Mechanistic Aspects of the Thermoreversible Gelation of Syndiotactic Poly(methyl methacrylate) in Toluene

Buyse, Kris; Berghmans, Hugo; Bosco, Marcella; Paoletti, Sergio

doi:10.1021/ma981017t

Cited by 33 publications

(52 citation statements)

References 11 publications

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“…The straight line nature of the plots support that coil‐to‐rod transition is the first step of the gelation processes in both the systems. This mechanism is similar to the gelation of poly (vinylidine fluoride) (PVF 2 ) in glyceryl tributyrate or in diesters26, 27 and syn‐PMMA in toluene 37. The former polymer transforms from coil to TGTG conformer while the later one transforms from coil‐to‐helix structure prior to aggregation (gelation).…”

Section: Resultsmentioning

confidence: 66%

Nanocrystalline Metal Oxides as Unique Chemical Reagents/Sorbents

et al. 2001

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A new family of porous inorganic solids based on nanocrystalline metal oxides is discussed. These materials, made up of 4-7 nm MgO, CaO, Al2O3, ZnO, and others, exhibit unparalleled destructive adsorption properties for acid gases, polar organics, and even chemical/biological warfare agents. These unique sorption properties are due to nanocrystal shape, polar surfaces, and high surface areas. Free-flowing powders or consolidated pellets are effective, and pore structure can be controlled by consolidation pressures. Chemical properties can be adjusted by choice of metal oxide as well as by incorporating other oxides as monolayer films.

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Section: Resultsmentioning

confidence: 66%

Nanocrystalline Metal Oxides as Unique Chemical Reagents/Sorbents

et al. 2001

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“…[10] A st-PMMA gel started melting at around 40 8C, while the st-PMMA/C 60 gel maintained its gel structure over 60 8C resulting from encapsulation of the C 60 molecules within the helical cavity of st-PMMA, thereby acting to reinforce the st-PMMA physical gel ( Figure S2 and Table S1 in the Supporting Information). [10] A st-PMMA gel started melting at around 40 8C, while the st-PMMA/C 60 gel maintained its gel structure over 60 8C resulting from encapsulation of the C 60 molecules within the helical cavity of st-PMMA, thereby acting to reinforce the st-PMMA physical gel ( Figure S2 and Table S1 in the Supporting Information).…”

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confidence: 99%

“…We then investigated the thermal stabilities of the st-PMMA and st-PMMA/C 60 gels by measuring their melting behavior using 1 H NMR spectroscopy. [10] A st-PMMA gel started melting at around 40 8C, while the st-PMMA/C 60 gel maintained its gel structure over 60 8C resulting from encapsulation of the C 60 molecules within the helical cavity of st-PMMA, thereby acting to reinforce the st-PMMA physical gel ( Figure S2 and Table S1 in the Supporting Information). Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) profiles of the st-PMMA/C 60 films with different C 60 contents (11.7 and 23.5 wt %) revealed a crystalline structure of the st-PMMA/ C 60 complex ( Figure 2) that is essentially different from that of the st-PMMA film.…”

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confidence: 99%

Encapsulation of Fullerenes in a Helical PMMA Cavity Leading to a Robust Processable Complex with a Macromolecular Helicity Memory

et al. 2007

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“…1,4,5,119,120 Recently, a similar two-step mechanism of gelation through coil/helix transition was confirmed for synthetic polymers with stereo-regularity. 121,122 It was found that, in solutions of syndiotactic poly(methyl methacrylate) in toluene, a fast intramolecular conformational change is followed by an intermolecular association leading eventually to gelation.…”

Section: Gelation Triggared By Polymer Conformational Transitionmentioning

confidence: 99%

Theoretical Study of Molecular Association and Thermoreversible Gelation in Polymers

Tanaka

2002

Polym J

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ABSTRACT:This paper reviews our recent theoretical studies of molecular association and thermoreversible gelation in polymer solutions and blends. We first classify fundamental types of association, and propose their static and dynamic characterization. We then develope general theory of associating polymers to study phase transitions induced by molecular association. These transitions include macro-and microphase separation, micellization, hydration, thermoreversible gelation and liquid-crystalization. As for the origin of associative forces, we focus on hydrogen bonding and hydrophobic aggregation. Detailed study on thermoreversible gelation with multiple cross-link junctions is presented. Paying special attention to the multiplicity and sequence length of the network junctions, we derive phase diagrams with coexisting gelation and phase separation, and compare them with experimental data. Local and global structures of the gel networks are studied from molecular point of view. The theory is applied to more complex thermoreversible gels such as binary networks (interpenetrating networks, alternating networks and randomely mixed networks), hydrated networks with high-temperature gelation, gelation strongly coupled to polymer conformational transitions such as coil-to-helix transition. To study dynamics of thermoreversible gels, a simple transient network model is introduced, and creation and annihilation of junctions in the networks are theoretically described. Stationary non-linear viscosity and the dynamic mechanical moduli are calculated as functions of the shear rate, frequency and the chain disengagement rate. From the peak of the loss modulus, the lifetime τ × of the junction is estimated, and from the high frequency plateau of the storage modulus, the number of elastically effective chains in the network is found. Transient phenomena such as stress relaxation and stress overshoot are also theoretically studied. Results are compared with the recent experimental reports on the rheological study of hydrophobically modified water-soluble polymers.KEY WORDS Associating Polymers / Thermoreversible Gelation / Junction Multiplicity / Multicriticality / Transient Networks / Shear Thickening / Elastically Effective Chains / This paper reviews our recent theoretical studies of molecular association and thermoreversible gelation in polymer solutions. We introduce new theoretical frameworks to study phase transitions induced by association of polymer chains and dynamics of aggregation/dissociation processes.In most polymer blends or solutions, polymer chains carry active groups interacting with each other via strongly associative forces which are capable of forming temporal bonds. Hence description of the system in terms of van der Waals type contact energy -or χ-parameter in lattice theoretical terminology -is insufficient. These associative interactions include hydrogen bonding, ionic aggregation, electrostatic interaction, micro-crystallite formation, stereocomplex formation, solvent-complex formation, etc. Since ...

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Mechanistic Aspects of the Thermoreversible Gelation of Syndiotactic Poly(methyl methacrylate) in Toluene

Cited by 33 publications

References 11 publications

Nanocrystalline Metal Oxides as Unique Chemical Reagents/Sorbents

Nanocrystalline Metal Oxides as Unique Chemical Reagents/Sorbents

Encapsulation of Fullerenes in a Helical PMMA Cavity Leading to a Robust Processable Complex with a Macromolecular Helicity Memory

Theoretical Study of Molecular Association and Thermoreversible Gelation in Polymers

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