Viscoelastic behavior of nematic monodomains containing liquid crystal polymers

Jamieson, A. M.; Gu, Dong‐Feng; Chen, F.L.; Smith, S. R.

doi:10.1016/s0079-6700(96)00009-3

Cited by 48 publications

(74 citation statements)

References 125 publications

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“…The viscoelastic nature of the Frank elasticity per se has already been investigated for liquid crystal polymers both in theory and experiment [Jamieson et al 1996]. Possible combined micro-macro rheological models are suggested in Figure 6, where the macroscopic model is not rate-sensitive while the microscopic model includes damping terms dependent onχ.…”

Section: Discussionmentioning

confidence: 99%

Rate dependence of indentation size effects in filled silicone rubber

Tatiraju

Han

2010

JOMMS

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Indentation experiments at the nanometer and micrometer range reported in the literature have shown that the deformation of polymers is -similarly to metals -size-dependent. In addition its size dependence, the deformation behavior of polymers is also known to be rate-dependent. Here silicone rubber is considered. In order to characterize the relation between size and rate-dependent deformation indentation tests of silicone at indentation depths of between 30 and 300 microns and loading times of between 1 and 1000 seconds are performed. In these experiments the hardness and dissipation increased with decreasing loading time and decreasing indentation depth. These experimental results are analyzed with a recently suggested indentation model which incorporates a Frank energy-related nonlocal deformation work. It is found that the indentation model is in good agreement with the experimental data. Evaluation of the experimental data indicates that the rate effects are mostly related to the nonlocal, size-dependent deformation.

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Section: Discussionmentioning

confidence: 99%

Rate dependence of indentation size effects in filled silicone rubber

Tatiraju

Han

2010

JOMMS

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“…To date, the only other measurements of negative tumbling parameters has been in discotic [13] systems and with melt SGLCPs [19]. By using polymers with a molecular weight that is typically at least an order of magnitude larger than other researchers [20], we were able to get much greater changes in viscoelastic properties using less polymer. Not only does this study open up new regimes of the tumbling parameter for study, but it also verifies some aspects of Brochard theory.…”

Section: P H Y S I C a L R E V I E W L E T T E R S Week Endingmentioning

confidence: 97%

“…Only in the high concentration limit of a polymer melt has < 0 been observed [19]. Strikingly, prior investigations have been limited to relatively short polymers (degree of polymerization D:P: 100) [20]. By examining much longer chains (D:P: 1200) with comparable anisotropy to previous systems (R ?…”

Section: Dñ Nmentioning

confidence: 98%

Shear Alignment Behavior of Nematic Solutions Induced by Ultralong Side-Group Liquid Crystal Polymers

Kempe

Kornfield

2003

Phys. Rev. Lett.

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Addition of a low concentration of a very long (430 kg=mol) side group liquid crystal polymer is shown to produce dramatic changes in the flow characteristics of a calamitic nematic liquid crystal. This polymer causes a typical flow-aligning nematic liquid crystal to align near the velocity gradient direction rather than near the velocity direction, corresponding to having a tumbling parameter < ÿ1, for concentrations greater than 7.5% polymer. Such flow-aligning behavior has not been reported previously in a calamitic nematic. The large molecular weight of the present polymer relative to those examined in the prior literature is responsible for these new phenomena.

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“…The phenomenon is obviously caused by smectic clusters. While rigid-rod polymers forming nematic phases in solution, such as poly(benzylglutamate) and hydroxypropylcellulose, and thermotropic main-chain liquid crystal polymers are mostly of the tumbling type [19], side-chain liquid crystal polymers can be either flow aligning or tumbling [7,20,21]. Using deuteron NMR spectroscopy to measure the director orientation during shear as a function of the applied shear rate, we have determined l for several sidechain polymers in bulk and in solution, and found both types of flow behavior [6][7][8].…”

Section: Introductionmentioning

confidence: 99%