Rheology and dynamics near phase separation in a polymer blend: model and scaling analysis

Ajji, Abdellah; Choplin, Lionel

doi:10.1021/ma00018a031

Cited by 119 publications

(139 citation statements)

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“…[17,19,[34][35][36] For quantitative studies of phase separation in binary PVME/PS blends [37] and ternary PVME/PS/HNPs nanocomposites, [35] the mean field theoretical approach of Ajji and Choplin [38,39] has been demonstrated to be very reliable for determining phase separation temperatures from the T-dependence of the bulk elastic modulus (G´) and the bulk loss modulus (G´´) at small strain and very low shear rates (i.e. in the linear regime).…”

Section: Resultsmentioning

confidence: 99%

A Nanotechnology Pathway to Arresting Phase Separation in Soft Nanocomposites

Pomposo

Luzuriaga

García

et al. 2011

Macromol. Rapid Commun.

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---------Direct observation of the miscibility improving effect of ultra-small polymeric nanoparticles (radius ~4 nm) in model systems of soft nanocomposites is reported. We have found thermodynamically arrested phase separation in classical poly(styrene) (PS) / poly(vinyl methyl ether) blends when PS linear-chains were totally replaced by ultra-small, single-chain PS nanoparticles as determined by thermo-optical microscopy measurements. Partial arrested phase-splitting on heating was observed when only some of the PS chains were replaced by unimolecular PS nanoparticles leading to a significant increase of the lower critical solution temperature (LCST) of the system (up to 40 ºC at 15 vol. % nanoparticle content). Atomic -2 -force microscopy and rheological experiments support these findings. Thermodynamic arrest of the phase separation process induced by replacement of linear-polymer-chains by unimolecular-polymer-nanoparticles could have significant implications for industrial applications requiring soft nanocomposite materials with excellent nanoparticle dispersion in a broad temperature range. IntroductionNanoparticles are currently ubiquitous in the nanotechnology arena showing a great impact in organic photovoltaics, [1] nanophotonics, [2] catalysis, [3] drug delivery, [4] and nanomedicine, [5] among other several fields. [6] A strong effort has been devoted in recent years to the efficient and shape-controlled synthesis of metallic, metal oxide and semiconducting (quantum dot) hard nanoparticles (HNPs). It is now well-established that HNP surface properties are mainly determined by chemical composition, surface chemistry (hydrophobic/hydrophilic balance), shape, size, porosity, roughness, and compositional heterogeneity. [7] Even when the progress in this field has been astonishing, highly-dense HNPs are sometimes far from ideal when employed in conjunction with soft matter (e.g. biomacromolecules). Compared to classical HNPs, the multi-gram synthesis of well-defined unimolecular polymeric nanoparticles in the sub-20 nm size range has been elusive until recently. The pioneering work of Hawker´s group[8] opened the way to new and highly efficient synthetic routes to monodisperse, ultrasmall (radius < 5 nm) soft nanoparticles (SNPs). [9][10][11][12][13][14][15][16] The rich phase behavior of nanocomposites containing HNPs has been investigated by combining computer simulations, [17,18] theory [19][20][21][22] and experiment. [23,24] Conversely, the miscibility (i.e.homogeneity at the nanoscale) behavior of soft nanocomposites consisting on unimolecular SNPs dispersed in a conventional polymer matrix remains largely unexplored, even if mimicking Nature´s soft nanocomposites is currently of great interest. Most thermodynamic (i.e. homogeneity) and rheological (i.e. dynamics) data correspond to simple blends of -3 -intramolecular cross-linked polystyrene (PS)-nanoparticles dispersed in a matrix of PS linearchains, displaying interesting non-Einstein viscosity behaviour. [25,26] Also computer simulations [27...

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Section: Resultsmentioning

confidence: 99%

A Nanotechnology Pathway to Arresting Phase Separation in Soft Nanocomposites

Pomposo

Luzuriaga

García

et al. 2011

Macromol. Rapid Commun.

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“…Ajji and Choplin [41] found that effects of phase separation on G 0 were more pronounced than on G 00 : Scholz et al [37] reported that the values of the dynamic moduli at high v ðv . 10 rad=sÞ for the immiscible blend of PP/Polyamide 6 were intermediate between those of PA6 and PP.…”

Section: Introductionmentioning

confidence: 99%

Miscibility of hexene-LLDPE and LDPE blends: influence of branch content and composition distribution

Hussein

Hameed

Sharkh

et al. 2003

Polymer

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The influences of branch content (BC) and composition distribution (CD) of hexene linear low-density polyethylene (LLDPE) on its miscibility with low-density polyethylene (LDPE) were investigated. Ziegler -Natta (ZN) and metallocene-LLDPE (m-LLDPE) were used to study the melt miscibility using rheological tools. Dynamic, steady shear and transient measurements were carried out in an ARES rheometer at 190 8C. The miscibility was revealed by the dependence of their h o ; h 0 ðvÞ; G 0 ; and N 1 ð _ gÞ on blend composition. The CD of LLDPE has influenced its miscibility with LDPE. The ZN-LLDPE blend with LDPE was found to be more miscible than an m-LLDPE of the same M w and similar BC. On the other hand, a high-BC m-LLDPE (32.2 CH 3 /1000 C) was found to be more miscible with LDPE than a low-BC m-LLDPE (14.4 CH 3 /1000 C) of the same M w and MWD. The high-BC m-LLDPE blends with LDPE were partially miscible and immiscibility is likely to develop in LDPE-rich blends. Agreement was observed between the measured rheology and theoretical predictions of Einstein, Scholz et al., Palierne, and Bousmina emulsion models. q

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“…Near g the time-temperature superposition principle ( -) is not valid [205], but it is obeyed for deutereous PS below LCST(PS) 40 C [202]. However, at higher temperatures their relaxation times deviate with a magnitude dependent on the molecular weight ratio [206][207][208][209][210]. Kim and Son [211] plotted log versus log for different compositions and temperatures; at 10 wt% PS the data formed a linear dependence independent of stretching from below to above LCST.…”

Section: Generalmentioning

confidence: 99%

“…Since blend morphology and kinetics of phase separation are expected to affect the rheological functions, great care is needed in collecting rheological data and interpreting them [223,224]. The two polymers have widely different glass transitions, g (PS) 373-378 and g (PVME) 227-247 K. The g of their blends shows a negative deviation from additivity, that is, PVME acts as a macromolecular solvent/plasticizer of PS, especially when the ratio of molecular weights, w (PS)/ w (PVME), is large [202][203][204][205][206][207][208][209]. When the ratio is about 2, a passage through the phase separation region affects but not , while for the ratio <1 the moduli increase upon entering the phase separation region.…”

Section: Influence Of Thermodynamics On Rheologymentioning

confidence: 99%

“…Furthermore, Gharachorlou and Goharpey [374], following Ajji and Choplin [209] theory, derived a simple relation between the dynamic moduli at the thermodynamic distance from spinodal, x x : Organoclays have been added to a great variety of polymer blends, replacing the single-component matrix with a multiphase one, either for compatibilization or reinforcement of blend. The most popular blends are PA-6/PP types, usually compatibilized with PP-MA [1,73,302].…”

Section: Rheology Of Blends With Nanoparticles Near Binodalmentioning

confidence: 99%

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Rheology of Polymer Blends

Utracki

2011

Encyclopedia of Polymer Blends

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The first polymer blend was patented in 1846 and since then blends have became ubiquitous. Blending may provide a full set of material properties, improving processability and/or specific properties. With the advancement of technology there is the notorious growth of complexity -while in the beginning blending involved two polymers, initially without a compatibilizer, more recent commercial alloys have up to five polymers, three compatibilizers, and frequently are reinforced with macro-or nanoparticles [1].Blends are classified as either thermodynamically miscible or immiscible, with the latter dominating. However, imposition of a flow affects the thermodynamic equi librium and it may enhance the miscibility of immiscible blends or vice-versa -there is an interrelation between rheology and thermodynamics. Similarly, flow affects the degree of deformation of the dispersed phase, thus in immiscible blends there are other interrelations between rheology and morphology, which affect the blend performance. To the complexity of polymer alloys and blends (PAB) behavior one must add the incorporation of solids, either in the form of filler and nanofiller particles or by simple fact of blending two components with widely different transition temperatures.Since the flow of PAB is complex, it is useful to revert to simple models, for example, for miscible blends to solutions or mixtures of polymer fractions, for immiscible blends to emulsions or suspensions, and for compatibilized blends to block copolymers (Table 2.1). It is also advisable to study flow behavior of multiphase systems at constant stress (not at constant deformation rate) [2,3].For miscible blends, the free volume theory predicts a positive deviation from the log-additivity rule (PDB, positively deviating blend). However, depending on the system and method of preparation, these blends may show a positive deviation, negative deviation, or additivity [4]. Upon mixing, the presence of specific interac tions may change the free volume and degree of entanglement, which in turn affect the flow behavior [5,6]. For immiscible blends the flow is similarly affected, but in addition there are at least three contributing phases: of the polymeric matrix, of the First Edition. Edited by Avraam I. Isayev.

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Rheology and dynamics near phase separation in a polymer blend: model and scaling analysis

Cited by 119 publications

References 7 publications

A Nanotechnology Pathway to Arresting Phase Separation in Soft Nanocomposites

A Nanotechnology Pathway to Arresting Phase Separation in Soft Nanocomposites

Miscibility of hexene-LLDPE and LDPE blends: influence of branch content and composition distribution

Rheology of Polymer Blends

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