Sulfonated Polystyrene Ionomers Neutralized with Mixtures of Various Cations Studied by Dynamic Mechanical and Small-Ang
- PDF / 94,886 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 54 Downloads / 156 Views
U3.8.1
Sulfonated Polystyrene Ionomers Neutralized with Mixtures of Various Cations Studied by Dynamic Mechanical and Small-Angle X-Ray Scattering Techniques Ho Seung Jeon, Ju-Myung Song, and Joon-Seop Kim Department of Polymer Science & Engineering, Chosun University, Gwangju 501-759, Korea ABSTRACT The effects of the addition of mixed cations, i.e. Na+/Cs+, Ba2+/Cs+, and Ba2+/Zn2+, 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 Tg 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. INTRODUCTION Ionomers are polymers containing a small amount of ionic groups along the relatively non-polar polymer backbone chains. According to the EHM model [1] for random amorphous ionomers, ionic aggregates, so-called multiplets, restrict the mobility of polymer chains surrounding them. When ion content increases, the number of multiplet increases. As a result, the size of restricted mobility regions also increases, and the regions start to overlap. At a certain ion content, the reduced mobility regions become large enough to have their own glass transition. The regions are now called clusters [1]. At this point, the ionomer starts to exhibit two glass transitions (Tgs); the Tg at low temperature is due to the glass transition of unclustered matrix regions, while the Tg at high temperature to the glass transition of clustered regions. It has been widely known that, in ionomers having the same polymer matrix, various factors including the size, oxidation state, position and type of ionic groups affect the cluster Tg of ionomers significantly [2,3]. Thus, in the present work we prepared sulfonated polystyrene (SPS) ionomers neutralized with mixtures of various cations and studied their dynamic mechanical properties and morphology by using dynamic mechanical thermal analysis (DMTA) and smallangle x-ray scattering (SAXS) techniques. With the results obtained from this study, one is able to deepen one’s understanding on the relationship between the type of
Downloaded from https:/www.cambridge.org/core. Cornell University Library, on 18 Apr 2017 at 03:41:14, subject to the Cambridge Core terms of use, available at https:/www.cambridge.org/core/terms. https://doi.org/10.1
Data Loading...
