Structure Properties Of Poly Research Articles

Thermal and structural properties of poly(vinyl alcohol) doped with hydroxypropyl cellulose

AbstractThe growth and importance of medical and related health care and hygiene textile sectors are attributed to the improvement and innovations in both textile technology and medical procedures. The aim of this study was to examine some of the structural properties of pure poly(vinyl alcohol) (PVA) and hydroxypropyl cellulose (HPC) doped PVA of different weight percentages. This will lead to the choice of the optimum conditions suited for specific medical and surgical applications for which textile materials are currently used. Thermogravimetry was used to develop an instrumental system for the study of thermal stability and for identification of the individual components of several polymer blends. Derivative thermogravimetry provided clear information and distinguished between different generic types. Also, differential scanning calorimetry and its derivatives gave accurate values of glass‐transition temperature and melting temperature and gave detailed features of the steps of weight loss and changes in the heat of fusion. The X‐ray diffraction technique was used to determine the crystallinity/amorphosity ratio and the change in crystallite size at different dopant concentrations. The effect of doping with HPC on PVA structure was studied with spectrophotometric analyses. Variations in the group coordination in the IR region were followed. The data obtained indicated that measurable and remarkable changes in the thermal stability of PVA occurred at different doping concentrations. This may have been because the diffusion of dopant caused structural changes in the polymer matrix. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1914–1923, 2005

Filling‐level effect on the physical properties of MgBr2‐ and MgCl2‐filled poly(vinyl acetate) films

AbstractThe structural properties of poly(vinyl acetate) (PVAc) films filled with different levels of MgBr2 or MgCl2 were investigated. Differential scanning calorimetry revealed that, at certain filling levels of MgBr2 or MgCl2, two new transitions appeared. The first one was due to the α relaxation (Tα) associated with a crystalline region, and the second was due to the melting temperature (Tm). This implies that a crystalline phase was formed in the polymeric matrix. Changes occurring in Tα, Tm, and the melting peak area as a function of the filling level were examined. The X‐ray diffraction (XRD) pattern revealed that the pure PVAc film was amorphous. However, the addition of MgBr2 or MgCl2 led to the formation of a crystalline phase in the polymeric matrix that depended on the filling level. XRD also demonstrated that the structural changes depended not only on the metal ions but also on the halide ions. Scanning electron microscopy images for the studied samples were examined. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 112–119, 2003

FTIR Spectroscopic Study on Effects of Temperature and Polymer Composition on the Structural Properties of PEO−PPO−PEO Block Copolymer Micelles

Fourier transform infrared spectroscopy was used to study the effects of temperature and polymer composition on the structural properties of poly(ethylene oxide)−poly(propylene oxide)−poly(ethylene oxide) (PEO−PPO−PEO) block copolymer micelles in D2O solutions. The intrinsic probe, methyl groups in PPO blocks, is very sensitive to the local environment and used to characterize the aggregation process. When the temperature approaches the critical micellization temperature, the antisymmetric C−H stretching band of methyl groups and the symmetric deformation band of methyl groups shift toward lower frequencies. It indicates that the methyl groups are experiencing a progressively less polar environment and the interaction of methyl groups with water molecules is weakened by heat. At higher temperatures, the symmetric deformation mode of methyl groups is composed of two bands, which are assignable to hydrated (the band at 1378 cm-1) and dehydrated states (the band at 1373 cm-1). Part of methyl groups are dehydrated, and a significantly nonpolar microenvironment is created. The proportion of dehydrated methyl groups in Pluronic micelles increases with an increase of temperature, which means exclusion of water from the micellar core and formation of micelles with a denser PPO core at higher temperatures. The composition of Pluronic polymers also has a strong effect on the structural properties of the micelles. A more hydrophobic Pluronic polymer would form micelles with a higher proportion of the dehydrated methyl groups.

Doping effects on the electronic and structural properties of poly(para-phenylene) investigated from first-principles

We have performed density functional calculations for an ordered structure of Na doped poly(para-phenylene) (PPP) at a doping level of 1/3 Na atoms per phenyl ring. Relaxing the geometry results in a quinoid structure. The electronic band structure reveals a semiconductor to metal transition upon doping. The computed dielectric function (DF) including interband as well as free carrier contributions compares well with electron energy loss spectra on Na-doped para-hexaphenyl.

Structural properties of poly(propylene oxide) from diffraction experiments and reverse Monte Carlo simulation

Structural characteristics of an amorphous polymer melt, poly(propylene oxide) (PPO), have been studied by combining neutron and x-ray diffraction experiments and computer modeling using the reverse Monte Carlo (RMC) technique. The neutron diffraction experiments were performed on hydrogenous as well as deuterated samples. The experimentally determined nearest-neighbor distances were found to be in good agreement with literature data. The RMC modeling was applied for interpretation of the diffraction data to obtain more detailed structural information on bond angles, intermediate and long range correlations. For the intermediate range structure, the experimental structure factors demonstrate a first diffraction peak at about 1.45 Å−1, which from the RMC produced model can be related to the interchain distance of an almost random packing of the polymer chains. To investigate the chain conformation, partial atomic pair correlation functions have been calculated for atoms belonging to monomers close in sequence. The results show that the most probable conformation is a “stretched” trans conformation, where two consecutive methyl groups are pointing in almost opposite directions. Calculated bond and dihedral angle distributions support this finding and demonstrate the ability of the RMC method to produce polymer structures in good agreement with experimental results.

On the influence of regioregularity on the structural properties of poly (alky Ithiophenes)

We present an overview of thorough, X-ray diffraction studies of the crystalline structure and conformation of the series of poly(alkylthiophenes) (PATs) samples. Three types of polymers have been subjected to these studies: “common” PATs, with ca 80% “head to tail” couplings; regioregular, pure “head to tail” PATs, and regioregular, pure “head to head, tail to tail” poly(4,4′-dialkyl-2,2′-bithiophenes). The samples containing n-hexyl, n-octyl and n-decyl groups have been investigated. The computer modelling has been intensively used in order to interpret the diffraction data. The results obtained show the importance of the coupling sequences on the structural properties of the polymers studied. The main effect is related to the average torsion angle-between two adjacent thiophene rings: it exhibits a rather low value for the “head to tail” and tail to tail” couplings, but it is remarkably higher for the “head to head” couplings. This leads to the important relations between the planarity and the crystallinity of all samples studied

Structural aspects of oriented poly(octylphenylthiophene) studied in bulk and sub-micron layers by X-ray diffraction

The structural properties of poly(3-(4-octylphenyl)thiophene) (POPT) in bulk solution-cast films and in ultra-thin spin-cast films were studied by X-ray diffraction. The structural aspects associated with an induced colour change of the spin-cast films are highlighted. In bulk form POPT is partial crystalline and is characterized by a lamellar structure in which stacks of planar thiophene main chains are uniformly spaced by the octylphenyl side chains. The polymer is preferentially oriented with the side chains normal to the substrate surface. The crystal structure resembles that of poly(3-octylthiophene), although the lattice parameters along the side chains (α-axis) and along the stacking direction ( b-axis) are larger in POPT. The ultra-thin (sub-micron) spin-cast films, on the contrary, are essentially amorphous, but exposure to chloroform vapour and/or heat leads to an increase of crystallinity, paralleling a red shift of the absorption spectrum.

Morphological and structural properties of poly[bis(p‐phenylphenoxy)phosphazene

AbstractPoly[bis(p‐phenylphenoxy)phosphazene] (PB(4‐Ph)PP) has been investigated employing X‐ray diffraction technique and electron microscopy. Its unit cell dimensions were determined to be a = 4,18 nm, b = 1,83 nm and c = 0,957 nm with space group Pca21. At 21 5–220°C , PB(4‐Ph)PP transforms into an anisotropic liquid‐like phase corresponding to a new molecular ordering array. The thicker films are composed of the linked globules approximately 100 nm in diameter. Upon drawing, the globules transform into a rod‐like morphology 15–40 nm in width and exhibit a highly oriented X‐ray diffraction pattern. These unusual morphological features have been compared with features found in poly[bis(phenoxy)phosphazene] and poly[bis(halophenoxy)phosphazene] polymers. X‐ray diffraction and crystallization results support a smectic‐like side chain morphology.

Electronic absorption and structural properties of poly(di-n-butylsilylene) precipitated from solution at low temperature

Electronic absorption and structural properties of poly(di-n-butylsilylene) precipitated from solution at low temperature

Effects of ion implantation on poly(dimethylsilylene-co-methylphenylsilylene)

The effects of ion implantation on the electrical and structural properties of poly(dimethylsilylene-co-methylphenylsilylene), (DMMPS) thin films have been investigated. Ionic species of krypton, arsenic, fluorine, chlorine, and sulfur were implanted at energies ranging from 35 to 200 keV and with doses of up to 1 × 10 16 ion cm 2. The conductivity of the polymer increased upon implantation reaching a maximum value of 9.6 × 10 −6 (Ω cm) −1 for the case of arsenic ion at a dose of 1 × 10 16 ion cm 2 and energy of 100 keV. The results showed that ion implantation induced conduction in DMMPS was primarily due to structural modifications of the material brought about by the, energetic ions. Infrared analysis and Auger electron spectroscopy showed evidence for the formation of a silicon carbide-like structure upon implantation.

Electrical and Structural Study on Ion Implanted Poly(Dimethylsilylene-Co-Methylphenylsilylene)

ABSTRACTThe effects of ion implantation on the electrical and structural properties of poly(dimethylsilylene-co-methylphenylsilylene), DMIOPS, thin films have been investigated. Ionic species of krypton, arsenic, fluorine, chlorine, and sulfur were implfgted at energies ranging from 35 to 200 key and with doses of up to 1 × 1016 ion/cm2. The conductivity of the polymer increased upon implantation reaching a maximum value of 9.6 × 10−6 (Ω cm)−1 for the case of arsenic ion at a dose of 1 × 1016 ion/cm2 and energy of 100 keV. The results showed that ion implantation induced conduction in DUMPS was primarily due to structural modifications of the material brought about by the energetic ions. Infrared analysis and Auger electron spectroscopy showed evidence for the formation of a silicon carbide-like structure upon implantation.

Conformation and structural properties of poly- p-phenylene terephthalamide

The molecular and crystalline structure of rigid chain aromatic polyamide of poly- p-phenylene terephthalamide (PPTA) was subjected to conformation analysis. Results of calculation show satisfactory agreement with those of X-ray micrography. Structural properties of PPTA chains, determining the behaviour of this system in concentrated solutions in H 2SO 4, were identified. It was established that molecular interactions have a marked effect on molecular mobility, which is one of the main causes of the high heat stability of PPTA.