Rodlike Poly Research Articles

Base sequence effects in double-helical DNA. II. Configurational statistics of rodlike chains.

AbstractMatrix generator techniques have been adapted to account for precise structural features of the nucleotide repeating unit and to translate the primary sequence of DNA base pairs into three‐dimensional structures. Chains have been constructed to reflect the local sequence‐dependent differences of bending and twisting of adjacent residues and various overall chain properties, including the average unperturbed moments of the end‐to‐end vector r and the mean angular orientation (〈γ〉 between base pair normals, 〈ϕ1〉 between long axes, and 〈ϕ2〉 between short axes) of terminal chain residues, have been computed. The chain backbone is treated implicitly in terms of the spatial fluctuations of successive base pairs. Motions are limited to low‐energy perturbations of the standard B‐DNA helix. Approximate potential energy schemes are used to represent the rules governing the patterns of local base–base morphology and flexibility. Theoretical predictions are compared with experimental observations at both the local and the macro‐molecular level. Initial applications are limited to the rodlike poly(dA) · poly(dT) and poly(dG) · poly(dC) helices. The former duplex is found to be more compressed and the latter more extended than random‐sequence DNA of the same chain length. The flexibility of the duplexes as a whole is described in terms of the average higher moments of the displacement vector ρ = r ‐ 〈r〉 and the likelihood of chain cyclization is estimated from the three‐dimensional Hermite series expansions of the displacement tensors. Emphasis is placed on theoretical methodology and the practical relevance of the calculated chain moments to observed physical properties.

Mesophase-Enhanced Polymerization and Chemo-Rheology of Poly(p-Phenylenebenzobisthiazole)

ABSTRACTThe phenomenon of mesophase-enhanced polymerization of the rodlike polymer poly(pphenylenebenzobisthiazole) in polyphosphoric acid was investigated. When the polymer concentration was greater than 5 wt%, the reacting mixture became anisotropic at an early stage of the polymerization. The reaction rate increased significantly at the isotropic-nematic phase transition as the rods were aligned in positions more favorable for the condensation reaction to occur. At 4.5 wt% of polymer, the reacting mixture remained isotropic for up to 1500 min of reaction time. The chemo-rheological properties of the 15 wt% reaction mixture indicate the occurrence of the phase change in either the shear viscosity or the first normal stress difference measurements.

Structure–Property Relationship of Solution-Spun Ppbt/Peek and Ppbt/Nylon 6,6 Composite Fibers

ABSTRACTPrevious work investigated the processing/structure/property relationships for solution spun composite fibers of rodlike poly(p-phenylene benzobisthiazole) [PPBT] with nylon 6,6 [N66] and poly(ether ether ketone) [PEEK] [1]. Evidence that these composite fibers were effectively reinforced by a network-like structure of PPBT was given. In the present investigation, the morphology and properties of wet, as-spun, and heattreated PPBT/nylon 6,6 and PPBT/PEEK composite fibers are contrasted to gain insight into the structure/property relations which result from these post-spinning processes. It is concluded that heat-treatment is simply a means of perfecting the network structure, thereby enhancing the tensile properties of the composite fibers.

Frank Elastic Constants and Leslie-Ericksen Viscosity Coefficients of Nematic Solutions of a Rodlike Polymer

The formation of a monodoraain nematic liquid crystal with a solution of the rodlike poly[1,4-phenylene-2,6-benzobisthiazole] will be described, along with the results of elastic and quasi-elastic ...

Phase behavior of the ternary system solvent: poly(?-benzyl L-glutemate) and polystyrene

Phase equilibria were investigated at 80°C for a ternary system involving a solvent benzyl alcohol, a rodlike polymer poly(γ-benzyl L-glutamate) (PBLG), and a flexible polymer polystyrene (PS). The fairly dilute solution of the two polymers was isotropic and monophasic. At greater concentrations, it was separated into two isotropic phases. Above an even higher critical concentration of the two polymers, three phases, a cholesteric (A1) and two isotropic phases (I1 and I2), coexisted at equilibrium. PBLG was contained exclusively in the phases A1 and I1, while PS was in the phase I2. The more concentrated solution was separated into a cholesteric phase and an isotropic phase. The latter contained PS but excluded PBLG, These features were discussed on the ground of the Flory theory by considering the polymer compatibility.

Molecular orbital conformational energy calculations of the aromatic heterocyclic poly(5,5′‐bibenzoxazole‐2,2′ diyl‐1,4‐phenylene) and poly(2,5‐benzoxazole)

AbstractInterest in potential high‐performance polymers, leading to characterization and development of the rodlike poly(p‐phenylene benzobisoxazoles) (PBO) and poly(p‐phenylene benzobisthiazoles) (PBT), has recently been extended to a related group of polymers referred to as AAPBO, ABPBO, AAPBT, and ABPBT. In this study, geometry‐optimized CNDO/2 molecular orbital calculations have been carried out on AAPBO and ABPBO model compounds to determine conformational energies as a function of rotation about each type of rotatable bond within the repeat units. For AAPBO, which contains two types of rotatable bonds per repeat unit, the bond between the benzoxazole group and p‐phenylene group prefers the coplanar conformation with a barrier to free rotation of 2.1 kcal mol−1, while the bond between the benzoxazole groups prefers a conformation approximately 60 degrees away from coplanarity with a barrier to coplanarity and to free rotation of 3.6 kcal mol−1. For ABPBO, which contains only the former type of rotatable bond per repeat unit, the coplanar conformations were preferred with a barrier to free rotation of 1.6 kcal mol−1. These results are in excellent agreement with the results of both theoretical and experimental studies on the structurally analogous PBO. They are also consistent with the liquid crystalline behavior found for ABPBO but not for AAPBO.

Rheological and rheo-optical studies of a constitutive equation for nematogenic solutions of rod-like polymers

Rheological and rheo-optical studies on solutions of the rod-like poly(1,4-phenylene-2,6-benzobisthiazole) are described for both isotropic and nematic solutions. The data include both steady-state and transient behaviour. For isotropic solutions it is found that a single-integral constitutive equation (a form of the B.K.Z. equation) represents the data available. For nematic solutions unexplained behaviour is observed for small κ, perhaps related to unstable flow in simple shear predicted for such solutions by some mechanistic theories for the parameters in the Leslie–Erickson constitutive equation. For larger κ the flow behaviour may be represented by a modified form of the single-integral equation.

High molecular weight poly(methyl alkyl fumarates): radical high polymerization of methyl alkyl fumarates and monomer-isomerization radical polymerization of methyl alkyl maleates

High molecular weight poly(methyl alkyl fumarate) were prepared through radical polymerization of methyl alkyl fumarates(MRF) and monomer-isomerization radical polymerization of methyl alkyl maleates(MRM). The polymerization reactivities(yield and viscosity) of MRFs and MRMs were found to increase with increasing of the bulkiness of the ester alkyl substituents, but MRFs showed generally higher reactivities than MRMs. These polymers were also observed to consist of less- or non-flexible rod-like poly(methoxy-carbonylmethylene-alt-alkoxycarbonylmethylene) structure depending on their bulkiness. The MtBF polymer did not melt, which showed somewhat decreased thermal stability.

Rotational motion of rod-like poly(benzyl glutamate)

Mouvement rotationnel de ce polypeptide en helice alpha par analyse de la forme des signaux des spectres RPE du PBLG marque au nitroxyde en solution diluee en fonction de la temperature et du solvant

Dielectric Relaxation of Rod-like Poly(n-hexyl isocyanate) in Nonpolar Solvents

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTDielectric Relaxation of Rod-like Poly(n-hexyl isocyanate) in Nonpolar SolventsJanet S. Anderson and Worth E. VaughanCite this: Macromolecules 1975, 8, 4, 454–457Publication Date (Print):July 1, 1975Publication History Published online1 May 2002Published inissue 1 July 1975https://doi.org/10.1021/ma60046a017RIGHTS & PERMISSIONSArticle Views46Altmetric-Citations4LEARN 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 (498 KB) Get e-Alerts Get e-Alerts

Intrinsic Viscosity Measurements on Rodlike Poly(n-butyl isocyanate) and Poly (n-octyl isocyanate)

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTIntrinsic Viscosity Measurements on Rodlike Poly(n-butyl isocyanate) and Poly (n-octyl isocyanate)A. J. Bur and L. J. FettersCite this: Macromolecules 1973, 6, 6, 874–879Publication Date (Print):November 1, 1973Publication History Published online1 May 2002Published inissue 1 November 1973https://doi.org/10.1021/ma60036a017RIGHTS & PERMISSIONSArticle Views90Altmetric-Citations29LEARN 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 (742 KB) Get e-Alerts Get e-Alerts

Extrapolation to Single-Relaxation-Time Behavior in Solutions of Poly(n-butylisocyanate)

The dielectric relaxation time of rodlike poly(n-butylisocyanate) (PBIC), (–CO–NR–)n, where R = C4H9, has been observed for dilute solutions as a function of the polydispersity in the PBIC molecular weight. The mode of relaxation is rotation about the minor axis of the rodlike molecule (end-over-end rotation). The dielectric relaxation time for this mode is a sensitive function of molecular weight, and a distribution of relaxation times Φ(τ) is observed whenever a distribution of molecular weights ψ(M) is present. A one-to-one correspondence between Φ(τ) and ψ(M) is established by observing the half-width W / 2 of the dielectric dispersion on a log frequency plot as a function of the ratio Mw / Mn, where Mn and Mw are the number and weight averages of ψ(M). Extrapolation of the W / 2 vs Mw / Mn data to the monodispersed case (Mw / Mn = 1.0) is carried out in order to determine whether or not a monodispersed sample has a single relaxation time. The accuracy of the extrapolated half-width suffers because the estimated uncertainty of the measured ratio Mw / Mn is ± 10%. The data do, however, satisfy a necessary condition for the presence of a single relaxation time. In the region Mw / Mn = 1.0 to 1.6, the experimentally observed Mw / Mn is in good agreement with Mw / Mn calculated from the observed Φ(τ). For these calculations it is assumed that each molecular species has a single relaxation time and that the molecular dipole moment is proportional to the molecular weight. A distribution ψ(M) may be obtained from the observed Φ(τ) if it can be assumed that all molecules have the same conformation.