Molecular Motions In Poly Research Articles

Piezoelectric properties and molecular motion of poly(β‐hydroxybutyrate) films

AbstractPiezoelectric, elastic, and dielectric properties of films of poly(β‐hydroxybutyrate) (PHB), an optically active natural polymer, were measured as functions of frequency and temperature. In mechanical properties, three relaxation processes were observed at 10 Hz: the α dispersion at 130°C, the β dispersion at room temperature, and the γ dispersion at −120°C. It was concluded from x‐ray diffraction and the thermal expansion coefficient that the α dispersion can be ascribed to thermal molecular motions in the crystalline phase, that the β dispersion is the primary dispersion due to the glass transition, and that the γ dispersion is related to local molecular motion of the main chains in the amorphous phase. Piezoelectric relaxations were also observed in these relaxation regions. It is proposed that the high‐temperature process is due to ionic dc conduction. The piezoelectric relaxation at room temperature is ascribed to the increase of piezoelectric activity in the oriented noncrystalline phase, in which the sign of the piezoelectric modulus is opposite to that in the oriented crystalline phase.

Poly(O-acyl-hydroxy-L-proline) IV. Studies of Molecular Motions in Poly(O-acetyl, butyryl, hexanoyl, dodecanoyl, and benzoyl-hydroxy-L-proline) Films by the Spin Probe Technique

The molecular motion in poly(O-acetyl (Ac), butyryl (But), hexanoyl (Cap), dodecanoyl (Lau), and benzoyl (Bz)-hydroxy-L-proline (Hyp)) films was investigated by ESR measurements with 2,2,6,6-tetramethyl-4-hydroxypiperidine-1-oxyl (TEMPO) as the spin probe. As the length of acyl side chains increased, the temperature at which the separation of the outer extrema of ESR spectra reached 50 gausses (T50) decreased. The rotational correlation times (τc) obtained from the ESR spectra at −70°C for series of polymers were nearly the same. The values of τc at 130°C decreased with an increase in the acyl side chain length until the number of carbon atoms in the acyl chains reached 6. The activation energies of TEMPO in the polymers were less than 3 kcal mol−1 at low temperatures. At high temperatures, the activation energies of poly(O-Ac-Hyp) and poly(O-Bz-Hyp) differed scarcely from those at low temperatures. The activation energies of poly(O-But-Hyp), poly(O-Cap-Hyp), and poly(O-Lau-Hyp) were enhanced and particularly that of poly(O-Cap-Hyp), exceeding 10 kcal mol−1.

Dielectric relaxation and the molecular motion of poly(vinylidene fluoride) crystal form II under high pressure

The α dielectric relaxation of poly(vinylidene fluoride) crystal form II is studied under pressures up to 7 kbar at temperatures from 100° to 200°C. The isotherm for variation of the dielectric increment with pressure shows a maximum. This behaviour is examined on the basis of models of molecular motion for the α relaxation previously proposed; longitudinal disorder exists in the crystalline chains. The calculations reproduce the experimental results except for the pressure coefficient of the dielectric increment. The metastable conformation exists together with the most stable conformation in one chain, and dipole reversal parallel to the molecular axis occurs throughout the whole chain.

Molecular Motion in Poly(amino acid) VIII. β2-Form Crystals of Poly(D-glutamic acid)

The β2-form crystal of poly(D-glutamic acid) has a strong interaction between the sheets, in which chains are bound side by side by intermolecular hydrogen bonds. In this work, the molecular motion of poly(D-glutamic acid) in the fully annealed β2-form crystal was studied. The linear thermal expansion coefficient for the intermolecular periodicity, 10−5 (°C−1), was similar to that for the intersheet periodicity below 200°C, indicating that there is only ordinary thermal lattice vibration in the β2-form crystal. This finding differs from that for the β-form crystal having no interaction between the sheets. Above 200°C, the side chains began to move as a result of weakening of the strong interaction between the sheets, leading to disordering and degradation of the β2-form crystal. In the amorphous region, two segmental micro-Brownian motions occurred at 120°C and above 140°C. The former was attributed to free amorphous chains which have no hydrogen bonding between the carboxyl groups of the side chains, and the latter to the weakening of hydrogen bonds.

Molecular motion in poly(amino acid)s: 6. Molecular motion in a β-form crystal of poly(γ-methyl- d-glutamate)

The molecular motion in a β-form crystal of fully annealed poly(γ-methyl- d-glutamate) was investigated by means of an X-ray diffractometer and an infra-red spectrophotometer. The interchain periodicity (chains are bound side by side with intermolecular hydrogen bonds) increases linearly with increasing temperature, indicating ordinary thermal expansion of the lattice. The intersheet periodicty (sided chains pack into sheets) increases linearly up to 150°C and then the slope of the temperature dependence of the periodicty increases owing to the onset of active segmental motion of the side chains. It is evident from the temperature dependence of the wavenumber of the maximum of the infra-red absorption for NH stretching in the crystal that thermal expansion in the direction of the hydrogen bond is hardly affected by the segmental motion of the side chain.

Effect of side chains on molecular motion of poly (alkyl methacrylates) with isothermal annealing at temperatures below glass transition temperature

Abstract In this study, an estimation was made of the effect of side chains on the rate of enthalpy relaxation that occurred during isothermal annealing at temperatures below Tg. For the purpose of the analysis of the relaxation process, the relaxation time and activation energy obtained assuming a single relaxation time were used. Bulk-polymerized atactic poly(methyl methacrylate), poly(ethyl methacrylate), poly(isopropyl methacrylate), and poly(tert-butyl methacrylate) were used as samples. The enthalpy change that occurred during annealing in the glassy state was expressed in terms of variations in the enthalpy displacement from the equilibrium glassy state (excess enthalpy). The kinetics of the enthalpy relaxation was analyzed in terms of the excess enthalpy, δHt. δHt = δHO exp(-t/τ) From the relaxation time at a constant degree of enthalpy decrease, it was shown that the rate of the relaxation was influenced by the side chain. With a larger side chain, the relaxation time became longer. Considering t...

Mechanisms for crystal phase transformations by heat treatment and molecular motion in poly(vinylidene fluoride)

Mechanisms for crystal phase transformations by heat treatment and molecular motion in poly(vinylidene fluoride)

NMR study of molecular motion in poly(ethylene oxide)

Proton second moment and spin-lattice relaxation times T1, T1e and T1D for helical poly (ethylene oxide) 5000 over a wide temperature range are measured. The results of CW and pulse experiments corroborate the existence of a motional process in the crystalline region of the polymer interpreted as oscillation or rotation of molecules around their helical axes. The activation energy for this type of motion is found to be 12 kcal/mole.

ChemInform Abstract: A NUCLEAR MAGNETIC RESONANCE STUDY OF THE LOCAL CONFORMATION AND MOLECULAR MOTIONS OF POLY(N5‐(3‐HYDROXYPROPYL)‐L‐GLUTAMINE) IN AQUEOUS SOLUTION

Chemischer InformationsdienstVolume 11, Issue 23 Physical Organic Chemistry ChemInform Abstract: A NUCLEAR MAGNETIC RESONANCE STUDY OF THE LOCAL CONFORMATION AND MOLECULAR MOTIONS OF POLY(N5-(3-HYDROXYPROPYL)-L-GLUTAMINE) IN AQUEOUS SOLUTION B. PERLY, B. PERLYSearch for more papers by this authorC. CHACHATY, C. CHACHATYSearch for more papers by this authorA. TSUTSUMI, A. TSUTSUMISearch for more papers by this author B. PERLY, B. PERLYSearch for more papers by this authorC. CHACHATY, C. CHACHATYSearch for more papers by this authorA. TSUTSUMI, A. TSUTSUMISearch for more papers by this author First published: June 10, 1980 https://doi.org/10.1002/chin.198023049AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume11, Issue23June 10, 1980 RelatedInformation

A nuclear magnetic resonance study of the local conformation and molecular motions of poly(N5-(3-hydroxypropyl)-L-glutamine) in aqueous solution

A nuclear magnetic resonance study of the local conformation and molecular motions of poly(N5-(3-hydroxypropyl)-L-glutamine) in aqueous solution

The effect of fillers on the molecular motions of poly(methyl methacrylate)

Abstract The effect of fillers on the molecular motions of PMMA was investigated by using the method of dielectric relaxation. Carbon black, white carbon and CaCO3 were used as fillers in amount of 0 – 30% by weight. At higher frequencies (> 3 KHz), the molecular motions of the main chain (a dispersion) and the side chain (s dispersion) were converged into a single peak. In the lower frequency regions (30 – 600 Hz), the individual motions can be separated, and the effect of filler on the motions can be identified. The results differ from PMMA block copolymer systems having an island‐sea structure.

Molecular Motions of Poly(γ-monosubstituted-benzyl D-glutamate) in the Solid State

Dielectric measurements were performed at frequencies ranging from 30 Hz to 300 KHz and at temperatures between −150 and 120°C for the following Poly(γ-monosubstituted-benzyl D-glutamate)s; Poly(γ-o-chlorobenzyl D-glutamate) (o-ClPBDG), Poly(γ-m-chlorobenzyl D-glutamate) (m-ClPBMDG), Poly(γ-p-chlorobenzyl D-glutamate) (p-ClPBDG), Poly(γ-p-nitrobenzyl D-glutamate) (p-NPBDG), Poly(γ-p-methylbenzyl D-glutamate) (pMePBDG) and a racemic mixture of p-ClPBDG and p-ClPBLG (p-ClPBDG+p-ClBLG). Each sample exhibited a dielectric loss maximum in the temperature range of 30—90°C. These loss maxima were attributed to the onset of large scale motion of side chains. The temperatures of maximum loss (the dispersion temperature) are shifted by the introduction of substituents. The dispersion temperature is highest for p-ClPBDG among three monochlorosubstituted PBDGs. For p-monosubstituted-PBDGs, p-NPBDG, which has the side chain with the largest dipole moment among three p-substituents studied, showed the highest dispersion temperature. The results are explained in terms of restriction caused by dipole–dipole interaction among dipoles in the side chain. The enormous relaxation strength of o-ClPBDG was considered to reflect a certain conformation of the side chain originating from steric hindrance between the ester and the o-substituent of a side chain. Racemic mixtures of p-ClPBDG and p-ClPBLG showed no evidence of the first-order solid–solid transition observed for racemic mixtures of PBDG and PBLG.

Molecular motion in poly(L‐histidine) in the solid state

AbstractMolecular motions in poly(L‐histidine) (PLH) and its hydrochloride in the solid state have been studied by NMR and dielectric measurements. Four relaxation processes, β,γ,δ, and ε, are observed for PLH. The δ relaxation is assigned to rotation of an imidazole ring about the CβCγ bond, since the observed activation energy of 2.7 kcal/mole agrees with the calculated energy barrier for rotation of the central imidazole ring about CβCγ in an imidazole trimer model and the experimentally determined dielectric relaxation strength is consistent with the theoretically estimated value based on the two‐state transition theory. The γ relaxation was attributed to the restricted rotational motion about CαCβ. The β relaxation is related to motion of water molecules bound by PLH. The ε relaxation is assigned to the wagging mode of imidazole groups in the defect region as observed for polymers containing pendent aromatic rings. No relaxation is observed in the hydrochloride of PLH due to the increased interaction between imidazolium cations as side groups. This is confirmed by the comparison of dipole moments of protonated and deprotonated imidazoles estimated by molecular‐orbital calculations.

The electrophysical properties of poly(arylate-arylenesulphone oxide) block copolymers

The molecular motion of poly(arylate-arylenesulphone oxide) block copolymers of the same total chemical composition but obtained by different methods, also of the corresponding homopolymers and mixtures thereof has been investigated, and their transition temperatures determined, by electrical conductivity, electret thermal analysis and dielectric loss methods. It was found that intermolecular interaction between the oligoarylate and oligo(arylenesulphone oxide) components occurs in the block copolymers, with the result that the glass temperature of the oligoarylenesulphone oxide) blocks is higher than that of the corresponding poly-(arylenesulphone oxide). Of the block copolymers studied the “regularly alternating” block copolymer has the lowest segmental mobility and the highest glass temperature.

Thermal sampling in polymers with distributed relaxations: PMMA

The thermal sampling (t.s.) technique, a modification of thermally stimulated discharge (t.s.d.), has been applied to investigate molecular motions in poly(methyl methacrylate) and to compare the results with the theory of t.s. It was found that the distribution of relaxation times is represented by a distribution in activation energies and the temperature dependence of relaxation times is governed by the compensation law. A statistical test confirmed the validity of the compensation effect in the case of glass transition in PMMA. A theory based on self-diffusion has been applied to explain this effect and good agreement of the calculated expansion coefficient with the dilatometric data was obtained.

NMR studies of conformation and molecular motion of poly(methyl methacrylate) in solution

AbstractNMR shift reagent, tris(dipivalomethanato)europium(III), was applied to the 1H NMR measurement of isotactic and syndiotactic poly(methyl methacrylate) in solution in the temperature range 25–80°C. The solvents used were benzene (C6D6), chloroform (CDCl3), and carbon tetrachloride (CCl4). By comparing the observed values of paramagnetically induced shift with the values of geometric factor calculated for several kinds of conformational models hitherto proposed for these polymers, the possible conformations of the respective polymers in solution were eludicated. Furthermore the variation, as a function of temperature, of the carbon‐13 spin‐lattice relaxation times of individual carbons of isotactic and syndiotactic poly(methyl methacrylate) in benzene and chloroform solutions were measured and the correlation between the molecular motion and the conformation is discussed. It is pointed out that the conformation depends both on the stereochemical configuration and the nature of solvent, and the molecular motion depends both on the conformation and the configuration.

Network properties: 3. A pulsed n.m.r. study of molecular motions in some AB-crosslinked polymers

This paper presents the results of a pulsed n.m.r. study of molecular motions in poly (methyl methacrylate) (PMMA) and poly (methyl acrylate) (PMA) chains in a series of multicomponent network polymers consisting of poly (vinyl trichloroacetate) (PVTCA) crosslinked with PMMA and with PMA, with emphasis on segmental motions. Results of ancilliary broad line n.m.r. and dilatometric studies are included; the latter demonstrate that in PMA containing polymers microphase separation of the components is complete while in PMMA containing polymers a mixed microphase of PVTCA and PMMA and a pure PMMA microphase are formed. α-Methyl group rotations in PMMA chains and segmental motions in both PMMA and PMA chains are modified with respect to those in the corresponding homopolymers. Modifications to the segmental motions in the crosslinking chains are attributed to the fact that their chain ends are attached to PVTCA chains. It is considered that the comparative rigidity of PVTCA chains ( T g ∼ 60°C) reduces segmental motions in at least portions of the PMA chains ( T g ∼ 5°C) while the comparative mobility of PVTCA enhances segmental motions in PMMA ( T g ∼ 100°C). Thus the molecular mobility of chains of one polymer is to some extent transmitted to chains of another polymer to which it is attached.

Molecular motions in poly( N-vinylsuccinimide)

The dielectric and pulsed n.m.r. relaxation of poly( N-vinyl succinimide) has been investigated as a function of frequency and temperature. Five loss processes (α to ϵ) have been observed and assigned to main chain motion (α, β) and ring deformations (γ, δ, ϵ) on the basis of comparative work with chemically analogous polymers previously reported 1–4.

Nuclear magnetic relaxation and molecular motion in poly(vinylidine fluoride)

AbstractPulsed NMR T1, T2, and T1ρ measurements are reported for poly(vinylidine fluoride) (PVF2). The results demonstrate clearly the presence of four relaxation processes, three amorphous and one crystalline. The α relaxation is undoubtedly a crystalline one, while β and γ are both amorphous, in agreement with earlier conclusions from dielectric and dynamic mechanical measurements. The fourth relaxation (β′) observed initially in the mechanical measurements of Kakutani, but undetected in dielectric experiments, has been confirmed in our results and the process is described by an activation energy of 15.1 kcl/mole. Motion of folds on the surface of crystal lamellae is deemed to be the responsible mechanism for the β′ relaxation. Two models have been considered in the interpretation of the α process; rotation of crystalline chains in the vicinity of defects and rotational oscillation of restricted amplitude of all crystalline chains about the main chain axes. Rotation of amorphous chains is a possible mechanism for the γ process while motions of a general nature are responsible for the β relaxation. Our experimental results again indicate that spin diffusion plays an important role in the overall NMR response of the polymer.

Molecular motion of poly(methyl methacrylate), polystyrene and poly(propylene oxide) in solution studied by 13C n.m.r. spin-lattice relaxation measurements: effects due to distributions of correlation times

The 13C n.m.r. spin lattice relaxation times and Nuclear Overhauser Enhancements have been measured for solutions of poly(methyl methacrylate) (PMMA) in o-dichlorobenzene, polystyrene (PS) in pentachloroethane and poly(propylene oxide) (PPO) in CDCI 3 as a function of temperature. For PS and PMMA a T 1 minimum is observed close to ambient temperature. The single correlation time theory of relaxation is inadequate to explain the relaxation data, but within experimental error, the data can be interpreted in terms of either the Cole-Cole distribution of correlation times, the log − χ 2 distribution or a conformational jump model of chain dynamics.