Block copolymers near the microphase separation transition. 1. Preparation and physical characterization of a model system

Bates, Frank S.; Bair, H. E.; Hartney, Mark A.

doi:10.1021/ma00140a019

Cited by 56 publications

(84 citation statements)

References 11 publications

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“…Peak broadening accompanied with the relatively small discontinuity in heat capacity has been observed in highly crosslinked polymeric systems (Chang, 1992). It has also been shown that the breadth of the glass transition increases as polymers are mixed into miscible poly-blends or covalently linked together into homogeneous copolymers (Bates et al, 1984). It is improbable that new covalent bonds (bonding energy in the range of 180-450 kJ/mol) in between molecules (cross-links) are being created during evaporation or oxidation in asphalt.…”

Section: Transition Broadeningmentioning

confidence: 93%

Glass Transition and Phase Stability in Asphalt Binders

Kříž

Stastna

Zanzotto

2008

Road Materials and Pavement Design

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Major aspects of the glass transition of asphalt binders are described and an extensive literature review of the phenomenon and its relation to chemical composition is presented. The glass transition of asphalt binders was studied by modulated differential scanning calorimetry and also via dynamic mechanical analysis. A certain analogy between the glass transition of amorphous polymers and asphalts is suggested. The overall transition was found to be very broad on the temperature scale. The effects of evaporation of light-end components and oxidation on asphalt phase stability and glass transition were studied. It was suggested that phase incompatibility may exist in asphalts; however, the phase separation is observable after long-term isothermal conditioning at a temperature within the glass transition range. Based on the presented results, it is suggested that phase incompatibility develops if there is a discontinuity in the molecular distribution. Such discontinuity may be present in some neat binders as well as in severely oxidized or aged asphalt binders.

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Section: Transition Broadeningmentioning

confidence: 93%

Glass Transition and Phase Stability in Asphalt Binders

Kříž

Stastna

Zanzotto

2008

Road Materials and Pavement Design

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“…This behavior is analogous to the results on copolymers of 1,4 polybutadiene-1,2 polybutadiene with decreasing monomer lengths. 35 In the final state after St v É 44 min (Fig. 8) the PBT crystallinity is very small and the glass transition behavior represents a mixed amorphous state.…”

Section: Characterization Of the Influence Of Transesterification On mentioning

confidence: 98%

Investigations of transesterification in PC/PBT melt blends and the proof of immiscibility of PC and PBT at completely suppressed transesterification

Pompe

Häußler

1997

J. Polym. Sci. B Polym. Phys.

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“…For example, Kennemur et al 42 showed using a DSC measurement that ΔT g ≅ 0 for PtBS−PMMA-236 due to mixing of the blocks across the domain interfaces; similar effects occur with the other systems near T ODT . 51,52 Also, we have assumed that the different blocks of the diblock copolymers relax independently and ignore the fact that they are tethered to the interface. While these idealizations are not strictly valid, especially in the case of entangled blocks, we believe the ratio τ r , based on the estimated values for τ A and τ B , provide valuable insight into the influence of chain dynamics on the viscoelastic response in block polymers.…”

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confidence: 99%

Influence of Composition Fluctuations on the Linear Viscoelastic Properties of Symmetric Diblock Copolymers near the Order–Disorder Transition

et al. 2015

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Rheological evidence of composition fluctuations in disordered diblock copolymers near the order−disorder transition (ODT) has been documented in the literature over the past three decades, characterized by a failure of time−temperature superposition (tTS) to reduce linear dynamic mechanical spectroscopy (DMS) data in the terminal viscoelastic regime to a temperature-independent form. However, for some materials, most notably poly(styrene-b-isoprene) (PS−PI), no signature of these rheological features has been found. We present small-angle X-ray scattering (SAXS) results on symmetric poly(cyclohexylethylene-b-ethylene) (PCHE−PE) diblock copolymers that confirm the presence of fluctuations in the disordered state and DMS measurements that also show no sign of the features ascribed to composition fluctuations. Assessment of DMS results published on five different diblock copolymer systems leads us to conclude that the effects of composition fluctuations can be masked by highly asymmetric block dynamics, thereby resolving a long-standing disagreement in the literature and reinforcing the importance of mechanical contrast in understanding the dynamics of ordered and disordered block polymers. M aterials with nanoscale features are being incorporated into emerging technologies with applications in energy, 1 electronics, 2 and medicine. 3 Block polymers are a class of materials for which synthetic methods offer precise control over chemical architecture, morphology, dynamics, and morphological length scale. 4 As a consequence, they are an active area of research with potential uses in a diverse array of products, including batteries, 5 lithographic materials, 6 and drug delivery. 7 A fundamental understanding of block polymer phase transitions, nanoscale morphologies, and processing is an essential prerequisite to integration into future commercial products. 8,9 It is well established that volumetrically symmetric AB diblock copolymers ( f = 1/2) of finite molecular weight undergo an order−disorder phase transition (ODT) characteristic of the Brazovskii class, for which the change from an ordered lamellar phase (LAM) to an isotropic disordered phase (DIS) is weakly first-order. 10−13 Thermally driven fluctuations in local composition profoundly influence block copolymer phase behavior near this fluctuation-induced phase transition, destroying the second-order ODT anticipated by mean-field theory (i.e., infinite molecular weight limit). 10,14 Here, we present dynamic mechanical spectroscopy (DMS) results that help elucidate how differences in the individual A-and B-block relaxation times of an AB diblock copolymer are manifested in linear oscillatory viscoelastic measurements.A host of experimental techniques, including small-angle Xray scattering (SAXS), 15−18 small-angle neutron scattering (SANS), 11,12,19 differential scanning calorimetry (DSC), 13 transmission electron microscopy (TEM), 20−22 rheology, 23−25 and others, 26−32 have confirmed the presence of composition fluctuations in the disordered phase of block po...

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Block copolymers near the microphase separation transition. 1. Preparation and physical characterization of a model system

Cited by 56 publications

References 11 publications

Glass Transition and Phase Stability in Asphalt Binders

Glass Transition and Phase Stability in Asphalt Binders

Investigations of transesterification in PC/PBT melt blends and the proof of immiscibility of PC and PBT at completely suppressed transesterification

Influence of Composition Fluctuations on the Linear Viscoelastic Properties of Symmetric Diblock Copolymers near the Order–Disorder Transition

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