Mean Sequence Length Research Articles

Synthesis of 2-phenoxy-2-phenylethyl acrylate and copolymerization with 2-phenylethyl acrylate: Estimation of monomer reactivity ratios, thermal and optical properties

ABSTRACTA new aromatic based monomer 2-phenoxy-2-phenylethyl acrylate (PPEA) was synthesized. Copolymers of PPEA with 2-phenylethyl acrylate (PEA) were prepared by free radical polymerization. The reactivity ratios were estimated using various graphical methods. Structural parameters of the copolymers were obtained by calculating the dyad monomer sequence fractions and the mean sequence length. Optical properties of polymers such as refractive indices and UV-Visible absorption were investigated. The glass transition temperature and thermal degradation behavior of the copolymers were studied. Combined with the RI, transparency and thermal properties, prepared copolymers hold great promise as materials for intraocular lens applications.

Metallocene-mediated cationic polymerization of vinyl ethers: Kinetics of polymerization and synthesis and characterization of statistical copolymers

ABSTRACTThe cationic polymerization of ethyl, n-butyl and iso-butyl vinyl ether, EVE, BVE and iBVE, respectively, was efficiently conducted using bis(η5-cyclopentadienyl)dimethyl hafnium, Cp2HfMe2, or bis(η5-cyclopentadienyl)dimethyl zirconium, Cp2ZrMe2 in combination with either tris(pentafluorophenyl)borate, B(C6F5)3, or tetrakis(pentafluorophenyl)borate dimethylanilinum salt, [B(C6F5)4]−[Me2NHPh]+, as initiation systems. The evolution of polymer yield, molecular weight and molecular weight distribution with time was examined. In addition, the influence of the initiating system, the monomer and the reaction conditions on the control of the polymerization was studied. Furthermore, statistical copolymers of EVE with BVE were prepared employing Cp2HfMe2 and [B(C6F5)4]−[Me2NHPh]+ as the initiation system. The reactivity ratios were estimated using both linear graphical and non-linear methods. Structural parameters of the copolymers were obtained by calculating the dyad sequence fractions and the mean sequence length, which were derived using the monomer reactivity ratios. The glass transition temperatures, Tg, of the copolymers were measured by Differential Scanning Calorimetry, DSC, and the results were compared with predictions based on several theoretical models. The kinetics of thermal decomposition of the copolymers along with the respective homopolymers was studied by thermogravimetric analysis within the framework of the Ozawa-Flynn-Wall and Kissinger methodologies.

Statistical Ring Opening Metathesis Copolymerization of Norbornene and Cyclopentene by Grubbs' 1st-Generation Catalyst.

Statistical copolymers of norbornene (NBE) with cyclopentene (CP) were prepared by ring-opening metathesis polymerization, employing the 1st-generation Grubbs’ catalyst, in the presence or absence of triphenylphosphine, PPh3. The reactivity ratios were estimated using the Finemann-Ross, inverted Finemann-Ross, and Kelen-Tüdos graphical methods, along with the computer program COPOINT, which evaluates the parameters of binary copolymerizations from comonomer/copolymer composition data by integrating a given copolymerization equation in its differential form. Structural parameters of the copolymers were obtained by calculating the dyad sequence fractions and the mean sequence length, which were derived using the monomer reactivity ratios. The kinetics of thermal decomposition of the copolymers along with the respective homopolymers was studied by thermogravimetric analysis within the framework of the Ozawa-Flynn-Wall and Kissinger methodologies. Finally, the effect of triphenylphosphine on the kinetics of copolymerization, the reactivity ratios, and the kinetics of thermal decomposition were examined.

Investigation of sludge conditioning performance and mechanism by examining the effect of charge density on cationic polyacrylamide microstructure

The relation between the microstructure and sludge conditioning performance and mechanism of cationic polyacrylamide (CPAM) (low charge density (CD) CPAM C1, medium CD CPAM C4, and high CD CPAM C7) was extensively studied and recognized in this study. Igarashi and Pyun models based on reactivity ratio characterized the microstructure of the polymers. Results indicated that the blockness percent and mean sequence length of acrylamide (AM) unit decreased, whereas those of cationic unit increased with CD. Effect of dosage on sludge conditioning performance and mechanism was studied by measuring turbidity, filter cake moisture content (FCMC), specific resistance of filtration (SRF), floc size distribution, and zeta potential. The longest AM unit sequence length and separated cationic unit of C1 were concluded to be responsible for bridging. Moreover, the conditioning disadvantages of AM were as follows: narrow flocculation window, high optimum dosage, and maximum FCMC. On the contrary, the highest cationic blockness percent of C7 favored efficient charge neutralization, which contributed to the generation of the lowest optimum dosage. However, the SRF was significantly high, which posed as a difficulty for future treatments. The medium cationic blockness percent and mean AM unit sequence length of C4 led to the combination of charge neutralization and bridging effect with a wide flocculation window and the lowest FCMC and SRF.

Statistical Copolymers Of Benzyl Methacrylate And Diethylaminoethyl Methacrylate: Monomer Reactivity Ratios And Thermal Properties

Statistical copolymers of benzyl methacrylate (BzMA) and diethylaminoethyl methacrylate (DEAEMA) were prepared by free radical polymerization. The reactivity ratios were estimated using the Finemann-Ross, inverted Finemann- Ross, and Kelen-Tüdos graphical methods, along with the computer program COPOINT. Structural parameters of the copolymers were obtained by calculating the dyad monomer sequence fractions and the mean sequence length. The glass-transition temperature (Tg) values of the copolymers were measured and examined by means of several theoretical equations, allowing the prediction of these Tg values. The kinetics of thermal degradation behavior of the copolymers was also studied by thermogravimetric analysis and compared with the respective homopolymers.

Radical copolymerization of acrylic acid and OEGMA475: Monomer reactivity ratios and structural parameters of the copolymer

Alternative copolymers of acrylic acid (AA) and oligo(ethylene glycol) methyl ether methacryate (475 g/ mol (OEGMA475)) macromer, having various amounts of two monomers, were synthesized using aqueous solution free radical copolymerization at 50 ±C with ammonium persulfate (APS) as an initiator. The structures of the copolymers were confirmed by nuclear magnetic resonance (NMR) spectroscopy. In fact, samples with different molar ratios of two monomers in deionized water were prepared and subsequently copolymerization reaction was performed to low conversion levels (below 10%). Monomer reactivity ratios of OEGMA475, AA pair were estimated using the Finemann-Ross (FR), inverted Finemann-Ross (IFR), Kelen-Tudos (KT), extended Kelen-Tudos (EKT), Mayo-Lewis (ML) and Yezrelieve-Brokhina-Roskin (YBR) graphical methods. The value ranged from 0.908 to 0.963 for rOEGMA and from 0.208 to 0.243 for rAA depending on conversion percentage and calculation methods of monomer reactivity ratios. In all the cases, rOEGMA×rAA rAA indicate that the resulting copolymer has a tendency toward alternation with an azeotropic point in MOEGMA=0.905. Structural parameters of the copolymers were obtained by calculating the dyad monomer sequence fractions and the mean sequence length.

Synthesis, Characterization and Antimicrobial Screening of Coumarin Copolymers

Acryloyloxy-4-methylcoumarin (ACU) monomer was polymerized with N-cyclohexyl- acrylamide (NCA) in different feed ratio using AIBN (Azobisisobutyronitrile) as initiator in DMF. The copolymers were characterized by 1 H NMR spectroscopy and the copolymer compositions were determined by 1 H NMR analysis. The reactivity ratios of monomers were determined using linear methods like Fineman-Ross and Kelen-Tudos. The value showed that ACU is more reactive than NCA. The copolymers contained a higher proportion of ACU units. Mean sequence lengths of copolymers were estimated from r1 and r2 values. ACU unit increases in a linear fashion in the polymer chain as the concentration of ACU increases in the monomer feed. The copolymers were tested for their antimicrobial properties against selected microorganisms.

Transcriptome characterization via 454 pyrosequencing of the annelid Pristina leidyi, an emerging model for studying the evolution of regeneration

BackgroundThe naid annelids contain a number of species that vary in their ability to regenerate lost body parts, making them excellent candidates for evolution of regeneration studies. However, scant sequence data exists to facilitate such studies. We constructed a cDNA library from the naid Pristina leidyi, a species that is highly regenerative and also reproduces asexually by fission, using material from a range of regeneration and fission stages for our library. We then sequenced the transcriptome of P. leidyi using 454 technology.Results454 sequencing produced 1,550,174 reads with an average read length of 376 nucleotides. Assembly of 454 sequence reads resulted in 64,522 isogroups and 46,679 singletons for a total of 111,201 unigenes in this transcriptome. We estimate that over 95% of the transcripts in our library are present in our transcriptome. 17.7% of isogroups had significant BLAST hits to the UniProt database and these include putative homologs of a number of genes relevant to regeneration research. Although many sequences are incomplete, the mean sequence length of transcripts (isotigs) is 707 nucleotides. Thus, many sequences are large enough to be immediately useful for downstream applications such as gene expression analyses. Using in situ hybridization, we show that two Wnt/β-catenin pathway genes (homologs of frizzled and β-catenin) present in our transcriptome are expressed in the regeneration blastema of P. leidyi, demonstrating the usefulness of this resource for regeneration research.Conclusions454 sequencing is a rapid and efficient approach for identifying large numbers of genes in an organism that lacks a sequenced genome. This transcriptome dataset will be a valuable resource for molecular analyses of regeneration in P. leidyi and will serve as a starting point for comparisons to non-regenerating naids. It also contributes significantly to the still limited genomic resources available for annelids and lophotrochozoans more generally.

Synthesis and Characterization of Copolymers of Methyl Methacrylate and 2-Ethoxyethyl Methacrylate

The free-radical initiated copolymerizations of methyl methacrylate (MMA) with 2-ethoxyethyl methacrylate (2-EOEMA) were carried out using 2,2-azo-bisisobutyronitrile (AIBN) as the initiator in 1,4-dioxane solutions. The co- polymer products were characterized by IR, 1 H-NMR, and 13 C-NMR spectroscopic techniques. The reactivity ratios of the monomers were computed by the Fineman-Rose (F-R) and Kelen-Tudos (K-T) methods at lower conversion, using the IR data. The results are in good agreement with each other and the mean reactivity ratios for MMA/EOEMA copolymers are r1=0.8436, r2= 0.7751, and r1r2 = 0.6614. The reactivity ratios indicate the formation of random copolymers, which have been supported by the azeotropic composition evaluations. The distribution of monomer sequence along the copolymer chain has been calculated using a statistical method based on the reactivity ratios. The probability of finding the mean sequence lengths of 2-EOEMA and MMA units has also been evaluated.

Interaction of hen production type, age, and temperature on laying pattern and egg quality

The effect of production type (layer vs. broiler breeder), age (onset and end of laying cycle), and temperature (20 and 28°C) on various aspects of the egg production process and quality was evaluated. Highly significant differences were detected between laying hens and broiler breeders (P ≤ 0.001) in all production parameters. Similarly, age significantly affected rate of lay (P ≤ 0.001; 75.4% for young vs. 62.6% for old), mean sequence length (P ≤ 0.001; 7.7 d for young vs. 2.6 d for old), and time of oviposition (P ≤ 0.001). However, there was no effect of temperature on rate of lay, sequence length, or feed intake. Significant interactions between hen type and age were apparent in rate of lay (P ≤ 0.001), sequence length (P ≤ 0.001), and time of oviposition (P ≤ 0.001). A significant interaction between production type and age (P ≤ 0.015) was evident in egg weight, but egg component proportions were dependent only on hen type. Egg shape index was significantly affected by age (P ≤ 0.004), by temperature (P ≤ 0.028), and an interaction between type and age (P ≤ 0.001). Specific gravity declined with age (P ≤ 0.035) and increasing temperature (P ≤ 0.013).

Statistical copolymers of methyl methacrylate and 2‐methacryloyloxyethyl ferrocenecarboxylate: Monomer reactivity ratios, thermal and electrochemical properties

AbstractStatistical copolymers of methyl methacrylate (MMA) with 2‐methacryloyloxyethyl ferrocenecarboxylate (MAEFC) were prepared by free radical polymerization. The reactivity ratios were estimated using the Fineman‐Ross, inverted Fineman‐Ross, Kelen‐Tüdos, and extended Kelen‐Tüdos graphical methods. Structural parameters of the copolymers were obtained by calculating the dyad monomer sequence fractions and the mean sequence length. The glass‐transition temperature (Tg) values of the copolymers were measured and examined by means of several theoretical equations, allowing the prediction of these Tg values. The thermal degradation behavior of the copolymers was also studied and compared with the respective homopolymers. Cyclic voltammetry was employed to study the electrochemical properties of the copolymers. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

Radical copolymerization of 2-vinyl pyridine and oligo(ethylene glycol) methyl ether methacrylates: Monomer reactivity ratios and thermal properties

Statistical copolymers of 2-vinylpyridine (VP) with oligo(ethylene glycol) methyl ether methacrylates of two different molecular weights (300g/mol (OEGMA300) and 1100g/mol (OEGMA1100)), were prepared by free radical polymerization. The reactivity ratios of these two sets of monomers were estimated using the Finemann–Ross, the inverted Finemann–Ross and the Kelen–Tüdos graphical methods. Structural parameters of the copolymers were obtained by calculating the dyad monomer sequence fractions and the mean sequence length. The effect of the length of the oligo(ethylene glycol) group on the copolymer structure is discussed. The glass-transition temperature (Tg) values of the VP copolymers with OEGMA300 were measured and examined in the frame of several theoretical equations, allowing the prediction of these Tg values. The copolymers of VP with OEGMA1100 exhibited the characteristic melting endotherm, due to the crystallinity of the methacrylate sequences and glass transition temperatures attributed to the PVP sequences.

Facile, efficient functionalization of polyethylene via regioselective copolymerization of ethylene with cyclic dienes

AbstractThe copolymerizations of ethylene with cyclic dienes [dicyclopentadiene (DCPD) and 2,5‐norbornadiene (NBD)] using bis(β‐enaminoketonato)titanium complexes [PhN = C(R2)CHC(R1)O]2TiCl2 (1a: R1 = CF3, R2 = CH3; 1b: R1 = t‐Bu, R2 = CF3; 1c: R1 = Ph, R2 = CF3) have been investigated. In the presence of modified methylaluminoxane, these complexes exhibited high catalytic activities in the copolymerization of ethylene with DCPD or NBD, affording high molecular weight copolymers with unimodal molecular weight distributions. 1H and 13C‐NMR spectra reveal ethylene/DCPD copolymerizations by catalysts 1a–c proceeds through the enchainment of norbornene ring. Catalysts 1a and 1c showed a tendency to afford alternating copolymers. More noticeably, catalysts 1b and 1c bearing bulky substituents on the ligands promote ethylene/NBD copolymerization without crosslinking, affording the copolymer containing intracyclic double bonds. The NBD incorporation as high as 27.2 mol % has been achieved by catalyst 1c. Moreover, the microstructures of the copolymers were further confirmed by the measurement of reactivity ratios and dyad monomer sequences as well as mean sequence lengths. The intracyclic double bonds of ethylene/DCPD or ethylene/NBD copolymers can be fully converted into polar groups such as epoxy, amine, silane, and hydroxyl groups under mild conditions. Convenient synthesis of hydroxylated polyethylene can be provided for the first time through the ring opening reaction of epoxide. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1764–1772, 2010

Copolymers of Phenoxyethyl Methacrylate with Butyl Methacrylate: Synthesis, Characterization and Reactivity Ratios

Phenoxyethyl methacrylate (POEMA) and butyl methacrylate (BMA) were copolymerized by free-radical copolymerization using α,α′-azobisisobutyronitrile (AIBN) in 2-butanone solution at 333±1 K. Copolymers were characterized by FTIR, 1H-NMR and 13C-NMR spectroscopic methods and by comparison of the spectra with the corresponding homopolymers. Thermogravimetric analysis of the copolymers was carried out in order to know their thermal stability. Copolymer composition was established by 1H-NMR analysis. Monomer reactivity ratios (MRR) were computed using the classical Fineman – Ross (FR) and Kelen – Tüdos (KT) procedures. MRR were also estimated using a nonlinear computational fitting procedure, known as reactivity ratios error in variable model (RREVM). The mean sequence lengths of the copolymers were estimated and suggest that random copolymers were obtained.

Copolymerization of tetradecene‐1 and octene‐1 with silyl‐protected 10‐undecen‐1‐ol using a Cs‐symmetry hafnium metallocene catalyst. A route to functionalized poly(α‐olefins)

AbstractStatistical copolymers of tetradecene‐1 and octene‐1 with 1‐tert‐butyldimethylsilyloxy‐10‐undecene were synthesized by metallocene catalyzed copolymerization. The Cs‐symmetry hafnium metallocene [(p‐Et3Si)Ph]2C(2,7‐di‐tert‐BuFlu)(Cp)Hf(CH3)2 and tetrakis(pentafluorophenyl) borate dimethylanilinium salt ([B(C6F5)4]−[Me2NHPh]+) were employed as the catalytic system, in the presence of trioctylaluminum (TOA) as a scavenger. The monomer reactivity ratios were calculated using the Finemann‐Ross, inverted Finemann‐Ross, and Kelen‐Tüdos graphical methods. The structural parameters of the different copolymers were obtained from the calculation of the dyad monomer sequence fractions and the mean sequence lengths derived via the reactivity ratios. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 876–886, 2009

Copolymers of Phenoxyethyl Methacrylate with Glycidyl Methacrylate: Synthesis, Characterization and Reactivity Ratios

The free radical copolymerization of phenoxyethyl methacrylate (POEMA) and glycidyl methacrylate (GMA) was carried out using α,α′-azobisisobutyronitrile (AIBN) in 2-butanone solution at 333 ± 1 K. The copolymers were characterized by FTIR, 1H-NMR and 13C-NMR spectroscopic methods. Thermal properties of the copolymers were also studied by thermogravimetric analysis (TGA). The compositions of the copolymers were established by 1H-NMR analysis. The monomer reactivity ratios were computed using the Fineman–Ross (F-R) and Kelen–Tüdos (K-T) methods. These parameters were also estimated using a nonlinear computational fitting procedure, known as reactivity ratios error in variable model (RREVM). The mean sequence lengths determination indicates that the copolymers obtained are random in nature. Differences in the reactivity ratios obtained by the classical methods and RREVM were observed. GMA is more reactive than POEMA and although the copolymers are random, some tendency to GMA small block formation is reported.

Novel copolymers of N-(4-bromophenyl)-2-methacrylamide with glycidyl methacrylate: Synthesis, characterization, monomer reactivity ratios and thermal properties

The acrylamide monomer, N-(4-bromophenyl)-2-methacrylamide (BrPMAAm) has been synthesized by reacting 4-bromoaniline with methacryloyl chloride in the presence of triethylamine(NR 3) at 0–5 °C. Copolymers of N-(4-bromophenyl)-2-methacrylamide (BrPMAAm), with glycidyl methacrylate (GMA) were synthesized in 1,4-dioxane solution at 70 ± 1 °C using 2,2′-azobisisobutyronitrile (AIBN) as an initiator with different monomer-to-monomer ratios in the feed. The copolymers were characterized by FTIR, 1H-and 13C NMR spectroscopy. The copolymer composition was evaluated by nitrogen content (N for BrPMAAm-units) in polymers led to the determination of reactivity ratios. The monomer reactivity ratios for BrPMAAm (M 1)–GMA (M 2) pair were determined by the application of conventional linearization methods such as Fineman–Ross ( r 1 = 0.2893; r 2 = 0.7114), Kelen–Tüdös ( r 1 = 0.3361; r 2 = 0.8645) and extended Kelen–Tüdös ( r 1 = 0.3096; r 2 = 0.8577) as well as by a non-linear error variables model (EVM) method using a computer program, RREVM ( r 1 = 0.3453; r 2 = 0.8606). The mean sequence lengths determination indicated that the copolymer was statistically in nature. The polydispersity indices of the polymers determined using gel permeation chromatography suggest a strong tendency for chain termination by disproportionation. Thermal decomposition of the polymers occurred in three stages in the temperature range of 100–500 °C and the glass transition temperature ( T g) range of 94–165 °C.

Extent of variation within a laying flock: attainment of sexual maturity, double-yolked and soft-shelled eggs, sequence lengths and consistency of lay

1. An experiment was conducted to determine the amount of variation that exists within a population of laying hens in age at first egg, the number of birds that did not come into lay, the prevalence of soft-shelled and double-yolked eggs, sequence characteristics and consistency of lay. 2. Oviducal problems accounted for most of the poor laying performance. About a third of the flock produced double-yolked or soft-shelled eggs at the onset of lay, the proportion being influenced by the age at photostimulation. In some instances these aberrations interrupted sequences. Differences in laying performance were particularly evident in mean sequence length, mean prime sequence length and mean pause length both within and between individuals. Furthermore, sequence length did not always decline in a regular fashion with advancing age. 3. The information gathered here has been used to develop a mechanistic, stochastic population model for laying hens.

Novel Copolymers of N‐(4‐Bromophenyl)‐2‐Methacrylamide with 2‐Acrylamido‐2‐Methyl‐1‐Propanesulfonic Acid

The new acrylamide monomer, N‐(4‐Bromophenyl)‐2‐methacrylamide (BrPMAAm) has been synthesized by reacting 4‐Bromoaniline with methacryloyl chloride in the presence of triethylamine(NR3) at 0–5°C. The radical‐initiated copolymerization of (BrPMAAm), with 2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid (AMPS) has been carried out in dimethylformamide (DMF) solution at 70±1°C using 2,2′‐azobisisobutyronitrile (AIBN) as an initiator with different monomer‐to‐monomer ratios in the feed. The copolymers were characterized by FTIR, 1H‐ and 13C‐NMR spectroscopy. The copolymer composition was evaluated by nitrogen content (N for AMPS‐units) in polymers led to the determination of reactivity ratios. The monomer reactivity ratios for BrPMAAm (M1)‐AMPS (M2) pair were computed using the Fineman‐Ross (F‐R), Kelen‐Tüdös (KT) and Extended Kelen‐Tüdös (EKT) methods. These parameters were also estimated using a non‐linear computational fitting procedure, known as reactivity ratios error in variable model (RREVM). The mean sequence lengths determination indicated that the copolymer was statistically in nature. By TGA and DSC analyses, the thermal properties of the polymers have been studied. The antimicrobial effects of polymers were also tested on various bacteria, and yeast.

Copolymers of N-cyclohexylacrylamide and n-butyl acrylate: synthesis, characterization, monomer reactivity ratios and mean sequence length

Copolymerization of N-cyclohexylacrylamide (NCHA) and n-butyl acrylate (BA) was carried out in dimethyl- formamide at 55±1°C using azobisisobutyronitrile as a free radical initiator. The copolymers were characterized by 1H-NMR spectroscopy and the copolymer compositions were determined by 1H-NMR analysis. The reactivity ratios of the monomers were determined by both linear and non-linear methods. The reactivity ratios of monomers determined using lin- ear methods like Fineman-Ross (r1 = 0.37 and r2 = 1.77 ), Kelen-Tudos (r1 = 0.38 and r2 = 1.77), ext. Kelen-Tudos (r1 = 0.37 and r2 = 1.75) Yezrieler-Brokhina-Roskin (r1 = 0.37 and r2 = 1.77) and non-linear methods like Tidwell-Mor- timer (r1 = 0.37 and r2 = 1.76), ProCop (r1 = 0.36 and r2 = 1.82). The Q and e values for NCHA are 0.67 and 0.68 respec- tively. Mean sequence lengths of copolymers are estimated from r1 and r2 values. It shows that the BA units increases in a linear fashion in the polymer chain as the concentration of BA increases in the monomer feed.