Ju-Myung Song

Preparation and thermal properties of liquid crystalline ionomers having mesogenic ester side chains containing three phenyl groups

A series of liquid crystalline (LC) copolymers having both the repeat units of mesogenic ester side chains containing three phenyl groups and the repeat units possessing an acid group were prepared. The acid groups of the LC copolymers were neutralized with sodium acetate to give a varying degree of neutralization. It was found that the LC properties of the ionomers depended strongly on both the relative amount of the units having the mesogenic side chains and the amount of ionic units. It was also observed that the formation of the nematic phase of the LC ionomers was suppressed by the increase in ion contents. After the analysis of the thermal data of the phase transitions, it was suggested that the transition temperatures of the LC phases of the copolymers and their ionomer forms, and the temperature ranges for the LC phases were affected by the relative amounts of both mesogenic and acidic units and by the degree of neutralization, simultaneously.

Randomly Sulfonated Liquid Crystalline Polymers Containing Triad Mesogen of Butylene Terephthalate

A thermotropic liquid crystalline polymer (LCP) containing a terephthaloyl bis(4-oxybenzoyl) (Triad) rigid moiety and a butylene terephthalate flexible unit was solution-polymerized and was subsequently partly sulfonated. It was found that the introduction of sulfonic acid groups to the LCP did not change the position of the DSC peak for the nematic-to-isotropic transition of the LCP (T n-i). However, the sulfonation induced a peak related to the melting of crystalline phase of the Triad domains (T m(T)). When the acid groups of the sulfonated LCP were neutralized with NaOH, the T n-i DSC peak shifted to lower temperatures with a strong decrease in its size, but the T m(T) DSC peak did not change its position strongly. Furthermore, a new peak for the melting of crystalline phase of the butylenes domains (T m(BT)) appeared at much lower temperatures. The above results suggested that the sulfonation introduced ionic characters to the TLCP polymer successfully; as expected, it changed the liquid crystalline characters of the TLCP significantly.

Sulfonated Polystyrene Ionomers Neutralized with Mixtures of Various Cations Studied by Dynamic Mechanical and Small-Angle X-Ray Scattering Techniques

The effects of the addition of mixed cations, i.e. Na + /Cs + , Ba 2+ /Cs + , and Ba 2+ /Zn 2+ , to the acid form sulfonated styrene copolymers on their dynamic mechanical properties and morphology were investigated. It was found that the matrix glass transition temperatures did not change with the ratio of the one cation to the other. As expected, however, the ratio of one cation to the other in the mixed cations affected cluster glass transition temperatures significantly. It was also found that the activation energies for the glass transitions for the matrix phase remained constant, while those for the cluster phase changed with the ratio of the two cations. In addition, the position of the SAXS peak was found to be affected by the type of cations. From the results obtained above, the decrease in the cluster T g with increasing the amount of cesium and zinc cations in Na/Cs, Ba/ Cs, and Ba/Zn mixtures, were explained on the basis of the considerations of the size, charge, and type of cations, which alter the degree of clustering as well as ion-hopping mechanism.