Dielectric study of poly(methylacrylate) plus poly(4-hydroxystyrene) or plus poly(4 hydroxystyrene-co-4-methoxystyrene) blends near the glass transition

Prolongo, M. G.; Salom, C.; Masegosa, Rosa M.; Moreno, Susana Lozano; Rubio, Ramón G.

doi:10.1016/s0032-3861(97)00057-8

Cited by 13 publications

(11 citation statements)

References 29 publications

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“…31 The fragility calculated from our experimental data for the SHS copolymer ( 142) is therefore reasonable in comparison to that determined for PS with compa- rable M w (140). 39 The blend fragility increases rather significantly with increasing SHS content (Table 1), in accordance with previous results on PVPh blends with poly(methyl acrylate), 40 poly(vinyl ethyl ether), 17 poly-(vinyl acetate), and poly(ethylene-co-vinyl acetate). 16 It has been concluded previously that the backbones of strong glass formers are smooth, compact, symmetric, and flexible, and polymers with less flexible backbones and/or sterically hindering groups exhibit high fragility.…”

Section: Drs 331 Shs Copolymersupporting

confidence: 91%

Dielectric Studies of Poly(ethylene oxide)/Poly(styrene-co-p-hydroxystyrene) Blends: Influence of Hydrogen Bonding on the Dynamics of Amorphous Blends

2003

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The segmental dynamics of a poly(styrene-co-p-hydroxystyrene) random copolymer [SHS, 50 wt % HS] and its amorphous, melt-miscible blends with poly(ethylene oxide) were investigated using broadband dielectric relaxation spectroscopy. The fragility of the neat copolymer was found to be close to that of polystyrene with comparable molecular weight, consistent with the idea that intramolecular hydrogen bonding primarily enhances the monomer friction coefficient and Tg, while having little effect on fragility. Despite the large mobility difference between the component polymers, a single cooperative segmental relaxation is observed for the blends (SHS concentration g 60%), demonstrating the coupling ability of intermolecular hydrogen bonds. Blend fragility increased significantly with SHS content, reflecting the combined contribution of the two components. The most intriguing finding was a fast process in blends containing g80 wt % SHS. The available evidence supports its assignment to noncooperative segmental relaxation of PEO repeat units, having some similarities to the modified segmental dynamics of nanoconfined polymers.

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Section: Drs 331 Shs Copolymersupporting

confidence: 91%

Dielectric Studies of Poly(ethylene oxide)/Poly(styrene-co-p-hydroxystyrene) Blends: Influence of Hydrogen Bonding on the Dynamics of Amorphous Blends

2003

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“…Although it is difficult to capture the R relaxation of PVPh by DRS or DMA, a dielectric study of styrene-co-4-vinylphenol [STVPh] random copolymers with up to 18 mol % VPh found a fragility of 92, independent of VPh content. 51 An increase in fragility has also been observed in other hydrogen-bonded polymer blends compared to their nonhydrogen-bonded counterparts, e.g., poly(methyl acrylate)/PVPh, 52 poly(vinyl acetate)/PVPh, and PVPh/poly-(ethylene-co-vinyl acetate) with vinyl acetate content of 70 wt % [EVA70]. 53 However, we did not observe any significant change in fragility for PEMA/PVPh blends with PVPh concentration up to 40%, which we attributed to the relatively high fragility of PEMA (∼84).…”

Section: Segmental Relaxation Of Blends Figure 3 Presents the Drs Spe...mentioning

confidence: 96%

Coupling of Component Segmental Relaxations in a Polymer Blend Containing Intermolecular Hydrogen Bonds

2002

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The segmental relaxations of poly(4-vinylphenol)/poly(vinyl ethyl ether) [PVPh/PVEE] blends, with PVPh content from 10 to 50 wt % and having a very large Tg difference between the components, have been investigated using broadband dielectric spectroscopy. Although a single Tg was observed for all compositions in DSC measurements, two segmental R processes for blends with low PVPh concentration are highly probable. The slow process is attributed to the relaxation of intermolecular hydrogen-bonded PVPh and PVEE segments, while the fast one is assigned to unassociated PVEE segments. However, at PVPh concentrations g30 wt %, most PVEE segments are hydrogen-bonded to PVPh and the blends exhibit a single R relaxation. This behavior is compared to that of other miscible blends with large Tg contrast but having weak intermolecular interactions. The observed behavior is explained by the role of intermolecular hydrogen bonding, which is believed to be capable of coupling the segmental relaxations of PVEE and PVPh, which would otherwise exhibit two distinct segmental relaxation processes due to their large intrinsic mobility difference. The time-temperature superposition principle, which fails for many polymer blends, is successful in blends with higher PVPh content, indicating thermorheological simplicity of this dynamically asymmetric blend. Finally, increases in both the fragility and the coupling parameter are clearly observed in the blends compared to neat PVEE, confirming that intermolecular coupling is enhanced by hydrogen bonding.

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“…The dielectric spectrometer used was the same of a previous work [28], although in the present work case an Alpha-N Novocontrol analyzer was used in the frequency range from 10 -2 Hz to 10 6 Hz. A liquid nitrogen cryostat mantained the temperature within ±0.1K.…”

Section: Experimental and Molecular Dynamics Methodsmentioning

confidence: 99%

Dielectric and molecular dynamics study of the secondary relaxations of poly(styrene-co-methylmethacrylate) copolymers: Influence of the molecular architecture

et al. 2011

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The effect of the structure of copolymers (random, alternate or diblock) on their dynamics has been studied by dielectric spectroscopy. Six copolymers of styrene and methyl methacrylate (three diblocks, one alternate and two random) have been studied. The results show that the sub-T g transitions of the diblock samples can be described by one asymmetric Havriliak-Negami (HN) function, while two are necessary for the rest of the copolymers (β and γ relaxations). The characteristic times of the sub-T g relaxations show an Arrhenius temperature dependence and there is a strong coupling of the α and β relaxations at high temperatures. The deconvolution of the merging relaxations has been made in the framework of the Williams Ansatz set out in terms of Havriliak-Negami distributions. The γ relaxation may be assigned to the rotation of the methyl methacrylate group in a styrene-rich environment. The Molecular Dynamics simulations of a poly(methyl methacrylate) homopolymer and of the alternate copolymer are in qualitative agreement with the experimental results, although they predict smaller values for the activation energy of the sub-T g relaxations.

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Dielectric study of poly(methylacrylate) plus poly(4-hydroxystyrene) or plus poly(4 hydroxystyrene-co-4-methoxystyrene) blends near the glass transition

Cited by 13 publications

References 29 publications

Dielectric Studies of Poly(ethylene oxide)/Poly(styrene-co-p-hydroxystyrene) Blends: Influence of Hydrogen Bonding on the Dynamics of Amorphous Blends

Dielectric Studies of Poly(ethylene oxide)/Poly(styrene-co-p-hydroxystyrene) Blends: Influence of Hydrogen Bonding on the Dynamics of Amorphous Blends

Coupling of Component Segmental Relaxations in a Polymer Blend Containing Intermolecular Hydrogen Bonds

Dielectric and molecular dynamics study of the secondary relaxations of poly(styrene-co-methylmethacrylate) copolymers: Influence of the molecular architecture

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