Energy transfer between phosphors and conjugated polymers was investigated using a fluorene trimer (F3) as a model conjugated material. The phosphors studied were bis-cyclometalated iridium complexes (FP, PPY, BT, PQ, and BTP), with triplet energies of 2.6, 2.4, 2.2, 2.1, and 2.0 eV, respectively (based on phosphorescence spectra). Stern-Volmer analysis of luminescent quenching shows that energy transfer from either FP or PPY to F3 is an exothermic process with Stern-Volmer quenching constants (kqSV) of near 109 M-1 s-1 while energy transfer from BT, PQ, and BTP is endothermic (kqSV = 107-106 M-1 s-1). On the the basis of above results, the triplet energy of F3 is estimated to be less than 2.3 eV (530 nm). This study suggests that conjugated polymers, which typically have lower T1 energies than F3, should also quench phosphorescent emission in thin films and organic light-emitting diodes (OLEDs) incorporating these and related phosphorescent dopants.

A number of acrylamideaery late copolymers were synthesized in which the acrylate (CH2=CHC00(CH2CH20)"R) is hydrophobic on account of the presence of a 1,1-dihydroperfluorooctyl group or a dodecyl group connected to the acrylate via a -(CH2CH20)" hydrophilic spacer ( = 0-3).Copolymerization of these monomers was initiated by sodium metabisulfite and ammonium persulfate at 60 °C in aqueous media in the presence of surfactants and acetone. The low shear viscosities of 0.5 wt % solutions of these copolymers as a function of comonomer molar content gave bell-shaped curves having maxima at 0.10-0.60 mol % comonomer, consistent with competitive interand intramolecular hydrophobic association. The copolymers having perfluorocarbon pendent groups gave higher viscosities at lower comonomer content. Furthermore, for both the hydrocarbon-and perfluorocarbon-containing copolymers the viscosities increased, and the comonomer content at the viscosity maximum decreased, with increasing spacer length. The increased effectiveness of the longer spacers is attributed to entropy effects in the formation of polymer assemblies.

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Macrocyclic polystyrene (PS) was synthesized by initiation of styrene by naphthalide anion or benzylic dianions in the presence of Li or K ions followed by reaction of the resulting PS dianions with dibromomethane (DBM) or 1,4-bis(bromomethylbenzene) (DBX) in THF at -78 °C under high dilution conditions. MALDI and NMR studies of the DBM cycles showed the presence of 1,2-diphenyl linkages. Fluorescence studies on the DBM cycles show strongly enhanced and anomalous structured emission bands between 300 and 320 nm attributable to linear chains containing styrenic chain end impurities. This indicates rapid metal bromine exchange to give chain end benzyl bromides that eliminate with polystyryl anion to give small (<1.0%) fractions of styrene type chain end structures. In comparison, the cycles obtained with DBX show only the PS monomer and excimer bands at 285 and 330 nm, respectively, and appear to be substantially free of such side reactions. These DBX coupled cycles show up to a 2-fold enhancement in the monomer fluorescence at low MW compared with matching linear polystyrenes that show essentially no MW dependence. This may be due to the increased rigidity of the cycles as molecular weights decrease and appears to be a general feature for cyclic vinyl aromatic polymers.

Fluorine‐containing hydrophobically associating polymers have been synthesized by copolymerization of acrylamide with a small amount of an acrylate or methacrylate having a fluorocarbon containing ester group. It was found that hydrophobic associations occurring between these fluorocarbon chains was stronger than the interactions of the corresponding hydrocarbon comonomers and depend on the length of the fluorocarbon chain. The rheological properties of the copolymer solutions were studied. The solutions were found to be highly pseudoplastic but the viscosity loss was completely reversible upon removal of shear. Evidence for hydrophobic association of the fluorocarbon groups was obtained by the dependence of the Brookfield viscosity on temperature, the addition of NaCl, and the addition of organic solvents, urea, and surfactants.

Water-soluble poly(N,N-dimethylacrylamide) (PDMA) and poly(N-acryloyl-N ‘-methylpiperazine (PAMP) were prepared in tetrahydrofuran at −78 °C by anionic polymerization in the presence of monofunctional initiators such as (triphenylmethyl)lithium, or -cesium or the difunctional initiators (1,1,4,4-tetraphenylbutyl)lithium, -potassium, or -cesium or cesium naphthalenide. Polymerizations initiated especially in the presence of cesium as counterion proceeded in a homogeneous manner and gave polymers having controlled molecular weights and narrow molecular weight distributions in quantitative yields. However, the polymerization results in polymers with a lower molecular weight and a broad molecular weight distribution at higher reaction temperatures. Size exclusion chromatography, 1H NMR spectroscopy, and intrinsic viscosity measurements support the clean anionic polymerization of DMA with few side reactions at −78 °C. Attempted anionic polymerizations of methacrylamide monomers such as N,N-dimethylmethacrylamide and N-methacryloyl-N ‘-methylpiperazine are described as well. NMR spectroscopy, differential scanning calorimetry, and solubilities of the resulting polymers revealed the influence of the initiator counterions on the polymer tacticity.

Hydrophobically modified (HM) associating water-soluble poly(N,N-dimethylacrylamide) (PDMA) polymers were prepared by free-radical copolymerizations of DMA and 2-(N-ethylperfluorooctanesulfonamido)ethyl acrylate (FOSA). The polymerizations were carried out in deionized water in the presence of ammonium persulfate at 50 °C or in bulk in the presence of AIBN at 65 °C. The copolymerization kinetics monitored simultaneously by 19F and 1H NMR spectroscopy indicates that DMA and FOSA is incorporated at the same relative rates throughout the polymerization. The viscosities of the polymer solutions were measured on a Brookfield viscometer and an Ubbelohde capillary viscometer. A large viscosity enhancement was observed in comparison with PDMA homopolymer solutions. The effects of polymer concentration, shear rate, surfactants, salts, and temperatures on the reduced and Brookfield viscosities were investigated. Interestingly, the aqueous solution of the copolymer prepared in bulk exhibits both hydrophobic interaction and polyelectrolyte effects in the presence of anionic perfluorocarbon surfactant. The resulting polymers were also characterized by size exclusion chromatography and by 1H and 19F NMR spectroscopy.

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