Effect of Compressed CO<sub>2</sub> on Phase Transitions and Polymorphism in Syndiotactic Polystyrene

Handa, Y. P.; Zhang, Zhiyi; Wong, Betty

doi:10.1021/ma9712209

Cited by 143 publications

(185 citation statements)

References 43 publications

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“…It is worth noting that a nanoporous structure in these crystals can be prepared by removing the incorporated solvent in acetone or supercritical carbon dioxide (scCO2). [21][22][23][24][25] Similar molecular structures have been reported for syndiotactic poly(p-methylstyrene) (sPPMS); the all-trans conformation (forms III, IV, and V) induced by annealing, and the ttgg conformation (forms I and II) induced by organic solvents. [26][27][28] In addition, three clathrate forms of -, -, and -classes which contain solvent in the crystal unit have been reported.…”

Section: Introductionsupporting

confidence: 61%

Absorption Kinetics of Phenol into Different Size Nanopores Present in Syndiotactic Polystyrene and Poly (p-methylstyrene)

Furukawa¹,

Nakaoki²

2013

Polymer Science

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Section: Introductionsupporting

confidence: 61%

Absorption Kinetics of Phenol into Different Size Nanopores Present in Syndiotactic Polystyrene and Poly (p-methylstyrene)

Furukawa¹,

Nakaoki²

2013

Polymer Science

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“…In addition, scCO 2 is an ecofriendly solvent. The phase transition and polymorphism of sPS induced by CO 2 were reported by Handa et al 15 They found that sPS undergoes the solid-solid phase transition which cannot be induced by ordinary organic solvents. They also found that the phase transition and glass transition temperatures in compressed CO 2 are lower than those in ambient states, indicating that a compressed or a supercritical CO 2 is an effective plasticizer for sPS.…”

mentioning

confidence: 69%

Crystallization Condition of Glassy Syndiotactic Polystyrene in Supercritical CO2

Nakaoki

Fukuda

Nakajima

et al. 2003

Polym J

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ABSTRACT:Polymorphism of syndiotactic polystyrene (sPS) induced by supercritical CO 2 (scCO 2 ) was investigated as functions of temperature and pressure by using infrared spectroscopy and X-ray diffraction. When a glassy sPS was incubated in scCO 2 at 18 MPa, a modification with the trans-trans-gauche-gauche (t 2 g 2 ) conformation appeared between 40• C and 80• C, and the planar zigzag form appeared above 60• C. Both forms coexisted between 60• C and 80• C. Below the critical temperature of CO 2 (31.1 • C) no crystallization occurred at any pressure. When the pressure of CO 2 is below the critical pressure (7.2 MPa), the t 2 g 2 form did not appear at any temperature but the planar zigzag form appeared above 90• C. These results indicate that incubation in supercritical CO 2 is necessary for the formation of the t 2 g 2 form. On the other hand, the planar zigzag form was obtained irrespective of the physical states of CO 2 , but depended on the incubation temperature and pressure. This indicates that the conformational stability of the planar zigzag form depends only on the thermal factors. The crystallization temperature into the planar zigzag form decreased with increasing pressure of CO 2 due to the plasticizer effect of CO 2 . KEY WORDS Crystallization / Syndiotactic Polystyrene / Supercritical CO 2 / Infrared Spectroscopy / Syndiotactic polystyrene (sPS) exhibits polymorphism. So far four crystal modifications and two mesomorphic phases have been reported, since Ishihara et al. 1 succeeded the synthesis of highly syndiotactic polystyrene. [2][3][4][5][6][7][8] The molecular conformation of the α and β forms is planar zigzag but that of the γ and δ forms is t 2 g 2 . Kobayashi and his coworkers revealed the characteristic vibrational modes for these conformations using the infrared and Raman spectroscopies. [9][10][11][12][13] It is worth noting that the formation of the modifications with the t 2 g 2 sequence requires the assistance of an organic solvent. Several methods are known to obtain the t 2 g 2 crystal forms, i.e., casting from an organic solution, soaking the glassy sPS in an organic non-solvent, and exposing the glassy sPS in vapor of an organic solvent. For example, chloroform, benzene, toluene, and other many aromatic compounds were found to induce the δ-form. 5, 9 Since the δ-form is one of the host-guest type crystals formed by the sPS chains and solvent molecules, the cavity created by the sPS chains in the crystal is believed to play an important role to form the complex structure. 8,14 The γ-form also takes the t 2 g 2 conformation but is formed without solvents. 5,11 These crystal structures have been investigated in terms of various methods. Among them, the infrared spectroscopy is very sensitive to conformational changes and provides information not only on the lo- † To whom correspondence should be addressed.cal vibrations such as the stretching and bending modes but also on the molecular symmetry defined by the factor group analyses. The symmetries of the planar zigzag and the t 2 g ...

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“…The absorption of CO 2 results in considerable swelling in amorphous polymers and crystallization in semicrystalline polymers by reordering polymer chains at lower temperatures. 7,8,13,36 Figure 1 shows the XRD patterns for the untreated sample and the samples saturated with CO 2 at 1.4, 2.1, 2.8, 3.5 and 5.5 MPa and 25 • Cf o r2 4h . The untreated sample is amorphous as evident from the XRD analysis.…”

Section: Results and Discussion Co 2 -Induced Crystallizationmentioning

confidence: 99%

“…11 Under a CO 2 environment, the crystalline melt point (T m ) and cold crystallization temperature (T c ) are also depressed. 10,12,13 To date CO 2 foaming has been mainly applied to amorphous polymers. The foaming process of a semicrystalline polymer is much more complex than that of an amorphous polymer due to the presence of non-plasticized crystals.…”

Section: Introductionmentioning

confidence: 99%

Carbon dioxide‐induced crystallization in poly(L‐lactic acid) and its effect on foam morphologies

Liao

Nawaby

Whitfield

2010

Polymer International

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The effect of carbon dioxide (CO2) on the physical properties of poly(L‐lactic acid) (PLLA) and on the formation of crystalline domains was investigated. The presence of CO2 in the matrix was found to induce crystallization in PLLA, with the crystallinity increasing with increasing CO2 pressure. The combination of saturation conditions and formation of crystalline domains was studied for its effect on the formation of porous morphologies in PLLA. Moreover, the effect of CO2 on PLLA properties and formation of porous structures was further exploited by first creating crystalline domains in samples using CO2 at various pressures at 25 °C and then re‐saturating the same samples with CO2 at a constant pressure of 2.8 MPa and 0 °C. This paper reports on the solubility of CO2 at 25 and 0 °C in PLLA, crystallization and subsequent effect on foam morphologies when processed using different saturation cycles. Unique and intriguing morphologies were obtained by specifically controlling the properties of PLLA. Copyright © 2010 Crown in the right of Canada. Published by John Wiley & Sons, Ltd

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Effect of Compressed CO₂ on Phase Transitions and Polymorphism in Syndiotactic Polystyrene

Cited by 143 publications

References 43 publications

Absorption Kinetics of Phenol into Different Size Nanopores Present in Syndiotactic Polystyrene and Poly (p-methylstyrene)

Absorption Kinetics of Phenol into Different Size Nanopores Present in Syndiotactic Polystyrene and Poly (p-methylstyrene)

Crystallization Condition of Glassy Syndiotactic Polystyrene in Supercritical CO2

Carbon dioxide‐induced crystallization in poly(L‐lactic acid) and its effect on foam morphologies

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Effect of Compressed CO2 on Phase Transitions and Polymorphism in Syndiotactic Polystyrene

Cited by 143 publications

References 43 publications

Absorption Kinetics of Phenol into Different Size Nanopores Present in Syndiotactic Polystyrene and Poly (p-methylstyrene)

Absorption Kinetics of Phenol into Different Size Nanopores Present in Syndiotactic Polystyrene and Poly (p-methylstyrene)

Crystallization Condition of Glassy Syndiotactic Polystyrene in Supercritical CO2

Carbon dioxide‐induced crystallization in poly(L‐lactic acid) and its effect on foam morphologies

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Effect of Compressed CO₂ on Phase Transitions and Polymorphism in Syndiotactic Polystyrene