Luminescent molecules and polymers are active component in light-emitting diodes; however, the aggregation and excimer formation in concentrated solution or in the solid film states had limited their applications. Therefore, this study used poly(methyl methacrylate) (PMMA) as separator to prevent the formations of aggregate and excimer and to enhance quantum efficiency. Basically, two systems are involved: (1) Inorganic phosphorescent irdium complex PMMA was doped with inorganic iridium complex IrQB by using THF as solvent. IrQB/PMMA films prepared from dilute solutions exhibit two emissions centered at 560 and 640 nm, respectively; in contrast, only 640-nm emission was observed for films from concentrated solutions. Experimentally, these two bands showed variations on the emission intensity with increasing temperature. Aggregation of IrQB is suggested to be responsible for the 560-nm emission. Chain conformation of PMMA in the solution state strongly affects the incorporated IrQBs and their emission properties. (2) Polybenzoxazines Polybenzoxazines with the built-in fluorenscent fluorine moiety are linear in nature; however, the inherent hydrogen-bond (H-bond) interactions in polybenzoxazines decrease the inter-chain distance and cause the chain aggregation. With the added PMMAs, new H-bonding from the carbonyl groups in PMMA and the hydroxyl groups in polybenzoxazine enhances the mutual miscibility between these two components and decreases the possibility of aggregate formation in polybenzoxazines. Quantum efficiency is therefore promoted by this approach.

A series of immiscible crystalline-crystalline diblock copolymers, poly(ethylene oxide)-b-(£`-caprolactone) (PEO-b-PCL), were blended with (3-phenyl-3,4-dihydro-2H-1,3-benzoxazin-6-yl) methanol (Pa-OH). FT-IR analyses provide that the ether group of PEO is a stronger hydrogen bond acceptor than the carbonyl group of PCL with the hydroxyl group of Pa-OH. Pa-OH after curing results in the excluded and confined PCL phase based on differential scanning calorimeter (DSC) analyses. In addition, the mesoporous structure was proved with the increasing the ratio of PCL to PEO in block copolymers by small angle X-ray scattering (SAXS), transmission electron microscopy (TEM) analyses and N2 adsorption-desorption isotherms (BET) The poly(styrene-b-4-vinyl pyridine) diblock copolymer was blended with Pa-OH monomer. FT-IR analyses demonstrate the intermolecular hydrogen bonding interaction between the pyridine group of P4VP and the hydroxyl group of Pa-OH. After curing, the block copolymers were incorporated into polybenzoxazine resin to access the nanostructure through the reaction induced microphase separation mechanism by TEM and SAXS analyses.

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A new method for polybenzoxazine synthesis was developed and carried out throughout this work. Bisphenol-A, hexamethylenediamine, and paraformaldehyde were reacted through Mannich condensation reaction forming polybenzoxazine precursors. The reaction was followed by Gel Permeation Chromatography (GPC) as a molecular weight determination method in order to decide the end of reaction. The synthesized product, polybenzoxazine precursors, was polymerized thermally. Polybenzoxazine precursors were also characterized by using spectroscopic methods, 1H-NMR and FTIR, giving an approximation to structural determinations. Thermal characterization of precursors and polybenzoxazine showed that the materials had two exotherms at around 220&ordm / C and 260&ordm / C. The first exothermic peak was an indication of polymerization and preliminary crosslinking reactions while the second peak was due to the final polymerization of polybenzoxazine precursors. These precursors showed no significant structural change in isothermal period of 20 minutes at 200, 220, 225, 235&ordm / C. Mechanical tests were performed on the polybenzoxazine films. The films cured at 180&ordm / C possessed a tensile strength at break 21.04 (&plusmn / 3.56) MPa and an average elongation of 2.7 (&plusmn / 0.93) %. Young&rsquo / s modulus was calculated as 0.93 (&plusmn / 0.05) GPa for polybenzoxazine films.

Synthesis of a polymer with benzoxazine units in the main chain backbone by a trifunctional phenol, a difunctional amine, and paraformaldehyde was achieved. Thermal, mechanical and spectroscopic characterization and the viscosity properties of the synthesized polymer were studied. In the first step of this study, a fast and feasible method for the synthesis of the benzoxazine precursors was developed since some methods mentioned in the literature about the synthesis of the benzoxazine derivatives last long time. The second step was to polymerize the benzoxazine precursors thermally. The curing of benzoxazine precursors was done via ring opening polymerization at 150 oC and a final polymerization was observed at about 250 oC. 1H NMR, 13C NMR and FT-IR spectroscopies revealed the characteristic peaks for the formation of benzoxazine ring. Among them, 13C NMR gave important clue on the formation of the benzoxazine. The thermal characterization of the benzoxazine precursors and the polymers indicated that the ring opening polymerization of these precursors started at around 110 oC and a final polymerization was about at 230 oC. Differential Scanning Calorimetry thermograms of the polybenzoxazine indicated a secondary transition at around 270 oC. An onset decomposition of the benzoxazine oligomers started around 100 oC in Thermal Gravimetric Analysis thermograms performed under N2 atmosphere and two major maximum weight losses were observed at 273 oC and 439 oC. However, polybenzoxazine showed a starting degradation at about 260 oC and the maximum weight loss temperatures were seen at 296 oC and 465 oC. Viscosity variation of the reaction mixture was studied by Ubbelohde Viscometer at 30 oC. Viscosity results indicated that the increase in the intrinsic viscosity of the reaction mixture till 50th minute and followed by a decrease due to possible branching and the intra-crosslinking of the benzoxazine oligomers. Mechanical properties of the polymer films, prepared by compression molding at 180 0C, were investigated. Test results showed that low tensile strength whereas comparatively high elongation.

Polymers play an integral part in the semiconductor electronic industry. Due to the expanding diversity of a polymer s structural design and the resulting properties, different polymers serve as different components in the makeup and fabrication of the electronic package. The limiting factor in computer processing speed shifts from the transistors gate delay to the interconnect delay below a circuit line width of 1.8 μm for interlayer dielectrics. Silicon dioxide has been used as the insulating layer between metal lines for many computer chip generations. Low dielectric constant polymers will need to supplant silicon dioxide as interlayer dielectrics in order to develop reliable circuits for future generations. Along with serving as interlayer dielectrics, low dielectric constant polymers are also incorporated in first and second level electronic packaging. Deposition and patterning of these polymers can be significantly reduced by using photodefinable polymers. Most photodefinable polymers are in a precursor form for exposure and development in order to dissolve in industrial developers. Once developed, the polymer precursors are cured to produce the final polymer structure. This temperature is as high as 350 oC for many polymers. Thermal curing sets limitations on the use of the polymer in the electronics industry because of either the unwanted stress produced or the incompatibility of other electronic components that do not survive the thermal cure. In addition to a low dielectric constant and photodefinability, many other properties are needed for successful implementation. Polymers must be soluble in organic solvents in order to spin coat films. Water absorption increases the dielectric constant of the patterned films and can lead to various adhesion problems and cause delamination of the film. Mismatches between the coefficients of thermal expansion in adjacent layers can produce residual film stresses which leads to warping of the substrate or interfacial delamination. The glass transition temperature must be high because the thermal expansion is greatly increased when the glass transition temperature is exceeded. A high Young s modulus is also required to withstand external forces from thermal, electrical, and packaging stresses. The goal of this research was to develop novel, low dielectric, photodefinable polymers that can be processed at low temperatures. All polymers discussed will contain one of two monomers with hexafluoroalcohol (HFA) functional groups. Fluorine provides many properties that are advantageous for low dielectric applications whereas alcohols absorb water and increase the dielectric constant. Characterization of the polymers show the effect the fluorine has on the alcohol s high water absorption. All polymers will be synthesized by condensation polymerization of a diamine with a dianhydride or diacid chloride. All other polymers will contain a novel HFA diamine. A new thermoplastic polymer structure based on the cyclization of an HFA situated ortho to an amide linkage produces a benzoxazine ring in the polymer backbone. Cyclization to form polybenzoxazines occurs at temperatures considerably lower than that needed to form polyimides. The lowest processing temperatures are achieved with protection of the HFA that can be cleaved with a photoacid generator.

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