Linear Rheology of Architecturally Complex Macromolecules:  Comb Polymers with Linear Backbones

Kapnistos, M.; Vlassopoulos, D.; Roovers, Jacques; Leal, L. Gary

doi:10.1021/ma050644x

Cited by 195 publications

(343 citation statements)

References 47 publications

Supporting

Mentioning

314

Contrasting

Unclassified

Order By: Relevance

“…Concerning the latter, we note that it is significantly smaller than more commonly chosen value of p 2 = 1/12 [46,47], but this choice was found to simultaneously fit all rheological data of asymmetric star and other branched polymers [6,23,24,48,49].…”

Section: Ii4 Modelingmentioning

confidence: 89%

Stress growth and relaxation of dendritically branched macromolecules in shear and uniaxial extension

Huang¹,

Costanzo²,

Das³

et al. 2017

Journal of Rheology

Self Cite

View full text Add to dashboard Cite

We present unique nonlinear rheological data of well-defined symmetric Cayley-tree poly(methyl methacrylates) in shear and uniaxial extension. Earlier work has shown that their linear viscoelasticity is governed by the hierarchical relaxation of different generations, whereas the segments between branch points are responsible for their substantial strain hardening as compared to linear homopolymers of the same total molar mass at the same value of imposed stretch rate. Here, we extend that work in order to obtain further experimental evidence that will help understanding the molecular origin of the remarkable properties of these highly branched macromolecules. In particular, we address three questions pertinent to the specific molecular structure: (i) is steady state attainable during uniaxial extension? (ii) what is the respective transient response in simple shear? and (iii) how does stress relax upon cessation of extension or shear? To accomplish our goal we utilize state-of-the-art instrumentation, i.e., filament stretching rheometry (FSR) and cone-partitioned plate (CPP) shear rheometry for polymers with 3 and 4 generations, and complement it with state-of-the-art modeling predictions using the Branch-on-Branch (BoB) algorithm. The data indicates that the extensional viscosity reaches a steady state value, whose dependence on extension rate is identical to that of entangled linear and other branched polymer melts. Nonlinear shear is characterized by transient stress overshoots and the validity of the Cox-Merz rule. Remarkably, nonlinear stress relaxation is much broader and slower in extension compared to shear. It is also slower at higher generation, and rate-independent for rates below the Rouse rate of the outer segment. For extension, the relaxation time is longer than that of the linear stress relaxation, suggesting a strong 'elastic memory' of the material. These results are 2 described by BoB semi-quantitatively, both in linear and nonlinear shear and extensional regimes. Given the fact that the segments between branch points are less than 3 entanglements long, this is a very promising outcome that gives confidence in using BoB for understanding the key features. Moreover, the response of the segments between generations controls the rheology of the Cayley trees. Their substantial stretching in uniaxial extension appears responsible for strain hardening, whereas coupling of stretches of different parts of the polymer appears to be the origin of the slower subsequent relaxation of extensional stress. Concerning the latter effect, for which predictions are not available, it is hoped that the present experimental findings and proposed framework of analysis will motivate further developments in the direction of molecular constitutive models for branched and hyperbranched polymers.

show abstract

Section: Ii4 Modelingmentioning

confidence: 89%

Stress growth and relaxation of dendritically branched macromolecules in shear and uniaxial extension

Huang¹,

Costanzo²,

Das³

et al. 2017

Journal of Rheology

Self Cite

View full text Add to dashboard Cite

show abstract

“…The LVE properties of monodisperse amorphous linear polymer melts and their blends [14][15][16] represent a validation tool for a number of constitutive models (e.g., [17][18][19][20][21][22]) aimed at predicting the rheological behavior of complex polymer systems (e.g., [23][24][25]). This is because of their "simple" topological structure (i.e., entangled polymer chains), which has allowed, over the past 40 years, the establishment of a solid theoretical framework built on the pioneering tube model developed by de Gennes [26] and Doi and Edwards [27].…”

Section: A Linear Polyisoprene Meltsmentioning

confidence: 99%

i-Rheo: Measuring the materials' linear viscoelastic properties “in a step”!

Tassieri

Laurati

Curtis

et al. 2016

Journal of Rheology

View full text Add to dashboard Cite

We present a simple new analytical method for educing the materials' linear viscoelastic properties, over the widest range of experimentally accessible frequencies, from a simple step-strain measurement, without the need of preconceived models nor the idealization of real measurements. This is achieved by evaluating the Fourier transforms of raw experimental data describing both the time-dependent stress and strain functions. The novel method has been implemented into an open access executable "i-Rheo," enabling its use to a broad scientific community. The effectiveness of the new rheological tool has been corroborated by direct comparison with conventional linear oscillatory measurements for a series of complex materials as diverse as a monodisperse linear polymer melt, a bimodal blend of linear polymer melts, an industrial styrene-butadiene rubber, an aqueous gelatin solution at the gel point and a highly concentrated suspension of colloidal particles. a)

show abstract

“…Also, this would not explain the low E a of this process. Van Ruymbeke et al [61] and Kapnistos et al [62] found that pom-poms and combs with unentangled arms do not significantly affect the arms; i.e., the molecules behave like linear chains with a slightly lengthened relaxation time scale. Chen et al [56] found the same for LLDPE.…”

Section: Effect Of the Side Chains On The Low Frequency Propertiesmentioning

confidence: 99%

Evidence of intra-chain phase separation in molten short-chain branched polyethylene

Stadler¹

2011

Express Polym. Lett.

View full text Add to dashboard Cite

Abstract. Intramolecular phase separation is usually associated with block-copolymers, but the same phenomenon is also obtainable by random-copolymers. In this article, evidence of intramolecular phase separation is reported for a linear octadecene-ethene copolymer, which shows an evolving 'yield point' at a long time and low frequency. This is attributed to a partial phase separation of the long short-chain branches. In creep recovery, this behavior is evident as increasing elastic steady-state creep recovery compliance J e 0 . In contrast to 'normal' block-copolymers, this special polymer has an increase in phase separation with temperature, which is caused by the chemical composition and the short chain segments in the side chain domain, leading to a high surface fraction. Vol.5, No.4 (2011) 327-341 Available online at www.expresspolymlett.com DOI: 10.3144/expresspolymlett.2011 * Corresponding author, e-mail: fjstadler@jbnu.ac.kr © BME-PT length in their paper, as it cannot be determined due to the synthesis method. Such block-copolymers are usually thermorheologically complex [9,14,15]. The group of Bates [9,10], for example, found that below the order-disorder transition temperature, i.e., in the ordered state, the sample behaves like a gel and thermorheologically simple, while in the disordered state, a clear thermorheological complexity is found. The higher the temperature, the less pronounced the long-term relaxation process and, thus, the more similar is the data to a single-phase polymer melt. Recently, it was also proven that pure ethylene-/!-olefin copolymers with very long comonomers (C26) can be phase separating in the solid state, if their comonomer content is sufficiently high [16]. This effect is different from the previous cases, because it only involves one type of chain and, furthermore, occurs on random copolymers. Hence, it is an effect that occurs only on a short length scale, as shown by the fact that the length of the comonomers used were 18 and 26 carbons. Thus, the second phase has to encompass only the maximum of 24 terminal carbons; realistically, 16-20 carbons. This effect had a small trace in X-ray diffraction, which points to a weak side chain crystallization [17,18]. However, it was shown that the samples showing this phase behavior in the solid state [16] did not show it in the melt state, as the samples behaved like normal linear low density polyethylenes (LLDPEs), being only special because of their higher flow activation energy E a , which is the consequence of the side-chain content s c of the comonomer [19,20]. Phase separation in the melt is usually visible by traces of the interfacial tension [21] and different temperature dependencies of the individual blend components and the interfacial processes [22,23]. Hence, if other techniques don't show any trace, e.g., because of too low differences in the electron density in X-ray scattering, rheological behavior can provide a valuable aid to the characterization of phase separation. Recently, molecular dynamics studies revea...

show abstract

Linear Rheology of Architecturally Complex Macromolecules: Comb Polymers with Linear Backbones

Cited by 195 publications

References 47 publications

Stress growth and relaxation of dendritically branched macromolecules in shear and uniaxial extension

Stress growth and relaxation of dendritically branched macromolecules in shear and uniaxial extension

i-Rheo: Measuring the materials' linear viscoelastic properties “in a step”!

Evidence of intra-chain phase separation in molten short-chain branched polyethylene

Contact Info

Product

Resources

About