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Research output: Thesis › Doctoral Thesis
Research output: Thesis › Doctoral Thesis
}
TY - BOOK
T1 - Confinement of Nematic and Chiral Nematic Systems and Their Response to External Stimuli
AU - Kaufman, Jack
PY - 2022
Y1 - 2022
N2 - In this thesis, several examples of responsive liquid crystal elastomer microparticles are reported, as well as chiral nematic films. Bipolar nematic liquid crystal elastomer particles were of significant interest due their reversible shape change at the liquid crystal to isotropic phase transition. Furthermore, a spontaneous deformation of spherical droplets into spindle shaped particles upon irradiation with UV light was investigated. The spontaneous deformation and resulting particle surface morphology was studied to elucidate the phenomenon. Droplets and particles were subjected to external stimuli such as temperature and magnetic fields to produce samples with polar alignment not seen before in the literature.In addition, a microfluidic method is reported for the introduction of nanoparticles into bipolar nematic droplets with greater control of both droplet diameter as well as the number of nanoparticles within droplets compared to methods previously reported. To achieve this, polymer nanoparticles were dyed with fluorescent dye and suspended in organic solvent so that they were compatible with the microfluidic inner phase containing nematic monomer, photoinitiator and crosslinker in chloroform, to which they were added. After photopolymerisation, yielding nanoparticle infiltrated elastomer microparticles, we demonstrated, for the first time, a reversible shape change response to temperature of nematic elastomer microparticles with localised nanoparticles, an initial step for applications of these materials within areas such as micromechanics and soft robotics.Finally, doped chiral nematic systems were produced in the form of elastomer film and microparticle optical reflectors, and in some cases the dopant was extracted to produce chiral imprinted elastomers. Chiral doped monomer systems with tuneable selective reflection colours across the whole visible spectrum at room temperature are reported along with their responsiveness to temperature and pressure. Elastomer microparticles exhibited high quality optical properties after polymerisation, due to preserved internal mesogen alignment stemming from the particle size, monodispersity and overall quality of the droplets produced using our microfluidic method.
AB - In this thesis, several examples of responsive liquid crystal elastomer microparticles are reported, as well as chiral nematic films. Bipolar nematic liquid crystal elastomer particles were of significant interest due their reversible shape change at the liquid crystal to isotropic phase transition. Furthermore, a spontaneous deformation of spherical droplets into spindle shaped particles upon irradiation with UV light was investigated. The spontaneous deformation and resulting particle surface morphology was studied to elucidate the phenomenon. Droplets and particles were subjected to external stimuli such as temperature and magnetic fields to produce samples with polar alignment not seen before in the literature.In addition, a microfluidic method is reported for the introduction of nanoparticles into bipolar nematic droplets with greater control of both droplet diameter as well as the number of nanoparticles within droplets compared to methods previously reported. To achieve this, polymer nanoparticles were dyed with fluorescent dye and suspended in organic solvent so that they were compatible with the microfluidic inner phase containing nematic monomer, photoinitiator and crosslinker in chloroform, to which they were added. After photopolymerisation, yielding nanoparticle infiltrated elastomer microparticles, we demonstrated, for the first time, a reversible shape change response to temperature of nematic elastomer microparticles with localised nanoparticles, an initial step for applications of these materials within areas such as micromechanics and soft robotics.Finally, doped chiral nematic systems were produced in the form of elastomer film and microparticle optical reflectors, and in some cases the dopant was extracted to produce chiral imprinted elastomers. Chiral doped monomer systems with tuneable selective reflection colours across the whole visible spectrum at room temperature are reported along with their responsiveness to temperature and pressure. Elastomer microparticles exhibited high quality optical properties after polymerisation, due to preserved internal mesogen alignment stemming from the particle size, monodispersity and overall quality of the droplets produced using our microfluidic method.
KW - actuation
KW - anisotropic
KW - anisotropic wrinkling
KW - bipolar configuration
KW - birefringence
KW - chiral dopant
KW - chiral nematic
KW - chiral
KW - chirality
KW - colour change
KW - droplets
KW - elastomer
KW - liquid crystal
KW - liquid crystal elastomer
KW - liquid crystal polymer
KW - magnetic alignment
KW - materials chemistry
KW - microdroplets
KW - microfluidics
KW - micro particle
KW - microscopy
KW - nanoparticle
KW - nanoparticle infiltration
KW - nanoparticles in microparticles
KW - nematic
KW - particles
KW - photonics cross-communication
KW - polarised light optical microscopy
KW - POM
KW - polymer
KW - selective reflection
KW - self-assembly
KW - shape change
KW - stimuli-responsive
KW - surface wrinkling
KW - twisted bipolar configuration
U2 - 10.17635/lancaster/thesis/1863
DO - 10.17635/lancaster/thesis/1863
M3 - Doctoral Thesis
PB - Lancaster University
ER -