Simulations of the electric field poling process for second-order NLO-
active polymeric materials containing dipolar chromophores were perfor
med by modeling the time-dependent dynamics of a dipole interacting wi
th an externally applied field and subsequent force-free relaxation, e
mploying several modifications of the Smoluchowski equation. The model
examines chromophore dipole alignment/relaxation processes in both tw
o- and three-dimensional space. The 3-D model predicts that at field-o
n equilibrium, the ratio, R, of the second-harmonic coefficients, d(33
)/d(31), approaches 3.0, in accord with static statistical-mechanical
models. In contrast, the 2-D model predicts R similar to 6.0. The dime
nsionality in which the rotational diffusion process is confined also
determines the rate of dipolar alignment/relaxation, with a slower rat
e predicted in the 2-D case. Suitability of the rotational diffusion m
odel for the alignment and relaxation dynamics of appended NLO chromop
hores in poled polymer films is also examined. At temperatures at or a
bove the glass transition temperature, T-g, experimentally measured d(
33) relaxation kinetics of a prototypical chromophore-functionalized p
olymer, N-(4-nitrophenyl)-(S)-prolinoxy poly(p-hydroxystyrene), (S)-NP
P-PHS, are well described by the bi-exponential expression predicted b
y the 3-D model. Below T,, however, the dynamics are not well modeled
as simple 3-D rotational diffusion, the apparent result of complex dyn
amical matrix interactions. Under all conditions examined, the experim
ental d(31) relaxation dynamics can be described approximately using t
he 2-D model. The temperature dependence of the relaxation rate above
T-g is well described by the Williams-Landel-Ferry (WLF) equation, whi
le below T-g, the reorientation process is Arrhenius-like. The d(33) g
rowth kinetics are found to be accurately approximated using expressio
ns derived from the 3-D rotational diffusion model. Below T-g the expe
rimental activation energy determined from field-on polarization is id
entical within experimental error to that determined for field-off dep
olarization.