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Birefringence gradient development during drying of solution cast functional films and their mechanical, optical and gas barrier properties

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  1. Tez No: 402342
  2. Yazar: ORÇUN YÜCEL
  3. Danışmanlar: PROF. MÜKERREM ÇAKMAK
  4. Tez Türü: Doktora
  5. Konular: Kimya Mühendisliği, Kimya, Chemical Engineering, Chemistry
  6. Anahtar Kelimeler: Belirtilmemiş.
  7. Yıl: 2013
  8. Dil: İngilizce
  9. Üniversite: The Unıversıty Of Akron
  10. Enstitü: Yurtdışı Enstitü
  11. Ana Bilim Dalı: Belirtilmemiş.
  12. Bilim Dalı: Belirtilmemiş.
  13. Sayfa Sayısı: Belirtilmemiş.

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Özet (Çeviri)

For the first time, the development of optical anisotropy gradient as a result of solvent evaporation for poly (amide-imide) (PAI) solution in Dimethylacetamide (DMAc) was investigated. Experiments were carried out using real time optical measurement with spectral birefringence technique coupled with off-line optical techniques such as Abbe refractometer and optical compensator method. Drying process induced temporal evolution of non-uniform out of plane birefringence profile through the thickness direction while in plane birefringence remained zero. The highest birefringence was observed at the substrate-solution interface at early stages of drying. Beyond a critical time, the formation of highly oriented layer was observed at the air-solution interface. This oriented layer progresses through the thickness direction as the solvent concentration is disproportionately reduced in these regions. Abbe refractometer results confirmed the anisotropy is preserved at longer drying times, air-solution interface birefringence becoming higher compared to substrate-solution interface. Overall, observations obtained by real-time measurement system agreed with off-line measurements. In additon, multifunctional single and triple-layer films exhibiting flexibility, high modulus and high gas barrier properties were developed using a soluble polyamide-imide (PAI) in dimethylacetamide (DMAc) with ammonium-modified montmorillonite (MMT, Cloisite 30B) mineral clay. The drying behavior and associated anisotropy development were determined real-time, using a newly developed real-time measurement system. Out-of-plane birefringence development occurred earlier for thinner neat samples caused by increased depletion rate of solvent. Addition of organoclay content resulted in a decrease in evaporation rate of solvent due to planar orientation of well exfoliated nanoplatelets as shown by TEM images and WAXS. This is in agreement with developed out-of-plane anisotropy during drying. Planar orientation of nanoplatelets resulted in excellent helium-barrier properties. Mechanical properties were optimized at 3wt% clay content. In a similar way, multifunctional nanocomposite films exhibiting flexibility, high modulus and high gas barrier properties were developed using a soluble polyamide-imide (PAI) in dimethylacetamide (DMAc) with graphene-oxide nanosheets (GO). Addition of GO content resulted in increase in evaporation rate of solvent. This was attributed to increase in hydrophobicity of the films with increased GO content as shown by contact angle measurements. Overall He permeability of dried hybrid films decreased over 40% even with very small GO content. Multi-layered optical retarder film exhibiting low birefringence dispersion and high optical clarity was developed using a solutions of polysulfone (PSF), polycarbonate-co-polymer (PCC) and a-tactic polystyrene (PS) in N-methyl pyrrolidone (NMP). The uniaxial and biaxial deformation behavior and associated anisotropy development were determined real-time, using a newly developed real-time measurement system. Machine Direction (MD) stretching resulted in negative retardation values at high deformation rates. This behavior was reversed upon inception of Transverse Direction (TD) stretching. Optimum Rth and R0 values were achieved at 1mm/sec stretch rate to compensate ECB-LCDs. Birefringence dispersion of films was found to be flattened.

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