Conformationally Sensitive Infrared Vibrations of the Syndiotactic Polystyrene/Ethylbenzene Complex

Moyses, Stephan; Spells, Stephen J.

doi:10.1021/ma981536w

Cited by 31 publications

(43 citation statements)

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“…One promising candidate is infrared (IR) spectroscopy, which is an important method for the characterization of polymer conformation [277], orientation [278], and solvent effects [279]. Newer developments in IR spectroscopy include time-resolved [280,281] and two-dimensional techniques [282,283] for dynamic processes in polymers, such as conformational changes, diffusion, and polymerization.…”

Section: Laser Application Of Polymersmentioning

confidence: 99%

Laser Application of Polymers

Lippert

2004

Polymers and Light

148

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Laser ablation of polymers has been studied with designed materials to evaluate the mechanism of ablation and the role of photochemically active groups on the ablation process, and to test possible applications of laser ablation and designed polymers. The incorporation of photochemically active groups lowers the threshold of ablation and allows high-quality structuring without contamination and modification of the remaining surface. The decomposition of the active chromophore takes place during the excitation pulse of the laser and gaseous products are ejected with supersonic velocity. Time-of-flight mass spectrometry reveals that a metastable species is among the products, suggesting that excited electronic states are involved in the ablation process. Experiments with a reference material, i.e., polyimide, for which a photothermal ablation mechanism has been suggested, exhibited pronounced differences. These results strongly suggest that, in case of designed polymers which contain photochemically active groups, a photochemical part in the ablation mechanism cannot be neglected. Various potential applications for laser ablation and the special photopolymers were evaluated and it became clear that the potential of laser ablation and specially designed material is in the field of microstructuring. Laser ablation can be used to fabricate three-dimensional elements, e.g., microoptical elements.Keywords Laser ablation · Ablation mechanism · Photopolymers · Polyimide · Spectroscopy This was not always true, of course. For many years, the laser was viewed as "an answer in search of a question". That is, it was seen as an elegant device, but one with no real useful application outside of fundamental scientific research. In the last two to three decades however, numerous laser applications have moved from the laboratory to the industrial workplace or the commercial market. Lasers are unique energy sources characterized by their spectral purity, spatial and temporal coherence, and high average peak intensity. Each of these characteristics has led to applications that take advantage of these qualities: -Spatial coherence: e.g., remote sensing, range finding and many holographic techniques. -Spectral purity: e.g., atmospheric monitoring based on high-resolution spectroscopies. -and of course the many other applications in communication and storage, e.g., CDs.All of these high-tech applications have come to define everyday life in the late twentieth century. One property of lasers, however, that of high intensity, did not immediately lead to "delicate" applications but rather to those requiring "brute force". That is, the laser was used in applications for removing material or heating. The first realistic applications involved cutting, drilling, and welding, and the laser was little more advanced than a saw, a drill, or a torch. In a humorous vein A.L. Schawlow proposed and demonstrated the first "laser eraser" in 1965 [4], using the different absorptivities of paper and ink to remove the ink without damaging the und...

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Section: Laser Application Of Polymersmentioning

confidence: 99%

Laser Application of Polymers

Lippert

2004

Polymers and Light

148

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“…11,13,[18][19][20][21]24,[27][28][29] By further heating at higher temperature, the γ form transfers to the R form of all-trans zigzag conformation. 18,24,29 In a series of papers, 22,23 we have studied the solventinduced crystallization phenomenon of sPS glass into the δ form by carrying out the time-resolved measurements of the infrared and Raman spectra and the X-ray diffraction and clarified the structural evolution process from the microscopic point of view. When an organic solvent is supplied to the glass sample, the random coils experience a so-called micro-Brownian motion and are regularized into short helical segments, which grow to longer helices and gather together to form a crystal lattice with organic solvent molecules.…”

Section: Introductionmentioning

confidence: 99%

“…That is to say, by investigating the solvent-exchange phenomenon in detail, we may obtain some important information on the characteristic structural features and polymersolvent interactions in the δ form crystal. The δ form is known to transfer to the γ form by heating 11,13,[18][19][20][21]24,[27][28][29] and to the δ e form by rinsing in acetone or methanol. 16,17,26 These phenomena are speculated also to be related with the unique structure of the δ form.…”

Section: Introductionmentioning

confidence: 99%

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Polymer−Solvent Interactions in Crystalline δ Form of Syndiotactic Polystyrene Viewed from the Solvent-Exchange Process in the δ Form and the Solvent Evaporation Phenomenon in the Thermally Induced δ−γ Phase Transition

Yoshioka

Tashiro

2003

Macromolecules

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The δ form, one of various crystalline forms of syndiotactic polystyrene (sPS), is a complex between sPS and solvent molecules. This crystalline form shows a solvent exchange between the originally absorbed solvent B and the newly supplied solvent A when the δ form sample was exposed to the solvent A atmosphere. We have carried out the time-resolved infrared spectral measurement during this solventexchange process and found that the solvent-exchange rate was almost common to any pair of solvents where the solvents A and B were toluene, chloroform, or benzene. On the other hand, when the δ form sample was heated above 150°C, it transferred to the γ form having no solvent molecules in the crystal lattice. The temperature, where most of solvent molecules were evaporated from the sample, was almost common to any kind of solvent originally absorbed in the δ form, as already pointed out by Gowd et al. [Macromolecules 2002, 35, 8509]. All these phenomena, i.e., the solvent-exchange phenomenon and the solvent evaporation phenomenon, were considered to come from the characteristic features of δ form crystal: the unique columnar structure and the relatively weak interactions between sPS chains and solvent molecules; the solvent molecules are trapped in the columns made by aggregated sPS chain stems. The solvent exchange was speculated to occur easily along the column axis. The evaporation of solvent in the δ-to-γ phase transition was considered to occur also along the column axis, and therefore almost no difference was observed for the different solvent system. When acetone was supplied to the δ form in the solvent-exchange experiment, the solvent originally trapped in the δ form was displaced by acetone molecules. But the original column structure was not affected by such a solvent exchangesdifferent from the cases of other such solvent as toluene, benzene, or chloroform. The structure changed from δ to δ e (empty δ) form for the first time when acetone evaporated from the sample at room temperature.

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“…The γ form was prepared by dipping the glassy sample into acetone 26 or by heating the δ form above 150°C and cooling to room temperature. 2,4,[17][18][19][20]23,24 b. Measurements. Identification of the thus-prepared three crystalline forms was made by measuring the X-ray diffraction profiles with a Rigaku RAD-ROC X-ray diffractometer.…”

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confidence: 99%

Infrared Bands Sensitive to the Chain Packing Mode in the Crystalline δ, δ_e, and γ Forms of Syndiotactic Polystyrene

Yoshioka

Tashiro

2003

Macromolecules

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Introduction. Syndiotactic polystyrene (sPS) shows a complicated polymorph depending on the crystallization conditions. The glassy sample prepared by quenching the melt crystallizes to the δ form in the atmosphere of organic solvent vapor. This δ form changes into the empty δ form (δ e ) by washing the δ form in boiling acetone. 16,23 By rinsing this sample in methanol, the more perfect δ e form is prepared. 25 In the δ e form the sPS chains with the TTGG helical conformation are packed, and all the solvent molecules are taken away but with keeping the empty spaces originally occupied by the solvents. 16 When the δ form is heated above 150 °C, it transforms to the γ form, 2,4,[17][18][19][20]23,24 in which the organic solvent molecules are purged away and only the sPS chains are closely packed in the crystal lattice. The sPS film cast from the acetone solution also gives the γ form. 26 Identification of the crystalline forms of δ, δ e , and γ is important in the structural study of the transition behavior among them. The X-ray diffraction method may be useful as a tool to identify these crystalline forms. [1][2][3][4][5][6][7][8][11][12][13][14][15][16][17][18][19][20][23][24][25][26] It is difficult, however, to distinguish concretely the positional relation between sPS chains and solvent molecules in the crystal lattice without the detailed structure analysis. 3,4,11,15 Rather, vibrational spectroscopy gives us more concrete information on the local packing structure and the polymer-polymer and/ or polymer-solvent interactions. It has been said for a long time that the infrared spectra of sPS are sensitive to the chain conformation [27][28][29][30][31] but are not very sensitive to the difference in chain packing mode. Moyses and Spell pointed out the spectral pattern difference between the R and γ forms in the 920-960 cm -1 region. 17 Recently, we have found that several infrared bands, in particular the bands in the region of 500-800 cm -1 , are different in their profiles between the δ, δ e , and γ forms, as will be described in the present paper. These characteristic bands are weak in intensity and seem to have been overlooked by many researchers for a long time. Since these three crystalline forms have essentially the same chain conformation, the difference in infrared spectra is considered to reflect a difference in chain packing mode or the difference in intermolecular interactions between polymer chains and/or between polymer chains and organic solvents. This spectral information is expected to be quite useful in the study of the structural changes occurring in the phase transitions between δ, δ e , and γ forms.Experimental Section. a. Samples. sPS samples (M w 203 000, M w /M n 3.01) were supplied by Idemitsu Petrochemical Co. Ltd., Japan. Glassy samples were prepared by quenching the melt into ice-water. The δ form was prepared by immersing the glassy sample directly into solvent. As the solvent, chloroform, toluene,

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Conformationally Sensitive Infrared Vibrations of the Syndiotactic Polystyrene/Ethylbenzene Complex

Cited by 31 publications

References 25 publications

Laser Application of Polymers

Laser Application of Polymers

Polymer−Solvent Interactions in Crystalline δ Form of Syndiotactic Polystyrene Viewed from the Solvent-Exchange Process in the δ Form and the Solvent Evaporation Phenomenon in the Thermally Induced δ−γ Phase Transition

Infrared Bands Sensitive to the Chain Packing Mode in the Crystalline δ, δ_e, and γ Forms of Syndiotactic Polystyrene

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Conformationally Sensitive Infrared Vibrations of the Syndiotactic Polystyrene/Ethylbenzene Complex

Cited by 31 publications

References 25 publications

Laser Application of Polymers

Laser Application of Polymers

Polymer−Solvent Interactions in Crystalline δ Form of Syndiotactic Polystyrene Viewed from the Solvent-Exchange Process in the δ Form and the Solvent Evaporation Phenomenon in the Thermally Induced δ−γ Phase Transition

Infrared Bands Sensitive to the Chain Packing Mode in the Crystalline δ, δe, and γ Forms of Syndiotactic Polystyrene

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Infrared Bands Sensitive to the Chain Packing Mode in the Crystalline δ, δ_e, and γ Forms of Syndiotactic Polystyrene