Modulus of three and four functional poly(dimethylsiloxane) networks

Macosko, Christopher W.; Benjamin, G. S.

doi:10.1351/pac198153081505

Cited by 61 publications

(36 citation statements)

References 2 publications

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“…32,33 Similar results were reported for some PDMS networks and the same networks having pendant chains. 33 For a good superposition, the temperature and density corrections in the vertical direction (b T ) were necessary, and the corrections obeyed the classical dependence 32 25 On the other hand, M x of NS (in which M n of the precursor PS is less than M e ) without guest chains is smaller than M e as simply expected, and the value of M x was estimated as 3 / 5 M e from the plateau shear modulus (G e ) 4.0 × 10 5 Pa) larger than G N o by a factor of 5 / 3 . An increase in E′ at high frequencies is observed for the networks containing guest chains, because the guest (unattached) chains behave as elastic chain when the concerning time scale is shorter than the relaxation time of guest chains τ g , i.e., ω > 1/τ g .…”

Section: Resultsmentioning

confidence: 99%

“…The polymeric precursor chain PL, whose molecular mass is much larger than the critical molecular mass for forming entanglement couplings for un-cross-linked PDMS melt (M c ) 1.66 × 10 4 ), 24 was used for preparing the host network with Mx ≈ Me whose mesh is primarily governed by trapped entanglements. The oligomeric precursor chain PS with Mn less than the entanglement spacing of Me ) 1.0 × 10 4 for PDMS 25 was employed to prepare the host network with a tight mesh of Mx < Me.…”

Section: Methodsmentioning

confidence: 99%

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Viscoelastic Relaxation of Guest Linear Poly(dimethylsiloxane) in End-Linked Poly(dimethylsiloxane) Networks

2001

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Dynamics of guest linear polymer trapped in permanently cross-linked network is investigated using the end-linked poly(dimethylsiloxane) (PDMS) networks with well-defined mesh sizes (M x) containing unattached linear PDMS. Viscoelastic relaxation behavior of the PDMS networks with the unattached PDMS has been examined as a function of the molecular mass of the guest PDMS (Mg) and the end-reactive precursor PDMS. Two host networks with different mesh characters and sizes, i.e., Mx ≈ Me (trapped entanglement dominant) and Mx < Me (cross-link dominant), were prepared by endlinking the sufficiently longer and shorter precursor PDMS relative to entanglement spacing (Me), respectively. The dynamic mechanical measurements reveal that the networks containing the guest chains show the definite maxima in loss factor tan δ at certain frequencies which are attributed to the viscoelastic relaxation of the guest chains, and in addition, the location of the tan δ peak shifts to the lower frequencies with increasing in Mg. The characteristic time τg, defined by the inverse of the frequency at the tan δ maximum, varies with Mg in good agreement with the predictions of the reptation theories, regardless of Mx. Interestingly, the reptation of the guest chains in the cross-link-dominant network of Mx < Me is markedly retarded relative to that in the entanglement-dominant network of Mx ≈ Me: τg in the crosslink-dominant network is larger than that in the entanglement-dominant network by a factor of nearly 10 5 . Such remarkable slowing-down of reptation is not simply explained in terms of only the reduction in Mx, which suggests that the effects of the high concentration of cross-link in the network of Mx < Me on the dynamics of guest chains must be considered.

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Viscoelastic Relaxation of Guest Linear Poly(dimethylsiloxane) in End-Linked Poly(dimethylsiloxane) Networks

2001

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“…This mixture was allowed to react at 120 °C for 3 h to prepare a PDMS gel. Some details of this double-liquid crosslinking reaction (catalyzed with a trace amount of Pt complex included in the neat PDMS prepolymer) are shown in Scheme 1: The vinyl group at a prepolymer end reacts with the monomethyl siloxane group in the chemically modified prepolymer 22) as well as with the end vinyl group of the other prepolymer. The former route of the reaction, possibly occurring more frequently than the latter 22) , gives a dangling prepolymer grafted onto a middle of the other prepolymer if the reaction efficiency is low, which was the case for the gel examined in this paper.…”

Section: Methodsmentioning

confidence: 99%

Viscoelastic Behavior of Scarcely Crosslinked Poly(dimethyl siloxane) Gel

Takahashi

Ishimuro

Watanabe

2006

J. Soc. Rheol., Jpn

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Linear viscoelastic behavior was investigated for a poly(dimethyl siloxane) (PDMS) gel formed through a bulk double-liquid crosslinking reaction of two types of vinyl-terminated PDMS prepolymers of the molecular weights M pre ≅ 35×10 rapidly decreased to its equilibrium plateau at the modulus G e = 2800 Pa. On a further decrease of ω well in the plateau regime of G', G" decreased in proportion to ω 0.3 . Thus, the gel exhibited the fast and slow relaxation processes characterized with these types of power-law behavior of G". The molecular weight between the crosslinks evaluated from the G e data (as well as the equilibrium swelling ratio in toluene), M c ≅ 340×103 , was about ten times larger than M pre . The crosslinking reaction was made in the bulk state but still gave such a scarce gel network (with M c ≅ 10 M pre ) possibly because a large amount of sol chains and dangling chains had diluted the trapped entanglements during the reaction. From the analysis of the G' and G" data on the basis of the above M c value and the intrinsic Rouse relaxation time, the fast relaxation process was assigned as the Rouse-like constraint release (CR) process of individual gel strands. The polydispersity of the strands was found to be essential for the power-law behavior (G"∝ω n with n ≅ 0.6) to be observed in the plateau regime of G'. The slow relaxation process was related to fluctuation of the crosslinking points, which is equivalent to cooperative Rouse-CR motion of many gel strands connected at these points.

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“…The mechanical properties of polymer networks may be tuned by changing the molecular weight of the polymer chains and by varying the stoichiometric imbalance given by the molar ratio between the reactive groups of the crosslinker and the vinyl groups of the PDMS [8][9][10][11][12][13] :…”

Section: Theorymentioning

confidence: 99%

Influence of micro- and nanofillers on electro-mechanical performance of silicone EAPs

et al. 2012

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The effect of different fillers on the mechanical and dielectric properties of soft elastomers has been investigated. It was found that the addition of a small amount of silica fillers would increase the Young's modulus significantly but not simultaneously increase the tear strength sufficiently for processing as thin films. Addition of nanoclay and barium titanate nanoparticles to the soft elastomers was shown to be very favorable for the enhancement of the dielectric properties without increasing the Young's modulus significantly and could be used for DEAP material in e.g. microprocessing where the tear strength is not crucial for processing. However, for elastomer film processing it is suggested that a combination of the nanoclay or barium titanate with either silica particles or bimodal networks would give the right tear strength together with the desired increased dielectric permittivity.

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Modulus of three and four functional poly(dimethylsiloxane) networks

Cited by 61 publications

References 2 publications

Viscoelastic Relaxation of Guest Linear Poly(dimethylsiloxane) in End-Linked Poly(dimethylsiloxane) Networks

Viscoelastic Relaxation of Guest Linear Poly(dimethylsiloxane) in End-Linked Poly(dimethylsiloxane) Networks

Viscoelastic Behavior of Scarcely Crosslinked Poly(dimethyl siloxane) Gel

Influence of micro- and nanofillers on electro-mechanical performance of silicone EAPs

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