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SynopsisThe polymerization of N-ethyl-2-vinylcarbazole and N-ethyl-3-vinylcarbazole by an anionic mechanism has been demonstrated. Polymerization reactions were monitored by ultraviolet/visible spectroscopy and Am, ,and e values for the propagating carbanions determined. The 2-vinyl monomer exhibits all the features of a standard "living" polymer; the carbanion is stable at ambient temperatures and high molecular weight, Bn -lo6, narrow distribution polymers and block copolymers with styrene have been prepared. The carbanion from the 3-vinyl monomer is much less stable and a clean polymerization can only be conducted a t temperatures below -6OOC.A comparison of the anionic polymerization characteristics of the N-, 2, and 3-vinyl carbazole monomer series is presented. 1133

Fluorine and proton NMR relaxation data of HFIB/VF2 have revealed an a relaxation associated with the glass transition. This relaxation is characterized by an activation energy of approximately 73 kcal/mol. The transition is observed in both the proton and fluorine data and the proton spin-spin relaxation times can be deconvoluted into crystalline and amorphous components above the glass transition temperature. A local mode relaxation with activation energy of ~9 kcal/mol is observed in the proton data. Reorientation of the CF3 groups is observed in the fluorine data with an activation energy of approximately 5 kcal/mol. What begins as two separate reorientational processes at low temperature probably becomes a complicated reorientational process in the high-temperature limit involving these two processes and the glass transition.

The electrical transport properties of three vinyl carbazole polymers have been examined to determine if the observed variations in NMR chemical shifts resulting from inter−ring shielding effects could be correlated with carrier mobilities in the polymers. Drift mobilities were measured in films of the polymers overcoated with thin layers of amorphous Se using a xerographic discharge technique. Under the conditions for observing trap free space charge limited currents the hole mobilities were calculated from Child’s law. The three polymers exhibited mobilities varying as the square of the electric field over the range of fields examined. P2VK which showed the overall largest upfield shift of the aromatic protons exhibited a mobility of 1.4×10−6 cm2/V⋅sec at a field of 4×105 V/cm. PVK which exhibit an intermediate degree of shielding had a mobility of 1.4×10−7 cm2/V⋅sec and P3VK which exhibits the smallest shielding effect had a mobility of 2.4×10−8 cm2/V⋅sec both at equivalent fields. Although P2VK showed the highest mobility it also accumulated the largest amount of trapped charge. At present not enough is known about the detailed microstructure of the polymers to identify the reason for this phenomon.

Proton spin-spin (T2) and spin-lattice (T1) relaxation times have been measured in order to elucidate the molecular dynamics in poly(N-vinylcarbazole) (PVK). Measurements were obtained on samples covering a broad range of molecular weights in air, O2, N2, and in vacuo. Correlation frequencies νc determined from NMR data were used in conjunction with dielectric data to construct transition maps. The α,β relaxations associated with main-chain and segmental motion exhibit temperature-dependent behavior very similar to that observed in polystyrene (PS). The γ relaxation in PVK is highly unusual in that it is dielectrically active and manifested in the T2 data only in the presence of O2. A detailed interpretation of this effect is provided, leading to the conclusion that O2 diffusion is severely restricted at low temperatures and that torsional oscillation of the carbazole group is responsible for the γ relaxation. It is proposed that the presence of O2 leads to relaxation by slow spin diffusion to the paramagnetic site at low temperatures but by direct paramagnetic relaxation by diffusing O2 molecules at high temperatures. This effect is related to the temperature-dependent lifetime of the O2-carbazole complex.