High Performance Polymers

Photo initiated cross linking of epoxides is very promising from the viewpoint of application to photocurable coating and photoresist. Although amines are known to be useful as crosslinkers for epoxides, only a few studies on the photoinitiated formation of amines are reported. This work describes the synthesis and characterization of copolymer comprised of one sort of material to induce water solubility such as N,N ^'-dimethyl acrylamide (DMAC); and another material to give the photoactive response such as glycidyl methacrylate (GMA). Various copolymers were prepared by free-radical solution polymerization typically in chloroform and azobisisobutyronitrile (AIBN) as initiator at 60—63^°C. Photocrosslinking reaction was induced using bis (4-formylaminophenyl) methane (FAPM) as a photobase generator. It was found that poor image pattern profile has been obtained after exposure to UV radiation with λ _max = 250 and 420 nm.

A number of thermosetting polyimide resin formulations have been prepared evaluated and used in the resin transfer molding (RTM) fabrication of S2-glass reinforced composite laminates. The resin formulations are based on combining varying amounts of 3, 4^'-oxydianiline and 4, 4^'-(1,3-phenylenedioxy) dianiline with 4, 4^'-bisphenol A dianhydride and 3, 3^', 4, 4^'-benzophenone tetracarboxylic dianhydride and terminated in 4-phenylethynyl phthalic anhydride. The initial viscosity and working life of the resins were measured to determine suitability for RTM. Composite laminates were prepared by degassing and then transferring the resins at 260 or 270 ^°C. A laboratory RTM system with process capabilities to 300^°C and 2000 psi, was built and utilized. The polyimide matrix was cured at 320 and 340^°C, with a dwell for 3 h at each temperature, under 280 psi hydrostatic pressure. The effect of three different Co-60 gamma irradiation doses on cryogenic (77K) mechanical and thermal properties was determined. Performance was compared to that of laminates prepared from a commercially available bismaleimide (RTM-651^®). The composites are being studied for their potential use as the electrical insulation in the super-conducting magnet coils of future fusion reactor devices such as the International Thermonuclear Experimental Reactor.

A novel polyazomethines bearing triphenylamine core and a proper model compound were synthesized and their spectroscopic (FTIR, ¹ H NMR) and optical (UV-vis, photoluminescence) properties and also a molecular dynamic calculations were investigated. The polymers which were soluble in organic solvents (chloroform, dimethylacetamide, m-cresol) and formed transparent foils, emitted blue light and their photoluminescence band and intensity were solvent dependent. Additionally, the effects of blending the new polyazomethines with other polymers—PMMA, polyvinylophenol on UV-vis spectra were examined. Non-covalent ionic-type interactions between azomethines and methanesulfonic acid (MSA), m-cresol (MC) and p-chlorophenol (pClp) were also investigated. The structure formation of azomethines complexes are discussed on the basis of ¹H NMR and FTIR. Photoluminescence and absorption properties of the azomethines compounds after doping with MSA, MC and pClp were tested.

Ionic liquids (ILs) represent a fascinating and potentially very valuable group of new solvents, which have the benefit of zero vapor pressure and therefore easier handling than many conventional solvents. They are attracting a lot of attention as volatile organic compound-free solvents, eco-friendly and green media. Room-temperature ionic liquids (RTILs) and particularly those based on substituted imidazolium cations, which can be synthesized easily from the commercially available starting material N-trimethylsilylimidazole and alkyl halides, are currently being extensively studied for a variety of applications. In this study a facile and efficient synthesis of heterocyclic polyamides by polycondensation of 4-(4-dimethylaminophenyl)-1,2,4-triazolidine-3,5-dione with various commercially available aliphatic diacid chlorides in the presence of RTILs and molten tetrabutylammonium bromide as an IL was performed. The effect of various reaction parameters, including the nature of the ILs, the amount of IL, the reaction temperature, and the reaction time were investigated to optimize the conditions for the preparation of heterocyclic polyamides. The polymerization proceeded well in ILs without any catalyst and polyamides were obtained with high yields and moderate inherent viscosities. A comparative study between the effects exerted by different ILs and the conventional polymerization method is also reported.

In the recent past, it has been found that the use of onium salts as acid-generating species has improved the performance of photoresists, particularly for microelectronic applications. However, little research has been dedicated to the use of these photo-initiators in aqueous-developable resists. This work describes the synthesis and characterization of some water-soluble polymers and investigates the feasibility of employing one of the onium salts in the formulation of a resist polymer for use in aqueous conditions. The ability of this onium salt to photo-initiate the cationic polymerization of epoxies residues was exploited using water-soluble copolymers, containing glycidyl methacrylate (GMA). The comonomers included methacrylic acid. Various copolymers were prepared by radical copolymerization typically in methyl ethyl ketone. It was found that the copolymer containing 85 mol.% of GMA unit in feed was soluble in aqueous base and crosslinked in the presence of photogenerated acid caused by acid-initiated ring opening polymerization of the pendant epoxide groups. A good pattern with reasonable resolution was attained by exposure to a UV lamp with λ = 365 nm light followed by a post exposure bake at 80^° C for 1 min.

An in situ process was used to prepare poly (1, 3-propylene glycol-hexanedioic acid)-functionalized carbon nanotubes using carboxylate-functionalized multi-walled carbon nanotubes, 1, 3-propylene glycol and hexanedioic acid as reactants. The functionalized carbon nanotubes were characterized using transmission electronic microscopy, Fourier transform infrared spectroscopy and thermogravimetric analysis. The results indicated that the carboxylate-functionalized carbon nanotubes chemically reacted and were linked with the polyester chains. The extent of polycondensation reaction could be controlled by the concentration of the carboxylate-functionalized carbon nanotubes in the reactant mixture. The carboxylate-functionalized carbon nanotubes were surrounded by a polyester matrix with a maximum thickness of approximately 3 nm.

A new aromatic diamine monomer containing both pyridine and fluorine, 2,6-bis(4-amino-2-trifluoromethylphenoxy-4 ^'-benzoyl)pyridine (BAFP), was successively synthesized by the nucleophilic substitution reaction of 2,6-bis(4,4^'-dihydroxybenzoyl)pyridine with 2-chloro-5-nitro-trifluoromethylbenzene in the presence of k₂CO ₃ in N,N-dimethylacetamide, and followed by reduction with SnCl₂ and HCl in ethanol. The polycondensation of BAFP with four aromatic dianhydrides afforded a series of novel aromatic polyimides containing both pyridine and fluorine. The reaction was conducted by the one-step thermal imidization method. The resulting polyimides were characterized for inherent viscosity, solubility, and thermo-oxidative stability. The polyimides exhibited excellent solubility in various solvents such as N-methyl-2-pyrrolidone (NMP), N,N-dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO) and chloroform. The glass-transition temperatures (T _g) were in the range of 206—227^°C. The polyimides displayed good thermal stability, e.g. the temperatures at the 5% weight loss range were at 487—543^°C in nitrogen and 463—521^°C in air, respectively. Wide-angle X-ray diffraction measurements revealed that the polyimides were predominantly amorphous.

The paper presents a non-isothermal kinetic study of the degradation process of some aromatic copolyethers containing a tetra-methylenic spacer. The polymers were synthesized using the phase transfer catalysis technique, starting from 1,4-dichlorobutane and various bisphenols (4,4^'-dihidroxyazobenzene, 4,4^'-dihydroxydiphenyl, bisphenol A and 2,7-dihydroxynaphthlene). Dynamic thermal analysis methods such as ATG, DTG and ATD were used. In order to work out the basic kinetic parameters and the reliance between activation energy and conversion degree, differential methods based on the `order reaction model' were applied and standard kinetic models were also used. The thermostability of the good samples up to 320^°C was demonstrated. The degradation mechanism took place by successive reactions, controlled by a nucleation process influenced by the polymer molecular structure.