Recent literature has shown that the thickness of dip-coated films has a V-shaped dependence on dip-coating rate when very slow rates are included. For supramolecular block copolymer films, small molecule (SM) uptake and film morphology are also rate-dependent, as shown previously for a poly(styrene-b-4-vinylpyridine) (PS−P4VP) block copolymer in THF solutions containing naphthol (NOH) and naphthoic acid (NCOOH). Here, these investigations are extended to p-dioxane, toluene, and CHCl 3 solutions. The V-shaped thickness dependence is validated for each solvent, but with the V minimum displaced to lower dip-coating rates and thicknesses for the solvents with lower vapor pressures (p-dioxane, toluene), thereby decreasing the dip-coating rate range of the "capillarity regime" (slow side of the V) and consequently extending that of the "draining regime" (fast side of the V). The SM/VP uptake ratio varies with the nature of the solvent, particularly in the capillarity regime, where it is higher for solvents that are weak SM-VP hydrogen-bond competitors (toluene, CHCl 3 ). The draining regime generally shows greater SM uptake than the capillarity regime, in some cases reaching the solution ratio, with higher uptake observed for the SM with greater hydrogen-bond strength (NCOOH > NOH). The variation in film morphology with solvent and dip-coating rate (spherical for toluene; spherical and cylindrical for p-dioxane; spherical, cylindrical, and lamellar for THF; and lamellar only for CHCl 3 ; for a block copolymer whose equilibrium morphology in the bulk is near the cylindrical/lamellar phase boundary) depends on the initial solution state (whether micellar or not and hardness of micelles) and the SM uptake ratio. These factors, along with solvent evaporation rate and film thickness, influence the kinetics of morphology development in the drying films, the point at which the kinetics are frozen in, the effective block ratio, and the orientation of the morphological structures.

The synthesis of a new series of cationic tail-end polyamphiphiles of the type, poly(ωpyridinium alkyl methacrylate)s with various 4-substituted pyridinium bromide groups and with spacers of 8, 12, and 16 methylene units, obtained by free radical polymerization in aqueous micellar solution, is described, and the thermal and structural characteristics in the solid-state have been studied. All of the polymers show a single glass transition in the range 39-105 °C, whose value depends strongly both on the spacer length, due to internal plasticization, and on the specific nature of the pyridinium moiety, where higher T g's can be related to greater rigidity of the pyridinium group. The polymers are all birefringent between crossed polarizers, in some cases up to their degradation temperatures. X-ray diffraction investigations indicate that they tend to self-organize into an amorphous lamellar morphology that appears to be better defined the longer the alkyl spacer and whose details depend also on the specific pyridinium moiety. Thus, it is shown that the effects of ionic interactions and of the amphiphilic character of the polymers on their thermal and structural properties are clearly modulated by the alkyl spacer length and by mesogen-related parameters such as rigidity and bulkiness.

A series of spacer-free ionic azobenzene-containing stoichiometric complexes was prepared from monosulfonated azo dyes and cationic polyelectrolytes [methylated poly(4-vinylpyridine) (PVP) and poly(dimethylaminoethyl methacrylate) (PDM)]. Their thermal and structural characteristics and optical responses, particularly photoinduced birefringence (PIB) and surface relief grating (SRG) inscription, were investigated as a function of selected molecular parameters. All of the complexes have high apparent T g values, 180-210°C, and show liquid crystal (LC) order of the single-layer SmA type from ambient to very high temperature, usually to degradation. The range of LC order is greater in the complexes of chromophores with longer alkyl tails and shorter in the complex of the chromophore with an OH end group and the complex of methyl orange (MO) with PDM. PIB, SRG quality, and diffraction efficiency were all shown to depend in a similar way on molecular structural features: the more rigid the molecular structure, the higher the PIB, the better its thermal and temporal stability, and the greater the SRG amplitude. Thus, a flexible alkyl unit in the polyelectrolyte component or in the chromophore tail or spacer reduces the optical performance, with a clear dependence on alkoxy tail length (e.g., no SRG formation was observed for the complex with a hexoxy tail), whereas the most rigid complex, MO/PVP, provides the best performance, contrasting with many previous literature reports that suggest a beneficial role for flexible spacers. The present paper shows that flexible moieties increase relaxation of photoinduced orientation. The hydroxyl end group also provides much improved PIB and SRG performance, attributed to its rigid structure along with a (temperature-dependent) physical cross-linking effect of H-bonding interactions.