Fractions Of Poly Research Articles

Conformational transition in (maleic anhydride mono-n-octyl itaconate) copolymer

The dependence of intrinsic viscosity [η] on temperature for fractions of poly(maleic anhydride-co-mono-n-octylitaconate) [p(MA-co-MOI)] was studied. A discontinuity in [η] as function of temperature similar to that of poly(mono-n-octylitaconate) (PMOI) is found which has been attributed to a conformational transition of the polymer chain. This conformational transition can be removed by the addition of poly(dimethylsiloxane) (PDMS). The effect is interpreted in terms of interpolymer complexation.

Molecular Characteristics of Poly(methacrylamidod-Glucose)1

Abstract The fractions of poly(methacrylamido D-glucose) with molecular weights 7< M·10-4< 550 have been studied in water by the methods of molecular hydrodynamics. Kuhn-Mark-Houwink equations were obtained. The hydrodynamic invariant and the sedimentation parameter were also calculated. The equilibrium rigidity and the hydrodynamic diameter of molecules modeling macromolecules in solution were evaluated on the basis of the theory of the wormlike necklace model with the effects of excluded volume taken into account at different values of the excluded-volume parameter. The effect of fraction polydispersity on the quantitative values of exponents in the equations of the Kuhn-Mark-Houwink type and the Kuhn segment length is discussed.

Adsorption and covalent immobilization of human serum albumin (HSA) and gamma globulins (gamma G) onto poly(styrene/acrolein) latexes with pyrene, dansyl, and 2,4-dinitrophenyl labels.

The poly(styrene/acrolein) latexes (P(SA)1 and P(SA)2), differing in poly(acrolein) content, were synthesized by the emulsifier-less emulsion-precipitation polymerization of styrene and acrolein. The fraction of poly(acrolein) in the surface layer was 0.35 and 0.50, for the P(SA)1 and P(SA)2 latex, respectively. Latexes were labelled with 2,4-dinitrophenylhydrazine (DNPH), dansylhdrazine (DAH), and 1-aminopyrene (APY). Surface concentration of labels varied from 4.20.10(-7) mol m-2 (for APY label on P(SA)1 latex) to 1.54.10(-6) mol m-2 (for DNPH label on P(SA)2 latex) reflecting the fraction of polyacrolein in the surface layer and bulkiness of the label. The differences between adsorption and covalent immobilization of human serum albumin and gamma globulins onto the P(SA)2 latex and onto its derivatives labelled with the 2,4-dinitrophenyl (DNP), dansyl (DA), and pyrene (PY) groups were small. The observation conforms to the hypothesis that polyacrolein forms domains on the surface of the P(SA) latexes and that after labelling some aldehyde groups are still available for the covalent immobilization of proteins. Labelled and parent latexes were used in the model slide and turbidimetric aggregation tests for the goat anti-HSA. The fluorescent latexes, labelled with APY and DAH, and latexes labelled and with DNPH were found to be suitable for the model tests, similarly as the nonlabelled ones, however, some differences in the sensitivity, depending on the presence and the nature of labels, were noticed. The standard goat anti-HSA serum (Sigma) was detected at maximum dilution equal to 2000 in the slide test, and in the dilution region from 1.8.10(3) to 4.7.10(6) times in the turbidimetric test.

Improvement of hydroxyvalerate fraction in poly(β-hydroxybutyrate-co-β-hydroxyvalerate) by a mutant strain of Alcaligenes eutrophus

In an effort to improve the strain activity of Alcaligenes eutrophus to produce poly(β-hydroxybutyrate-co-β-hydroxyvalerate) [P(HB-co-HV)], a mutant strain BK23 was obtained by MNNG mutagenesis. With the strain, the fraction of hydroxyvalerate (HV) and its yield from propionic acid were found to be significantly improved compared to those of the parent strain, A. eutrophus NCIMB 11599. In a fed-batch culture, the mutant strain produced 47 g/ l of P(HB-co-HV) with an HV fraction of 22 mol%, while the parent strain could yield only the much lower fraction of 10 mol%.

Functional Expression of GnRH Receptors in Xenopus Oocytes Injected with Salmon Brain RNA.

The brain of salmonid fishes contains two types of gonadotropin-releasing hormone (GnRH) peptide, salmon GnRH (sGnRH) and chicken GnRH-II (cGnRH-II). Although cDNA encoding the mammalian GnRH (mGnRH) receptor has been cloned and characterized in several mammalian species, structures of cDNAs of other GnRH receptors in non-mammalian vertebrates have not been determined yet. As a step to isolate cDNA clones for the sGnRH and the cGnRH-II receptors from masu salmon (Oncorhynchus masou) brains, we examined functional expression of these receptors electrophysiologically using Xenopus oocyte expression system. Oocytes injected with poly(A)+ RNA of the brain or the pituitary of the masu salmon responded to both sGnRH and cGnRH-II. Oocytes injected with poly(A) + RNA of pituitaries of the masu salmon responded to only sGnRH. The poly(A) + RNA of the brain was further fractionated according to the size. Injection of pooled fractions of poly(A) + RNA of a size range between 5.5 and 6.0 kb induced the oocyte response to sGnRH, but the response to cGnRH-II was not clearly induced. Injection of poly(A) + RNA of about 5.0-5.5 kb in size induced the response to cGnRH-II, but the response to sGnRH was not clearly detected. These results suggest that the sGnRH and cGnRH-II receptors are encoded by different RNA, and that the preference of the agonists of these two receptors are clearly different each other.

"Domain" Coil-Globule Transition in Homopolymers

The temperature-induced coil-globule transition has been studied in dilute aqueous solutions (with 200 mg/L SDS) for different fractions of poly(N-isopropylacrylamide) (PNIPAM) and poly-(N-isopropylmethacrylamide) (PNIPMAM) using scanning microcalorimetry, diffusion, and size-exclusion chromatography (FPLC). It has been shown that both these polymers undergo a coil-globule transition upon temperature increase. This transition is accompanied by cooperative heat absorption and a decrease of heat capacity, which makes it similar to the cold denaturation of globular proteins. The globule-coil transition is an all-or-none process only for the fractions with the lowest molecular weights (∼10 x 10 3 ) while fractions of larger molecular weights behave as if they consist of quasi-independent cooperative units, the domains. The number of domains in a macromolecule is proportional to the molecular weight of the polymer. This suggests that the domain character of cooperative transitions in large proteins does not, in principle, need evolutionary-selected amino acid sequences but can occur even in homopolymers.

Characterization of the chain stiffness for a mesogen‐jacketed liquid crystal polymer: Poly{2,5‐BIS [(4‐Methoxybenzoyl)Oxy] Styrene}

AbstractNarrow‐distribution fractions of poly{2,5‐bis[(4‐methoxybenzoyl)oxy] styrene} ranging in weight‐average molecular weight Mw from 1.1 × 105 to 1.96 × 106 were studied by static light scattering and viscometry in THF at 25 ° C. From Mw and the intrinsic viscosity [ η ] Mark‐Houwink‐Sakurada equation was formulated with K=7.54×10−4 and ≈=0.82. The relation between [ η ] and Mw was analyzed according to Bohdanecky for the Kratky‐Porod wormlike chain, the ranges of the mass per unit length ML and the persistence length q were estimated as 35 nm−1 M&lt;L42 nm&lt;−1 and 11.5 nm &lt;13.5 nm, respectively. The values of ≈ and q indicate that the polymer, though a liquid crystal polymer of the side‐chain type, has wormlike chain in dilute solution as most main chain liquid crystal polymers.

Dilute solution properties of poly(dimethyldiallylammonium chloride) in aqueous sodium chloride solutions

AbstractMW fractions of poly(dimethyldiallylammonium chloride) (PDMDAAC) were prepared by preparative size‐exclusion chromatography and characterized by static and dynamic light scattering, viscometry, size‐exclusion chromatography, and electrophoretic light scattering, in 0.50M NaCl solution. The behavior of fractions with MW &lt; 2 × 105 was as expected for a strong polyelectrolyte in a good solvent, with a Mark‐Houwink exponent of ca. 0.8, and MW‐dependencies of the hydrodynamic radius and the radius of gyration of corresponding magnitude. At higher MW, curvature appears in the MW‐dependencies, which can be best explained by the presence of branching. While this notably lowers the intrinsic viscosity at high MW, the electrophoretic mobility is unchanged regardless of molar mass. Thus, the branched polymers display the electrophoretic free‐draining behavior characteristic of linear polyelectrolytes. ©1995 John Wiley &amp; Sons, Inc.

Synthesis of polypropene‐block‐poly(ethylene‐co‐propene) by short‐period polymerization with MgCl2‐supported Ziegler catalyst

AbstractThe short‐period polymerization method was successfully applied to the synthesis of a novel diblock copolymer, polypropene‐block‐poly(ethylene‐co‐propene). The polymerization was carried out for ca. 0,1 s with a MgCl2‐supported Ziegler catalyst. The copolymers obtained showed unimodal curves in gel‐permeation chromatography without any peak in the low‐molecular‐weight region. After extraction with heptane, the fraction of poly(ethylene‐co‐propene) remained unchanged in the copolymer but disappeared in a commercial so‐called block‐type copolymer. All the results the formation of polypropene‐block‐poly(ethylene‐co‐propene), in which poly(ethylene‐co‐propene) is chemically linked with polypropene.

Photochemistry in polymer solids: 12. Effects of main-chain structures and formation of hydrogen bonds on photoisomerization of azobenzene in various polymer films

The free-volume distribution in various polymers and the effect of hydrogen bonds on the free-volume distribution were examined by using a photoisomerization of azobenzene as a photosensitive probe. Poly(methyl methacrylate) (PMMA), poly(vinyl alcohol) and phenoxy resin films containing molecularly dispersed azobenzene were irradiated over a wide temperature range (77–340 K). The final cis fraction for the trans to cis photoisomerization of azobenzene decreases with decreasing temperature in PMMA, and smaller fractions are produced than in polycarbonate at the same temperature. These differences are due to the fact that the local free-volume fluctuation of the methylene main chains of PMMA is smaller than that of the aromatic chains of polycarbonate. Since the side chains of PMMA compared to the main chains are larger than those of polycarbonate, the local free volume around the main chains is filled up by the side chains. Hence, the final cis fraction of azobenzene in PMMA is small. Furthermore, the final cis fraction in poly(vinyl alcohol) is smaller than that in PMMA. Since the hydrogen bonds among the polymer chains in poly(vinyl alcohol) restrict the local molecular motion at low temperatures, the azobenzene molecule is tightly seized by the matrix polymer chains and the free-volume fluctuation is restricted in poly(vinyl alcohol). The kinetic model considering the local fluctuation of the free volume was also applied to the results for PMMA, poly(vinyl alcohol) and phenoxy resin, and the parameters for the model in these polymers are discussed.

Dilute-solution characterization of poly(dihexoxyphosphazene)

Four fractions of poly(dihexoxyphosphazene) with molecular weights M w =2.3, 0.92, 0.25, and 0.026×10 6 , were studied in THF solutions at 25°C. The second virial coefficient decrease with increasing molecular weight. Two iterative numerical procedures were employed to combine all the experimental results, seeking the best choice of the parameters defining both the SEC calibration curve and the Mark-Houwink equation. The K and a constants of the Mark-Houwink equation allow the determination of the viscosity-average molecular weight of the four fractions and their molecular dimensions

Solution properties of poly(octadecyl methacrylate) in butyl acetate, 2. Semidilute solution

Semidilute solutions of a fraction of poly(octadecyl methacrylate) (PODMA) obtained by radical-initiated polymerization were investigated in the theta-solvent butyl acetate (BuAc) with static and dynamic light scattering (SLS, DLS, resp.) at four different temperatures between 13°C (near theta-temperature Θ) and 70°C. The molar mass of the investigated sample (PODMA 4) was 3,2 · 106 g · mol−1. A concentration region from dilute to 8 c* was covered, where c* = 1/[η] was taken as the coil overlap concentration, [η] denoting intrinsic viscosity. Above c = 3c* the DLS correlation function exhibited bimodal behaviour at all temperatures. At these concentrations one finds two “apparent” molar masses, radii of gyration and diffusion coefficients for each concentration. The smaller apparent molar masses, smaller radii of gyration and larger diffusion coefficients correspond to characteristics of the transient network. The larger apparent molar masses, larger radii of gyration and smaller diffusion coefficients may be attributed to the formation of inhomogeneities in the semidilute solution.

Hydrodynamic properties of poly(1‐vinyl‐2‐pyrrolidone) molecules in dilute solution

AbstractThe translational diffusion coefficient D0, the sedimentation coefficient S0, and the intrinsic viscosity [η] of samples and fractions of poly(1‐vinyl‐2‐pyrrolidone) were measured in a 0,1 M solution of sodium acetate in the molecular weight range 2 ≤ M · 10−3 ≤ 2200. For M &gt; 4 · 104 the following relationships were obtained: [η] = 8,86 · 10−5 · M0,74, D0 = 2,42 · 10−4 · M−0,58, and S0 = 2,14 · 10−15 ·. M0,42. For M &lt; 4 · 104 the corresponding relations are [η] = 5,0 · 10−4 · M0,56, D0 = 1,29 · 10‐4 · M−0,52 and S0 = 1,15 · 10−15 · M0,48. The hydrodynamic invariant is A0 = (3,2 ± 0,25) · 10−17 J · K−1 · mol−1/3 and the sedimentation parameter βs = (1,3 ± 0,17) · 107 mol−1/3. The temperature coefficient of the intrinsic viscosity is negative, viz. Δ ln[η]/ΔT = −6,3. 10M−3 K−1. The evaluation of the length of the Kuhn segment A and the hydrodynamic diameter d of chains representing the molecules of PVP in solution was conducted on the basis of the theory for the hydrodynamic properties of a wormlike necklace taking into account the excluded volume effects. The values of A agree with those obtained from the Burchard‐Stockmayer‐Fixman and Cowie‐Bywater equations, A = (2,1 ± 0,3) nm and d = (0,5 ± 0,13) nm.

Expression of the Na(+)-K(+)-2Cl- cotransporter in Xenopus oocytes

The Na(+)-K(+)-2Cl- cotransporter (NKCCT) is important in mediating net salt transport in a variety of cells. As a first step in obtaining structural information on this transport system, we attempted to express it in Xenopus laevis oocytes by injection of poly(A)+ mRNA from rat kidney. Four days after injection, batches of oocytes were tested for 86Rb uptake in presence and absence of 10 microM bumetanide to distinguish that fraction of influx mediated by NKCCT. In the absence of bumetanide, the oocytes formed a bimodal distribution with respect to 86Rb uptake, with some oocytes accumulating significantly more 86Rb than others. In the presence of bumetanide, or when Na was replaced with choline, that group of oocytes taking up more 86Rb did not appear. Sham-injected oocytes did not accumulate sufficient 86Rb to be distinguishable above background. Taken together, these data suggest that some of the mRNA-injected oocytes expressed the rat renal NKCCT. Crude poly(A)+ mRNA was separated by acid-urea agarose gel electrophoresis, and fractions were injected into oocytes. One fraction corresponding to messages of approximately 7 kilobases in length induced a bumetanide-sensitive 86Rb influx resembling that seen with total mRNA. Poly(A)+ mRNA fractionated on sucrose density gradients gave similar results. It is concluded that the rat kidney NKCCT has been expressed in Xenopus oocytes from a high molecular weight fraction of poly(A)+ mRNA.

Crystallization of sheared polymer melts: poly(ethylene oxide) fractions

Crystallization under controlled shear conditions has been optically monitored for a series of sharp molecular weight fractions of poly(ethylene oxide). The minimum shear rate (MSR) necessary to produce oriented crystalline morphologies exhibited a strong molecular weight (M) dependence: MSR=K/M1.47. The time necessary for erasure of orientation effects after crystal melting was also determined and found to be proportional to M1.42.

Further experimental evidences of the compatibility of poly(vinyl acetate) with poly(ethyl methacrylate) and its dependence on the ratio of the molecular weight of the two homopolymers

AbstractUsing various fractions of poly(ethyl methacrylate) (PEMA) and poly(vinyl acetate) (PVAc) of very narrow molecular weight distribution, a very wide range of 2–120 of molecular weight ratio M¯ν PEMA/M¯ν PVAc, (M¯ν)r was obtained. Studies of some tensile mechanical properties of films of the blends produced from solution on mercury confirmed strong dependence of the improvements of PVAc properties for blend with 18% PEMA on (M¯ν)r, especially in the range 5 ≤ (M¯ν)r &lt; 100. The density of the films of the blend was much higher than those of the individual polymers and increased monotonically with (M¯ν)r. Optical micrographs of the films of the blends showed interactions between the two polymers with 18% PEMA composition, which appears to be more intimate as (M¯ν)r increases, as further evidence of compatibility and miscibility of the two polymers.

Effect of the side chain structure on the glass transition temperature: Part 4. Molecular weight dependence of Tg in chalcogenides containing poly(methacrylates)

Glass transition temperature T g has been measured by DSC for several fractions of poly(benzylmethacrylate) (PBzM), poly(2-thienylmethyl methacrylate) (PTiM) and poly(2-selenolylmethyl methacrylate) (PSeM) and for one fraction of poly(2-furfurylmethyl methacrylate) (PFM) and poly(tetrahydrofurfurylmethyl methacrylate) (PHFM). The effect of the nature of the side group on T g is discussed. Various relationships between number average molecular weight M n and T g have been established. Linear relationships between T g and In P ( P = degree of polymerization) have been obtained for some of the systems studied here.

Thermal analysis and molecular weight dependence on glass transition of poly(ditrimethylene terephthalate)

Eight fractions of poly(ditrimethylene terephthalate)(PTMTMT) were characterized by viscometry, osmometry and thermal analysis. The four fractions of higher molecular weight fitted a linear variation of the glass transition temperature (Tg) with the inverse of the molecular weight, and the other ones showed a nonlinear behaviour. A value of the parameter b a = 0.84 was obtained when the Somcynsky-Patterson equation was used, showing that PTMTMT is a relatively flexible polymer and slightly more rigid than the preceding member of the series, poly(diethylene terephthalate) (PDET). Moreover, in order to evaluate the dependence of Tg with molecular weight, the Gibbs-DiMarzio equation was applied, using ϵ = 1160 cal mol −1 for reaching the best correlation This value also corresponds to flexible polymers.

Graft copolymerization of vinylpyridines onto cellulosic fibres by the ceric ion method. The monomer concentration effect

AbstractThe effect of monomer concentration on the graft polymerization of 4‐vinylpyridine (4‐VP) and of 2‐vinylpyridine (2‐VP) on cellulose and on partially carboxymethylated cellulose (PCMC) initiated by cerium ammonium nitrate (CAN) in dilute nitric acid has been examinated. The grafting parameters: grafting efficiency (GE), graft yield (G), graft frequency (GF), and ceric ion consumption ((Ceiv)c)were studied as a function of the monomer concentration. The fraction of poly(4‐vinylpyridine), P(4‐VP), in the graft polymer increased with increasing monomer concentration for both cellulosic substrates. The molecular weight of the grafted P(4‐VP) was obtained viscosimetrically after hydrolyzing away the cellulose backbone. When 2‐VP was grafted on PCMC and on unmodified cotton, the graft yields also increased with monomer concentration, but they were much smaller than in the previous case. Presence of carboxymethyl groups in cellulose enhanced G, GE, Mv, and GF.

Double lamellae of low-molecular-mass fractions of poly(ethylene oxide) crystallized from the melt

A ‘double-lamella’ morphology has been observed during a study of molecular segregation and nucleation of low-molecular-mass fractions of poly(ethylene oxide) (PEO) from the melt. It is only observed in cases of crystals with an odd number of folds per molecule. The formation of the double lamellae is thought to be based on association of the OH end-groups of the PEO chains. Ordered hydrogen bonding on facing folded crystals is being suggested as an explanation for the observation.