Thomas R. Price

Amine-Cured Bisphenol-Linked Phthalonitrile Resins

Abstract Neat polymerization of bisphenol-linked phthalonitrile monomers, which contain no active hydrogen atoms, is extremely difficult and requires several days of continuous heating at 260–290°C before a viscosity increase becomes evident. In the presence of a nucleophilic compound such as an organic amine, the cure time and temperature can be greatly reduced. The amine-cured polymers are more thermally stable than their neat cured counterparts. Preliminary results indicate that the amine causes no significant changes in the mechanical properties of the cured polymer. The bisphenol-linked phthalonitrile resins are particularly appealing as matrices for composite formulations due to the projected low material cost, the greatly improved processability, and the nonreactivity of the prepolymer at ambient temperature.

Photophysical Processes in Polymers. IV. Excimer Formation in Vinylaromatic Polymers and Copolymers

Excimer formation has been investigated in polystyrene, poly(1‐vinylnaphthalene), poly(2‐vinylnaphthalene), and in copolymers of 1‐vinylnaphthalene with styrene and with methyl methacrylate. Solid films as well as solutions were studied over the temperature range 77–298°K. In the solid polymers, interchain excimer formation is superimposed on the intrachain interaction observed in dilute solutions; intrachain excimer formation is essentially unaffected by the solvent in fluid solutions. Conformations that lead to excimer interaction in a solid solution are fixed by the temperature at which the solid is formed. Activation energies for intramolecular excimer formation for these polymers are somewhat less than those for the corresponding two‐unit model compounds and much less than those for the single‐unit model compounds. While excimer sites act as efficient singlet traps for intramolecularly migrating energy and act to decrease the triplet yield, they do not present a barrier to the transfer of energy to a...

Photophysical Processes in Polymers. III. Properties of Triplet Energy Traps in 1‐Vinylnaphthalene Copolymers

Emission spectra of two‐component atactic copolymers of 1‐vinylnaphthalene with styrene (PVN/S) and with methylmethacrylate have been investigated in a glassy matrix at 77°K. In PVN/S, the rate of intramolecular triplet energy transfer through segments derived from styrene exceeds that of intermolecular triplet transfer from polystyrene to piperylene; the migration occurs through chains having as many as 140 styrene‐derived units. Radiative triplet depletion within the 1‐vinylnaphthalene‐derived segments is manifested by (1) phosphorescence originating from units near the ends of the segments, and (2) delayed fluorescence due to free triplet annihilation within the segment, although some trapping may also take place. In contrast, delayed fluorescence from poly(1‐vinylnaphthalene) appears to result from several annihilation reactions, and serves to demonstrate fundamental differences between the homopolymer and copolymer.

Photophysical Processes in Polymers. VI. Spectroscopic Properties of 1‐Vinylpyrene and Poly(1‐Vinylpyrene)

The absorption spectra, corrected fluorescence spectra, and fluorescence quantum yields of 1‐vinylpyrene and poly(1‐vinylpyrene) are reported. The triplet‐triplet absorption spectrum of poly(1‐vinylpyrene) is compared to that of pyrene, and the excimer fluorescence of the polymer is studied as a function of temperature. Based upon the temperature dependence of the excimer emission, it is concluded that efficient formation and inefficient emission of nonequilibrium‐geometry pyrene excimers takes place in poly(1‐vinylpyrene). Radiative and radiationless transition mechanisms are discussed. Values reported for poly(1‐vinylpyrene) in fluid solution at room temperature are qFM ≅ 0, qFD = 0.44, qPM ≅ 0, φT = 0.005, kFD = 0.83 × 107sec−1, kGD = 1.0 × 107sec−1, kDM >∼ 1 × 107sec−1, and kTM <∼ 5 × 105sec−1.

Photophysical Processes in Polymers. V. Triplet Depletion in Solid Vinylnaphthalene Polymers and Copolymers

The results of a study of triplet energy trapping at 77°K are presented for vinylnaphthalene polymers and copolymers with styrene and methyl methacrylate. Delayed emission spectra originating from traps both intrinsic and extrinsic to the polymer chains are identified. In the solid polymers both intramolecular and interchain triplet energy migration occur, with eventual transfer to a trap at collisional distances of about 15 A. Extrinsic traps lead to phosphorescence and delayed fluorescence, while traps that are part of the polymer chain lead to delayed exciplex fluorescence. In the model compound 1‐ethylnaphthalene, only extrinsic trapping phenomena are observed. The influence of concentration on trapping phenomena in both polymers and the model compound is considered from the standpoint of chain or molecular aggregation.

Tetra(9,10-phenanthro)tetraazaporphyrin - phthalocyanine: Comparative electrical conductivities

Abstract Tetra(9,10-phenanthro)tetraazaporphyrin, H 2 TPTAP, has been synthesized and characterized for comparative electrical conductivity measurements with phthalocyanine, H 2 Pc, before and after iodine doping. The objective is to determine the effect on conductivity of fusing eight additional benzo rings to the periphery of the phthalocyanine ring. H 2 Pc doped to a (H 2 Pc)I 2.5 composition with a resistivity decreases from 10 15 to 1 ω cm, while H 2 TPTAP doped to a (H 2 TPTAP)I 0.26 composition with a corresponding resistivity change from 10 11 to 10 8 ω cm. Experimental data and the literature indicate that benzene rings fused to the periphery of the tetraazaporphyrin ring have little π-electron interaction. Similarly, the structure-conductivity correlation of data is interpreted as indicating that fusion of additional benzo rings has an insulating substituent group effect on oxidation of and charge transport between the tetraazaporphyrin rings in the polycrystalline solid.

The Role of Luminescence Spectroscopy in Polymer Science

Polymer science in general and the organic coatings field in particular have been slow to take full advantage of the phenomenon of luminescence as either a research or analytical tool. Equipment for the measurement of luminescence is no more complex or expensive nor less available than that now found in most laboratories for work in absorption spectroscopy. The techniques involved present little more difficulty than those involved in absorption work. It is the purpose of this report to point out some of the possibilities presented by luminescence methods in the characterization of polymers and copolymers in the coatings and plastics fields.