equation of state for copolymer systems. Using reactivity ratios of copolymerization kinetics, the model first computes the number of specific monomer sequences in the copolymer consisting of monomers A and B. Some of the AB and BA monomer sequences (i.e., diads) are then replaced by BB sequences to represent the screening effect of segment B on segment A in AB and BA sequences. The essential characteristic of the screening effect is the assumption that the solution properties of a copolymer correspond to those of another copolymer whose composition differs from that of the true copolymer. The screening effect theory is used to calculate miscibility maps for several poly(styrene-co-methyl methacrylate) random copolymers that exhibit lower critical solution temperature behavior and significant deviation from the classical Flory-Huggins model. For a fixed temperature, there is good agreement between the theoretical miscibility map and experiment. To represent the temperature dependence of the miscibility map with temperature-independent parameters, it is necessary to consider diad interactions by modeling the copolymer consisting of monomers A and B as a terpolymer consisting of monomers A, B, and C that represent AA, BB, and AB and BA diads, respectively, of the copolymer.

The Assessment of Homogeneous Grafting of Cellulose Nitrate

Abstract The homogeneous grafting of polymethyl methacrylate onto cellulose nitrate has been assessed by the techniques of spectroscopy and microscopy combined with chemical procedures. FTIR spectroscopic and electron microscopic evidence confirmed the existence of a true graft copolymer. Homogeneous grafting took place in both the surface layer and the interior of the supermolecular structure of cellulose nitrate. X-ray diffraction provided further evidence that the grafting reaction also occurred in certain ordered domains of cellulose substrate. It is suggested that the free radical graft copolymerization for cellulose nitrate could be performed via a mechanism of denitration and enolization rather than dehydrogenation.

Copolymerization of styrene and ethylene with monocyclopentadienyltitanium trichloride/methylaluminoxane catalyst. Characterization of the product

Styrene and ethylene were copolymerized in the presence of a catalytic system based on CpTiCl 3 and methylaluminoxane. 13C-NMR, FTIR, GPC and calorimetric techniques were employed to study the structure of the polymerization product. The 13C-NMR spectrum showed only three resonances which could be assigned to the methylene and methine protons of syndiotactic polystyrene and to the aliphatic carbon of polyethylene. Thus, the polymer was not a true copolymer but a mixture of polystyrene and polyethylene. Two melting endotherms and two molecular weight distributions were observed. In addition, a very low molecular weight (boiling butanone soluble) fraction was isolated. The existence of several polymerization products suggests the presence of more than one active species in the catalyst.

Polymerization of pNcollagen I and copolymerization of pNcollagen I with collagen I. A kinetic, thermodynamic, and morphologic study.

Previous observations established that pNcollagen III copolymerized with collagen I and decreased the diameter of the fibrils formed (Romanic, A.M., Adachi, E., Kadler, K.E., Hojima, Y., and Prockop, D.J. (1991) J. Biol. Chem. 266, 12703-12709). Here, procollagen I alone or mixtures of procollagen I and pCcollagen I were incubated with procollagen C-proteinase to generate pNcollagen I or mixtures of pNcollagen I and collagen I. The results confirmed previous reports that pNcollagen I assembles into sheet-like structures. They also demonstrated that polymerization of pNcollagen I exhibits a lag period and propagation phase similar to those seen with other protein self-assembly systems. In addition, the results demonstrated that pNcollagen I formed true copolymers with collagen I in that the presence of pNcollagen I increased the lag time, decreased the propagation rate, and increased the concentration of collagen I in solution at equilibrium. Copolymerization of pNcollagen I with collagen I, however, differed in two features from copolymerization of pNcollagen III with collagen I. One was that, in confirmation of previous work, copolymerization of pNcollagen I with collagen I markedly altered the circularity of the fibrils formed. The second difference was that the copolymerization increased the concentration in solution at equilibrium of pNcollagen I whereas copolymerization with collagen I was previously shown to decrease the concentration in solution of pNcollagen III. The increase in concentration in solution of pNcollagen I was explicable either by the assembly of soluble oligomers of pNcollagen I and collagen I, or by subtle changes in the activities of pNcollagen I and collagen I in the solid-phase. Comparison with previous data with pNcollagen III indicated that although pNcollagen I and pNcollagen III copolymerize with collagen I, there are marked differences in the two kinds of copolymers.

Copolymerization of pNcollagen III and collagen I. pNcollagen III decreases the rate of incorporation of collagen I into fibrils, the amount of collagen I incorporated, and the diameter of the fibrils formed

Previous observations suggested that pNcollagen III, the partially processed form of type III procollagen, coats fibrils of collagen I and thereby helps regulate the diameter of fibrils formed by collagen I. The previous observations, however, did not exclude the possibility that pNcollagen III was deposited on preformed collagen I fibrils after the fibrils were assembled. Here, mixtures of pNcollagen III and collagen I were generated simultaneously by enzymatic cleavage of precursor forms of the proteins. The results demonstrated that pNcollagen III forms true copolymers with collagen I. The presence of pNcollagen III both inhibited the rate at which collagen I assembled into fibrils and decreased the amount of collagen I incorporated into fibrils at steady-state equilibrium. In addition, the results demonstrated that copolymerization of pNcollagen III with collagen I generated fibrils that were thinner than fibrils generated under the same conditions from collagen I alone. Increasing the initial molar ratio of pNcollagen III to collagen I in the solution-phase increased the amount of pNcollagen III copolymerizing with collagen I and progressively decreased the diameter of the fibrils. Therefore, the copolymers were heterogeneous in that the stoichiometry of the two monomers in the fibrils varied. The results are consistent with a model in which pNcollagen III can regulate the diameter of collagen I fibrils by coating the surface of the fibrils and thereby allow tip growth but not lateral growth of the fibrils.

Cationic Copolymerization of Epichlorohydrin with Styrene Oxide and with Cyclohexene Oxide

Abstract Cationic copolymerizations of epichlorohydrin (ECH) (chloro-methyl oxirane) with styrene oxide (SO) (phenyl oxirane) and with 1,2-cyclohexene oxide (CO) (7-oxabicyclo [410] heptane) were carried out at 50°C by employing the salt triphenylmethyl hexachloro-antimonate (HC) (Ph3CSbCl6) as initiator. NMR spectra before and after attempted extractions of the polymeric products indicated that the resulting polymeric products were true copolymers and not mixtures of the respective homopolymers. Monomer reactivity ratios for both pairs of comonomers were determined; for one pair the values were r 1(ECH) = 3.29, r 2(CO) = 0.16 and for the second pair r 1(ECH) = 0.57, r 2(SO) = 0.16.

Fibres from mixtures of rigid-chain and flexible-chain polymers

In the present article we make an attempt to generalize the incomplete literature material on the characteristics of mixtures of polymers where at least one of them is a rigidchain polymer, as applicable to fibre-forming polymers and to fibres based on them. From the behavioral features of the polymer mixtures and the complex of properties acquired by the mixed fibre, it seems advisable to subdivide mixtures of flexible- and rigid-chain polymers on the basis of the ratio of the two components in them (systems with a large and with a low content of the rigid-chain polymer). Phase Equilibria in Three-Component Systems Involving a Solvent and Rigid- and FlexibleChain Polymers. PPTA and other rigid-chain polyamides are lyotropic liquid-crystalli ne (LC) substances, since they do not melt up to the decomposition point and form the LC state only in solution. Another group of fibre-forming LC polymers, mainly aromatic polyesters and polyazomethines, is characterized by a weaker intermolecular interaction due the absence of hydrogen bonds, and melts at lower temperatures; they belong to the thermotropic substances. A transition from the crystalline to the LC state is effected on the melting of these substances. Phase separation has been studied as yet only for the lyotropic polymers. As concerns mixtures involving thermotropic polymers, investigation of these is attended with large difficulties, caused by the occurrence of slow exchange reactions between the heterochain polymers in the case where they are mixed at high melt temperatures. Thereupon, apparently a physical mixture of the polymers can exist only for a short time, being transformed with the passage of time into a block-copolymer and a true statistical copolymers. The phase equilibrium state in a solution of a rigid-chain polymer with rod-like mole

Copolymerization of elemental sulfur with styrene

Copolymerization of elemental sulfur with styrene in the presence and absence of metallic sodium was studied at 120°C and 138°C. Propagation of the reaction was followed by gel permeation chromatography (GPC). Glass transition temperatures of all samples were obtained by differential scanning calorimetry (DSC). Reaction products were fractionated with a preparative-type GPC, and each fraction was characterized by DSC, vapor pressure osmometry, infrared spectrophotometry, and both proton and carbon-13 nuclear magnetic resonance spectrometry. Results indicate that the product is a true copolymer of styrene and sulfur. Kinetics of the copolymerization were studied using GPC to monitor styrene and sulfur concentrations. The initial rate of copolymerization (as followed by the consumption of styrene and sulfur) decreases with increasing initial styrene to sulfur ratio. From kinetic analyses, ratios of the rate constants of homo- and copolymerization were determined. Copolymerization of the reactants is more spontaneous than homopolymerization. The reactivity ratios obtained are 0.2 for styrene and 0.6 for sulfur.

Quasiliving Carbocationic Polymerization. XII. Forced Ideal Copolymerization of lsobutylene with Styrene

Abstract Forced ideal carbocationic copolymerization of isobutylene/styrene systems has been achieved by continuous addition of mixed monomer feeds to 2-chloro-2,4,4-trimethylpentane/TiCl4 in n-hexane/methylene chloride charge by keeping the input rate equal to the overall rate of copolymerization. The composition of the copolymers was identical to that of the feeds over the entire monomer concentration range. The number-average molecular weight of the copolymers increased almost linearly with the amount of consumed monomers at higher isobutylene concentrations in the feed. The molecular weight increase was less pronounced at higher styrene concentration because more methylene chloride had to be used in the solvent system to keep the copolymer in solution. The micro-structure of the copolymers is uniform as determined by gel permeation chromatography (UV plus RI) and 13C-NMR spectroscopy According to these studies, true copolymers have formed. The probability of triads in the copolymer has been determined.