Chemical and Biological Engineering Publications Chemical and Biological Engineering

5-15-2020

Polystyrene-block-Polydimethylsiloxane as a Potential Silica Polystyrene-block-Polydimethylsiloxane as a Potential Silica

Substitute for Polysiloxane Reinforcement Substitute for Polysiloxane Reinforcement

Liyang Shen Iowa State University lsheniastateedu

Tung-Ping Wang Iowa State University wangtpiastateedu

Fang-Yi Lin Iowa State University

See next page for additional authors

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Part of the Polymer Science Commons

The complete bibliographic information for this item can be found at httpslibdriastateedu

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Polystyrene-block-Polydimethylsiloxane as a Potential Silica Substitute for Polystyrene-block-Polydimethylsiloxane as a Potential Silica Substitute for Polysiloxane Reinforcement Polysiloxane Reinforcement

Abstract Abstract Here we report microphase-separated poly(styrene-block-dimethylsiloxane) (PS-b-PDMS) as a reinforcing filler in PDMS thermosets that overcomes the long-standing problem of aging in the processing of silica-reinforced silicone Surprisingly PS-b-PDMS reinforced composites display comparable mechanical performance to silica-modified analogs even though the modulus of PS is much smaller than that of silica and there is no evidence of percolation with respect to the rigid PS domains We have found that a few unique characteristics contribute to the reinforcing performance of PS-b-PDMS The strong self-assembly behavior promotes batch-to-batch repeatability by having well-dispersed fillers The structure and size of the fillers depend on the loading and characteristics of both filler and matrix along with the shear effect The reinforcing effect of PS-b-PDMS is mostly brought by the entanglements between the corona layer of the filler and the matrix rather than the hydrodynamic reinforcement of the PS phase

Disciplines Disciplines Chemical Engineering | Polymer Science

Comments Comments This document is the Accepted Manuscript version of a Published Work that appeared in final form in ACS Macro Letters To access the final edited and published work see DOI 101021acsmacrolett0c00211

Authors Authors Liyang Shen Tung-Ping Wang Fang-Yi Lin Sabrina Torres Thomas Robison Sri Harsha Kalluru Nacuacute B Hernaacutendez and Eric W Cochran

This article is available at Iowa State University Digital Repository httpslibdriastateeducbe_pubs430

Polystyrene-block-Polydimethylsiloxane as a Potential SilicaSubstitute for Polysiloxane ReinforcementLiyang Shen Tung-ping Wang Fang-Yi Lin Sabrina Torres Thomas Robison Sri Harsha KalluruNacu B Hernandez and Eric W Cochran

Cite This ACS Macro Lett 2020 9 781minus787 Read Online

ACCESS Metrics amp More Article Recommendations sı Supporting Information

ABSTRACT Here we report microphase-separated poly(styrene-block-dimethylsiloxane) (PS-b-PDMS) as a reinforcing filler inPDMS thermosets that overcomes the long-standing problem ofaging in the processing of silica-reinforced silicone SurprisinglyPS-b-PDMS reinforced composites display comparable mechanicalperformance to silica-modified analogs even though the modulusof PS is much smaller than that of silica and there is no evidence ofpercolation with respect to the rigid PS domains We have foundthat a few unique characteristics contribute to the reinforcingperformance of PS-b-PDMS The strong self-assembly behaviorpromotes batch-to-batch repeatability by having well-dispersedfillers The structure and size of the fillers depend on the loadingand characteristics of both filler and matrix along with the shear effect The reinforcing effect of PS-b-PDMS is mostly brought bythe entanglements between the corona layer of the filler and the matrix rather than the hydrodynamic reinforcement of the PSphase

Polysiloxane elastomer commonly known as siliconerubber has outstanding performance in a wide temper-

ature range and is widely used in aviation and aerospaceapplications12 However unfilled silicone rubbers such aspolydimethylsiloxane (PDMS) have poor mechanical proper-ties because of the flexible polymer chain thus makingreinforcement by filler essential It is well-known thatreinforcement by fillers improves the mechanical propertiesdramatically which involves a hydrodynamic effect brought bythe inclusion of rigid particles matrixminusfiller and fillerminusfillerinteractions34 Silica is widely used for silicone rubberreinforcement because of the high modulus and strongmatrixminusfiller bonding5minus7 Unfortunately silica-filled siliconecompounds require a few weeksrsquo storage called ldquobin-agingrdquo foroptimal physical properties before subsequent processing andvulcanization289 The precured compounds (silicone crepe)exhibit aging phenomena over long-term storage time4

including both hardening24minus11 and softening1213 Theinhibiting methods include adding plasticizers14 and pretreat-ment of the silica surface4 However remilling is usuallyrequired before further processing which pushes up the costand more importantly decreases the process repeatabilityOther than using inorganic fillers it is also possible to obtain

reinforcement by introducing glassy polymer domains withinthe elastomer Polymer blending is widely used in polymermodification because of easy processability15 PDMSpoly-styrene (PS) blends that were prepared by in situ radicalcopolymerization of styrene in a PDMS matrix showed

improved mechanical properties including 9-fold increasedtensile strength at 43 PS loading in comparison with neatPDMS elastomer16 However the mechanical properties ofimmiscible homopolymer blends are still poor because of thelack of adhesion among the constituent components whichoriginates from strong repulsive thermodynamic interactions17

Block copolymers formed from two or more polymer blockswith distinct properties may be another solution Themicroscopic segregation of these blocks can generate complexstructures and desirable properties Block copolymers arewidely applied as the well-known thermoplastic elastomerswhich are composed of hard and soft polymer blocks18 Theoutstanding strength and toughness are brought by thedeformable plastic microdomains from microscopic phaseseparation The PDMSminusPS multiblock copolymers showedeffective mechanical reinforcement with 30minus50 wt polystyrene19

For the PDMS with various thermoplastics vulcanization isunnecessary and the elastomers result from directly cooling themelt4 However the extensibility is impaired without cross-

Received March 13 2020Accepted May 12 2020

Letterpubsacsorgmacroletters

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linking A cross-linked block copolymer-filled PDMS compo-site may therefore be a preferential strategy to optimize thestrength and extensibility Several works in glassy polymertoughening have shown that block copolymers are able to acteffectively at low concentration in blends with homopolymersFor example epoxies can be toughened with trivial processingby using block copolymer self-assembly at low (5 wt ) blockcopolymer concentrations20minus22 Low molar mass poly-(butylene oxide)-containing diblock copolymers at 5minus10 wt loading can be used as modifiers to toughen poly(lactide)23

Inspired by this strategy we hypothesized that fillerminusmatrixinteractions in a block copolymer-reinforced PDMS thermosetcould contribute to reinforcement more than hydrodynamiceffects which depend on the modulus and volume fraction offiller Therefore the favorable interactions between the PDMSblock of a simple diblock copolymer and the PDMS matrix canenhance mechanical reinforcement The self-assembly behaviorof block copolymers is also a unique advantage over silicawhich leads to microscopic phase separation and improvesfiller dispersion PS is a well-studied choice as a reinforcinghard segment that can be easily synthesized with well-controlled polymerization PSminusPDMS materials were thusevaluated as fillers in PDMS having much better miscibilitythan homopolystyrene2425 As demonstrated below thecomparison between the reinforcing effects of PDMS-b-PSand silica reveals the potential of the block copolymer to be asilica substituteThe molecular characteristics of the two main polymeric

materials are included in Table 1 To control the molecular

weight precisely anionic polymerization was adopted tosynthesize volume symmetric PS-b-PDMS (diBCP) withnarrow molecular weight distribution28minus31 The syntheticmethods and molecular characterization are available in theSupporting Information Vinyl-terminated polydimethylsilox-ane (Gelest DMS-V31 28 kDa) was used as the polymermatrix The molecular weight of each block was chosen closeto that of the PDMS matrix The molecular weights of PDMSmatrix and PDMS block of diBCP are around the critical valueof linear PDMS chain entanglement which is approximately 30kgmol32

Spherical micelles wormlike or cylindrical micelles andclosed ldquobagsrdquo formed by flat bilayers called vesicles undercertain circumstances are the three basic structures from self-assembly when diblock copolymers dissolve in selectivesolvents or mix with polymer matrices33 In this work thePDMS matrix acts as the good ldquosolventrdquo for the PDMS blockand a nonsolvent for the PS block Figures 1 and S7 showrepresentative transmission electron microscopy (TEM)images of all diBCPPDMS blends at low and highmagnification respectively The experimental methods of

sample preparation and morphological characterization areincluded in the Supporting Information Though the results ofthermal characterization which are shown in Figure S6suggest complete incompatibility between PS and PDMSphases by no shift of the glass transition temperature of PS thefillers are well-dispersed and no macrophase separation isobserved As expected the diBCP forms micelles and vesicleswith different sizes and structures in the polymer matrix Itindicates that 10 wt is above critical micelle concentration(CMC) and the compounding temperature is above thecritical micelle temperatureSeveral parameters such as diBCP concentration and the

molecular weights of both diBCP and homopolymer matrixaffect the structure of self-assembled diBCP34 A homogeneousphase occurs in which the diBCP is molecularly dispersed assolute in the homopolymer matrix if diBCP concentration isbelow the CMC Within a certain concentration range abovethe CMC independent micelles are dispersed in thehomopolymer without long-range ordering The sample with10 diBCP loading reveals such morphology as the diBCPconcentration is increased further fillers begin to contactaggregate and overlap shown by the morphology of sampleswith 20minus60 wt diBCP loading Under current blendingconditions the low-diBCP loading blends (below 50) mayreach the thermodynamic equilibrium based on the sizedistribution of the micelles Further increasing the diBCP

Table 1 Molecular Characteristics of PDMS HomopolymerMatrix and PS-b-PDMS Diblock Copolymera

sample Mn (kgmol) MwMn f PS wPS

vinyl-terminated PDMS 28 157diBCP 61 108 047 049

adiBCP represents PDMS-b-PS diblock copolymer Number-averagemolecular weight and dispersity were determined by gel permeationchromatography Volume and weight fraction calculated based on 1HNMR results by using densities ρPDMS = 097 gcm326 and ρPS = 105gcm327

Figure 1 Representative TEM images of cryo-ultramicrotomedPDMS composites with PS-b-PDMS loading from 10 wt to 60 wt Scale bars are all 05 μm

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concentration will typically induce a transition from sphericalto cylindrical micelles35 as well as larger vesicles andmultilamellar vesicles with ldquoonion-like structuresrdquo20 Howeverthe morphology of samples with 20minus40 wt diBCP loadingshows that most of the vesicles remain unilamellar and evenshrink instead of becoming larger and multilamellar If thediBCP concentration keeps increasing a transition to well-ordered periodic phases such as lamellae and cylinders shouldtake place where the homopolymers act to swell itscorresponding domain of the diBCP34 However no orderedstructures are observed from the morphology of samples with50 and 60 wt diBCP loading The intense shear flow broughtby twin-screw compounding is the unique effect on thoseunusual behaviors A small-angle X-ray scattering (SAXS)comparison of the samples with and without shearing is shownin Figure S10 evidently shearing inhibits the formation ofordered structures and introduces kinetically trapped mor-phologies It has been reported that smaller unilamellar vesiclesor with less shells are formed with increasing shear rate in an

aqueous system36 and cylindrical micelles or bilayer tubes arealso developed from the deformation of elongated vesiclesunder strong shearing37 More cylindrical micelles are observedfrom the morphologies of samples with 40 wt to 60 wt diBCP loading than that of samples with low diBCP loadingThe formation of larger and multilamellar vesicles arerestrained by the high shear flow which leads to structureswith a smaller curvature such as cylindrical micelles andlamellar phases38 The shear-induced morphology is thentrapped by the high temperature curing process Similarbehavior has been observed in a block copolymer melt thephases formed after the shear-induced network-to-networktransition are stable to annealing for a long time39 It indicatesthat shearing process can be a suitable method for morphologycontrol in block copolymerhomopolymer blendsThe volume fraction of each block in the diBCP will also

affect the structure of self-assembled diBCP If the length ofthe insoluble block is larger than that of the soluble block inthe preferential solvent it tends to form vesicles Conversely

Table 2 Structural Parameters Extracted from SAXS Analysis of PDMS-b-PS Filled PDMS Samples Using the Core-ShellModela

scattering length density (SLD times10minus6 Aringminus2)

sample core radius (Rc nm) relative core polydispersity (σRc) shell thickness (Ts nm) core (ρc) shell (ρs) matrix (ρ0)

10 wt diBCP 930 plusmn 043 078 plusmn 005 519 plusmn 038 99 89 8920 wt diBCP 425 plusmn 040 053 plusmn 001 153 plusmn 010 90 101 92

aTheoretical SLD44 PDMS ((C2H6OSi)n 097 gcm3) SLD 90 times 10minus6 Aringminus2 (Cu Kα) PS ((C8H8)n 105 gcm3) SLD 96 times 10minus6 Aringminus2 (Cu Kα)

Figure 2 Effect of PS-b-PDMS content on mechanical properties of PDMS composites and the comparison with 25 and 30 wt silica-filled PDMScomposites (a) Elongation at break (b) Tensile strength (c) Youngrsquos modulus and (d) Toughness

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spherical micelles will be formed214041 This effect iscontrolled since the two blocks are approximately symmetricThe disparity between molecular weights of diBCP andhomopolymer matrix can affect the dimensions of self-assembled diBCP In the case of diBCP spherical micelles ifthe molecular weight of the soluble block of diBCP is similar orhigher than the homopolymer matrix the corona can beswelled by the homopolymer matrix and has larger thickness34

On the contrary the corona cannot be swollen if the molecularweight of soluble block of diBCP is much lower than that ofmatrix The micelles with swelled corona have stronger fillerminusmatrix interactions and therefore are more stable because thefree homopolymer chains penetrate the soluble block chainsand force them to extend into the matrix42

SAXS profiles with form factor fits of 10 and 20 wt diBCPloaded samples at room temperature are shown in Figure S8For the samples with higher loading the diversity of particlesize and shape interferes with the form factor fitting intenselyas well as strong interparticle correlations due to the denseparticle concentration revealed by TEM images The structuresstudied here are spherical micelles and vesicles according totheoretical prediction and TEM images The fitting is based ona coreminusshell model which can fit the transitional structuresmore universally than models based on single structure such aspolymer micelle model43 the details are included in theSupporting InformationTable 2 shows the quantitative information on size and

distribution from the SAXS models For spherical micelles thecore consists of PS microdomains and the shell can be ascribedto the PDMS phase swelled by PDMS matrix For vesicles PSformed the shell and the core is the PDMS block of the diBCPThe data are described by this model very well as can be seenfrom the fitting results The 10 wt diBCP loaded sample hasa smaller core size and larger shell thickness since the denselypacked PS block formed the core and the chains of PDMSblock are unperturbed in PDMS matrix The 20 wt diBCPloaded sample has a relatively smaller PDMS domain size dueto the constraint of PS shell The bilayer walls of vesicle haveapproximately doubled PS domain size The values ofpolydispersity indicate that these samples formed micelles inbroad size distribution which are confirmed by TEM imagesThe stressminusstrain curves of neat PDMS 10minus60 wt

diBCP-loaded PDMS composites are shown in Figure S5

which are compared with that of silica-filled composites Thedetails of sample preparation and tensile tests are included inthe Supporting Information The associated tensile strengthYoungprimes modulus elongation at break and toughness aresummarized in Table S1 The effect of diBCP content on thefour mechanical properties is illustrated in Figure 2 Overallthe diBCP addition enhances all four mechanical propertiesdramatically compared to the neat PDMS The high degree ofsample-to-sample reproducability indicates evenly dispersedfillers and microscopic phase separationThe mechanical properties have increasing values with

higher diBCP loading and the overall optimal condition is at50 wt loading The result indicates that increasing PScontent does improve strength as expected All BCP-filledsamples have similar linear behavior at small strain suggestingthat the deformation of samples remains Hookean The 50 and60 wt loading samples have an abrupt increase in modulus atlarge strain Natural rubber has a similar behavior due to strain-induced crystallization45 However the PDMS matrix isrubbery at room temperature since Tg and Tc are well below20 degC4 The stress increase is more likely caused by limitedextensibility of the network according to the non-Gaussianstatistical theory46 The effect of diBCP content on toughnessis similar to tensile strength and elongation at break sincelarger value of stress and strain at break increases the energyabsorption during extensionFigure 3 shows the relative Youngrsquos modulus of silica and

diBCP filled samples as a function of filler volume fraction Thedata of PDMSsilica samples are fit by the model containingthe well-known Guth and Gold equation47 that accounts forthe hydrodynamic effect and an additional exponential termwith two adjustable coefficients to accommodate theconspicuous increase at high filler loading due to therearrangement of filler at high loading48 which is eq 1

EE

A e

A B

1 25 141 ( 1)

0462 1610

B

0

2ϕ ϕ= + + + minus

= =

ϕ

(1)

Unlike the exponential growth behavior of PDMSsilicasamples the diBCP-filled samples exhibit a possible upperlimit The empirical equation is therefore modified with anexponential decay term in increasing form with two adjustable

Figure 3 Relative Youngrsquos modulus EE0 as a function of filler volume fraction and model fitting (a) silica (circles) and (b) PS block of PS-b-PDMS (triangles) E0 = 032 MPa

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coefficients and has the GuthminusGold equation removed whichis eq 2

EE

A e

A B

1 (1 )

3145 1850

B

0= + minus

= =

ϕminus

(2)

The reinforcing effect brought by silica can be contributedby the hydrodynamic effect of rigid particle inclusion thefillerminusmatrix interactions on the silica surface and fillerminusfillerinteraction For the diBCP-filled PDMS to correlate themechanical properties with morphology the increasinginterfacial area of self-assembled diBCP could contribute tothe improvement of mechanical properties with increasingdiBCP loading Unlike the aggregates and percolation networkof the silica fillers the PS micelle cores are unable to contacteach other directly to form the percolation network Theinterfacial adhesive force between the PS and PDMS phases isbrought by the physical entanglements of PDMS chains andthe covalent bonding between PS and PDMS phases withindiBCP The reinforcing effect brought by the fillerminusmatrixinteraction is weak at low-diBCP loading because of smallinterfacial area With higher loading of diBCP the increasingnumber of micelles vesicles and their aggregations enlarge theinterface area between filler and matrix and therefore enhancethe mechanical properties As the interfacial area increasesrapidly with the content of diBCP at the early stage and thenreaches to a limit so does the modulus which can be fit by theexponential decay term However the sample with 60 wt loading becomes weaker The breakage at smaller strainsuggests the cross-linking network became less stable whichmay be caused by overlapping and stacking of fillers Theinteraction energy of two overlapping micelles is repulsive andthe concentration of homopolymer chains in the outer shelldecreases which impairs the entanglement49 On the otherhand the sample with 60 wt loading has only 40 wt vinyl-terminated PDMS matrix which is the component that takespart in cross-linking shown in Scheme S2 The PDMS block ofdiBCP does not react with the cross-linking agents during theplatinum-catalyzed reaction When the block copolymer fillercontent is over 50 the modulus is affected by the decrease ofthe cross-linkable PDMS matrix contentThe comparison with the mechanical properties of silica-

reinforced samples shows the great potential of thepolystyrene-based block copolymers as reinforcing fillerseven with respect to commercially available silica reinforcedPDMS composites50 The performance of 50 wt diBCPloaded sample is taken as example The tensile strength rivalsthat of 30 wt silica loaded sample and out-performs 25 wt silica while boasting larger elongation-at-break For Youngrsquosmodulus the value is about 80 of that of 25 wt silica and50 of that of 30 wt silica which is remarkable since themodulus of homopolystyrene is less than one tenth of that ofsilica51

In conclusion a proof-of-concept strategy to substitute silicaby PS-b-PDMS as reinforcing filler for PDMS composites hasbeen successfully proposed and verified experimentally Theglassy PS phase as part of PS-b-PDMS diblock copolymer hasshown prominent reinforcing effect on PDMS The PDMScomposites with 50 wt loading have the optimal mechanicalproperties such as tensile strength The comparison with thesilica filled samples shows the potential of this polymer fillerAlthough the modulus of PS is much smaller than silica the

PS-b-PDMS filled composites exhibit similar mechanicalperformance as silica filled composites The well-defineddiblock copolymer is essential to provide controlled self-assembly structures which brings better filler dispersion andpromotes fillerminusmatrix interactions The increased interfacialarea and adhesive force also enhance the mechanicalproperties In addition the shear effect during blending is asuitable method for morphology control in block copolymerhomopolymer blends

ASSOCIATED CONTENTsı Supporting InformationThe Supporting Information is available free of charge athttpspubsacsorgdoi101021acsmacrolett0c00211

Experimental details and additional data (Schemes S1and S2 Figures S1minusS10 and Tables S1minusS3) (PDF)

AUTHOR INFORMATIONCorresponding Author

Eric W Cochran minus Department of Chemical and BiologicalEngineering Iowa State University Ames Iowa 50011 UnitedStates orcidorg0000-0003-3931-9169Email ecochraniastateedu

AuthorsLiyang Shen minus Department of Chemical and BiologicalEngineering Iowa State University Ames Iowa 50011 UnitedStates orcidorg0000-0001-9928-2877

Tung-ping Wang minus Department of Chemical and BiologicalEngineering Iowa State University Ames Iowa 50011 UnitedStates orcidorg0000-0001-6292-3933

Fang-Yi Lin minus Department of Chemical and BiologicalEngineering Iowa State University Ames Iowa 50011 UnitedStates orcidorg0000-0002-7235-2596

Sabrina Torres minus Kansas City National Security CampusKansas City Missouri 64147 United States

Thomas Robison minus Kansas City National Security CampusKansas City Missouri 64147 United States

Sri Harsha Kalluru minus Department of Chemical and BiologicalEngineering Iowa State University Ames Iowa 50011 UnitedStates orcidorg0000-0003-2001-2896

Nacu B Hernandez minus Department of Chemical and BiologicalEngineering Iowa State University Ames Iowa 50011 UnitedStates

Complete contact information is available athttpspubsacsorg101021acsmacrolett0c00211

NotesThe authors declare no competing financial interest

ACKNOWLEDGMENTSThe authors gratefully acknowledge the financial support ofHoneywell Federal Manufacturing and Technology throughContract Nos N000217245 and N000254419 administeredby Dr Sabrina Torres This work benefited from the NationalScience Foundation DMR-1626315 and the use of SasViewapplication originally developed under NSF Award No DMR-0520547 SasView contains code developed with funding fromthe European Unionrsquos Horizon 2020 research and innovationprogramme under the SINE2020 Project Grant AgreementNo 654000

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polystyrenepoly (dimethylsiloxane) blends J Polym Sci Part BPolym Phys 2004 42 898minus913(25) Hu W Koberstein J T Lingelser J P Gallot Y Interfacialtension reduction in polystyrenepoly (dimethylsiloxane) blends bythe addition of poly (styrene-b-dimethylsiloxane) Macromolecules1995 28 5209minus5214(26) Kataoka T Ueda S Viscosityminusmolecular weight relationshipfor polydimethylsiloxane J Polym Sci Part B Polym Lett 1966 4317minus322(27) Fox T G Jr Flory P J Second-order transition temperaturesand related properties of polystyrene I Influence of molecular weightJ Appl Phys 1950 21 581minus591(28) Bajaj P Varshney S K Misra A Block copolymers ofpolystyrene and poly (dimethyl siloxane) I Synthesis and character-ization J Polym Sci Polym Chem Ed 1980 18 295minus309(29) Chu J H Rangarajan P Adams J L Register R AMorphologies of strongly segregated polystyrene-poly (dimethylsilox-ane) diblock copolymers Polymer 1995 36 1569minus1575(30) Saam J C Gordon D J Lindsey S Block copolymers ofpolydimethylsiloxane and polystyrene Macromolecules 1970 3 1minus4(31) Zilliox J G Roovers J E L Bywater S Preparation andproperties of polydimethylsiloxane and its block copolymers withstyrene Macromolecules 1975 8 573minus578(32) Bagley E West D Chain Entanglement and Non-NewtonianFlow J Appl Phys 1958 29 1511minus1512(33) Hiemenz P C Lodge T P Polymer Chemistry CRC Press2007 pp 129minus131(34) Kinning D J Thomas E L Fetters L J Morphologicalstudies of micelle formation in block copolymerhomopolymerblends J Chem Phys 1989 90 5806minus5825(35) Kinning D J Winey K I Thomas E L Structural transitionsfrom spherical to nonspherical micelles in blends of poly (styrene-butadiene) diblock copolymer and polystyrene homopolymersMacromolecules 1988 21 3502minus3506(36) Bergmeier M Gradzielski M Hoffmann H Mortensen KBehavior of a charged vesicle system under the influence of a sheargradient a microstructural study J Phys Chem B 1998 102 2837minus2840(37) Shahidzadeh N Bonn D Aguerre-Chariol O Meunier JLarge deformations of giant floppy vesicles in shear flow Phys RevLett 1998 81 4268(38) Butler P Shear induced structures and transformations incomplex fluids Curr Opin Colloid Interface Sci 1999 4 214minus221(39) Cochran E W Bates F S Shear-induced network-to-networktransition in a block copolymer melt Phys Rev Lett 2004 93087802(40) Blanazs A Madsen J Battaglia G Ryan A J Armes S PMechanistic insights for block copolymer morphologies how doworms form vesicles J Am Chem Soc 2011 133 16581minus16587(41) Smart T Lomas H Massignani M Flores-Merino M VPerez L R Battaglia G Block copolymer nanostructures NanoToday 2008 3 38minus46(42) Borukhov I Leibler L Stabilizing grafted colloids in apolymer melt Favorable enthalpic interactions Phys Rev E StatPhys Plasmas Fluids Relat Interdiscip Top 2000 62 R41(43) Pedersen J S Form factors of block copolymer micelles withspherical ellipsoidal and cylindrical cores J Appl Crystallogr 200033 637minus640(44) Roe R-J Methods of X-ray and Neutron Scattering in PolymerScience Oxford Univ Press 2000 Vol 739 pp 9minus12(45) Mark J E The effect of strain-induced crystallization on theultimate properties of an elastomeric polymer network Polym EngSci 1979 19 409minus413(46) Doherty W O S Lee K L Treloar L R G Non-Gaussianeffects in styrene-butadiene rubber Br Polym J 1980 12 19minus23(47) Guth E Theory of filler reinforcement J Appl Phys 1945 1620minus25

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(48) Thomas D G Transport characteristics of suspension VIII Anote on the viscosity of Newtonian suspensions of uniform sphericalparticles J Colloid Sci 1965 20 267minus277(49) Leibler L Pincus P A Ordering transition of copolymermicelles Macromolecules 1984 17 2922minus2924(50) Johnston I McCluskey D Tan C Tracey M Mechanicalcharacterization of bulk Sylgard 184 for microfluidics and micro-engineering J Micromech Microeng 2014 24 035017(51) Tao R Simon S L Bulk and shear rheology of silicapolystyrene nanocomposite reinforcement and dynamics J PolymSci Part B Polym Phys 2015 53 621minus632

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