yusril yusuf - Academia.edu (original) (raw)

Papers by yusril yusuf

Advanced Materials Research, 2014

Advanced Materials Research, 2014

ABSTRACT

Proceedings of the 2014 International Conference on Physics, 2014

Proceedings of the 2014 International Conference on Physics, 2014

Journal of The Physical Society of Japan, 2001

Soft-mode turbulence (SMT) is a recently discovered type of spatiotemporal chaos observed in the ... more Soft-mode turbulence (SMT) is a recently discovered type of spatiotemporal chaos observed in the electrohydrodynamic instability (EHD) of a nematic liquid crystal with homeotropic alignment. Its novelty is that it occurs as the first supercritical bifurcation from a stable stationary state in the weakly nonlinear regime of EHD. A particle, small compared to the characteristic length of the macroscopic flow, injected in SMT travels with random velocity similar to a particle in Brownian motion. We find that the particle trajectory exhibits anomalous Brownian motion such as pumped flight and that the macroscopic diffusion constant due to weak turbulence is about 103 times larger than the diffusion constant associated with the rest state. The stochastic properties of SMT are discussed.

Journal of The Physical Society of Japan, 2005

We report electromechanical effects in a swollen polydomain liquid crystalline elastomer (POLY-LC... more We report electromechanical effects in a swollen polydomain liquid crystalline elastomer (POLY-LCE). Owing to the director reorientation, we could directly observe its deformation in the unconstrained elastomer gel state. Using optical image analysis, the deformation amplitude, threshold voltage, and temporal characteristics of the POLY-LCE were quantitatively measured with varying voltage and temperature. From the experimental results we discuss the deformation mechanism and property of the POLY-LCE.

Molecular Crystals and Liquid Crystals, 2004

Applied Physics Letters, 2008

A multifunctional main chain liquid crystal elastomer ͑MCLCE͒ with large mechanical and optical e... more A multifunctional main chain liquid crystal elastomer ͑MCLCE͒ with large mechanical and optical effects in applied electric fields is investigated, when MCLCE is swollen in a low molecular weight liquid crystal, 4-n-pentyl-4-cyanobiphenyl, a nematic solvent. The size change by the field effects is linearly proportional to the transmittancy change. This suggests the possibility of broad application as a field-induced-optical actuator device.

Assuming only incompressibility, in the simplest complete theory for monodomain liquid crystallin... more Assuming only incompressibility, in the simplest complete theory for monodomain liquid crystalline elastomers as rectangular parallelepipeds, we find two biaxial nematic phases, N2+ and N2- with a first order N2+-N2- transition exhibiting spontaneous shape change. We identify N2+ as icosahedral (Yh) and N2-, as simple orthorhombic (D2h) nematics. Using standard orientational mechanics, we derive the stress-strain behavior before swelling to

Molecular Crystals and Liquid Crystals, 2009

Swelling behavior and deformations of main chain liquid crystal elastomers (MCLCEs) have been rep... more Swelling behavior and deformations of main chain liquid crystal elastomers (MCLCEs) have been reported. The swelling agent used here is a low molecular weight liquid crystal (LMWLC), 4-n-pentyl-4-cyanobiphenyl (5CB). Monodomain MCLCE swells anisotropically with the swelling degree q mono = 11.9 and polydomain MCLCE swell isotropically in 3D with q poly = 12.1. These values are much larger than observed in swelling side-chain LCEs (SCLCEs). In the stress-strain measurement, the plateau area is found among two steep areas. The electromechanical effects of monodomain MCLCE is also observed, and the results show that the maximum contraction in ∥ is about 7%. The threshold for the onset of the electromechanical effect is about 10 V, which is larger than observed in SCLCEs.

Physica A-statistical Mechanics and Its Applications, 2002

We study the complex behavior in soft-mode turbulence (SMT), a recently discovered type of spatio... more We study the complex behavior in soft-mode turbulence (SMT), a recently discovered type of spatiotemporal chaos observed in electrohydrodynamic instability (EHD) of a nematic liquid crystal with homeotropic alignment. A particle, small compared to the characteristic length of the macroscopic ow, injected in SMT travels with random velocity such as an active Brownian motion. Tracking the particle trajectory induces changes in the ow velocity as a function of space and time (the Lagrange picture). The mean amplitude of the velocity is linearly proportional to the control parameter , normalized voltage in EHD. The probability density distribution of the particle velocity changes from LÃ evy for small to Gaussian distribution for large through intermediate distributions. The di erent regimes of anomalous di usions are also observed. The stochastic properties of SMT are discussed based on these results.

Physical Review E, 2005

We experimentally investigate, in detail, electromechanical effects in liquid-crystal elastomers ... more We experimentally investigate, in detail, electromechanical effects in liquid-crystal elastomers ͑LCEs͒ previously swollen with low-molecular-weight liquid crystals ͑LMWLCs͒. Both polydomain ͑POLY͒ and monodomain ͑MONO͒ LCEs were studied. We used a well known LMWLC, 4-n-pentyl-4-cyanobiphenyl ͑5CB͒ as a solvent. After swelling POLY and MONO LCEs ͑LSCE͒ with 5CB, shape changes were measured by recording the displacement of the edge of the swollen LCE at different voltages, V, and temperature. With 100 m distance between electrodes, measurable shape changes ͑ϳ1-20 m͒ are observed with small voltages ͑V ϳ 0.5-10 V͒. In particular, we note that, compared to unswollen L͑S͒CEs, a dramatic ϳ200 times decrease of the threshold field was found for electromechanical effects in swollen L͑S͒CEs. While swollen MONO LCEs showed electromechanical effects in the planar geometry, homeotropic MONO swollen with homeotropically oriented 5CB did not. This is easy to understand because, in the homeotropic case, the liquid-crystal preferred axis is already aligned with the field so the field has no reorienting effect. The inverse of the response time when the field was switched on in both POLY and MONO was proportional to E 2 , which is the same field dependence as the response time of LMWLCs. When the field was switched off, the relaxation time showed a field dependence different from that of LMWLCs that we attribute to relaxation of the LCE network.

We experimentally investigated the swelling behavior of liquid crystal elastomers (LCEs) in two a... more We experimentally investigated the swelling behavior of liquid crystal elastomers (LCEs) in two anisotropic solvents such as low molecular weight liquid crystals, 5mathrmCmathrmB5\mathrm{C}\mathrm{B}5mathrmCmathrmB and MBBA. The length of LCEs by swelling expanded more than 1.8 times of its initial length which depended on the director orientation. The volume change of swollen LCEs has been investigated as function of temperature and several phase transitions were observed in both optical and adifferential scanning calorimetry measurements. ElectrO-mechanical effects of swollen LCEs were also investigated in detail and drastic decrease of the critical field for electr0-mechanical effects, 1/4000 lower than dry LCEs, was obtained.

We experimentally investigated the swelling behavior of liquid crystal elastomers (LCEs) in two a... more We experimentally investigated the swelling behavior of liquid crystal elastomers (LCEs) in two anisotropic solvents such as low molecular weight liquid crystals, 5CB and MBBA.

Advances in Condensed Matter Physics, 2013

Nematic networks with three different concentrations of polar and nonpolar mesogens and the same ... more Nematic networks with three different concentrations of polar and nonpolar mesogens and the same concentration of a novel crosslinking agent give rise to unusual liquid single crystal elastomers (LSCEs) that are transparent monodomain nematic networks with smectic clusters. The largest spontaneous length change is observed in the sample with 70 mol% of the polar mesogen which also has the highest glass transition temperature and smectic clusters with a slowly increasing but nearly constant layer spacing on cooling from 90 ∘ C to 25 ∘ C. X-ray scattering intensity from smectic clusters with layer spacings that monotonically increase on cooling first increases to a maximum at * ∼ 60 ∘ C corresponding to clusters of about 30 layers. Below * , the scattering intensity decreases as the number of layers in a cluster decreases. To account for this surprising nonlinear behavior that correlates with nonlinear features of the networks' macroscopic spontaneous shape change and birefringence, a model is proposed where dislocations form in the layers at * . Below * , more dislocations form to break down the layer structure. The possibility of dislocation formation at * independent of mesogenic concentrations is attributed to a conformational change in the crosslinker which is present at the same concentration in the three LSCEs.

Physical Review E, 2002

A kind of electrohydrodynamic instability, the prewavy instability, in nematic liquid crystals is... more A kind of electrohydrodynamic instability, the prewavy instability, in nematic liquid crystals is reported. The characteristic of the instability was optically investigated and discussed in comparison with some similar instabilities. Obviously the instability partially shows an isotropic feature around the nematic-isotropic transition temperature. Owing to the characteristic properties of the flow and the spatial periodicity, it should be distinguished from a previously proposed isotropic instability.

Dynamical hysteresis in a self-oscillating polymer gel J. Chem. Phys. 137, 064103 (2012) Structur... more Dynamical hysteresis in a self-oscillating polymer gel J. Chem. Phys. 137, 064103 (2012) Structural properties of thermoresponsive poly(N-isopropylacrylamide)-poly(ethyleneglycol) microgels J. Chem. Phys. 136, 214903 (2012) Instability analysis of a programmed hydrogel plate under swelling J. Appl. Phys. 109, 063527 (2011) Effect of the concentration on sol-gel transition of telechelic polyelectrolytes J. Chem. Phys. 134, 034903 (2011) Additional information on AIP Conf. Proc.

An order parameter describes an elastomer where a liquid crystal is cross linked at a temperature... more An order parameter describes an elastomer where a liquid crystal is cross linked at a temperature TL far from its clearing temperature. At TL, there is a first order constant density phase transition where the order parameter vanishes and the elastomer has cubic symmetry. Below TL it is an icosahedral nematic and above a biaxial nematic. This theory quantitatively accounts for spontaneous shape change, nonlinear elasticity and gelation dynamics in a novel liquid crystal elastomer.

Advanced Materials Research, 2014

Advanced Materials Research, 2014

ABSTRACT

Proceedings of the 2014 International Conference on Physics, 2014

Proceedings of the 2014 International Conference on Physics, 2014

Journal of The Physical Society of Japan, 2001

Soft-mode turbulence (SMT) is a recently discovered type of spatiotemporal chaos observed in the ... more Soft-mode turbulence (SMT) is a recently discovered type of spatiotemporal chaos observed in the electrohydrodynamic instability (EHD) of a nematic liquid crystal with homeotropic alignment. Its novelty is that it occurs as the first supercritical bifurcation from a stable stationary state in the weakly nonlinear regime of EHD. A particle, small compared to the characteristic length of the macroscopic flow, injected in SMT travels with random velocity similar to a particle in Brownian motion. We find that the particle trajectory exhibits anomalous Brownian motion such as pumped flight and that the macroscopic diffusion constant due to weak turbulence is about 103 times larger than the diffusion constant associated with the rest state. The stochastic properties of SMT are discussed.

Journal of The Physical Society of Japan, 2005

We report electromechanical effects in a swollen polydomain liquid crystalline elastomer (POLY-LC... more We report electromechanical effects in a swollen polydomain liquid crystalline elastomer (POLY-LCE). Owing to the director reorientation, we could directly observe its deformation in the unconstrained elastomer gel state. Using optical image analysis, the deformation amplitude, threshold voltage, and temporal characteristics of the POLY-LCE were quantitatively measured with varying voltage and temperature. From the experimental results we discuss the deformation mechanism and property of the POLY-LCE.

Molecular Crystals and Liquid Crystals, 2004

Applied Physics Letters, 2008

A multifunctional main chain liquid crystal elastomer ͑MCLCE͒ with large mechanical and optical e... more A multifunctional main chain liquid crystal elastomer ͑MCLCE͒ with large mechanical and optical effects in applied electric fields is investigated, when MCLCE is swollen in a low molecular weight liquid crystal, 4-n-pentyl-4-cyanobiphenyl, a nematic solvent. The size change by the field effects is linearly proportional to the transmittancy change. This suggests the possibility of broad application as a field-induced-optical actuator device.

Assuming only incompressibility, in the simplest complete theory for monodomain liquid crystallin... more Assuming only incompressibility, in the simplest complete theory for monodomain liquid crystalline elastomers as rectangular parallelepipeds, we find two biaxial nematic phases, N2+ and N2- with a first order N2+-N2- transition exhibiting spontaneous shape change. We identify N2+ as icosahedral (Yh) and N2-, as simple orthorhombic (D2h) nematics. Using standard orientational mechanics, we derive the stress-strain behavior before swelling to

Molecular Crystals and Liquid Crystals, 2009

Swelling behavior and deformations of main chain liquid crystal elastomers (MCLCEs) have been rep... more Swelling behavior and deformations of main chain liquid crystal elastomers (MCLCEs) have been reported. The swelling agent used here is a low molecular weight liquid crystal (LMWLC), 4-n-pentyl-4-cyanobiphenyl (5CB). Monodomain MCLCE swells anisotropically with the swelling degree q mono = 11.9 and polydomain MCLCE swell isotropically in 3D with q poly = 12.1. These values are much larger than observed in swelling side-chain LCEs (SCLCEs). In the stress-strain measurement, the plateau area is found among two steep areas. The electromechanical effects of monodomain MCLCE is also observed, and the results show that the maximum contraction in ∥ is about 7%. The threshold for the onset of the electromechanical effect is about 10 V, which is larger than observed in SCLCEs.

Physica A-statistical Mechanics and Its Applications, 2002

We study the complex behavior in soft-mode turbulence (SMT), a recently discovered type of spatio... more We study the complex behavior in soft-mode turbulence (SMT), a recently discovered type of spatiotemporal chaos observed in electrohydrodynamic instability (EHD) of a nematic liquid crystal with homeotropic alignment. A particle, small compared to the characteristic length of the macroscopic ow, injected in SMT travels with random velocity such as an active Brownian motion. Tracking the particle trajectory induces changes in the ow velocity as a function of space and time (the Lagrange picture). The mean amplitude of the velocity is linearly proportional to the control parameter , normalized voltage in EHD. The probability density distribution of the particle velocity changes from LÃ evy for small to Gaussian distribution for large through intermediate distributions. The di erent regimes of anomalous di usions are also observed. The stochastic properties of SMT are discussed based on these results.

Physical Review E, 2005

We experimentally investigate, in detail, electromechanical effects in liquid-crystal elastomers ... more We experimentally investigate, in detail, electromechanical effects in liquid-crystal elastomers ͑LCEs͒ previously swollen with low-molecular-weight liquid crystals ͑LMWLCs͒. Both polydomain ͑POLY͒ and monodomain ͑MONO͒ LCEs were studied. We used a well known LMWLC, 4-n-pentyl-4-cyanobiphenyl ͑5CB͒ as a solvent. After swelling POLY and MONO LCEs ͑LSCE͒ with 5CB, shape changes were measured by recording the displacement of the edge of the swollen LCE at different voltages, V, and temperature. With 100 m distance between electrodes, measurable shape changes ͑ϳ1-20 m͒ are observed with small voltages ͑V ϳ 0.5-10 V͒. In particular, we note that, compared to unswollen L͑S͒CEs, a dramatic ϳ200 times decrease of the threshold field was found for electromechanical effects in swollen L͑S͒CEs. While swollen MONO LCEs showed electromechanical effects in the planar geometry, homeotropic MONO swollen with homeotropically oriented 5CB did not. This is easy to understand because, in the homeotropic case, the liquid-crystal preferred axis is already aligned with the field so the field has no reorienting effect. The inverse of the response time when the field was switched on in both POLY and MONO was proportional to E 2 , which is the same field dependence as the response time of LMWLCs. When the field was switched off, the relaxation time showed a field dependence different from that of LMWLCs that we attribute to relaxation of the LCE network.

We experimentally investigated the swelling behavior of liquid crystal elastomers (LCEs) in two a... more We experimentally investigated the swelling behavior of liquid crystal elastomers (LCEs) in two anisotropic solvents such as low molecular weight liquid crystals, 5mathrmCmathrmB5\mathrm{C}\mathrm{B}5mathrmCmathrmB and MBBA. The length of LCEs by swelling expanded more than 1.8 times of its initial length which depended on the director orientation. The volume change of swollen LCEs has been investigated as function of temperature and several phase transitions were observed in both optical and adifferential scanning calorimetry measurements. ElectrO-mechanical effects of swollen LCEs were also investigated in detail and drastic decrease of the critical field for electr0-mechanical effects, 1/4000 lower than dry LCEs, was obtained.

We experimentally investigated the swelling behavior of liquid crystal elastomers (LCEs) in two a... more We experimentally investigated the swelling behavior of liquid crystal elastomers (LCEs) in two anisotropic solvents such as low molecular weight liquid crystals, 5CB and MBBA.

Advances in Condensed Matter Physics, 2013

Nematic networks with three different concentrations of polar and nonpolar mesogens and the same ... more Nematic networks with three different concentrations of polar and nonpolar mesogens and the same concentration of a novel crosslinking agent give rise to unusual liquid single crystal elastomers (LSCEs) that are transparent monodomain nematic networks with smectic clusters. The largest spontaneous length change is observed in the sample with 70 mol% of the polar mesogen which also has the highest glass transition temperature and smectic clusters with a slowly increasing but nearly constant layer spacing on cooling from 90 ∘ C to 25 ∘ C. X-ray scattering intensity from smectic clusters with layer spacings that monotonically increase on cooling first increases to a maximum at * ∼ 60 ∘ C corresponding to clusters of about 30 layers. Below * , the scattering intensity decreases as the number of layers in a cluster decreases. To account for this surprising nonlinear behavior that correlates with nonlinear features of the networks' macroscopic spontaneous shape change and birefringence, a model is proposed where dislocations form in the layers at * . Below * , more dislocations form to break down the layer structure. The possibility of dislocation formation at * independent of mesogenic concentrations is attributed to a conformational change in the crosslinker which is present at the same concentration in the three LSCEs.

Physical Review E, 2002

A kind of electrohydrodynamic instability, the prewavy instability, in nematic liquid crystals is... more A kind of electrohydrodynamic instability, the prewavy instability, in nematic liquid crystals is reported. The characteristic of the instability was optically investigated and discussed in comparison with some similar instabilities. Obviously the instability partially shows an isotropic feature around the nematic-isotropic transition temperature. Owing to the characteristic properties of the flow and the spatial periodicity, it should be distinguished from a previously proposed isotropic instability.

Dynamical hysteresis in a self-oscillating polymer gel J. Chem. Phys. 137, 064103 (2012) Structur... more Dynamical hysteresis in a self-oscillating polymer gel J. Chem. Phys. 137, 064103 (2012) Structural properties of thermoresponsive poly(N-isopropylacrylamide)-poly(ethyleneglycol) microgels J. Chem. Phys. 136, 214903 (2012) Instability analysis of a programmed hydrogel plate under swelling J. Appl. Phys. 109, 063527 (2011) Effect of the concentration on sol-gel transition of telechelic polyelectrolytes J. Chem. Phys. 134, 034903 (2011) Additional information on AIP Conf. Proc.

An order parameter describes an elastomer where a liquid crystal is cross linked at a temperature... more An order parameter describes an elastomer where a liquid crystal is cross linked at a temperature TL far from its clearing temperature. At TL, there is a first order constant density phase transition where the order parameter vanishes and the elastomer has cubic symmetry. Below TL it is an icosahedral nematic and above a biaxial nematic. This theory quantitatively accounts for spontaneous shape change, nonlinear elasticity and gelation dynamics in a novel liquid crystal elastomer.