| Over the last two decades, advances in electronics have revolutionized the speed with which we perform computing and communications of all kinds. Three key technologies were combined to create a platform that enabled the electronic revolution: semiconductor materials, automated microfabrication of integrated electronic circuits, and integrated electronic circuit design. As a result, the mass manufacturing of low-cost integrated circuits has become possible. However, currently, bandwidth demand is outgrowing the performance of electronics in many applications. Signal propagation and switching speeds in the electronic domain are inherently limited. One area where these limitations are clearly seen is in telecommunications, where bandwidth expansion is desperately needed. To overcome these barriers, we must enter a new computing and communications revolution based on photonics which is known to outperform electronics in many areas. Photonics applications have an extremely large information capacity (very broad bandwidth) and very low transmission losses and heat generation, are immune to crosstalk and electromagnetic interference, and are lightweight and smaller in size compared to electronics. Photons also do not interact linearly when multiple wavelengths propagate in an optical medium, and thus allow parallel processing of different wavelengths. Moreover, photonics plays a crucial and complementary role to electronics in many application domains. Examples of successful uses of photonics can be found in broadband communications, high-capacity information storage, and large-screen and portable information displays.Polyimide (PI), an important high-performance plastic, has many excellent properties, such as excellent thermal stability, good mechanical properties, low coefficient of thermal expansion and high radiation resistance. In recent years, hyperbranched PIs have received considerable attention due to their low viscosity, good solubility and other attractive properties. Misutoshi Jikei et al. reviewed the synthesis and properties of hyperbranched polyimide. Jie Yin and Bershtein et al. investigated the application of hyperbranched polyimide (HBPI) in photosensitive materials and gas separation membrane, respectively. Compared to conventional linear polymers, hyperbranched polymers show attractive properties such as low viscosity, excellent solubility in organic solvents and facile functionalization. Besides the structure investigation of hyperbranched polymers, more and more studies are focused on their new applications, such as optical and electronic materials, polymer electrolytes, nanotechnology and other high-tech areas. Our laboratory explored several fluorinated hyperbranched polyimides (FHBPIs) for optical waveguide materials. The unique hyperbranched structure allows the isotropic orientation of PI's rigid aromatic segments, and thus reduces its birefringence value. The obtained polymers have excellent thermal stabilities and show low optical absorption in the near infrared region. Generally, highly branched polymers have poor mechanical properties because of the formation of globular macromolecules, i.e., due to the lack of chain entanglements. In this work, we used nonideal A2+B3 polymerization strategy to obtain some novel fluorinated hyperbranched polyimides (FHBPIs).Firstly, novel anhydride-terminated fluorinated hyperbranched polyimides (FHBPIs) were successfully prepared by condensation of a triamine monomer,1,3,5-tris (2-trifluoromethyl-4-aminopheoxy) benzene (TFAPOB), and series of aromatic ether dianhydride monomers with different flexible linear length via chemical imidization technique, respectively. The obtained FHBPIs have high thermal stability and good solubility in organic solvents. Their special hyperbranched structures and high fluorine contents give them fantastic optical property and low dielectric constant. Moreover, mechanical properties of FHBPIs have been improved by increasing the linear length of repeat units, and self-standing FHBPI films can be formed by solvent casting method. Rib-type polymeric waveguide device has been successfully prepared by using FHBPI-4d.In chapter 3, novel fluorinated linear-hyperbranched copolyimides (co-FHBPI) have been successfully prepared by condensation of 1,3,5-tris(2-trifluoromethy-4-aminopheoxy) benzene (TFAPOB),1,4-bis(4-amino-2-trifluoromethylphenoxy) benzene (6FAPB) and 4,4'-(2-(3',5'-ditrifluoromethylphenyl)-1,4-phenylenedioxy)-diphthalic anhydride monomers with different feed ratio, followed by reaction 3-ethynylaniline. The obtained polymers have high thermal stability and good solubility in organic solvents. The Tg refractive index, birefringence and Young's moduli regularly changed by combination of TFAPOB and 6FAPB content in the copolymer. Moreover, cured ethynyl terminated co-FHBPI 50 (E-coFHBPI 50) had good chemical resistance for common solvents and exhibited higher thermal stability than co-FHBPI. Rib-type polymeric waveguide device has been successfully prepared by using E-coFHBPI 50.In chapter 4, three series of soluble poly (ether imide)s (PEIs) were prepared from the obtained dianhydrides by two-step chemical imidization methods. Experimental results indicated that all the PEIs had glass transition temperature between 200℃and 230℃, the temperature at 5% weight loss between 520℃and 590℃under nitrogen. The PEIs showed great solubility by the introduction of bulky pendant groups and were capable of forming tough films. The cast PEI films (80-91μm in thickness) hand tensile strengths in the range of 88-117 MPa, tensile modulus in the range of 2.14-2.47 GPa, and elongation at break from 15 to 27%; high optical transparency, with a UV-vis absorption edge of 357-377 nm; low dielectric constants of 2.73-2.82 and low water uptakes (<0.66 wt%). These spin-coated PEI films present a minimum birefringence value as low as 0.0122 at 650 nm.
|
PDF Full Text Request