Molecular Orientation Of Poly Research Articles

Enhancing the Mechanical Properties of Poly(vinyl alcohol) Fibers by Lithium Iodide Addition.

The effect of lithium iodide (LiI) on the mechanical strength, properties, and molecular orientation of poly(vinyl alcohol) (PVA) fibers spun by wet spinning and then heat-stretched was studied. The stretchability of LiI-PVA fibers was improved, and the rupture during stretching was suppressed compared to PVA fibers. In addition, the tensile strength and elastic modulus of the thermally stretched fibers have been significantly improved. It was also found that the addition of LiI improves the molecular orientation of PVA. This was achieved because LiI reduced the hydrogen bonds between the molecular chains of PVA, resulting in reduced crystallinity. Most of the LiI in the fiber could be removed by a coagulation bath and washing during the spinning process. This means that LiI is eventually removed, and the heat-treatment strengthens the hydrogen bonds, resulting in excellent mechanical strength.

Strain-induced crystal growth and molecular orientation of poly(isobutylene-isoprene) rubber at low temperatures.

With the combination of a low-temperature extension rheometer and in situ synchrotron radiation wide-angle X-ray diffraction (SR-WAXD), the strain-induced crystallization (SIC) of poly(isobutylene-isoprene) rubber (IIR) was studied in the low-temperature region (-60 °C → 25 °C). The detailed structural evolution of IIR during the SIC is summarized in the strain-temperature space, where three distinct temperature zones are defined. The absence of the SIC in zone I (T > 0 °C) results in the poorest drawability of IIR among all measured temperatures. And with respect to the lowest temperature zone III (-60 °C < T < -50 °C), the SIC still occurs with low ultimate crystallinity (ca. 0.9%). More complicated structural evolution induced by the strain occurs in the intermediate-temperature zone II (-50 °C ≤ T ≤ 0 °C). The orientation ratio of the amorphous part Oa increases monotonically with the increment of the strain, but reaches a platform with Hencky strain ε > ca. 1.8. Meanwhile, the strain-induced crystal growth of IIR is evidenced by the dramatic increment of the lateral crystallite size of (110) and (113) planes. Moreover, the retraction experiment further reveals the network evolutions of IIR: suffering from low ultimate crystallinity (<ca. 9%), the network chain of IIR remains in series upon fracture. The current study clarifies the contribution of the SIC and molecular orientation to the self-enhanced mechanical properties of IIR at low temperatures.

Analysis of the Molecular Orientation of Poly(3-hexylthiophene) on Silicon Treated with Silane Coupling Agents, by Infrared p-Polarized Multiple-angle Incidence Resolution Spectrometry

The molecular orientation of poly(3-hexylthiophene) (P3HT) thin film on silicon substrate treated with silane coupling agents was evaluated by infrared (IR) p-polarized multiple-angle incidence resolution spectrometry (pMAIRS). It was found that the orientation is altered by interaction between the end group of the silane coupling agent and the P3HT ring. The amino group forming the end group of the silane coupling agent strongly influences the P3HT molecular orientation, causing it to shift to a more perpendicular direction with respect to the substrate.

Nanoimprinting-induced molecular orientation in poly(3-hexylthiophene) nanogratings and its extraordinary retention after thermal annealing

Face-on orientation of poly(3-hexylthiophene) nanogratings induced by nanoimprinting and its remarkable retention after thermal annealing.

Influence of side chains on the self-alignment capability of electroluminescent polyfluorenes.

We report a significant role of side chains in the propagation of molecular orientation upon annealing the liquid crystal phase of polyfluorenes. Direct rubbing of poly(9,9-di(octyl)fluorene) led to the orientation of polymer segments in the top-most region of the film and enhanced propagation of this orientation along the rubbing direction was observed upon annealing. In contrast, the rubbing-induced molecular orientation of poly(9,9-di(ethylhexyl)fluorene) segments completely disappeared upon annealing in the nematic melt state. The higher order of the side chain structures in poly(9,9-di(octyl)fluorene) were found to allow the propagation of the three-dimensional molecular alignment. From integrated experimental and density functional theory studies, we propose that side chain interdigitation generates a unique alignment behavior of poly(9,9-di(octyl)fluorene).

Preferable Molecular Orientation of Poly(3-hexylthiophene) on Self-Assembled Monolayers: Molecular Dynamics Simulation

Using molecular dynamics simulations, we theoretically investigate the molecular orientation of poly(3-hexylthiophene) (P3HT) on hydrophobic and hydrophilic self-assembled monolayers (SAMs). In particular, we study the effects of roughness at the SAM surfaces on the molecular orientation of P3HT molecules put on the surface. The energetically preferable molecular orientation does not change by the roughness we introduced. The roughness induces more frequent transition between the edge-on and face-on orientations, when a small number of P3HT molecules are put on the hydrophobic SAM.

Abnormal Anti-Stokes Raman Emission and Infrared Dichroism Studies on Poly(p-phenylenevinylene)/Single-Walled Carbon Nanotube Composites

Using surface-enhanced Raman scattering (SERS) and Fourier transform infrared spectroscopy (FTIR) in the grazing angle incident reflection geometry, new data concerning the abnormal anti-Stokes Raman emission (AASRE) and the molecular orientation of poly(p-phenylenevinylene) (PPV) deposited on metallic supports of Ag and Au are reported. The particular dependencies of the anti-Stokes Raman intensity on the Raman shift, the sample thickness, and the incident pump intensity are highlighted in this paper. In the spectral range of 800–1000 cm–1, the FTIR spectra of PPV films deposited on Ag and Au supports show a dichroism similar to that reported for the free-standing PPV film. Significant differences are reported in the spectral range of 1400–1700 cm–1 for the s-and p-polarized FTIR spectra of PPV films deposited on Au and Ag supports. The annealing treatment at 110 °C of the PPV precursor solution in the presence of single-walled carbon nanotubes (SWNTs) induces a noncovalent functionalization of carbon na...

Imaging of Two-Dimensional Distribution of Molecular Orientation in Poly(ethylene oxide) Spherulite Using IR Spectrum and Birefringence

The two-dimensional quantitative imaging of molecular chain orientation is presented together with a chemical FT-IR imaging, in comparison with the optical birefringence imaging. The molecular chain orientation of the spherulite of poly(ethylene oxide) (PEO) is visualized using the four polarizations method of FT-IR imaging. The magnitude of orientation function and the azimuth angle of orientation axis are calculated with the FT-IR absorbance measured with a linear polarizer settled at four different angles. Retardation and the slow axis in a refractive index ellipsoid are calculated using transmission intensity measured with an electrical-controlled variable elliptical analyzer and a circular polarizer. In spite of the 6 times difference of the spatial resolution, the azimuth angle image determined from FT-IR imaging detects the change of molecular chain orientation, giving the similar line profiles of azimuth angle to that of slow axis determined from birefringence on the spherulite interface. A good c...

Molecular orientation of poly(3-butylthiophene) friction-transferred films

Oriented thin films of regioregular-poly(3-butylthiophene) (P3BT) were prepared by friction transfer method. Molecular orientation of P3BT in the friction-transferred films was investigated with grazing-incidence X-ray diffraction (GIXD), polarized ultraviolet–visible (UV) spectra, and infrared (IR) spectra. Polarized UV spectra showed the polymer backbones were aligned in the friction direction. GIXD measurements suggest that a axis in P3BT film is normal to the substrate, that is, π-stacking direction tends to be parallel to the substrate. This orientation is different from those of friction-transferred poly(3-hexylthiophene) and poly(3-dodecylthiophene).

Thermal Behavior and Molecular Orientation of Poly(ethylene 2,6-naphthalate) in Thin Films

Studies on structural orientation of polymers near the surface and interface or in confined geometry mostly dealt with the resulting anisotropic arrangements of the involving polymer molecule. The molecular dynamics during the orientation process of a target polymer was, however, not concerned so far. In the present study, molecular orientation of poly(ethylene 2, 6-naphthalate) (PEN) thin films during isothermal and nonisothermal crystallization was investigated by the combination of in situ reflection−absorption infrared spectroscopy (RAIR) and grazing incidence X-ray diffraction (GIXD) techniques. The results disclose that the naphthalene ring and CO in PEN molecule is prone to alignment parallel to the film surface during the formation of α-form crystalline. In situ RAIR measurements further suggest that the kinetics of molecular orientation exhibits clearly different from that of crystallization. In situ GIXD experiments done by synchrotron radiation also reveal the structural developing process during the orientation, in which the naphthalene ring rotates to be more parallel to the surface than the lattice plane containing b and c axes. Furthermore, the possible mechanisms for the observed orientation in PEN thin films are also discussed.

The effect of multi-walled carbon nanotubes on the molecular orientation of poly(vinyl alcohol) in drawn composite films

Poly(vinyl alcohol) (PVA)/multi-walled carbon nanotube (MWNT) composite films were prepared by casting a DMSO solution of PVA and MWNTs, whereby the MWNTs were dispersed by sonication. A significant improvement in the mechanical properties of the PVA drawn films was achieved by the addition of a small amount of MWNTs. The initial modulus and the tensile strength of the PVA drawn film increased by 30% and 45% respectively, with the addition of 1 wt% MWNTs, which are close to those calculated from the rule of mixtures, and were strongly dependent upon the orientation of the PVA matrix. The mechanical properties, however, were not improved with a further increase in the MWNT content. The orientation of MWNTs in the composite was not well developed compared to that of the PVA matrix. This result suggests that the improvement of the molecular orientation of the PVA matrix plays a major role in the increase of the mechanical properties of the drawn PVA/MWNT composite films.

Thermal Hysteresis and Thickness Dependence of the Molecular Orientation of Poly(di-n-hexylsilane) in the Film State

Molecular orientation of poly(di-n-hexylsilane) adsorbed on poly(vinyl alcohol) film has been studied by making use of the stretching technique. Dichroic ratio, Rd, strongly depended on the thickness of poly(di-n-hexylsilane) thin film and the highest value ca. 19 was observed at the film thickness of 110 +/- 30 nm. The thermal hysteresis of the molecular orientation was observed in the heating-cooling cycles. By studying the fluorescence spectrum it was confirmed that a portion of the poly(di-n-hexylsilane) molecules were in transoid conformation even at 320 K, although most of poly(di-n-hexylsilane) molecules were in disordered conformation (conformation D). This poly(di-n-hexylsilane) in transoid conformation is formed in the stretching process and may play a role of crystallization nucleus to induce the whole orientation of the poly(di-n-hexylsilane) in the film state.

Molecular Orientation of Poly(Ethylene Terephthalate) and Poly(Butylene Terephthalate) Probed by Polarized Raman Spectra: A Parallel Study

Poly(ethylene terephthalate) (PET) and poly(butylene terephthalate) (PBT) samples uniaxially drawn above Tg and beyond the yield point exhibit significant differences in their molecular orientation behavior as probed by polarized Raman spectra. The quasi-amorphous PET samples, drawn close to the Tg, manifest considerable molecular orientation development; however, when drawn above Tg + 30 degrees C, they exhibit significant molecular orientation relaxation. The semi-crystalline PBT samples maintain prominent molecular orientation even when drawn 110 degrees C above Tg. The drawing process, in PET samples, when resulting in molecular orientation, is accompanied by a gauche-trans transformation of the glycol linkage and a concurrent initiation of crystallinity development. In PBT specimens, it gives rise to a coexistence of alpha- and beta-type crystalline phases. Phase alpha is predominant at high draw temperatures, i.e., Tg + 110 degrees C, while phase beta dominates at low draw temperatures, i.e., Tg + 10 degrees C. PBT samples, with beta-phase predominance, left at relevant draw temperatures without stress, exhibit a beta-alpha phase change though no molecular orientation relaxation occurs. A note is made of the fact that complete molecular orientation analysis of PBT segments utilizing the depol method gives more reliable results than the simplified analysis assuming a cylindrical tensor for the 1614 cm(-1) symmetric stretch of the para-disubstituted benzene ring of PBT. In this context, segments of PBT specimens rich in alpha-phase exhibit higher molecular orientation than those with beta-phase predominance.

Investigation of surface molecular orientation of poly(dimethylsiloxane-co-diphenylsiloxane)-modified poly(amic acid) films using dynamic contact angle measurements, NEXAFS and XPS

Since poly(dimethylsiloxane)-modified poly(amic acid) was not wetted by the photoresist, poly(dimethylsiloxane-co-diphenylsiloxane)-modified poly(amic acid) was synthesized to improve the wettability of photoresist. From a study on dynamic contact angles of water, the initial advancing contact angles on poly(dimethylsiloxane)-modified poly(amic acid) and those on poly(dimethylsiloxane-co-diphenyl-siloxane)-modified poly(amic acid) are almost the same, but the equilibrium advancing contact angles on poly(dimethylsiloxane-co-diphenylsiloxane)-modified poly(amic acid) are much smaller than those on poly(dimethylsiloxane)-modified poly(amic acid). The decrease in equilibrium advancing contact angles on poly(dimethylsiloxane-co-diphenylsiloxane) appears to indicate migration of phenyl groups to the surface in the polar environment. Thus, photoresist could be wetted on the poly(dimethylsiloxane-co-diphenylsiloxane)-modified poly(amic acid) film. Near-edge X-ray absorption fine structure spectroscopy (NEXAFS) and X-ray photoelectron spectroscopy (XPS) were used to investigate the orientation and surface migration of molecules in poly(dimethylsiloxane-co-diphenylsiloxane).

Molecular orientation of poly(ethylene terephthalate) and buried interface characterization of TiO2 films on poly(ethylene terephthalate) by using infrared-visible sum-frequency generation

The surface molecular orientation of biaxially stretched poly(ethylene terephthalate) (PET) films and the buried interface between TiO2 layer and PET substrate have been investigated by using infrared-visible sum-frequency generation (SFG). The surface SFG spectra showed a pronounced peak at 1710 cm−1 which is characteristic of the CO stretching vibration in an ester function. The polymer chains at the surface appear to be well aligned. After deposition of a TiO2 layer on PET surface by using oxygen-radical beam assisted method, SFG spectra exhibited a band at 1688 cm−1, which suggests the formation of Ti–O–C bonds. Oxygen radical affects phenyl ring part and induces a ring-opening reaction.

Surface electronic structure and molecular orientation of poly(9-vinylcarbazole) thin film:: ARUPS and NEXAFS

The molecular orientation at the surfaces of poly(9-vinylcarbazole) (PvCz) thin films was studied by angle-resolved ultraviolet photoelectron spectroscopy and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. The observed take-off angle ( θ) dependence of photoelectron intensities from top π band peaks clearly at larger θ than the calculated one for the three-dimensional isotropic random orientation model. The results indicate that there are more pendant groups with large tilt angles than the three-dimensional isotropic random orientation model, which is in good agreement with the result obtained from NEXAFS spectroscopy. The surface electronic states of PvCz may be rather dominated by σ(C–H) states at the pendant carbazole group than π states

Evidence of molecular orientation in poly(3-butylthiophene) films by electron spin resonance measurements

Evidence of molecular orientation in poly(3-butylthiophene) films by electron spin resonance measurements

X-ray method of the evaluation of molecular orientation in poly(ethylene terephthalate) fibres

X-ray method of the evaluation of molecular orientation in poly(ethylene terephthalate) fibres

Effects of microdomain structures on the molecular orientation of poly(styrene-block-butadiene-block-styrene) triblock copolymer

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTEffects of microdomain structures on the molecular orientation of poly(styrene-block-butadiene-block-styrene) triblock copolymerShinichi Sakurai, June Sakamoto, Mitsuhiro Shibayama, and Shunji NomuraCite this: Macromolecules 1993, 26, 13, 3351–3356Publication Date (Print):June 1, 1993Publication History Published online1 May 2002Published inissue 1 June 1993https://doi.org/10.1021/ma00065a018RIGHTS & PERMISSIONSArticle Views363Altmetric-Citations58LEARN 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 (1 MB) Get e-Alerts Get e-Alerts

Molecular Orientation of Poly(2,2′;-Bipyridine-5,5′-Diyl) Film Prepared by Vacuum Deposition on the Glass Substrate as Determined with SHG Technique

Abstract We have found that vacuum-deposited poly(2,2′-bipyridine-5,5′-diyl) PBPy aligns along glass substrate surface using SHG technique. The SHG activity originates from the interface where the PBPy molecules coordinate to acidic Si-O-H group on the glass surface.