Abstract
Our work can be divided into two parts. One is to discuss the syntheses and characterizations of containing bromine ferroelectric liquid crystalline polymers and the other is to study the syntheses and characterizations of containing halogen ferroelectric liquid crystalline polymers.The study of the characterizations of containing bromine ferroelectric liquid crystalline polymers is to adopt the three different kinds of spacer lengths (n=1, 2, 3) and four different sorts of grafted ratios (15mol%, 35mol%, 55mol%, 100mol%) for understanding the liquid crystalline phases behaviors and relationships of the dielectric relaxation phenomenon. We can find when the spacer lengths are shorter and grafted ratios are more, the liquid crystalline phase tends to cholesteric phase (Ch). In contrast, when the spacer lengths are longer and grafted ratios are less, it enhances the stability and range of the chiral smectic C phase (Sc*). Besides, it can also be seen that the glass transition temperature rises with the LC contents and spacer units. The melting point also gets higher as the spacer units descend. Moreover, the X-ray diffraction instrument is used to investigate the samples and it is found that the layer spacing increases with the temperature in the Sc* phase.In the dielectric analysis, the Goldstone mode relaxation is observed in our entire samples even though the series of PSn12Bs100 don't present the Sc* phase. It is because the external electric filed induces the phase change to produce the similar Sc* property. Furthermore, the Goldstone mode intensity gets weaker as the LC contents decrease. However, the β-relaxation is suppressed as the LC contents increase. It represents that the more meogen units hinder the free rotation. Therefore, it can enhance the intensity with introducing the longer spacer length and raising the temperature.The study of the syntheses and characterizations of containing halogen ferroelectric liquid crystalline polymers is to use two kinds of grafted ratios (15mol%, 100mol%) and three lateral halogen substituted groups (F, Cl, Br) in the longest spacer (n=3) in order to discuss the relationships between the dipole moment and the atom size.We can find that PS312Fs100 and PS312Cs100 both have the Sc* phase and Ch phase and PS312Bs100 only has the Ch phase. It can be proved again that the larger substituted group (Br) destroys the laminar structure and twists the polymer main chain. Then, all of the copolymers both have the wide Sc* phase. However, PS312Fs15 has the narrow Sc* phase. The reason is that the size of the fluorine atom is the smallest so it leads to the tighter arrangement and the higher temperature of the Sx phase. As a result, we can say that the proper size substituted atom (Cl) have the wide Sc* phase in general.In the dielectric analysis, the Goldstone mode relaxation can be investigated. It can be concluded that no matter what grafted ratios are, the sequence of the Goldstone mode intensity is containing F, Cl and Br group. Therefore, the capability of the molecular motion is related to the mass (size) of the substituted group. Moreover, the melting points are similar with the above. It is due to the dual effects of the atom size (mass) and dipole moment. Furthermore, the α、β、γ relaxations also have the same phenomenon. As a result, it could be proved that the sequence of melting point difference between the homopolymers and copolymers is less. It could be because of the arrangements of the all samples are similar. From this view, the controlling factor still is the size (mass) effect but the dipole moment effect can't be ignored.