Comonomer Feed Ratio Research Articles

Condensation and Polycondensation of Terephthaldehyde with Methyl D-Hexopyranosides

The condensation and polycondensations of terephthaldehyde (1) and methyl D-hexopyranosides (gluco-, galacto- and mannopyranoside) are described. Methyl α-D-glucopyranoside and methyl α-D-galactopyranoside react with 1 to give mono-5 a and 6 a and diacetals 5 b and 6 b. Their structures were confirmed by NMR and IR spectroscopy. The polycondensation of methyl α-D-mannopyranoside (4) with 1 was studied in various solvents within the temperature range of 80–140°C. Regardless of the conversion or the initial comonomer feed ratios the composition of polycondensates depended on the reaction conditions leading to the formation of materials with diverse solubilities, molecular weights and optical properties. The regioselective polycondensation of 1 and 4 was examined by the 1H NMR spectroscopy of polymer 7. In the case of five-membered cyclic acetal units, mixtures of the endo-H and exo-H dioxolan-2-yl system diastereomers are formed. Experimental examples of functionalization via ester units in polymer molecules 8 are described and the efficiency of the reaction routes and procedures are evaluated. The molecular weight was estimated by size-exclusion chromatography (SEC) measurements before and after the functionalization.

Copolymerizations of ω-Pentadecalactone and Trimethylene Carbonate by Chemical and Lipase Catalysis

Copolymerizations of ω-pentadecalactone (PDL) with trimethylene carbonate (TMC) were studied using chemical and enzyme catalysts. By using stannous octanoate, methylaluminoxane (MAO), or aluminum isopropoxide, copolymerizations of PDL with TMC with 1:1 feed ratio resulted in either homo-polyTMC or PDL/TMC block copolymers. These catalysts polymerize TMC more rapidly than PDL. A copolymerization catalyzed by MAO gave poly(TMC-co-16 mol % PDL) with Mn 26.4 × 103g/mol and randomness numder (B) about 1.1. The sodium ethoxide-catalyzed copolymerization led to products with low Mn (<6.8 × 103) but nearly random sequence distribution. The copolymerization of PDL with TMC was also studied by using lipase catalysts. Of the six lipases evaluated for PDL/TMC copolymerizations in toluene at 70 °C, an immobilized form of lipase B from Candida antarctica (Novozyme-435) was preferred. Changing the PDL/TMC comonomer feed ratio from 1:10 to 10:1 (mol/mol) provided copolymers that ranged in Mn and PDL mol % from 7.3 × 103 to 25.2 × 103 and 28 to 88, respectively. In contrast to the chemical catalyst systems, Novozyme-435 catalysis showed that PDL was consumed more rapidly than TMC. Also, in contrast to most of the chemical catalysts, 1H and 13C NMR analyses showed that the copolymers from Novozyme-435 catalysis were able to give a random distribution of the repeat units at extended reaction times. Furthermore, in contrast to TMC polymerization in the presence of preformed polyPDL with MAO, Novozyme-435 catalyzed polymerization led to random copolymers.

Using Kinetics and Thermodynamics in the Controlled Synthesis of Low Molecular Weight Polymers in Free-Radical Polymerization

A simple way of controlling molecular weights in the free-radical copolymerization of styrene and α-methylstyrene (AMS) is presented and investigated by simulation via the program package PREDICI®. It is shown that the molecular weight of the product copolymers may be varied in a wide range (from M̄Cw = 500 to 2·106) by variation of the comonomer feed ratio and the reaction temperature. The reasons for this simple molecular weight control are associated with the AMS comonomer and are threefold: (i) AMS has a low propagation rate coefficient, due to the increased steric requirements of the monomer, (ii) AMS has a high transfer to monomer constant (CM) in comparison with styrene and (iii) AMS has a low ceiling temperature, so that the effective propagation rate coefficient decreases with increasing temperature. In addition to the styrene/AMS system, other comonomer systems showing similar kinetic and thermodynamic features (e. g. the styrene/methyl ethacrylate (MEA) system) may also be used to generate a wide range of molecular weights. The possibilities for controlling molecular weight and end group functionalities by replacing the slowly propagating monomer by a functional monomer are discussed.

Using Kinetics and Thermodynamics in the Controlled Synthesis of Low Molecular Weight Polymers in Free-Radical Polymerization

A simple way of controlling molecular weights in the free-radical copolymerization of styrene and a α-methylstyrene (AMS) is presented and investigated by simulation via the program package PREDICI®. It is shown that the molecular weight of the product copolymers may be varied in a wide range (from w = 500 to 2 · 106) by variation of the comonomer feed ratio and the reaction temperature. The reasons for this simple molecular weight control are associated with the AMS comonomer and are threefold: (i) AMS has a low propagation rate coefficient , due to the increased steric requirements of the monomer, (ii) AMS has a transfer to monomer constant (CM) in comparison with styrene and (iii) AMS has a low ceiling temperature, so that the effective propagation rate coefficient decreases with increasing temperature. In addition to the styrene/AMS system, other comonomer systems showing similar kinetic and thermodynamic features (e. g. the styrene/methyl ethacrylate (MEA) system) may also be used to generate a wide range of molecular weights. The possibilities for controlling molecular weight and end group functionalities by replacing the slowly propagating monomer by a functional monomer are discussed.

Electrochemical preparation and characterization of conducting copolymers : poly(pyrrole-co-indole)

Copolymerization of pyrrole and indole was achieved electrochemically in acetonitrile containing lithium perchlorate as supporting electrolyte. The copolymer compositions can be altered by varying the comonomer feed ratios during preparation. The copolymers were characterized by conductivity measurements, cyclic voltammetry, scanning electron microscopy, UV-visible and IR spectroscopic techniques. A possible scheme for the copolymerization mechanism has been suggested.

Ring-opening polymerization of oleochemical epoxides catalyzed by aluminoxane/acetyl acetone

Terminal epoxides based on oleochemicals were homopolymerized and copolymerized to high molecular weight polyethers ( M w=2.3 × 10 5–29.0 × 10 5 g/mol, GPC based on polystyrene calibration standards) with a comb structure using aluminoxanes/acetyl acetone catalysts. Poly(methyl ω-epoxy alkanoates) were achieved in yields of 56–92% after reaction times of 72 h at 100°C. ω-Epoxy undecenyl silyl ethers were polymerized in yields of 40–94% after 24 h. Copolymerization of 1,2-decene oxide with C 10, C 11 and C 14 ω-epoxy alkanoates was performed under identical conditions in almost quantitative yields in 24–48 h ( M w=1.5 × 10 5–8.3 × 10 5 g/mol). The copolymers exhibited compositions similar to the comonomer feed ratio. Sodium salts and polyacids from poly(methyl ω-epoxy alkanoates) were obtained by alkaline hydrolysis and neutralization with acetic acid. A poly(epoxy alcohol) was synthesized by cleaving the corresponding trimethylsilyl ether.

Synthesis and Characterization of Poly[(1-trimethylsilyl-1-propyne)-co-(1-(4-azidobutyldimethylsilyl)-1-propyne)] Copolymers

Poly(trimethylsilylpropyne) copolymers with bromobutyl side chains were synthesized from 1-trimethylsilyl-1-propyne and 1-(4-bromobutyldimethylsilyl)-1-propyne using a TaCl5/Ph3Bi catalyst system in toluene. After polymerization, azide groups were introduced into the polymers by phase transfer catalysis to yield poly[(1-trimethylsilyl-1-propyne)-co-(1-(4-azidobutyldimethylsilyl)-1-propyne)] copolymers. Results from thermal analyses, elemental analyses, and IR spectroscopy confirm that the azide content in the copolymers matches the original comonomer feed ratios. Films of the copolymers were thermally cross-linked in vacuo, with the rate of azide decomposition monitored by the loss of the azide absorption band in the IR. For a copolymer with 15 mol % azide content, an activation energy of 130 kJ/mol was calculated from IR data collected over the azide decomposition temperature range. For the copolymer with the highest azide content (20 mol %), DSC measurements give −1.2 kJ/g for the enthalpy of azide deco...

A Novel Series of Copolymers Containing 2,5-Dicyano-1,4-phenylenevinylene-Synthetic Tuning of the HOMO and LUMO Energy Levels of Conjugated Polymers

A series of copolymers of 2,5-dicyano-1,4-phenylenevinylene and 2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene were synthesized by Wittig reaction. The HOMO and LUMO energy levels of copolymers can be easily tuned by controlling the feed ratio of co-monomers.

A novel series of copolymers containing 2,5-dicyano-1,4-phenylene-vinylene--synthetic tuning of the HOMO and LUMO energy levels of conjugated polymers

A series of copolymers of 2,5-dicyano-1,4-phenylenevinylene and 2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylenevinylene were synthesized by Wittig reaction. The HOMO and LUMO energy levels of copolymers can be easily tuned by controlling the feed ratio of co-monomers.

Comparison of characteristics of SAN–MMT nanocomposites prepared by emulsion and solution polymerization

Nonextractable styrene-acrylonitrile copolymer-montmollironite (SAN- MMT) nanocomposites were prepared by two different intercalation process: (1) a usual one-step emulsion copolymerization in the presence of the Na 1 -MMT; and (2) a solution copolymerization with MMT modified by dimethyl dihydrogenated tallow ammonium. For comparative purposes, the copolymerization conditions (such as comonomer feed ratio and the polymerization temperature and times) were set up to be the same. The X-ray diffraction pattern demonstrated that the net increase of basal spacing of the purified emulsion products (0.76 nm) far exceeded that of composite (0.39 nm) prepared by solution method. The average molecular masses recovered from the composite extracts revealed Mw 5 53 3 10 4 for emulsion products, while the composite made by solution yielded Mw 5 4.8 3 10 4 g/mol. Likewise, the hybrid from the emulsion polymerization exhibited higher stress at maximum load over the solution products. The dispersibility of MMT particles in the polymer matrix was investigated by using optical microscopy (OM) and scanning electron microscopy (SEM) for those unextracted samples. It was found that almost complete hybrids were obtained when the styrene (ST)-acrylonitryl (AN) comonomer was emulsion polymerized in the presence of Na 1 - MMT, yielding both better miscibility and intercalation capability. © 1999 John Wiley &

Liposome fusion induced by pH‐sensitive copolymer: Poly(4‐vinylpyridine‐coN,N′‐diethylaminoethyl methacrylate)

Copolymers of 4-vinylpyridine (4VP) or N,N′-diethylaminoethyl methacrylate (DEAEMA) were synthesized with various comonomer feed ratios (30 : 70, 50 : 50, and 70 : 30). Charge densities along the polymeric chain were changed in a pH-dependent manner. The copolymers induced membrane fusion of negatively charged liposomes followed by aggregation in a pH-dependent manner, which was investigated by resonance energy transfer. It was found that pH-dependent fusion of liposomes was dependent on the composition of 4VP and DEAEMA in the copolymer with the degree of protonation proportional to the difference in pKa value of the two monomers. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2305–2309, 1999

Liposome fusion induced by pH-sensitive copolymer: Poly(4-vinylpyridine-co-N,N?-diethylaminoethyl methacrylate)

Copolymers of 4-vinylpyridine (4VP) or N,N′-diethylaminoethyl methacrylate (DEAEMA) were synthesized with various comonomer feed ratios (30 : 70, 50 : 50, and 70 : 30). Charge densities along the polymeric chain were changed in a pH-dependent manner. The copolymers induced membrane fusion of negatively charged liposomes followed by aggregation in a pH-dependent manner, which was investigated by resonance energy transfer. It was found that pH-dependent fusion of liposomes was dependent on the composition of 4VP and DEAEMA in the copolymer with the degree of protonation proportional to the difference in pKa value of the two monomers. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2305–2309, 1999

Electrochemical synthesis of highly electroactive polydiphenylamine/polybenzidine copolymer in aqueous solutions

Poly(diphenylamine- co-benzidine) has been synthesized by electrochemical copolymerization of diphenylamine with benzidine in aqueous solutions. The composition of the copolymer and thus the electroactivity and conductivity of copolymer could be altered by variation of the comonomer feed ratios. The rate of copolymer formation is much higher than the homopolymerization. Electrochemical investigations indicate that reactivity of diphenyl amine for polymer formation is greater than that of benzidine, because of stability of diradical cations of benzidine. The copolymer which is formed under optimum conditions is much more electroactive than the corresponding homopolymers. Cyclic voltammetric studies show that the electroactivities of both benzidine and diphenyl amine moieties are apparent in copolymers.

Synthesis, Modification, and Characterization of l-Lactide/2,2-[2-Pentene-1,5-diyl]trimethylene Carbonate Copolymers

This paper explores the copolymerization of l-lactide (l-LA) with 2,2-[2-pentene-1,5-diyl]trimethylene carbonate (cHTC). Since cHTC has a cyclohexene group, this provided a route for preparing poly(lactic acid), (PLA), based chains decorated with controlled quantities of CC substituents. Ring-opening copolymerizations of l-LA with cHTC were successfully conducted in bulk by using AlR3−H2O (R = ethyl, isobutyl), Al(OiPr)3, ZnEt2−H2O and Sn(Oct)2 as catalysts. Comparison of these copolymerizations showed that the Sn(Oct)2 catalyst system gave copolymers of relatively higher molecular weight. Increasing the reaction time of Sn(Oct)2 catalyzed copolymerizations from 6 to 24 h resulted in higher copolymer cHTC content and yield but lower copolymer molecular weight. Variation of the comonomer feed ratio was useful in regulating the content of cyclohexene pendant groups in the copolymer. However, regardless of the catalyst used, the mole percent of cHTC incorporated into the copolymer was lower than that used in the monomer feed. Determination of the comonomer reactivity ratios for Sn(Oct)2 catalyzed copolymerizations gave values of 8.8 and 0.52 for l-LA and cHTC, respectively. All gel permeation chromatography (GPC) traces showed unimodal molecular weight distributions. Determination by 13C-NMR of the copolymer sequence fractions HLL, LLL, LLH, HLH, HL, and LH (H = cHTC units, L = l-lactyl units) showed that they were close to those calculated by assuming a Bernoulli statistical propagation. On the basis of these results and the effects of reaction conditions on the copolymer sequence distribution, a mechanism which involves insertion of cHTC into the polymer chain was proposed. Studies by differential scanning calorimetry (DSC) showed that cHTC units in the copolymers disrupted ordering of the l-PLA crystalline phase. Furthermore, the glass transition temperatures (Tg) ranged from 60 (l-PLA) to 33 °C (P(cHTC)). Conversion of CC to epoxy side groups was successfully carried out by using 3-(chloroperoxy)benzoic acid at room temperature with only small decreases in copolymer molecular weight.

Titanocene−Methylaluminoxane Catalysts for Copolymerization of Styrene and Ethylene: Synthesis and Characterization of Styrene−Ethylene Copolymers

The copolymerization of styrene and ethylene has been performed using a titanocene-based catalytic system of cyclopentadienyltitanium triphenoxide (CpTi(OPh)3) and methylaluminoxane (MAO). The catalyst system exhibited a high catalytic activity of 104−105 g (mof Ti·h)-1 and was found to selectively (more than 90 wt %) give an elastoplastic and amorphous styrene−ethylene (S−E) copolymer with a well-defined random/alternating microstructure and a single glass transition (Tg) as thoroughly characterized by solvent fractionation, GPC, 13C NMR, DSC, and WAXD. Under the reaction conditions employed, up to 54.5 mol % of styrene could be introduced into the copolymer chains. The composition, microstructure, molecular weight of the copolymers, and catalytic activity of the copolymerization are strongly dependent upon the comonomer feed ratio, polymerization temperature (Tp), CpTi(OPh)3/MAO mole ratio, and trimethylaluminum (TMA) content or structure in MAO. For 300 ⩽ Al/Ti < 1000, the copolymerization product was ...

Aliphatic Phenylene Vinylene Copolymers: Tuning the Color of Luminescence through Co-monomer Feed Ratios

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTAliphatic Phenylene Vinylene Copolymers: Tuning the Color of Luminescence through Co-monomer Feed RatiosM. Hay and F. L. KlavetterCite this: J. Am. Chem. Soc. 1995, 117, 27, 7112–7118Publication Date (Print):July 1, 1995Publication History Published online1 May 2002Published inissue 1 July 1995https://doi.org/10.1021/ja00132a011RIGHTS & PERMISSIONSArticle Views370Altmetric-Citations87LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-AlertsSupporting Info (2)»Supporting Information Supporting Information Get e-Alerts

A high-field 13C-NMR study of the aqueous copolymerisation of acrylonitrile and vinyl acetate. Microstructural observations

A detailed examination has been undertaken of the high field 13C-NMR spectrum of various acrylonitrile/vinyl acetate copolymers prepared by radical initiation in a heterogeneous aqueous batch reaction (taken to low conversion). It has been possible to establish the triad, tetrad and pentad sequences for copolymers employing sequence patterns and peak fractions as an aid to peak assignments. These results indicate that the copolymer cotacticity is virtually independent of the comonomer feed ratio.

Electrochemical copolymerization of aniline with o-aminobenzonitrile

Electrochemical oxidative copolymerization of aniline with o-aminobenzonitrile in an aqueous acid solution gave a copolymer film with a polyaniline-like structure in which some of the phenyl rings had a cyananide group. For the copolymerization, the applied potential was cycled between −0.2 and 0.9 V vs. saturated calomel electrode at the rate of 50 mV s −1. The proportions of the two monomer units in the copolymer, which were calculated from their ir spectra, absorbance of CN of the o-aminobenzonitrile unit, changed as their comonomer feed ratio in the solution changed. Cyclic voltammograms of the resulting copolymer films were quite different from those of either homopolymer. The color of the copolymer films changed from blue, the color for the homopolymer of aniline, to gold, the color for the homopolymer of o-aminobenzonitrile, depending on the composition of the copolymer film.

Polyaniline Derivative with External and Internal Doping via Electrochemical Copolymerization of Aniline and 2,5‐Diaminobenzenesulfonic Acid on IrO2 ‐ Coated Titanium Electrode

Copolymerization of 2,5‐diaminobenzensulfonic acid (DABSA) and aniline (AN) was performed electrochemically by cyclic voltammetry on titanium electrodes in 1M . The copolymerization rate is strongly dependent on the amount of DABSA in the comonomer feed. The compositions of the copolymeric films were determined by x‐ray photoelectron spectroscopy and were controlled by changing comonomer feed ratios. The copolymer compositions can be expressed in terms of comonomer feed ratios by a simple copolymer model showing that the reactivity ratio of aniline increases by increasing the amount of DABSA in the comonomer feed. The composite film of DABSA‐AN copolymer with waterborne polyurethane was prepared and its conductivity was measured for comparing the effect of DABSA in the comonomer feed. Scanning electron microscope (SEM) photographs show that there exist clear differences in morphology of the polymer films at various DABSA concentrations.

Optically active polymers, 2. Copolymerization of limonene with maleic anhydride

AbstractCopolymerization of maleic anhydride (MA) and (R),(S)‐limonene (LIM) was studied in various solvents, using 2,2′‐azoisobutyronitrile (AIBN) and benzoyl peroxide (BPO) as initiators and radiation (60Co γ‐source) within the temperature range of 20–70°C. Regardless of conversion or initial comonomer feed ratios, the composition of LIM‐MA copolymers ranged from about 1 : 1 to 1 : 1,6 and was dependent on the reaction conditions, leading to a formation of materials with diverse solubilities, degrees of crosslinking and molecular weights. The main product consists of a 1 : 1 LIM‐MA copolymer with pendant 4‐methyl‐3‐cyclohexenyl residues. At higher conversion these alicyclic unsaturations lead to crosslinking. No reference to cyclocopolymerization was detected.