Gelation Mechanism of Syndiotactic Polystyrene in Bromoform

Rudder, Jan De; Berghmans, Hugo; Schryver, F. C. De; Bosco, Marcella; Paoletti, Sergio

doi:10.1021/ma020973e

Cited by 36 publications

(36 citation statements)

References 28 publications

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“…The gel is formed by a mechanism combining an intramolecular conformational transition of coil into helix with an intermolecular association forming a network. [19] But up to now no conclusion could be drawn about the morphology of these cross-links. The gels reach their maximal G 0 value when they are prepared at 30 8C.…”

Section: Discussionmentioning

confidence: 99%

“…This is not what is observed when such gels are formed in good solvents. [19,21] A possible explanation could be the vicinity of the liquidliquid demixing domain that will inevitably lead to an important increase in the concentration fluctuations. These fluctuations can cause a decrease in the quality of the obtained network and hence of the modulus of the gel.…”

Section: Discussionmentioning

confidence: 99%

“…The rate of the coil-helix transition that is at the origin of this structure formation is strongly temperature dependent and decreases very rapidly with increasing temperature. [19,[21][22][23][24] At T > 45 8C this rate decreases and less helix conformation is observed by FTIR. From 45 8C on, structure formation will proceed mainly through the formation of the meso-amodification.…”

Section: Discussionmentioning

confidence: 99%

“…The gels are in general very weak compared to gels of sPS formed in good solvent. [19] Optical Measurements…”

Section: Rheological Observationsmentioning

confidence: 99%

See 3 more Smart Citations

Competition between gelation and crystallization in solutions of syndiotactic polystyrene in cis-decalin

Rudder

Berge

Berghmans

2002

Macromol. Chem. Phys.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

“…The gels are in general very weak compared to gels of sPS formed in good solvent. [19] Optical Measurements…”

Section: Rheological Observationsmentioning

confidence: 99%

See 2 more Smart Citations

Competition between gelation and crystallization in solutions of syndiotactic polystyrene in cis-decalin

Rudder

Berge

Berghmans

2002

Macromol. Chem. Phys.

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“…6 Recent studies in the temperature-concentration phase diagrams of sPS gels have suggested that solvent molecules are intercalated between sPS chains in the TTGG conformation, and the number of solvent molecules involved is dependent on the gelation solvent. [7][8][9][10][11] The ordered TT conformation was observed on gelation of sPS in big size solvent like octadecyl benzoate. 12 Time-resolved small-angle neutron scattering (SANS) experiments also showed that the gelnetwork structure formation occurred in parallel to the conformational ordering of sPS chains.…”

mentioning

confidence: 99%

Solvent Effect on Junction Size in Syndiotactic Polystyrene Physical Gel

Shimizu

Wakayama

Wada

et al. 2005

Polym J

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ABSTRACT:In order to estimate the junction point size of syndiotactic polystyrene (sPS) physical gels formed in chloroform, toluene, benzene, and o-dichlorobenzene, gel-melting temperatures were measured as a function of polymer concentration. The size in number of styrene units was estimated with the aid of the Tanaka and Stockmayer theory (TS theory), which is based upon the conjecture that junction points of a gel are aggregates comprised of units in length and sequences in cross section. According to measurement of in situ FT-IR, the junction points of sPS/ organic solvent gels were suggested to be aggregates of sPS chains with helical structure of TTGG conformation regardless of the difference in solvents. Quantitative analysis by the TS theory led to the results that the size was little dependent upon the sPS molecular weight for each sPS/organic solvent system. On the other hand, the size was strongly affected by solvents, i.e., in sPS/o-dichlorobenzene gel was the largest among the solvents used in the present study, while that in sPS/chloroform gel was the smallest. This solvent effect on the junction point size probably arises from the difference in magnitude of polymer/solvent interaction. [DOI 10.1295/polymj.37.294] KEY WORDS Syndiotactic Polystyrene / Polystyrene / Thermoreversible Gel / Junction Size / Gel-melting Temperature / Time-resolved FT-IR / Syndiotactic polystyrene (sPS) is of considerable scientific and industrial interest as a rigid high performance semicrystalline material. It is known that sPS polymer has two types of molecular chain conformations in its crystalline region: one is the all-trans planar zigzag structure (TT), and the other is the helical conformation (TTGG). 1-5Like other crystalline or semicrystalline polymers, sPS polymer also converts to thermoreversible gel in suitable organic solvents such as toluene or chloroform. Kobayashi et al. investigated the gelation process of sPS with time-resolved Fourier transform infrared (FT-IR) spectroscopy and showed that highly ordered TTGG conformations are formed on gelation. 6 Recent studies in the temperature-concentration phase diagrams of sPS gels have suggested that solvent molecules are intercalated between sPS chains in the TTGG conformation, and the number of solvent molecules involved is dependent on the gelation solvent.7-11 The ordered TT conformation was observed on gelation of sPS in big size solvent like octadecyl benzoate.12 Time-resolved small-angle neutron scattering (SANS) experiments also showed that the gelnetwork structure formation occurred in parallel to the conformational ordering of sPS chains. 13The thermoreversible gelation of highly stereoregular polymers such as sPS and syndiotactic poly-(methyl methacrylate) is considered to proceed in two steps:14-16 A first step is an intramolecular coil-tohelix transition; This change in molecular conformation is then followed by an intermolecular association of multiple helix segments, which leads to the formation of network structure. This gelation mechanism is ...

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Viscoelastic behavior of thermosetting epoxy mixtures modified with syndiotactic polystyrene during network formation

Tercjak

Serrano

Remiro

et al. 2006

J of Applied Polymer Sci

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ABSTRACT:The rheological behavior of thermosetting epoxy mixtures modified with thermoplastic syndiotactic polystyrene (sPS) was monitored during the curing of the epoxy resin. The selected thermosetting system was diglycidyl ether of bisphenol A cured with 4,4Ј-methylene bis(3-chloro-2,6-diethylaniline) in the presence of various compositions of sPS (from 2.5 to 12.5 wt %). The storage and loss shear moduli of the systems were monitored during network formation. The validity of the Winter-Chambon criterion for the accurate determination at the gelation point from rheological data was demonstrated. The influence of the sPS concentration on the dynamic rheological properties of the samples was investigated. The experimental data showed that at sPS concentrations lower than 7.5 wt %, phase separation induced a quick increase in the viscosity, which was related to a crystallization-induced phase separation of sPS. For sPS concentrations higher than 7.5 wt %, near the phase-inversion composition, the rheological behavior of the mixtures was characteristic of a cocontinuous structure. After the viscosity jumped at the onset of phase separation, a decrease in the viscosity was found, and later on, the viscosity increased again because of gelation. Additionally, the influence of the cure temperature on the rheological properties was studied.

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Gelation Mechanism of Syndiotactic Polystyrene in Bromoform

Cited by 36 publications

References 28 publications

Competition between gelation and crystallization in solutions of syndiotactic polystyrene in cis-decalin

Competition between gelation and crystallization in solutions of syndiotactic polystyrene in cis-decalin

Solvent Effect on Junction Size in Syndiotactic Polystyrene Physical Gel

Viscoelastic behavior of thermosetting epoxy mixtures modified with syndiotactic polystyrene during network formation

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