In Silico Molecular Design, Synthesis, Characterization, and Rheology of Dendritically Branched Polymers: Closing the Design Loop

Kimani, Solomon M.; Hoyle, David M.; Read, Daniel J.; Das, Chinmay; McLeish, Tom; Chang, Taihyun; Lee, Hyojoon; Auhl, Dietmar

doi:10.1021/mz300059k

Cited by 35 publications

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“…The efficiency of the two coupling methods are compared and the 'purified' star polymers characterised by both SEC and Temperature Gradient Interaction Chromatography (TGIC). Whilst SEC has been the characterisation method of choice for many decades, for the analysis of molecular weight and molecular weight distribution of polymers, in recent years TGIC has emerged as a technique capable of significantly enhanced resolution compared to SEC, especially in the characterisation of branched polymers [12,14,[68][69][70][71]] -a subject recently reviewed in detail [72]. In the current work TGIC revealed low levels of heterogeneity in the purified (fractionated) stars -heterogeneity which could not be detected by SEC.…”

Section: Introductionmentioning

confidence: 67%

Synthesis and temperature gradient interaction chromatography of model asymmetric star polymers by the “macromonomer” approach

Agostini¹

2013

European Polymer Journal

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. (2013) 'Synthesis and temperature gradient interaction chromatography of model asymmetric star polymers by the "macromonomer"approach.', European polymer journal., 49 (9). pp. 2769-2784. Further information on publisher's website:http://dx.doi.org/10.1016/j.eurpolymj.2013.06.021Publisher's copyright statement: NOTICE: this is the author's version of a work that was accepted for publication in European Polymer Journal. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be re ected in this document. Changes may have been made to this work since it was submitted for publication. A de nitive version was subsequently published in European Polymer Journal, 49, 9, 2013Journal, 49, 9, , 10.1016Journal, 49, 9, /j.eurpolymj.2013.021. Additional information:Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. Abstract. We describe herein the synthesis and characterisation of a series of asymmetric three arm polystyrene stars via the "macromonomer" approach. The stars have been designed as model polymers to probe branched polymer dynamics and in particular to establish the chain-length of side-arm which precipitates a change in the rheological properties of the resulting polymers from "linear-like" to "star-like". Thus, a homologous series of three arm stars have been prepared in which the molar mass of two (long) arms are fixed at 90 000 gmol -1 and the molar mass of the remaining (short) arm is varied from below the entanglement molecular weight (M e ) to above M e . The arms were prepared by living anionic polymerisation, resulting in well-defined chain lengths with narrow molecular weight distribution. In contrast to the usual chlorosilane coupling approach, the macromonomer approach involves the introduction of reactive chain-end functionalities on each of the arms, either through the use of a functionalised (protected) initiator or a functional end-capping agent, which allows the stars to be constructed by a simple condensation coupling reaction. In this study we will compare the relative efficiency of a Williamson and 'click' coupling reaction in producing the stars. Most significantly, although this approach maybe a little more time-consuming than the more common silane coupling reaction, in the present study the "long" arm may be produced in sufficient quantity such that all of the asymmetric stars are produced with long arms of identical molecular weight -the only remaining variable being the molecular weight of th...

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Section: Introductionmentioning

confidence: 67%

Synthesis and temperature gradient interaction chromatography of model asymmetric star polymers by the “macromonomer” approach

Agostini¹

2013

European Polymer Journal

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“…Predominantly these studies have been aimed at understanding the impact of chain branching upon the melt rheology of such polymers. Commonly studied branched architectures include the simplest branched structure, star polymers [1][2][3][4][5] , and increasingly complex architectures such as miktoarm stars 6,7 , graft/comb polymers [8][9][10][11][12][13] , H-shaped polymers [14][15][16][17] and dendritically long-chain branched polymers [18][19][20][21][22][23][24][25][26][27][28] . Chain-branching in block copolymers has also been explored with a view to understand the influence of architecture upon phase separation.…”

Section: Introductionmentioning

confidence: 99%

Chain Architecture as an Orthogonal Parameter To Influence Block Copolymer Morphology. Synthesis and Characterization of Hyperbranched Block Copolymers: HyperBlocks

Hutchings

Agostini²,

Hamley

et al. 2015

Macromolecules

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(2015) 'Chain architecture as an orthogonal parameter to inuence block copolymer morphology. The synthesis and characterisation of hyperbranched block copolymers : HyperBlocks. ', Macromolecules., 48 (24). pp. 8806-8822. Further information on publisher's website:http://dx.doi.org/10.1021/acs.macromol.5b02052 Publisher's copyright statement: This document is the Accepted Manuscript version of a Published Work that appeared in nal form in Macromolecules, copyright c American Chemical Society after peer review and technical editing by the publisher. To access the nal edited and published work see http://dx.doi.org/10.1021/acs.macromol.5b02052. Additional information:Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. HyperBlocks with a commercially available linear ABA triblock copolymeric thermoplastic elastomer were prepared. Moreover, the "macromonomer" approach is the only feasible route to prepare hyperbranched block copolymers. The solid-state morphology of the resulting materials was investigated by a combination of transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS) which showed a dramatic impact of the chain architecture on the resulting morphology. Whilst the linear ABA triblock copolymers showed the expected microphase-separated morphology with long-range order dependent upon composition, no long-range order was observed in the HyperBlocks. Instead the HyperBlocks revealed a microphase-separated morphology without long-range lattice order, irrespective of macromonomer composition or molecular weight. Furthermore, when HyperBlocks were subsequently blended with a commercially available linear ABA triblock copolymer (Kraton D1160 TM ) the HyperBlock appeared to impose a microphase separated morphology without long-range lattice order upon the linear copolymer even when the HyperBlock is present as the minor component in the blend at levels as low as 10% by weight.

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“…This observation indicates the omission of important physics from current models for these industrially important materials, whose processing properties depend on extreme molecular extension. Introduction.-Predicting the viscoelastic properties of branched polymer melts from their molecular architecture remains one of the great challenges in polymer physics [1][2][3]. One outstanding problem is the lack of consensus of the evolution of stress in the start-up of constant strain-rate extensional flow.…”

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confidence: 99%

Creep Measurements Confirm Steady Flow after Stress Maximum in Extension of Branched Polymer Melts

et al. 2013

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We provide conclusive evidence of nonmonotonic mechanical behavior in the extension of long-chain branched polymer melts. While nonmonotonic behavior is known to occur for solids, for the case of polymeric melts, this phenomenon is in direct contrast with current theoretical models. We rule out the possibility of the overshoot being an experimental artifact by confirming the existence of steady flow after a maximum in the ratio of stress to strain rate versus strain under both constant stress and constant strainrate kinematics. This observation indicates the omission of important physics from current models for these industrially important materials, whose processing properties depend on extreme molecular extension. Introduction.-Predicting the viscoelastic properties of branched polymer melts from their molecular architecture remains one of the great challenges in polymer physics [1][2][3]. One outstanding problem is the lack of consensus of the evolution of stress in the start-up of constant strain-rate extensional flow. While one laboratory [4] has reported a maximum in stress followed by a steady value, other laboratories have legitimately questioned the maximum [5][6][7] and even challenged the existence of steady extensional flow [8,9]. The molecular origin of a stress maximum is unclear inasmuch as nonlinear models [10] specifically designed for branched polymers show a monotonic increase of stress in constant strain-rate extension.Here, we report observations of extensional flow not with a constant strain rate but with a constant stress (creep). In addition to probing the transient behavior, the creep protocol also allows the measurement of the ultimate steady extensional viscosity. The uniqueness of the steady extensional viscosity independent of the start-up protocol is apparently not a settled matter as evidenced by the reporting of two viscosities at the same steady strain rate [11,12]. The experiments are compared to the small strain predictions [13,14] to illustrate the departure from linear material behavior.A major challenge in extensional rheometry is that large deformations are needed to approach a steady flow state. Deformations are measured in units of Hencky strain defined as ¼ ln, where ¼ L=L 0 is the stretch ratio, L 0 is the initial length, and L is the final length of a given cylindrical shape. The strain rate _ is the time derivative of the Hencky strain. In the classical controlled deformation extensional experiment, a constant _ is imposed and the stress is monitored as a function of time. Typically, Hencky strains larger than four are required to establish a steady tensile stress. However, in many extensional flow devices, sample inhomogeneity will prevent control of the kinematics

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In Silico Molecular Design, Synthesis, Characterization, and Rheology of Dendritically Branched Polymers: Closing the Design Loop

Cited by 35 publications

References 35 publications

Synthesis and temperature gradient interaction chromatography of model asymmetric star polymers by the “macromonomer” approach

Synthesis and temperature gradient interaction chromatography of model asymmetric star polymers by the “macromonomer” approach

Chain Architecture as an Orthogonal Parameter To Influence Block Copolymer Morphology. Synthesis and Characterization of Hyperbranched Block Copolymers: HyperBlocks

Creep Measurements Confirm Steady Flow after Stress Maximum in Extension of Branched Polymer Melts

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