Copolymers monolayer characteristics

Lin et al. [17] studied the dynamics of copolymers adsorbed on an air-water interface. These measurements complemented the static measurements described above and in Fig. 4. The extent of the polymer films perpendicular to the surface is small compared to penetration distance and wavelength so that EWDLS is most sensitive to variation of composition in the plane of the interface. Figure 7 shows the measured normalized autocorrelation I (/) for different surface pressures. Frames a-d were taken during the first compression of the monolayer, and frames e-h were taken during the second compression. The difference between the two sets of measurements is an indication of structural changes induced by compression cycling. The frames e-g can be compared to the data in Fig. 4. The solid lines in the three frames are fits to a sum of two exponential functions, each with a characteristic decay time. The fast decay constant has a characteristic associated with diffusive motion of the disks. The slow decay constant ( several seconds) was ascribed to the dynamics of the associations of disks. 

Samples of styrene-dimethylsiloxane and poly (2,6-diphenyl )phenylene ether-dimethylsiloxane block copolymers were also examined as spread films. The styrene-siloxane copolymers included AB, ABA, and repeating block copolymer types. In these cases, as with the polycarbonate, the organic homopolymers do not form monolayers when we try to spread volatile solvent solutions on water. The characteristics of the copolymer spread films, however, were similar to those of the BPAC—DMS copolymers. In all cases, sigmoidal 7r-A curves were obtained, and surface pressures above 10 dynes/cm were unstable. (All of the samples examined had organic blocks of 15 or more monomer units.) A typical curve, for a styrene-dimethylsiloxane repeating block copolymer (19), is shown in Figure 4. 

Thus, for block copolymers based on dimethylsiloxane with alkylene glycols as surface-active additives there is a relation between the structure of the epoxide system in the hquid state and that in the hardened state. This allows regulation of the properties of polyepoxides using the thermodynamic characteristic of these surfactant solutions in monofunctional epoxide compoimds. In addition, it is found that the introduction of surfactants of the epoxide series to polyepoxides affects the parameters of the pol5rmer structiue rather differently, depending on the arrangement (parallel or perpendicular) of lyophobic groups of KEP-2 in a monolayer with respect to the interface. 

The self-assembly of arborescent PS-gro -PEO copolymers spread as monolayers at the air/ water interface was recently investigated (Njikang et al., 2008a). AFM imaging was used to examine the influence of molecular structure and composition on the characteristics of the... 

---